F 271 S22 opy 1 Issued June 30, 1913. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY.— Bulletin 165. A. D. MELVIN, Chief of Bureau. THE MANUFACTURE OF CHEESE OF THE CHEDDAR TYPE FROM PASTEURIZED MILK. BY J. L. SAMMIS, PH. D., Associate Professor of Dan y Husbandry, College of Agriculture', University of Wisconsin, AND A. T. BRUHN, Expert Cheese Maker, Dairy Division, Bureau of Animal Industry. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1913- Issued .Imi" 31, I"!'' U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY, —Rui.iF.TiN ]<3=>. A. D. iMELVIN, CHihF oi- Bureau. THE MANUFACTURE OF CHEESE OF THE CHEDDAR TYPE FROM PASTEURIZED MILK. BY J. L. SAMMIS, I^H. D., AssocJafe Professor of Dairy Husband r\\ Collej^c of Aj^riaiiiure, ( 'niversity of II 'isconsiit, AND A. T. BRUHN. Expert Cheese Maker, Dairy Dix'ision, Bureau of Animal Industry. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1913. THE BUREAU OF ANIMAL INDUSTRY. Chef: A. D. Melvin. Assistant Chief: A. M. Farrington. Chiff Clerk: Charles C. Carroll. Animal Husbandry Division: George M. Rommel, chief. Biochemic Division: M. Dorset, chief. Dairy Division: B. H. Rawl, chief. Field Inspection Division: R. A. Ramsay, chief. ^feat Inspection Division: R. P. Steddom, chief. Pathological Division: John R. Mohler, chief. Quarantine Division: Richard W. Hickman, chief. Zoological Division: B. H. Ransom, chief. Experiment StatioJi: E. C. Schroeder, superintendent. Editor: James M. Pickens. DAIRY DIVISION. B. H. Rawl, chief. Helmer Rabild, in charge of Dairy Farming Invesligatiovs. S. C. Thompson, in charge of Dairy Manufacturing Invcstig-Jions. L. A. Rogers, in charge of Research Laboratories. Ernest Kelly, in charge of Market Milk Investigatin}}^. Robert McAdam, in charge of Renovated Butter Inspection. 9 D. OF 0. JUL 1i 1313 LETTER OF 'I RANSMITTAL. U. S. Department of Agriculture, Bureau of Animal Industry, ^Vasliington, D. C, January 30, 1913. wSir: T liavo tho honor to transmit for publication as a bulletin of this bun^au the accompan^ano; manuscript entitled "The Manufac- ture of Cheese of the Cheddar Type from Pasteurized Milk, " by Prof. J. L. Sammis, of the College of Agriculture, University of Wisconsin, and Mr. A. T. Bruhn, expert cheese maker in the Dairy Division of tliis bureau. The work herein described was con(kictcd at Madison, Wis., in cooperation between the Dairy Division and the Wisconsin Agricultural Experiment Station. The Dairy Division has been represented at Madison by L. D. Bushnell, Alfred Larson, and Miss Alice C. Evans, bacteriologists, in succession; S. K. wSuzuki and E. F. Flint, chemists, and J. W. Moore, F. W. Laabs, and A. T. Bruhn, expert cheese makers, in succession, all of whom have assisted at various times in this work. The Wis- consin Station lias been represented by Prof. Sammis, who from the beginning has had charge of the cooperative experinients in tlie manu- facture of the Chechiar type of cheese from pasteurized milk. The comj)arison of this cheese with tliat made from raw milk by tbe regular factory method has been systeniatically and thoroughly carried out under a variety of conditions by the use of (hiplicate vats of milk, one of these being pasteurized in eacli instance. During 1910 and 1911, especially in the latter year, the \\v\\ |)rocess was per- fected and a large quantity of the pasteurized cheese was ma(h^ under commercial conditions and placed upon the open market. The results are fully described, also the proc(>ss of making the cheese, and it is shown that the use of pasteurized milk is highly satisfactory and economical. As pathogenic bacteria have been found to survive for several months in cheese made from raw milk, the pasteurization of milk in making cheese is also desirable for the protection of the healtli of the consumer. Respectfully, A. D. Melvin, Chief of Bureau. Hon. James Wilson, Secretary of Agriculture, CONTENTS. Page. Introductory 9 The need for a new method of cheese making 9 Faults to 1)0 corrected in milk for cheese making 10 The necessity for the pasteurization of milk for cheese making 11 Amount of heat necessary to destroy various bacteria 12 Previous attempts to make cheese from pasteurized milk 13 Dithculties met in making chcsese from pasteurized milk 14 Difhculties overcome by acidulation of pasteurized milk 15 The pasteurization process 18 Pasteurization in a discontinuous or "held" pasteurizer 18 Continuous and ' ' held ' ' pasteurization compared 18 Selection of best temperature for pasteurization in the continuous machine . 20 Objections to higher temperatures than 160°-165° F. for pasteurization. ... 23 Effect of pasteurization on the properties of cheese curd 25 The different types of continuous pasteurizers used 28 The acidulation jjrocess 28 The standard acidity of milk for cheese making 28 Comparison of different kinds of acid for cheese making 30 The ))roportion of hydrochloric acid required daily 30 Testing milk for acidity 31 Preserving the tenth-normal solution 32 Diluting normal alkali to tenth-normal 32 Adding acid to milk after pasteurization 33 Calculating the amount of acid to be added '. 33 Preparation of normal hydrochloric acid in the cheese factory 35 General directions for pasteurizing and acidulating milk 37 Making ready to pasteurize 38 Starting and stopping the pasteurizer 39 Starting and stopping the acidulator 40 The use of bacterial starter in the new process 40 The reason for adding starter in making pasteurized-milk cheese 40 A practical sterilizer for the cheese factory 42 Preparation of the starter 43 Method of making cheese by the new process 45 General arrangement of schedule 45 Uniform proportion of color used in 1911, and rennet required 46 Adding starter, color, and rennet to the milk 47 Cutting, stirring, and heating the curd 48 Drawing the whey, matting, cutting, and turning the curd 49 Milling, salting, and hooping the curd 49 Pressing and dressing the cheese 50 Drying, paraffining, and curing 50 Branding and selling the cheese 51 Testing cheese for moisture when dressed in the hoop 52 5 6 CONTENTS. Page. Results of two years' trial of the new method 53 Increased yield of cheese obtained by the new process 53 Apparatus and methods of study 53 Search for systematic errors in experiments on yield of cheese 56 Shrinkage before paraffining, and yield of paraffined cheese 60 Shrinkage and yield of cured cheese 62 The causes of the increased yield from pasteurized milk 69 The losses of fat from vat and press 69 The increased moisture content of pasteurized-milk cheese 73 The quality of pasteurized-milk cheese 75 Scores and criticisms of pasteurized and raw milk cheese 75 Cheese cured at Madison at normal temperature 75 Cheese cured in the South 79 Cheese cured in warm room at Madison 84 Cheese cured in cold storage 85 Exceptional differences between the raw and pasteurized milk cheese. 86 Summary of discussion of scores 87 The demand for pasteurized-milk cheese 88 Opinions of purchasers 89 The extra cost of making pasteurized-milk cheese 89 Further trials of the new process in cheese factories 90 Summary 90 Preliminary and comparative work with the old and new methods 90 Some advantages from the use of pasteurized milk and hydrochloric acid. . 92 Outline of the new method 93 ILLUSTRATIONS. PLATES. PsEe. Plate I. Outfit used in testing milk for acidity (Manns'sacid test) and in testing slrongth of hydrochloric acid used in cheese making 32 IL The continuous disk pasteurizer, and apparatus used in acidulating pasteurized milk 32 IIL The continuous "flash" paaleurizer, and apparatus used in acidulatiii,,' pasteurized milk 32 IV. Transferring acid from full to empty carboy by means of siphon 36 V. Vat strainer for straining milk into receiving vat 30 VI. A uniform layer of curd, showing use of curd gauge 48 TEXT FIGURES. Fig. 1. A combined sterilizer, cooler, and incubator for cheese-factory starter.. 43 2. Method of marking cheese 52 3. Distribution of total scores of pasteurized and raw milk cheese 78 4. Distribution of flavor scores of pasteurized and raw milk cheese 78 5. Distribution of texture scores of pasteurized and raw milk cheese 79 6. Distribution of total scores of pasteurized and raw milk cheese 81 7 THE MANUFACTURE OF CHEESE OF THE CHEDDAR TYPE FROM PASTEURIZED MILK. INTRODUCTORY. THE NEED FOR A NEW METHOD OF CHEESE MAKING. Economy of time and labor and ini})roved quality and uniformity of the cheese produced make the large cooperative factory mure profitable to farmers than the small factory, provided they retam the control, if not the complete ownership, of it. There are two objections sometimes raised against tlie replacement of four or five small cheese factories in a neighborhood by one large, better- equijjped, better-manned, and more economical cheese factory, ■ namely: First, that by present factory methods cheese makere could not make as good cheese from milk gathered over a large territory, because it would be longer on the road to the factory and therefore would not be so fresh as otherwise; second, farmers object to haul- ing milk a great dLstance, even to a good cheese factory. The only way to get a large, first-class cheese factory located within a short distance of a sufficient milk supply is to centralize the latter — that is, to keep as many of the best cows on every farm as the land will su])])ort. Until (his is done there will be many factories which must th'aw milk from a large area. Some modification of present cheese-factory methods is needed by which milk from a large territory can be successfully handled. The great amount of inferior cheese on the market and the lack of uniformity which characterizes the product of the present cheese factory of average size is due primarily to the variable quality of the milk supply from different farms, especially as to the presence of dirt and bacteria, which produce faulty flavors and textures in great variety, and to the variable ripeness or acidity of the milk received from day to day, dependmg upon the care given to it on the farm, its age, etc. The immediate effect of these conditions is that cheese makers hi their effort to produce cheese of uniform quality from milk of variable quality must necessarily use methods which vary from day to day and from factory to factory. Under this system each vat of milk must be watched carefully at every stage of its manufacture, and the 9 10 CHEDDAR CHEESE FROM PASTEURIZED MILK. cheese-making process must be hastened, or delayed, or modified every day, according to the cheese makers' judgment. The yield of cheese also varies from day to day, depending upon the quality of the milk and the method used in handling it. The ideal conditions for cheese making require an absolutely clean and perfect milk supply, and this can not be realized until methods of milk production on the farm are vastly improved. In the mean- time a process for treating milk daily at the factory so as to bring it into practically uniform condition for cheese making purposes is needed. Such a process should include means for stopping the ripening and the growth of harmful bacteria, etc., in the m'dk as soon as it is received at the factory, in order that it may be ripened with a clean starter, in a uniform manner, daily. The process should be applicable to milk of any degree of ripeness which can properly be accepted as fit for cheese making from a sanitary standpoint. When mUk is thus brought by a preliminary treatment into uniform condi- tion at the factory, both as to acidity and as to bacterial content, the present variable and irregular methods of making cheese could ^probably be replaced by a routine process, operated upon a fixed time schedule without variation from day to day. As a result, it is to be expected that the uniformity, quality, and yield of cheese would be much improved as compared with that obtained by the older methods. In many other lines of manufacture in recent years preliminary proc- esses have been devised for bringing raw materials into uniform condition before they enter the manufacturing process, and improved products, increased economies, and larger output and profits have resulted. It is desirable that the same general methods of improve- ment which have been used with success m other lines be applied also to the cheese-making industry. FAULTS TO BE CORRECTED IN MILK FOR CHEESE MAKING. The defects most commonly met with in milk, which must be cor- rected by such a preparatory process as that contemplated, are of bacterial origin. A variable content of laciic-acid bacteria causes milk when received at the factory to exhibit different degrees of acidity and also causes the subsequent development of acid in the milk and curd, while in the vat, to go on at varying rates. On account of the important influence which acidity has upon the rate at which whey is expelled from curd, as pointed out in a previous bulletin,^ it may well be said that this is the leading controlling factor in the manufacture of American Cheddar cheese. Therefore it is of prime importance to secure milk of uniform acidity with which to ' Sammis, J. L., Suzuki, S. K., and Laabs, F. W. Factors controlling the moisture content of cheese curds. U. S. Department of Agriculture, Bureau of Animal Industry, Bulletin 122. Washington, 1910. See p. 29. NECESSITY FOE PASTEURIZATION. 11 begin cheese making, and also to provide for subsequent acid de- velopment at a practically fixed rate every day in order to avoid the present troubles due to irregular acid formation. Those bacteria which produce gas or tainted, unclean flavors are all too common in milk, and are the cause of much trouble in tlie cheese factory. Bacteria which produce diseases such as tuberculosis, typhoid fever, diphtheria, dysentery, etc., have often been found in milk, although it is difficult to prove that any person ever contracted these diseases from eating cheese. These and other bacterial infec- tions of raw cream and milk for city trade are usually combated by pasteurization; this is true, like^Aise, in butter making, and with skim milk when used for feeding stock. It seems reasonable, therefore, that any process, such as pasteurization, which will kill the acid, taint, gas, and disease-producing organisms in milk would also im- prove the quality of the cheese produced therefrom. THE NECESSITY FOR THE PASTEURIZATION OF MILK FOR CHEESE MAKING. In view of the possible presence of tubercle bacilli in market cheese, Mohler ' in 190(S recommended the "pasteurization of the milk in order to make the cheese perfectly safe." Mohler, Washburn, and Doane - prepared and studied cheese from milk to wliich cultures of bacillus tuberculosis had been added. They inoculated guinea pigs with such cheese at various periods of time after its manufacture and found that — Advancing cases of generalized tuberciilosis were developed (in guinea pigs) by means of inoculation of cheese 220 days old, and that slight tubercular lesions were caused by the injection of an emulsion of cheese when 261 days old." They add: If it is possible to use pasteurized milk iu the manufacture of cheese without injuring the product a simple solution of the problem is offered to the cheese manufacturer in the process known as pasteurization. These authors also give a brief resume of previous work on this subject in Europe and America. It is evident that the bacillus of tuberculosis not only retains its Ufe but also its virulence in cheese for a considerable period of time, and that cheese made from raw, unpasteurized milk should therefore be considered as a possible carrier of tubercle bacilli. There is a strong tendency at the present time to cure American cheese more rapidly than in the past, so that it commonly reaches 'Mohler, John R. Conditions and diseases of the cow injuriously affecting the milk. U. S. Treasury Department, PubUc Health and Marine-Hospital Service, Hygienic Laboratory, Bulletin 4L Washing- ton, 1908. See p. 495. 2 MohJer, John R., Washburn, Henry J., and Doane, C. F. The viability of tubercle bacilli in cheese, Twenty-sixth Annual Report of the Bureau of Animal Industry, U. S. Department of Agriculture (.1909), pp. 187-191. Washington, 1911. 12 CHEDDAE CHEESE FROM PASTEURIZED MILK. the consumer at a less age than four months. It has also been shown ' that practically all — 95 to 98 per cent — of the bacteria present in milk are retained in the cheese. These facts serve to emphasize the desirability of pasteurizing milk for cheese making. An ordinance passed by the common council of the city of Chicago July 13, 1908, contemplated the pasteurization of milk used for cheese making, although at that date no practical methods for making American cheese from pasteurized milk had been published. The ordinance was as follows: Cheese. Be it ordained by the city council of the city of Chicago, * * * Section 2. It shall be unlawful to sell any such cheese in the city of Chicago unless there be stamped on the package in plainly legible letters of not less than one-eighth inch type: "Made of milk (or cream) from cows free from tuberculosis as shown by tuberculin test," or "made from milk (or cream) pasteurized according to the rules and regulations of the department of health of the city of Chicago * * *. " Sec. 4. This ordinance shall be in full force and effect from and after January 1, 1909. AMOUNT OF HEAT NECESSARY TO DESTROY VARIOUS BACTERIA. The question as to what temperature of pasteurization will kill disease-producing bacteria in milk is of interest to the consumer and all connected with the business. The thermal death point of various pathogenic organisms is already well known. Rosenau states as a result of his work and that of others that "milk heated to 60° C. (140° F.) and maintained at that temperature for two minutes will kill the typhoid bacillus." The great majority of these organisms are killed by the time the temperature reaches 1 or 2 degrees below the point named and few survive to 140° F. The diphtheria bacillus succumbs at comparatively low tempera- tures. Oftentimes it fails to grow after heating to 55° C. (131° F.). Some occasionally survive until milk reaches 60° C. (140° F.). The cholera vibrio is similar to the diphtheria bacillus so far as its thermal death point is concerned. The dysentery bacillus is somewhat more resistant to heat than the typhoid bacillus. It sometimes withstands heating at 60° C. (140° F.) for live minutes. All, however, are kiUed when held at this temperature for ten minutes.^ In 1904 Russell and Hastings ^ found that the tubercle bacillus is killed by heating at 71° C. (160° F.) for one minute. From the foregoing it is clear that pasteurization at 71° C. (160° F.) for one minute, and in most cases for a shorter period, is effective in ' Sammis, J. L., Suzuki, S. K., and Laabs, F. W. Factors controlling the moisture content of cheese curds. U. S. Department of Agriculture, Bureau of Animal Industry, Bulletin 122. Washington, 1910. See p. 29. 2 Rosenau, Milton J. The thermal death points of pathogenic microorganisms in milk. U. S. Treasury Department, Public Health and Marine-Hospital Service, Hygienic Laboratory, Bulletin 56, pp. 683-686. Washington, 1909. 3 Russell, H. L., and Hastings, E. G. Eflect of short periods of exposure to heat on tubercle bacilli In milk. Wisconsin Agricultural Experiment Station, Twenty-first Annual Report (1904), pp. 178-192. Mad- ison, 1904. See p. 185. PREVIOUS ATTEMPTS WITH PASTEURIZED MILK. 13 destroying pathogenic bacteria in milk and preventing their entrance into cheese. Babcock and Russell/ from their experiments upon the thermal destruction of galactase, state that "lieating (lie enzym solutions for 10 minutes at 76° C. (169° F.) suffices to destroy tlie dig(>stive fer- ment galactase, and even at 71° C. (160° F.), for tlie same exposure, its action was materially reduced." It seems hkely, therefore, that an exposure to 160° F. for 1 minute or less in the continuous pas- teurizer would not greatly weaken the action of this enzym in milk for cheese-making purposes.^ Much less attention has been paid by bacteriologists to the tiiermal death point of those bacteria in nu'lk wluch produc(^ gas and tainted flavors in cheese. , Moore and Ward ^ have described a gas-producing bacillus isolated from milk and from gassy cheese which "is destroyed in freshly inocidated small tubes of bouillon when exposed to a tem- perature of 60° C. (140° F.) for 10 minutes in a closed water bath." It is to be lioped that in the future investigators will determine also the minimum temperature required to kill various species of milk bacteria with an exposure of 1 mmute or less as in the continuous pasteurizer. PREVIOUS ATTEMPTS TO MAKE CHEESE FROM PASTEURIZED MILK. The possibility of ninking American chees<> from p;isteurized milk luis been studied at sevcn'al experiment stations and i^lsc where. TJie two difficulties met with are: First, the fact, long known, tliat heated milk coagulates slowly with rennet, giving a loose, spongy curd wliicli is not suital)le for cheese making because it is too fragile to be handled. Second, pasteurization causes curd to ex])el wh<'y more slowly than otherwise. In order to restore the coagulabdity with rennet to pasteurized milk, Klein and Kirsten '' in 1S9S added calcium chlorid and a bac- terial starter and were able to obtain fairly good limburger and otlier soft cheeses. Tlie}^ used for 100 kilograms of skim milk 100 to 125 cubic centimeters of .a solution containing in 100 c. c. 40 grains of calcium chlorid, corresponding to 20 grams calcium oxid. ' Babcock, S. M., Russell, H. L., and Vivian, Alfred. Properties of galactase: A digestive ferment of milk. Wisconsin Agricultural -Experiment Station, Fifteenth Annual Report (1898), pp. 77-86. Madison, 1898. See p. 82. 2 Kastle, Joseph H., and Roberts, Norman. The chemistry of milk. IT. S. Treasury Department, Public Health and Marine-Hospilal Service, Hygienic Laboratory, Bulletin 56, pp. 315-417. Washington, 1909. ' Moore, V. A ., and Ward, A. R. An inquiry concerning the source of gas and tiiint producing bacteria in cheese curd. New York (Cornell) Agricultural Experiment Station, Bulletiji 15S. Ithaca, 1899. See p. 236. < Klein and Kirsten, A. Versuche, befreffend die Wiederherstellung der Verkasumgsfiihigkeit erliitzter Milch durch Chlorcalciumzusatz. Milch-Zeitung, vol. 27, no. 50, pp. 785-787, Dec. 10; no.51, pp. SO.3-805, Dec. 17. Leipsic, 1891?. See also Fleischmann, W. Lehrbuch der Milchwirtschaft. 4th edition. Leipsic, 1908. See pp. 304, 305. 14 CnEDDAR CHEESE FROM PASTEURIZED MILK. In Denmark a kind of cheese is made from pasteurized skim milk to which about 10 per cent of buttermilk is added so as to bring the acidity up to about 0.21 per cent just before adding rennet.^ In 1907 Dean - stated as a result of experiments in the use of cal- cium chlorid with pasteurized milk for cheese making "the coag- ulum was of a soft, weak nature and the cheese tended to be soft and porous." He also added 1^ to 3 per cent of bacterial starters to milk pasteurized at 180° F. and ripened some time before adding rennet. The rennet coagulated the milk, but the curd was weak in body. He noted an increased yield of cheese, but the cheese tended to be open and weak in body and texture. He adds: On the whole the results are not very satisfactory and we shall require more light on the subject of making pasteurized milk cheese before we could recommend the method to Canadian cheese makers. In 1910 C. A. Publow ^ mentioned briefly some experiments in making cheese from pasteurized milk, adding to each 100 pounds of milk 2 cubic centimeters of a 25 per cent solution of calcium chlorid and 2 or 3 pounds of bacterial starter. The details of the method and the opinions of cheese judges other than the author respecting the product are not pubhshed. At this station in previous years efforts have been made to obtain good American cheese from pas- teurized milk ^^'ith the aid of calcium chlorid, but without success. DIFFICULTIES MET IN MAKING CHEESE FROM PASTEURIZED MILK. Pasteurization of milk prevents or greatly delays subsequent coagulation with rennet. The curd from such miUv when finally cut into cubes expels moisture with much greater difficulty than a raw-milk curd, probably because of some chemical change produced in the casein by the heat of pasteurization. Rapid acid formation by bacterial action which occurs in raw milk and raw-milk curds does not occur in the pasteurized material. The presence of a mod- erate amount of lactic acid in raw-milk curds greatly hastens the separation of whey from the curd, and the lack of acid development in pasteurized-milk curds is another condition favoring the retention of excessive moisture in the curd and cheese. The addition of calcium chlorid to milk which has been pasteurized is known to restore in a measure the coagulabihty of the milk with rennet, but we have observed, as Publow* points out, that, although coagulation begins in about five minutes, "the curd does not become firm enough for cutting in the usual time and should not be cut before it is firm." Although the addition of calcium chlorid restores I Decker, John W. Cheese making. 5th edition. Madison, Wis., 1909. See p. 194. »Dean, H. n. Experiments in cheese making. Ontario Agricultural College, Thirty-third Annual Report (1907). Toronto, 1908. See p. 120. » Publow, Charles A. Fancy cheese in America. Chicago, 1910. See p. 20. * Loo. cit. See p. 21. DIFFICULTIES OVERCOME BV ACIDULATION. 15 the coagulability with rennet, it does not correct the acidity and the other difficiihies mentioned above as being caused by pasteurization. The lack of acidity in such curd might be supplied by adding starter to the pasteurized milk and lipening for several hours before startmg tlie cheese making, but the resulting loss of time would prohibit this practice in factories. Where both starter and calcium chlorid are added to milk after pasteurization, as suggested by Publow, and the cheese-making process is begun at once without waiting for ripening, tlie daily variations in natural acidity of the milk used produce cor- responchng variations in the moisture content of the cheese which affect its quahty. (See Table 1.) What is needed in place nf calcium chlorid for addition to pasteur- ized milk is something which will not only restore the coagulabiHty with rennet, but which will also bring up the acidity without delay to a sufficiently high percentage to induce reasonably rapid and com- plete soj)aration of whey from curd. A uniform acidity is necessary daily so as to avoid daily variations in moisture content of cheese. DIFFICULTIES OVERCOME BY ACIDULATION OF PASTEURIZED MILK. The substance which has been found to meet all of thv, foregoing r(M|uirements and which appears to be unobjectionable from all stand- points is hydrochloric acid. While it might appear im})racticable at first glance to acidulate milk in large quantities daily at a factory, yet u]M)n trial this is found to be (Mitirely practicable; and it has now been (lon(> almost daily for nearly three years, without any trouble arising from coagulation of the milk with acid at any time. In Table 1 is shown the moisture content of green cheese obtained on 12 days from pasteurized milk by the use of calcium chlorid in the proportions suggested by Publow (see p. 14) and by the use of hydrochloric acid, using always sufficient acid to raise the acidity of the milk to 0.2.5 ])er cent calculated as lactic acid. The milk used in the two vats was taken from the same receiving vat full of milk, after thorough mixing. It was all pasteurized alike and one-half was then treated with calcium chlorid and the other with hydrochloric acid. These were then made up into cheese separately and were sampled for moisture at the time the cheeses were dressed, after pressing one hour.^ From the table it can be seen that whenever the acidity of the milk used was low (0.16 to 0.18 per cent) the moisture content of the cheese made with calcium clilorid was high (40 to 44.45 per cent), and when the acidity was high (0.21 to 0.23 per cent) the moisture content was low (38 to 40 per cent). But in all cases where hydrochloric acid was added instead of calcium chlorid the moisture content of the ctird was 37.5 to 40 per cent, whether the natural acidity of the milk was high or low. » Thfi correctness of this method of sampling cheese for the moisture test is demonstrated in the latter 7 art nrthis bulletin, 16 CHEDDAR CHEESE FROM PASTEURIZED MILK. Table 1. — Comparison of moisture content and qvalily of cheese made with calcium chlorid and with hydrochloric acid. Acidity of milk when pas- teur- ized. How made. Moisture content of dressed cheese. Score. Criticism. Date made. Fla- vor. Tex- ture. Flavor. Te.xture. 1911. Aug. 18 Do Aug. 22 Do July 28 Do Aug. 23 Do Aug. 24 Do Aug. 2.5 Per ct. 0.165 .16.5 .165 .165 .17 .17 .175 .175 .175 .175 . 175 .175 .185 .185 .190 .190 .21 .21 .21 .21 22 '.22 .31 1S7 Calcium chlorid . . . Hydrochloric acid . Calcium chlorid... Hydrochloric acid. Calcium chlorid . . . Hydrochloric acid. Calcium chlorid . . . Hydrochloric acid. Calcium chlorid... Hydrochloric acid. Calcium chlorid.. . Hydrochloric acid. Calcium chlorid . . . Hydrochloric acid. Calcium chlorid . . . Hydrochloric acid. Calcium chlorid . . . Hydrochloric acid. Calcium chlorid . . . Hydrochloric acid. Calcium chlorid . . . Hydrochloric acid, .do Per cent. 42.25 37.70 42.35 38.80 41.50 37.70 44.27 39.20 44.27 39.62 44.45 39.02 42.90 39.90 41.50 39.95 39.20 39. 62 38.70 38.60 40.60 39.95 39. 05 37.58 38 41i 40 41 38 4U 39| 40J 37 41 m 4U 40 4U 39 41i 41 41 39 41i 41 41 26 27* 26 27J 24 28 25i 27 25 26J 26* 28' 25 28 26 27i 26 26i 26^ 27 26i 27* Flat, pungent Clean Curdv, loose, weak. Trifle loose. Flat, lacking Clean and 0. K... Lacks acid Trifle acid Low, lacking Trifle sharp Sour-milk flavor . . Trifle sharp Clean and O.K... 0. K Weak, sticky. Trifle weak." Wet and sticky. Trifle sticky. Trifle weak. Do. Very loose, weak. Trifle weak. Sticky, loose, short. Aug. 11 Do Bitter, lacks acid.. O.K Coarse, loose. Sept.4 Do Aug. 17 Do Sweet, bitter .\cid aftertaste Tastes sal tv do ■ Weak, mechanical holes. Mechanical holes. Weak and sticky. Loose, sticky. Sweet holes. Trifle loose. Short, sticky. Trifle short. Aug. 16 Do Aug. 2S Do Vinegar flavor Clean and 0. K... Trifle bitter ..do Aug. 7 Aug 10 ....do Aug 21 '?i-i do Calcium chlorid . . . Hydrochloric acid. 38.67 -Average . . . 42.00 38.95 39.45 41.23 25.73 27.36 Do From the above table it is evident that when milk is acidulated w4th hydrochloric acid after pasteurization, as in the new method, the moisture content of the green cheese is not affected by the ripeness of the milk before pasteurization and is quite constant betw^een 37.5 and 40 per cent. This advantage does not attend the use of calcium chlorid. The daily variations of moisture content shown in column 4, which are between 37.5 and 40 per cent, are doubtless due to causes other than acidity, and did not noticeably affect the rjuality of the cheese. The scores and criticisms show that the cheese made with calcium chlorid was neither as uniform nor as good m cjuality as that made with hydrochloric acid. The addition of hydrochloric or lactic acid to cream to raise its acidity without delay, preparatory to churning, was attempted by Babcock in 1888.^ The addition of a commercial acid to raw milk to raise its acidity without waitmg for bacterial action w^as suggested to the waiter in 1905 by Dr. S. M. Babcock, chief chemist of the Wisconsin Experiment ^Station, and during the years 1905-6 the effort was made, folio wmg the suggestion of Dr. Babcock, to avoid the necessity for ripening milk for cheese making at the factory and 1 Babcock, S. M. Churning tests. Wisconsin .Agricultural Experiment Station, Fifth .Annual Report, 1888, p. 111-121. Madison, 1888. See p. 118. See also patent granted to .\Iiiller, Milch-zeitung, vol. 23, no. 19, p. 301, Bremen, May 12, 1894; also notes on this subject in same volume, pp. 425, 464, 701, 750. DIFFICULTIES OVERCOME BY ACIDULATION. 17 to substitutp for such ripoiiing the addition of a oonimorcial arid to the milk as soon as it was received. Immediately after acidulating the milk it was heated to 86° and rennet was added and the process completed in the usual maimer. These exjieriments showed conclu- sively that a commercial acid such as hydrochloric acid can be added to milk without in any way damaging the quality of the cheese obtained. However, the (juality of cheese obtained from ovempe or tainted milk was not im})roved by the use of the acid, and it was concluded that acidulation alone does not offer sufficient advantages to warrant its recommendation to cheese makers. The addition of acids to pasteurized milk for cheese making was begun by the writer in 1907. Pasteurization and acidulation of milk appear to be complementary processes, each supplying what the other lacks and together forming the basis of an improved method of chee,se making. Since the use of calcium chlorid in pasteurized-milk cheese will not be referred to again in this paper, two other points will be mentioned here in which the use of hydrochloric acid is more advantageous. These are: First, that the hydrochloric acid curds always begm to thicken 6^ to 7 minutes after rennet is added, while with calcium chlorid the first visibl{> coagulation occurs earlier if the milk used is very ripe and later if the milk is sweet, thus varying from day to day, as shown in Table 2. Second, the percentage of fat lost in the whey is on the average about 0.14 per cent greater in the method using cal- cium chlorid than when hydrochloric acid is used, as also shown in Table 2. This is probably because calcium chlorid curds are always more mushy and easier to break up in stirring than curds made with hydrochloric acid. The latter are really superior in this res])ect to curds obtained by the regular factory methods. I'able 2.— Comparison of calcium chlorid with hydrochloric acid as to their effects on cheese made icith pasteurized milk. Date. Time required for vi.sihlp, coagula- tion after adciinp; rennet. Per cent of fat in whey at time of drawing whey and ma 1 1 i n g curd. Acidity of milk used. Calcium chlorid. Hydro- chloric acid. Calcium chlorid. Hydro- chloric acid. 1911. July 28 Aup. 11 16 17 18 22 23 24 25 28 Average.. Minutes. 14 15 6 4 14 Hi 18 18 16 6i Minutes. 7 7 7 7 7 7 7 7 7 Per cent. 0.23 .35 .16 .21 .32 ..32 .-.iO .42 .38 .17 Per cent. 0.13 .14 .12 .14 .19 .18 .20 .20 .16 .13 Per cent. 0.17 .185 .21 .21 .165 .165 .175 .175 .175 .22 .295 .159 79994°— Bull. 165—13- 18 CHEDDAE CHEESE FROM PASTEURIZED MILK. THE PASTEURIZATION PROCESS. PASTEURIZATION IN A DISCONTINUOUS OR "HELD" PASTEURIZER. In May, 1907, one day's milk supply was divided in two portions, one of which was made up by the regular method and the other was pasteurized for 18 mmutes at 160° F. and acidulated with hydro- chloric acid. The pasteurized vat gave the best-flavored cheese after curing, though it was inferior in texture to the other. On March 12 and 27, 1908, milk pasteurized at 140° for 20 minutes and then acidu- lated gave such good cheese that a systematic study of the combined process of pasteurization and acidulation was begun in July, 1908. Cheese was made from milk pasteurized at 140° F. for 20 minutes, either in a Potts pasteurizer or in the cheese vat, by running first steam and then cold water into the jacket. At the same time part of the milk supply after mixing and dividing was used for making cheese by the regular methods. The scores given to the two lots of cheese thus obtained are shown below: Table 3. — Comparison of flavor and texture of cheese made from raw m,ilk andjrom milk pasteurized at 140° F. for 20 minutes. Pasteurized cheese. Regular make. | Date made. Flavor. Texture. Flavor. Texture. 1908. Julv 16 3S.3 26.2 36.2 27.8 17 40.0 27.0 38.5 26.25 IS 41.7 27.5 39.25 27.0 20 40.8 26.3 37.3 26. 75 21 41.2 26.0 41.2 26.2 22 41.3 26.8 38.0 26.75 23^ 40.8 26.7 39.5 26.5 24 41.0 27.25 38.3 26.25 31 Average.. 40.25 26.25 36.5 26.5 40.59 27.00 38.30 26.66 The scoring was done by J. W. Moore and F. W. Laabs. In every case but one the pasteurized cheese had better flavor and there was little difl'erence in texture between the two lots. CONTINUOUS AND "hELD" PASTEURIZATION COMPARED. On account of the large volume of milk which must be handled daily in a cheese factory, and the greater expense involved in providing arrangements of sufficient capacity for heating and cooling 5,000 to 7,000 pounds of milk at one time as compared with the small cost of a continuous pasteurizer, most of the later work was done with continuous pasteurizers. These can be used for handling any required volume of milk, a larger quantity simply necessitating a COMPARISON OF CONTINUOUS AND " HELD " PASTEURIZATION. 19 longei tini(> for ninniu more ])ractical factory metliod, it was determined to lise both methods in c<)m])aris()n on the sam(> nnlk for several (hiys. On eio;lit days, between »Iuly 16 and 24, 190S, half of the milk was pas- teurized at 140° for 20 minut(^s and the otlier half at either 150°, 160°, or 170° in the continuous machhie. The elTectiveness of the two methods of })asteurization was jmln^ed from the mcrease in acidity observed iji the whey within the time from cuttint:; curd to drawing whey specified in each case. Table 4. — Increase of aciditi/ after pasteurization by continuous and by held processes. Pate. Milk held at 140° for 20 minutes. Milk pasteurized at 150°. • Instan- taneous. Milk pasteurized at 160°. Instan- taneous. Milk pasteurized at 170°. Instan- taneous. In- crease. Time. In- crease. Time. create. ^ime. In- crease. Time. H. m. 1908. July 16 17 18 20 21 22 23 24 Per ct. 0.11 .068 .055 .01 .02 .03 .078 .018 n. m. 2 57 2 17 2 17 2 31 2 10 2 21 2 10 2 30 Per ct. H. TO. Per ct. H. m. 0. 055 3 .03 2 59 .03 1 2 46 Per ct. 0.01 .01 .035 .053 3 30 3 30 3 20 3 8 0.01 2 40 1 From the above it can be seen that where milk is lughiy inociPated when raw, as on July 16, 17, 18, and 23, the acidity of the whey rose 0.05, 0.06, 0.07, and 0.11 per cent in about 2\ hours after pasteur- izing at 140° for 20 minutes, while it rose only about half as high in 3 hours after pasteurizing at 160° or 170° in the continuous machine. A further substantial difference between curds from milk pasteur- ized on the one hand at 140° for 20 mhiutes and on the other at 160° in the continuous machine is that the former curds often become mel- low and greased on the surface and leak white whey after milling, in this respect resembling some raw-milk curds. Tt was supposed at first, from analogy to ordinary factory methods, that the curd which became mellow and somewhat greased on the surface and which leaked more or less white whey was more likely to turn out well than the other, which was supposed to be lacking in acid or acid-forming bacteria. The observation was made that a curd from milk pasteur- ized at 170° and afterwards treated with 5 per cent starter did not become mellow in the least, while curds from the same day's milk pasteurized at 140° for 20 minutes and then treated with tliree- 20 CHEDDAR CHEESE FEOM PASTEURIZED MILK. fourths per cent starter, became very mellow and abundantly greased before milling. It was judged unnecessary, thereafter, to wait for mellowness or any other evidence of bacterial action or acid develop- ment in a pasteurized-milk curd. If a sufficient proportion of starter has been added after pasteurization, it is perfectly certain that the bacteria are present in the curd, and will take part in the curing on the shelf. From this point of view the mellowness which the 140° curds occasionally exhibit is to be regarded as objectionable and as evidence of lack of uniformity between different days' make, and smce this never occurs with nidk pasteurized at 160° in the continuous machine the latter appears preferable. The cause for the greater increase of acidity in whey after cutting curd from mOk pasteurized at 140° for 20 minutes, as shown above, is no doubt the fact that the milk thus j^asteurized contained more living, active bacteria than that pasteurized in the continuous machine. Samples were taken for bacteriological count in every case immediately after pasteurizing, and then three-fourths per cent of starter was added to each vat, followed immediately by rennet as soon as the vat could be heated. Bacterial counts were made on these samples by Mr. L. D, Bushnell, bacteriologist, as follows : Table. 5. — Number of bacteria per cubic centimeter in raw and pasteurized milk. Date. Raw milk. Pasteurized milk. At 140° for 20 minutes. In continuous machine. 1908. July 17 18 20 21 22 23 24 Number per c. c. 102,000,000 72, 000, 000 119,000,000 30,000,000 173,000,000 360,000,000 65,000,000 Number per c.c. 2,206,000 2,620,000 262, 000 33,000 320,000 15,320,000 62,000 Number per c. c. 652, 000 1,960,000 200,000 9,200 38,000 1,300,000 1,100,000 "F. 160 160 170 170 170 170 150 SELECTION OF BEST TEMPERATLTKE FOR PASTEURIZATION IN THE CONTINUOUS MACHINE. The temperature selected should be high enough to insure that the ripening of the milk shall be uniformly checked daily, regardless of the bacterial content of the milk used, and it should not be so high as to injure the quality of the cheese. Tests were made as follows: On several days the milk supply after mixing was divided into four lots, one of which was made up by regular methods, the others were pasteurized at 140°, 150°, and 160° and made up in separate vats. The cheese after curing was examined by several BEST TEMPERATURE FOR PASTEURIZATION. 21 expert cheese judges, including Messrs. U. S. Baer, Robert AIcAdam, H. J. Noyes, F. W. Laabs, and Gottlieb Marty, whose scores are given in Table 6 : Table 6. — Quality of cheese made from raw milk and from milk pasteurized at different temperatures in the continuous-disk machine. Date. Pasteurized at — 140° F. 150° F. 160° F. Flavor. Tex- ture. Flavor. Tex- ture. Flavor. Tex- ture. Flavor. Tex- ture. 1908. July 14 15 IG 17 20 21 22 15 16 17 20 21 22 23 24 40.0 40.5 38.0 38.0 40.0 41.0 37.0 28.5 28.5 28.0 28.5 28.5 28.5 28.0 41.5 41.0 40.0 41.0 41.0 41.0 38.0 28.5 29.0 29.0 29.0 28.5 28.5 28.0 43.0 41.0 41.0 42.0 42.0 41.5 39.0 41.0 44.0 42.0 40.0 44.0 41.5 38.0 44.5 43.0 40.5 44.0 41.0 40.0 40.0 44.0 37.0 40.0 35.0 43.0 40.0 43.5 36.0 28.5 29.0 29.0 29.0 29.0 29.0 27.5 27.5 28.0 28.0 27.0 28.0 28.5 23.0 29.5 29.0 28.0 29.0 28.0 28.0 27.0 29.0 29.5 25.0 25.5 27.0 28.0 28.5 26.0 40.0 30.0 36.0 38.0 39.0 35.0 38.0 40.0 40.0 38.0 38.0 30.0 37.0 40.0 35.0 37.0 42. 33. 30. 37.0 39.0 36.0 42.0 37.0 44.0 36.0 43.0 32.0 28.5 27.0 28.0 28.5 29.0 28.0 27.0 26.0 26.0 26.0 24.0 27.0 26.0 26.0 26.5 26.0 27.0 28.0 28.0 25.0 26.0 28.0 28.0 27.0 26.0 27.0 28.0 28.0 In nearly every case the 100° pasteurized-milk cheeses were cleaner in flavor and scored higher than the check, and in every case they scored higher than the cheeses pasteurized at 140° and 150°. The difi'erent judges scored the cheese at difl'erent ages, which will account for the wide variation of some scores. Bacterial counts made by Mr. W. H. Wright* show that pasteurization at 160° is more effective than at lower temperatures. This is well illustrated in Table 7. 'Unpublished work by W. H. Wright, instructor in agricultural bacteriology, Uiiiversity of Wisconsin. oo CHEDDAR CHEESE FROM PASTEURIZED MILK. Table 7 .^Bacterial content of milk pasteurized at different temperatures in the continuous- disk machine. Date. Bacteria per cubic centimeter. Raw milk. Milk pasteurized at— 140° F. 150° F. 160° F. 1909. July 22 23 24 6,080,000 600,000 50,000 60,000 23,000 423, 000, 000 11,600,000 5,800,000 1,540,000 600, 000 139,000 That the use of 160° for pasteurization is high enough to kill most of the bacteria in milk, so as to meet requirements such as tliose of the Cliicago ordinance previously referred to on ])age 12, is shown in Table 8 by the followmg bacterial counts made by Mr. Alfred Larson in 1909: Table 8. 'Bacterial cnnient of milk before and after, pasteurization in the continuous- disk machine at 160° F. Date. Bacteria per cubic centimeter. Decrease. Raw milk. Pasteurized milk. 1909. Per cent. Aug. 1" 161,600,000 223,350 99.8 18 43,300,000 1,275,000 97. 19 57,600,000 211,000 99.6 20 16,560,000 252, 160 98.5 21 20, 938, 000 40,960 99.8 22 15,548,000 420, 250 97.0 24 89,750,000 544,250 99.0 26 44,075,000 86, 120 99.8 27 76,000,000 30, 450 99.9 28 78,825,000 166, 400 99.8 31 148,200,000 77,560 99.9 Sept. 1 25,836,000 9,670 99.9 2 51,650,000 52,125 99.9 14 27,150,000 29, 2.50 99. 9 16 77,6.50,000 341,600 99. 6 17 38,900,000 136,350 99.6 IS 124,700,000 159,880 99.8 19 00,280,000 287, 500 99.5 21 185,000,000 477,600 99.0 22 63,500,000 263, 200 99.7 23 45,525,000 142,300 99.7 28 18,376,000 202,600 98. 8 29 13,660,000 31,000 99.7 30 980,000 14,580 98.5 1910. July a 6,500,000 27, 000 99.6 12 1,600,000 25,000 98.5 13 5,250,000 17,200 99.7 14 4,700,000 36,000 99.3 15 10, 000, 0(X) 28,700 99.7 20 5,350,000 21,000 99.6 Sept. 19 2,525,000 30,000 98.8 OBJECTIONS TO HIGH TEMPERATURES FOR PASTEURIZATION. 23 Similar doterniiiiations were made by Aliss A. C. Evans upon milk ]>asteurized in the continuous "flash" macliine in 1910. They are shown in Table 9: Table 9. — Bacterial content of milk before and after pasteurization in the continuous ' 'flash' ' machine at 160° F. Number of bacteria per cubic centimeter. Date. Killed by pasteuriza- Raw milk. Pa.steurized milk. tion. 1910. Per cent. Aug. 3 7, 950, 000 4,700 99.95 4 4,250,000 15,300 99.65 5 9,750,0atHng cheese dealers indicate that the proportion of consumers preferring the liigh-flavored cheese is very smaD. Most of the cheese sold to-day is only a few wa^eks old, because the dealers geiieraUy avoid long storage, preferring quick sales and immediate profits. This makes it practically impossible for most consumers to develop a taste for any but the new mild cheese sold in most markets. The steady sales of pasteurized-milk cheese during the past two years indicate that the flavor of the 160° pasteurized product is satisfactory for filhng regular orders. Indeed, it is an open question whether most of the "liigh snappy" flavor often observed in old cheese is not due to the long-continued, slow development of those same taints and oflp flavors from unclean milk wliich we recognize as objectionable when they develop rapidly. 24 CHEDDAR CHEESE FROM PASTEURIZED MILK. The use of liigher temperatures than 160° for pasteurization was tried on several da^s, with the result that the flavor production in the cheese was practically prevented and the texture was inferior. The scores given to these cheeses are tabulated below: Table 10. — Quality of cheese from milk pasteurized at different temperatures in the continuous-disk machine. Pasteurized at Pasteurized at Pasteurized at 160° F. 170° F. 180* F. Date made. Flavor. Texture. Flavor. Texture. Flavor. Texture. 1909. Oct. 12 40 29 3S 27 35 15 13 40 29 39 28 35 15 14 40 28i 38 27 35 15 The scoring was done by Mr. F. W. Laabs. The 180° cheeses have no Cheddar flavor, but taste hke first-class cottage cheese. They are so crumbly and short that it is impossible to draw a sohd phig. They keep well, and it is possible that a good trade might be built by the sale of tliis product under some such name as "pressed cottage cheese." In all cases the use of 160° for pasteurizing milk gave better cheese than higher temperatures. Three reasons have been suggested why the milk pasteurized at 180° gives flavorless cheese: First. If bacteria are the essential cause of flavor production, it would appear hkely that the necessary kinds of milk bacteria are destroyed by the high temperature of pasteurization. Second. If milk enzyms such as galactase are the essential cause of flavor production, these enzyms are perhaps destroyed by the use of 180°. Third. It may be that the casein or otlier native milk constituent which in normal cheese undergoes cleavage, forming the flavor-giving substances present in ripened cheese, is changed chemically either in composition or as to constitution by the heating to 180°, so that upon cleavage by bacteria, enzyms, acids, or other agencies it yields differ- ent cleavage products, lacking the flavor, etc., which characterize normal cheese. In attempting to test the first of these possible explanations a variety of substances have been added as starters to milk after pas- teurizing at 180° or other high temperatures in order if possible to supply the bacteria or enzym needed for normal curing and flavor production. Among the special starters so used were pure cultures of various bacteria; raw milk up to 20 per cent of the vat contents; cultures of bacteria isolated from milk and cheese capable of develop- EFFECT OF PASTEURIZATION ON CHEESE CURD. 25 ing 1.6 per cent or more lactic acid in milk (described by Hastings'); cheese of various ages rubbed to creamy consistency with milk and added in different proportions through a hair sieve to the pasteurized milk in the vat; cultures made by adding cheese in this maimer to milk and incubating overnight before adding to the cheese vat. All of tliese materials were added to milk which had been pasteurized at high temperatures u]) to 180°, and cheese was made therefrom; but in no case was it possible to get a normal flavor development in the resulting cheese. The lack of flavor ])roduction under these circumstances, where many kinds of bacteria and starters were added to the ])asteurized milk, seems to indicate that the casein, etc., in milk thus treated is incajjable of cleavage into the flavor-giving substances; in other words, tiiat the casein, etc., is changed chemically by the heat of ])as- teurization. There is additional evidence that such a change occurs. EFFECT OF PASTEURIZATION ON THE PROPERTIES OF CHEESE CURD. A series of cheese curds made from milk pasteurized at 160°, 170°, 180°, or higher temperatures show a regular gradation of certain char- acteristics. The higher the temperature of })asteurization tJie more tenaciously the curd retains moisture and the more difficult it is to ex])el the whey by ordinary means. Tjiis is shown in the foUowing ex])eriment: The milk in the receiving vat each morning was thor- oughly mix(Hl and then divided into three ])ortions which were run through the ])asteurizer at different temperatures and made up into cheese in different vats. Three-fourths per cent of starter was added to each vat and the milk and curds were handled in all respects as nearly alike as possible, the only difference being in the temperature of pasteurization. The curds in separate hoo])s were pressed in the same press, and the next morning moisture tests were made on each. This entire work was repeated on several days. The results are shown in Table 11. Table 11. — Moisture content of green cheese made from milk pasteurized at dij/'erent tem- peratures in the continuous-disk pasteurizer. Date. Milk pasteurized at— 160° F. 170" F. 180° F. 1909. Oct. 12 13 14 Per cent. 38.4 37.0 39.0 Per cent. 42.2 39.9 40.7 Per cent, 46.6 43.5 45.5 ' Hastings, E. G., Hammer, B. W., and Hoffman, C. Studies on the bacterial and leucocyte content of milk. Wisconsin Agricultural Experiment Station, Researcli Bulletin 6. Madison, June, 19U9. 26 CHEDDAR CHEESE FROM PASTEURIZED MILK. Each per cent given is the average of two closely agreeing dupli- cates. It is seen that in every case the higher temperatures of pas- teurization cause higher moisture content in the green cheese. These curds were all cut with a three-eighths-inch knife and heated to 104° in the whey. Even when a 180° curd was cut with one-fourth inch curd knives and a 160° curd with three-eighths inch knives, the moisture content in the former remained higher, as is shown in the following experiment : Table 12. — Moisture content, of curds madefrom milk pasteurized nt different temperatures in the continuous-disk pasteurizer and cut with knives of different sizes. Milk pasteurized at 1G(J° F. Milk pasteurized at 180° F. Time after cutting curd. Cut into f-ineh cubes. Cut into |-inch cubes. Cut into J-ineh cubes. //. TO. 1 Per cent. t)7. b 60.1 47.2 43.3 42.2 41.4 Per cent. 70.0 63.9 52.4 47.2 45.9 45.1 Per cent. 66.5 61.0 50.6 46.0 44.6 43.9 2 Drew whey... 2 30 3 30 Milled curd... 4 .30 Salted curd... 4 50 Hooped curd. Each per cent in the tahle is the average of two closeh' agreeing moisture determinations. It is unquestionably true that pasteurized-milk curds retain mois- ture more tenaciously than raw-milk curds, and this effect is more nnirked the higher the temperature used in the ])asteurization. It therefore follows that the higher the temperature used in the })asteur- izer the greater w411 be the weight of cheese obtained from pasteurized milk. The yield ])er hundred pounds of milk weighed before j)asteur- ization in each vat on three days is given in Table 13. Table 13.- Yield of cheese per hundred pounds of 7nilk pasteurized at different tempera- tures. Date made. Temperature of pasteurization. 160° F. 170° F. 180° F. 1909. Oct. 12 13 14 Pounds'. 12. 28 12. 10 11.93 Pounds. 13. 42 12.97 12.70 Poimd.'i. 15. 42 14.53 14.44 It will be shown later that the yield of cheese obtained by pasteur- izing at 160° is slightly greater than that obtained from raw milk, so that in this res])ect the effect of pasteurization is distinctly noticeable even when the lower temperature is used in the ]nisteurizcr. Again, EFFECT OF PASTEURIZATIOX ON CHEESE CURD. 27 among the peculiarities of pasteurized-milk curds is their decreased ])()wer to coalesce or fuat when on the rack or in the })ress. Tliis effect is not noticeable with milk })asteurized at 160° to 165°, but is perceptible at 170° and is very marked when the milk was pasteurized at 180° or hiuher. The 180° curd cubes when piled on the rack pack together like raisins or figs in a box but do not coalesce or unite, and by rubbing the finger over the mass at any time the pieces can be ])ulled a})art. The same effect is noticed when the curd is pressed in the hoo]). The ])ieces ])ack together tiglitly but do not unite; and at any time (hiring the curing a ])lug drawn with a trier will either come out in fragments or will break into })ieces instantly when han- dled. Iiist(>ad of milling such a curd, it is merely stirred or shaken apart with the hands. These two ])eculiarities of pasteurized-milk curds, which can not be remedied or avoichnl by any otlier means tlian reducing tlie tem- })erature of the ])asteurization,, considered tog(>ther witli the im])os- sibility of d(>v(d()])ing Cheddar fhivor after ])asteurization at high tem])eratures, a])])ear to indicate tliat the ])asteurization ])roduces some de(>])-seate(l cliange in the chejiiical constitutior; of casein. Another ])eculiarity of ])asteurize(l milk, that of coagulating with rennet oidy with great tlifficulty, need only be jnentioned in this connection, l)ecause in the ])roeess of cheese making her(> described the addition of Jiydrochloric acid to the })asteurized juilk entirely restores the coagulability witli rejuiet, ])ro(lucing a curd in many res])ects su])erior to and easier to handle than the curd co3umoidy obtained in the r(>gular way from raw milk. From what has been said it will be seen that the use of 160° to 165° for ])asteurization offers many jiractical advantages. It is sufficiently high to check elfectually the further ri])ening of the milk during the next few hours, while the use of 150° is not high enough for this ])ur- ])ose. Furtherii.ore, 160° gives cheese of cleaner f-Iavor than 140° or 150° (no doubt by more effectual destruction of taint-producing bacteria) or than raw milk, as shown in Ta})le 6. It may be mentioned also that over 99 ])er cent of the total bacterial content of the milk is destroyed by use of 160°, as shown in Tables 8 and 9. The 160° is ])referred to 170° or 180° because tlie cheese obtained by the use of 160° is more nearly like the best American cheese in inoisture content (see Table 11) and in texture and flavor. (See Table 10.) So far as it is possible to say at the present time, the use of 160° is sufficient to kill most probably 99 ])er cent of the gas and taint- forming bacteria in milk. It can not' be claimed that they are all killed, because it is true that when very unclean milk is handled by this process the cheese sometimes shows slight traces of unclean flavors, though not enough to affect the market value. While gas and pin lioles have often been seen during the seasons of 1909, 1910, 28 CHEDDAR CHEESE FROM PASTEURIZED MILK, and 1911 in cheese made by regular methods at this factory, no gas whatever was seen in any curd or cheese mad& during 1909 or 1911, and the gassy cheese obtained, nine days in succession, in 1910 was demonstrated to be due to the use by mistake of a gassy starter which was added to the milk after pasteurization. The fault arose at that time from the inefficient means then at hand for preparing and heat- ing milk for propagation of the starter. An improved steam sterilizer was at once set up for this purpose, which prevented all further diffi- culty of this sort during the past two years. The temperature finally selected as most completely securing the advantages and avoiding the disadvantages of pasteurization for cheese makmg is 160° to 165° F. In practice the pasteurizer is set running at 163° and held there as closely as possible. THE DIFFERENT TYPES OF CONTINUOUS PASTEURIZERS USED. Two different pasteurizers were used in this work %vith entire success, being apparently e(|ually effective in producing the desired results at 160° to 165°. Tliese were a disk machine of 2,000 pounds per hour capacity and a "flash" machine of 1,200 ])ounds capacity per hour. (See Pis. II and III.) The choice between these two types of pasteurizing machines for use in this process a])pears to depend upon their relative cost and ease of operation and cleaning, rather than upon any difference in effectiveness. They were used alternately on successive days for several weeks, and on three days, September 1 , 12, and 19, 1910, the milk was divided, one-half being run through each. The cheese was first class in each case and showed no differ- ences that could be traced to the use of different machines. THE ACIDULATION PROCESS. THE STANDARD ACIDITY OF MILK FOR CHEESE MAKING. Milk as it flows from the pasteurizer varies daily in acidity and is lacking in bacteria of the lactic-acid type, needed to aid in cheese curing. By the atldition of sufficient hydrochloric acid to raise the acidity of the milk to 0.25 per cent (as lactic acid) after pasteurizing, and of three-fourths })er cent of a first-class starter, the pasteurized milk is brought daily into standard condition both as to acidity and bacterial content for cheese-making purposes. The reasons for adding acid and starter as specified will now be given in detail. The standard acidity is 0.25 per cent, and the acidity of pasteur- ized milk is raised to this figure rather than to 0.20 or 0.30 per cent for the following reasons: First. In regular cheese making the acidity of whey when drawn is, on the average, about 0.17 per cent, corresponding to an acidity STANDARD ACIDITY OF MILK. 29 of milk of about 0.25 per cent. Anyone can test the correctness of tliis statement by transferring a pint of milk from a cheese vat, just before adding rennet, to a small tin pail, keeping the milk sample at the same temj^erature as the vat and titrating the milk in the pail as well as wliey from the vat at intervals. When the whey reaches 0.17 per cent the milk reaches nearly 0.25 per cent. The control of acidity at the instant the whey is drawn is connnonly regarded as most important in regular cheese making. "With milk pasteurized at 160° there is little or no increase of acidity (usually a])out 0.01 per cent) in whey, before the whey is drawn. The acidity of milk is adjusted to 0.25 per cent in this process after pasteurizing in order to })arallel ordinary working conditions at the time of drawniig the whey. Second. IMixed milk in the factor}^ cheese vat is commonly at 0.16 to 0.18 per cent acidity when received, although often at 0.19 to 0.21 per cent. It should never be over 0.23 per cent acidity. It is found that an addition of hydrochloric acid equal to at least 0.02 per cent of lactic acid is required to restore the coagulabihty with rennet to such milk after ])asteurization, but the daily addition of only 0.02 per cent of acid would leave the jnilk of varying acidity, which is objectionable. If 0.20 per cent were adopted as the standard acidity, after adding 0.02 per cent in the form of hydrocldoric acid, this rule would exclude from use all milk having a higher acidity than 0.18 per cent when received, whicli it is not desirable to do. Only rarely is a vat full of milk at 0.23 per cent acidity received at any factory, but even such milk can be handled in the routine manner at the stand- ard acidity of 0.25 ])er cent by adding the required 0.02 per cent of hydrochloric acid after pasteurization. It might be stated as a matter of record, not as a precedent for factory practice, that vats of milk of 0.24 to 0.28 per cent acidity when received have been successfully made up into good cheese with- out varying the process in any particular, excepting that only enough acid is added after pasteurization to raise the acidity 0.01 per cent, which is sufficient to restore the rennet coagulation to such ripe jnilk. The only apparent limit of acidity for milk to be handled by this process is that the milk should not, of course, be sour enough to curdle in the pasteurizer, and this limit is reached at or about 0.30 per cent. However, it should be recognized by everyone that milk that has reached 0.30 per cent or even 0.25 per cent acidity before it gets to the cheese factory must have received very poor care and attention on the farm and must be entirely unfit for cheese making from a sani- tary point of view. 30 CHEDDAR CHEESE FEOM PASTEUEIZED MILK. COMPARISON OF DIFFERENT KINDS OF ACIDS FOR USE IN CHEESE MAKING. Of the more common acids — sulphuric, hydrochloric, and phos- phoric — the first is the least convenient to handle, especially in a cheese factory, because of the great amount of heat liberated when it is diluted, and the impossibility of diluting it in the carboy in which it is received. Hydrochloric acid is much better in this respect as it can be readily diluted with an equal volume of water by pouring the water into the acid with no danger and very little heat evolution. Thus diluted it fumes very little, if at all, and can be readily and accu- rately standardized by titration with normal caustic soda and phenol- phthalein indicator. Phosphoric acid can be purchased in carboys of about 50 per cent strength, requires no dilution in the carboy, and liberates little or no heat when diluted. The choice between hydrochloric acid and acid marie from phos- phorus is greatly in favor of the former because of the high cost of the latter. Recently, however, phosphoric acid made from bone ash or bone black has been put on the market in this country, containing about 45 per cent free phosphoric acid and less t^han 1 per cent each of hydrochloric acid, sulphuric acid, and phosphates of iron and alumina, this product being offered at 6 cents a pound in paraffined barrels. The price of this acid is very nearly the same as that of chem- ically pure hydrocliloric acid for equal neutrahzing power. Chemically pure hydrochloric acid is and has been for years a stand- ard article of manufacture, whose purity is tested daily by use in hundreds of laboratories. On the other hand, the manufacture of phosphoric acid from bone ash in a form free from objectionable impurities has been accomplished only very recently. A number of cheeses were made with phosphoric acid, but these showed no advantage over those made with hydrochloric acid ; indeed they seemed to have a slight peculiarity of flavor, as a rule, after curing. Most of the cheeses made from pasteurized milk have so far been made with hydrochloric acid, and the use of this acid is described and recom- mended in the present bulletin. The selection of hj^drochloric acid was made because it is cheap and more easily obtained than any other chemically pure acid, and being a natural constituent of gastric juice in the human stomach, no objection could be raised on sanitary or other grounds against its use in this process. THE PROPORTION OF HYDROCHLORIC ACID REQUIRED DAILY. It is necessary to determine first what the acidity of each vat of the mixed milk is, in order after pasteurizing to add the requisite quantity of hydrochloric acid to bring the acidity up to 0.25 per cent. Where only one vat of milk is to be pasteurized and only one workman TESTING MILK FOR ACIDITY. 31 is employed it is probably better to weif!:h in all the milk then stir the vat well and take out a half cupful of milk for the acid test. Where two men are employed and it is desired to start the pasteurizer running as early as possible (before the receiving vat is full), the intake man should take from each weig^h can of milk a sampling tube full, mixinf; these samples in a pint jar. The acidity of this mixed sample will then be the same as the average acidity of all the milk run into the vat. As soon as one vat full of milk (say 5,000 pounds) has been run from the weigh can into the receiving vat, tlie pint jar containing the sample for the aciti test is handed from the intake to the man running the pasteurizer, together with the total weight of milk run into that vat. The pasteurizer was started when periiaps only half of tliis milk had been received, but the receiving vat is still about half full, and after making the acid test on the sample the operator can tell exactly how much more hydrochloric acid must be afhled, while pasteurizing the remaining milk in order to bring the acidity of the whole vat up to the right point, or 0.25 per cent. TESTING MILK FOR ACIDITY. In determining the acidity of milk, measure a 17.6 cubic centimeter pipette full of milk sample into a white cliina cup, whicii should be shallow and wide rather than narrow and deep. Add two drops of phenolphthalein inchcator and while shaking or stirring the milk in the cup run in tenth-normal alkali (Manns's solution) from a burette, rapidly at first, and later by single drops, until the faint pink color pro- duced by the last drop does not disappear on thorough mixing. The volume of tenth-normal alkali used is read from the burette, and this volume divided by 20, which can be done mentally, gives the exact acidity of the milk in per cent of lactic acid by weight. For example, if the volume of alkali solution used was 3.2 cubic centimeters the acidity is 3.2 divided by 20, which equals 0.16 per cent. Subtracting the acidity of the raw milk from 0.25 per cent shows how nmch the acidity of the milk is to be raised with hydrochloric acid after ]ias- teurizing. For example subtracting 0.16 per cent from 0.25 per cent leaves 0.09 per cent, which shows that the acidity is to be increased 0.09 per cent with hydrochloric acid. The outfit needed for testing milk is shown in Plate I. It consists of: 1. A burette with rubber tip and pinchcock; capacity 25 c. c, with Yo c. c. graduations. 2. A 17.6 c. c. pij)ette as used for the Babcock test. 3. A white chhia teacup, which is best if shallow and wade and with flat bottom. 4. A support for the burette, which may be an iron stand and clamp, or a wooden strip with a hole in it, fastened to a window casing, as shown at the left in Plate I. 32 CHEDDAR CHEESE FROM PASTEURIZED MILK. 5. A nibber-stoppered bottle of Manns's solution (tenth-normal alkali) which may be purchased at $1 per gallon of dealers in dairy supplies, or may be made by diluting the normal alkali solution, which must be purchased as it is required in this process a,s described on page 36. 6. A 2-ounce or 4-ounce bottle of phenolphthalein indicator solu- tion. 7. The additional outfit required for use in this process of cheese- making is also shown in the figure. It consists of 1 gallon of normal alkali (ten times as strong as Manns's neutralizer), a 50 cubic centir meter measuring flask, a 500 cubic centimeter measurmg cylinder, and a 2 cubic centimeter pipette, which should be accurately made. A gallon of normal caustic alkali contains about 5 ounces of caustic soda, worth about 15 cents, and should cost the cheese maker no more than a gallon of tenth-normal solution — that is, about SI. PRESERVING THE TENTH-NORMAL SOLUTION. Instead of using the large bottle of tenth-normal solution to fill the burette wdth, it is much better to get a smaller bottle, holding 6 or 8 ounces, also provided with a rubber stopper, and to fill this smaller bottle occasionally from the larger bottle, which is then put away, tightly stoppered, in a safe place. The small bottle is kept near the burette and used (lady in filling it, and the large bottle is thus protected from unnecessary exposure, loss of strength, and from danger of spiUing. The use of two bottles in this manner has proven most satisfactory in this laboratory and dairy school during the past four years. It is recommended ^ as a means of avoiding loss of strength through exposure to the air, which has heretofore been the greatest difficulty to overcome in the use of Manns's test in the cheese factory. DILUTING NORMAL ALKALI TO TENTH-NORMAL. One may prepare tenth-normal alkali by diluting the normal alkali as follows: Pour into a 500 cubic centimeter graduated cylinder exactly 50 cubic centimeters of the normal solution measured in the 50 cubic centimeter flask. Add at once 450 cubic centimeters of pure water, either rain water or condensed steam. Pour the mixture into a clean glass bottle, mix by shaking, and keep stoppered with a rubber stopper to avoid loss of strength by exposure to air. If the mixture is muddy or turbid, the water used in diluting was not pure. A slight turbidity may be neglected. 1 Sammis, J. L. The preservation of Mann's alkaline solution in cheese factories. Hoard's Dairyman, vol. 40, No. 41, p. 1200. Fort Atkinson, Wis., Nov. 12, 1909. 165, Bureau of Ammal Industry, U. S. Dept. of Agriculture. Plate I. 05 ])osite (),000, which is 53.3; a(hl to this the figure op])osite 700, which is (i.2; then a(hl tlu^ figure o])posite 50, which is 0.44; the total gives the number of pounds of acid recpiired, namely, 59.9 pounds. PREPARATION OP NORMAL HYDROCHLORIC ACID IN THE CHEESE FACTORY. Chemically ])ure hych'ocliloric-acid sohitiou, as ])urclias(Ml iii car])oys containing a])()ut 120 ])()uiids ea<^ii, contains about 40 ])vr cent l)y weight of hydrochloric acid and (iO per cent of water, and costs about 7 cents a ])oun(L Its stnnigth varies somewhat, and it must be diluted with water before it can be achled to milk in this ])ro('ess. The preparation of normal-strength acid used in cheesemaking is carried on at the cheese factory in tv/o ste})s, as follov,'s: First step. — Remove the wooden cap from the top of a fresh carboy of acid and loosen the glass ])lug in the neck by tap])ing it on diirerent sides very gently with a })iece of wood (not metal) until it can be drawn out readily with the hand. Set an empty carboy alongside the newly opened carboy. Fill both limbs of a glass siphon with water, removing all air bubbles, and insert the two limbs into the carboys at once, as shown in Plate IV. When the siphon is in place, as shown in the lower figure, the acid will flow from the full carboy into the other until in about half an hour each is practically half fuU. Now fill up 36 CHEDDAR CHEESE FEOM PASTEURIZED MILK. each carboy nearly to the neck with water, leaving space enough beneath the neck to permit mixing the contents readily by shakmg. Tip each carboy up on one edge and rock vigorously for about five minutes with the stopper out to induce thorough mixing. The liquid gets slightly warmer on mixing, and it is stoppered and left to stand overnight to cool and is then called "dilute" acid. To determine how much further each carboy of dilute acid requires to be diluted with water to make it exactly "normal" in strength, set up the burette used in ]\Ianns's test, but fill it with normal alkali solu- tion, which is 10 times as strong as that used in testing milk. Using a 2 cubic centimeter pipette, transfer exactly 2 cubic centimeters of the dilute acid from the carboy to the porcelain cup containing a little pure water, letting the pipette drain into the cup half a minute by the watch and blowing out the last drop of acid from the tip into the cup. Now add one or two drops of indicator and after reading the level of alkali in the burette, draw out the alkali from the burette, precisely as in testing milk, rai)idly at first, later by single drops while shaking the cup in a circle until the last (h'op added produces a distinctly pink color which remains throughout the entire liquid after thorough mix- ing. Read and record the volume of alkali solution used. Rinse out the cup, fill up the burette, shake up the acid in the carboy for a minute and test another 2 cubic centimeters of the acid for the sake of accuracy. If the contents of the carboy were thorouglily mixed at first, the two titrations will agree closely, not diil'ering by more than 0.20 cubic centimeter. If they do not agree, the carboy contents were probably not weU mixed at first, and should be given another very thorough shaking for five minutes, after which the titrations are repeated. Once thoroughly mixed the acid and water remain mixed, and never need to be shaken again. Suppose that in the two tests the 2 cubic centimeters of acid rec|uired 11 and 11.2 cubic centimeters of normal alkali to produce the pmk color, the average being 11.1 cubic centimeters. Divide the volume of alkali by 2 — the volume of acid used — which gives in this case ^' =- 5.55. This means that the acid is 5.55 times as stron" acid is drawn from the carboy into a gallon glass bottle through a glass sij)hon, which is fh'st filled with water. The water used in tlu^ siphon is so small in volume^ — about 1 per c(>nt of a gallon — that it does not noticeably affect the strength of the acid. There is nothing dilKcult about the preparation of normal-strength hydrochloric acid for use in cheese making, and anyone who knows how to titrate milk for acidity can learn to do this also. To test the cor- rectness of the work when completed, transf(>r two cubic centimeters of the acitl with a pipette from the acidulator to the porcelam cuj), and titrate it with, the normal alkali ui the burette. The volume of alkali required should be between 1.9 cubic centimeters and 2.1 cubic centimeters, or, better, exactly equal to the volume of acid used. The degree of accuracy required in this whole process is very easily attained, as quite satisfactoiy results will be obtained in acidulating milk if the normal acid used is anywhere between 0.95 and 1.05 normal. GENERAL DIRECTIONS FOR PASTEURIZING AND ACIDULATING MILK. The method described is well adajited for use in a large factory. At a factory handling two to three large vats of milk daily two men should be employed. The inspection and weighing of milk at the intake is performed by one man while the other makes the determi- tions of acidity and runs the })asteurizer. After the milk is all in and })asteurized the two men work together, heating ui) the vats, 38 CHEDDAR CHEESE FROM PASTEURIZED MlLK. adding the starter, color, and rennet to the vats at least 10 or 15 min- utes apart. They cut the curds in the same order, each 25 minutes after the rennet has been added, and start the agitators in each curd as soon as cut. The vats are heated up and the whey is drawn from the vats in the same order, both men working- together in putting the curds on the rack, fhiishing each vat of curd m time to handle the next. If more than three vats are handled in one factory, additional help will be needed, especially for bandaging hoops, turning cheese, and other labor. \\^iere only one vat of milk is handled daily, the milk is run first into the receiving vat, from which it flows into the pasteurizer, through the coolei', and into the cheese vat. If two vats of milk are handled daily, the first milk received may be run mto one cheese vat, from which it is pasteurized into the other cheese vat, while the milk received later is run into the steel receiving vat, from which it is pasteurized into the second cheese vat. If throe or more vats of milk are handled daily, the receiving vat and the first cheese vat are filled alternately with milk from the in- take, and alternately emptied through the jxisteurizer into the other cheese vats. It is only necessary to see to it that the last vat filled from the intake shall be the receiving vat in order that this last milk may be run into one of the cheese vats after pasteurization. One re- ceiving vat is needed in addition to the necessary cheese vats wherever this ])rocess is used. MAKING READY TO PASTEURIZE. Since pasteurization is essentially a cleaning process, care should be taken to keep the make room, the vats, machinery, etc., and every- thing with which the pasteurized milk comes in contact as clean as possible. Although milk flows intermittently from the weigh cans, it is de- sirable that the pasteurizer, once started, shall run continuously, with a steady milk sui)])ly, and for this purpose a receiving vat is pro- vided. The milk should be run into the receiving vat through a strainer which will remove all flies, straw, etc., and which can not by accident fail to work ])ropcrly. Such a strainer is shown m Plate V. It is set up by slipping a piece of seamless cheese bandage over the wooden frame of the vat strainer and placing the metal part on top. The metal part collects all large pieces of dirt and prevents the milk from splashing over the side. The two thicknesses of cheese- cloth effectually remove finer particles of dkt. This arrangement has been used in this series of experiments for about two years and is heartily recommended. Of course the cloth should be scalded daily. OPERATION OF THE PASTEURIZER. 39 The weigh can, conductors, receivmg vat, and pasteurizer should be washed daily, immediately after use, and again linsed with clear hot water before use, if necessary. The pasteurizer and cooler and the connecting pipes should be washed thoroughly daily. Just before starting the pasteurizer each morning the operator should rinse out the cheese vat and steam it by running steam into the jacket. The ])asteurizer and delivery pipes, especially those parts which are hi contact with the cooled pasteurized milk, should be also scalded or steamed. This can be done by running a couple of pails of hot water into the heathig compartment, heating it there to 180° or higher, and running it over the cooler without having any cold water inside the cooler. Where only one vat of milk is being pasteurized, the acidulator may be set on the edge of the vat, but to avoid moving it, when several vats of milk are handled daily, the acidulator should be set near th(> pasteurizer and the acidulated milk run into the different vats through a moval)le conckictor, as shown in Plate III. STARTING AND STOPPING THE PASTEURIZER. Wlien milk enough has been received to insure a continuous supj)ly for the pasteurizer, the latter may be started. First, see that everything is in place and that the pump supplying water for cooUng is running. Set the pasteurizer in motion, turn on a little steam, and run enough milk into the heating compartment nearly to fill it so as to register its temperature on the naked glass bulb of the thermometer placed near the exit to the cooler. Do not allow any milk at all to run into the cooler. If any does by accident, draw it out and scald the cooler with a pail of hot water. Open the steam valve to the full running capacity. Wlien the thermometer in the milk registers about 155° start the milk supply again and adjust so that the thermometer stands at 162° at the exit from the heater. ITse care to see that no milk at all is allowed to nin to the cooler at a temperature below 160°. If any irregularity occurs in starting, it is much better that the first milk should be heated higher than 160°, even up to 180°, rather than that any portion should pass over into the cheese vat without reaching 1 60°. It will do no harm at all if for a few minutes at first milk at 170° or 180° passes over into the cooler, because this milk will at least be thoroughly pasteurized, but if milk at 140°, or any temperature below 160°, passes over it may carry over harmful bacteria which ma}' injure the entire vat of cheese. A file mark on the steam-valve handle is a great help in quickly adjust- ing the steam supply to the right point. Once adjusted, and with steady milk and steam supply, the pasteur- izing temperature remains nearly constant and i-equires only momen- 40 CHEDDAR CHEESE FROM PASTEURIZED MILK. tary iiispecli(>n every few minutes. No doubt an automatic tempera- lure-controlling device could be used to advantage here. Although the thermometer now supplied with some forms of pasteurizers is metal jacketed to prevent breakage, yet in all the experiments here reported this metal-cased thermometer was found to register more slowly than a naked glass-bulbed thermometer, set in a rubber stopper. The latter kind has been in use two years without breaking and is therefore preferred. In stopping the pasteurizer for any reason, the operator should remember to stop the acidulator first, then the milk supply, and last of all the steam. If the stoppage is for long, as at the end of tlie day's run, the hot milk in the heating compartment is drawn out in a pail (its temperature should be 160° or above) and added to the vat. The milk in the cooler is also drained and rinsed, if desired, into the vat. The water supply for cooling must be ample so that a thermometer placed in the millc flowing from the cooler is not above 85° at any time, and preferably at 80° or lower, since the milk in the vat can easily be heated to 85°-86° for setting with rennet, but can not so well be set, or easily cooled, if above 86°. STARTING AND STOPPING THE ACIDULATOR. As soon as the pasteurizer has been started and regulated the pinchcock at the acidulator is opened, allowing one or more small streams of hydrochloric acid to run into the millc. The height of the liquid in the acidulator should be marked on the glass scale with a pencil or string, when starting, and another mark placed lower down on the scale to show how much acid is to be drawn out for that vat of milk. B}'' this means the operator can see from any part of the room when the acidulator is ready to be stopped. Always stop the acidulator before stopping the milk. THE USE OF BACTERIAL STARTER IN THE NEW PROCESS. THE REASON FOR ADDING STARTER IN MAKING PASTEURIZED-MILK CHEESE. The addition of the required amount of hydrochloric acid to milk raises its acidity at once to 0.25 per cent, but does not cause any fur- ther increase of acidity at any time. Of the acid thus added, only about one-fortieth remains in the curd, the rest escaping in the whey. No chemical method has been found for increasing the acidity of a curd on the rack, so that if acid plays any important part in the cheese- curing process, it will be necessary to add bacteria to the milk in order to develop the necessary acid in the curd and cheese. A number of THE USE OF BACTERIAL STARTER. 41 expcrimonls were performed in wliich the milk supply was divided and made up in diirerent vats, using diiYerent proportions of starter. The cheese was finally scored by Mr. J. W. Moore with the following results: Table 16. -Qiinlifij of cheese made from pasteurized milk with varying amounts of starter added. Date. made. Cheese No.i Propor- tion of starter. Tempera- ture of jjasteuri- zatiou. Score. Flavor. Texture. 10(W. Auu. 17 IS 19 20 21 22 .31 .>:-o:it 1 1070c 1079 lOSl 10S3 10S,5c 1087 1SS9 1091 1093c 1095 1097 1099 1101c 1 103 1105 JlO.lc im 1113 1115 1117c 1119 1121 1123 11.57c 1159 llfil 1103 1 10.5c 1 107 11(19 1170 1173c 1175 1177 1179 1024 l(>2i) Per edit. T. 40. .50 40. 50 41.25 42.50 41.00 41.75 41.00 4t).25 40.. 50 41.25 42.50 42. 75 41.25 42. .50 42. 25 40.75 42. 25 42. .50 42. .50 39. .")l) 42. 25 41.75 42.25 41.00 41.00 42. .50 42. ,50 39. 00 40. ,50 42.00 42. .50 40. 00 41.00 41.00 41.. 50 Sour. Sour. 27.00 27^25 2.S. 00 27.25 27.75 27.25 27.00 27. (XI 27. (H) 27.75 2S. m 27.00 2s. 25 h.m 27.25 27! 25 27.00 27! 00 27. (K) 27.00 2S. 00 28.00 2S. .50 20. 00 27.. 50 2,S. (M) 27. (Kl 2fi.(K) 27.00 27.00 Color-cut. Color-cut. 0. 25 . ,50 .75 157 157 157 .25 ..50 .75 157 157 157 !.50 .75 157 1.57 157 .75 1.57 1.57 . 75 1.00 1.25 1.57 1.57 1.57 .75 1.00 1.25 1.57 1.57 1.57 Noii(>. .3 .0 102 102 162 None. .3 .0 11)2 lt>2 102 Noiii'. .3 .0 3.0 5. 102 ]il2 102 1 "e" in thi^ column imlicates raw-milk cheese. These scores may he summarized as follows: Tahle 17. — Summary of scores in Tabic 16. Average scores. Numlier of cheese-; 1 scored. Flavor. Te.xture. Comtiined, Per cent. 3 40. S3 20.33 (i7. 16 0. 25 to 0. 30 7 41.04 27.53 (9,18 .5 to .0 41. SS 27.54 (;9, 42 42. 04 27. .50 09.. 54 1.(1 ■) 42. 12 27. 25 09.37 1.25 - 42, .37 27.37 (■i9. 75 42 CHEDDAR CHEESE FEOM PASTEURIZED MILK. These scores indicated that the cheese obtained by three-fourths, one, or one and a quarter per cent starter are about equally good, considering both flavor and texture, and the use of three-fourths per cent starter has been continued since August, 1908, to the present time, with good results. The starter used should be first class in quaUty, just beginning to thicken, containing the maximum number of lactic acid bacteria in active condition, and free from all objection- able germs or flavors. Only a starter above criticism, such as every good cheese maker should know how to prepare, can be used with pasteurized milk. If the starter is at all tainted it is sure to damage the flavor of the cheese to some extent. With raw, badly tainted milk, especiaQy in warm weather, a starter of only fair quahty will often greatly improve the quaUty of a vat of cheese, but pasteurized milk is freed from practi- cally all taints by the pasteurization, and to such milk only the best starter can safely be added. The importance of a good starter was made apparent when, begin- ning June 9, 1910, nine days' make of pasteurized-milk cheese proved to be gassy and oft" flavor, and bacteriological examination of the starter as well as of the cheese demonstrated the presence of the same gas-forming organism in both. It was clear that the organisms in question did not pass through the pasteurizer, since their thermal death-point was found to be lower than the pasteurization tempera- ture (160°) employed in the j^rocess. Therefore there could be no doubt that the improper preparation of milk for propagating "startoline" was the cause of the trouble in this case. A PRACTICAL STERILIZER FOR THE CHEESE FACTORY. The essential equipment for propagating a starter is some sort of a sterihzer, an incubator, and a sup])ly of a dozen pint cream bottles which are best provided with fairly tight tin covers about 2 inches deep. Various diflerent sterihzcrs have been recommended, the sim- plest being an inverted tin pail covering the bottles of milk on the steam table. For use as an incubator, a small covered shotgun can may be steamed out daily, and after placing the bottles therein and adjusting the cover it may be carried to the ice box, the cellar, a hay cooker, or any room of suitable temperature. Wliere bottles of starter must be handled and carried about there is always some danger of their becoming infected, and this can only be prevented by intelligent work on the part of the operator. On account of its small size a culture propagated in a bottle is often called a "startoline," meaning a Httle starter. A combined sterilizer, cooler, and incubator made of galvanized iron has been devised, and used in our work during the past year with entire satisfaction. Its use saves time in PKEPARATtON OF THE STARTER, 43 htindling and reduces the danger of contamination to a mininnini. It is shown in figure 1 . The apparatus consists of a galvaiiized-iron container with cover, a movable false bottom, and with steam, water, and drain connections. Where i)int bottles are used, the ])erforated shelf is raised and set on lugs as shown. If quart bottles are used, the perforated l)ottom is lowered, so that- the to]) of the l)()ttle always stands at the top of the sterilizer. vjai- fon CAP FOR -^MnrruFS^' -'■'' niLK BOTTLE WATER BOTTLE J INUI v.nL^ 4 x a Fig. 1. — Combined stcrilizor, cooler, and inciilnitor for eliepse-factory starter. PREPARATION OF THE STARTER. The bottles having been cleaned and fiUed nearly full with the l)est whole milk obtainable are each covered with a tin ca}) and set in the sterihzer, together with one bottle of water carrying the ther- mometer. The Hd is })ut on and the steam turned on very slowly at first, by turning handle a. After the thermometer ])rojec-.ting through the small hole in the hd shows that the contents of the bottles are heated to 200° or above, the steam is left running for three quarters of an hour, and then turned off. To cool the bottles of steriUzed mdk o])en valve h and slowly run in cold w^ater, wliich escapes at the overflow c. If the water is turned on l)y mistake faster than the 44 CHEDDAR CHEESE FROM PASTEURIZED MILK. overflow can carry it off, the tin caps will keep it from entering the bottles of milk. When the thermometer sliows that the bottle con- tents are cooled to about 70° the water may be turned nearly or entirely off. The bottle of "startoline" from the previous day, which has not yet been opened, is now brought in and a portion, about a tablespoonful by guess, is poured into each bottle of newly sterilized milk in the apparatus, lifting the tin caps for an instant for tliis purpose. The room should be free from drafts, floating dust, or other source of contamination, and the transfer should be made as quickly and carefully as possible. The cap is then replaced and the cover put on. The temperature of the water can be kept between 60° and 70° for a few hours, and in the evening, in summer, if the weather is very warm, a piece of ice can be added to -the water. This daily process of propagating the "startoline" was performed in the cheese factory during the year 1911 by Mr. A. T. Bruhn, with entire success, carrying along the same culture of bacteria throughout the year. Each day after inocidating the fresh bottles of milk, the remainder is examined by pouring out a httle in a teaspoon or cup, to be tasted and smelled to see that it is in good condition;' and if so, the remainder in the jar is used in making up starter for the next day's cheese A'at in the following manner: To prepare starter from this "startoline," jdace in a shotgun can about eight or nine pounds of milk for each thousand received daily, cover up, and heat in a tub or deep pail of water by passing steam until the water is boiling and a thermometer in the milk reads at least 180°. Keep it at this temperature for three-quarters of an hour and then cool by filling the tub with cold water, A dash stirrer whose handle is slipped through the smallest possible hole cut in the cover is a convenience and saves opening the can for stirring. Wlien thor- oughly cool — about 70^ — add to the contents of the can the remain- ing contents of the "startoline" jar, as stated above. Stir this weU and leave for five or six hours at this tem})erature, after which it may be put in a cooler place to stand overnight. The general principle on which the temperature of starters, etc., is regulated is that the starter should ripen only fast enough so as to be barely tliick, or- just getting tliick, when required for use next day. If the acidity increases too rapidly at first, the bacteria are kept too long before use in a liighly acid medium, not favorable to their growth, and in general this is to be avoided. The tliickening of the milk at about 60° or 70° may be taken as an incUcation that the acidity is in the neighborhood of six-tenths per cent, wiiich is about as liigh as it ought to go for this purpose. To control the temperature for ripening is not so likely to be troublesome as to avoid getting dirt and foreign bacteria into the "startoline" or starter after it has been once thoroughly sterihzed. 1 To test further the quality of the starter, a bottle of the thickened milk, unshaken and unopened, may be set away in a warm place for a day or two, to see if gas bubbles or unpleasant flavors develop. TIME SCHEDULE FOR MAKING CHEESE. 45 Strictly spealdng it is impossible to sterilize milk so perfectly as to kill all s{)ores hy one such heating, and on this account attention should be given to selecting the best ])ossible milk for starter maldng. At the beginning of the season a small bottle of bacterial starter can be obtained from dealers or from a college of agriculture. It is well to begin propagating the starter several days before cheese making is to begin, and also to carry along two or more starters from different sources, separately, in order that if one is lost or found unsuitable another may be at liand. METHOD OF MAKING CHEESE BY THE NEW PROCESS. GEXERAL ARRANGEMENT OF SCHEDULE. In making cheese by the new method the cheese maker is reheved of a great deal of the uncertainty wliich attends cheese making by the ordinary methods. Having inspected the milk at the intake and rejected any tliat is curdled or otherwise unfit for use, he determines by means of Manns's acid test the acidity of the entire vatful of mixed milk. This may be anywhere from 0.14 to 0.25 per cent, or even a little liigher, but if much above 0.28 per cent the milk is hkely to curdle and clog tlie pasteurizer. He then runs the milk through tlie pasteurizer and adds to the cold milk as it flows into the cheese vat enough dilute hydrochloric acid to raise the acichty of the whole vat to just 0.25 per cent (calculated as lactic acid). Three-quarters per cent of a first-class starter is added, and after heating to 85° the color and rennet are stirred in immediately. The rest of the ])rocess is conducted according to a fixed time schedule, which is never varied. The time from adding rennet to hooping the curd is always exactly five liours and fifteen minutes, and the intermediate process is as shown in Table IS. This is carried on every day in the season without exception. Wliile it may be found desirable or convenient at some factories to modify somewhat tliis routine, described below, j^^et it appears practically certain that whatever routine of operations is adopted at any factory, it can be followed without mocUfication throughout the season. Table 18. — Time schedule for making cheese by the new method. Operation. Adding rennet Cutting the curd Beginning to heat Turning off steam Placing rack after drawing whey Milling the curd Salting the curd Hooping the curd 46 CHEDDAR CHEESE FROM PASTEURIZED MILK. For example, if the rennet were added to the milk at exactly 9 o'clock the curd would be ready to put in the hoops five hours and fif- teen minutes later, i. e., at 2.15 in the afternoon. As soon as the reimet is added it is best to have a written schedule showing the time when each operation should be performed. Having once learned how to perform each operation in tliis method of cheese making it is only necessary to do everytliing in as uniform manner as possible in order to get satisfactory results daily throughout the season. There is never any need to hurry the process if the milk was overripe at the beginning, because the lactic-acid bacteria are practically all killed by the pasteurization. The same is also true of the gas-forming bacteria, so there is no time lost in worldng gas out of the curd. There is no reason for waiting to ripen the milk at the beguming of the process before adding rennet. UNIFORM PROPORTION OF COLOR USED IN 1911, AND RENNET REQUIRED. Color. — Tliroughout the season of 1911 two-thirds of an ounce of a standard make of cheese color per thousand pouncls of milk was used, giving the clieese a mecUum shade of color. These cheeses were sliipped into a number of different cities and appeared satisfactory to dealers in all parts of the country, except in Philadelphia, Pa., and Boston, Mass., where some dealers asked for white and others for liighly colored cheese, as is shown by the following extracts from letters. Where more tlian one extract appears from the same city they are from chfferent dealers. Boston, Mass Our market uses white cheese exrhisively. Boston, Mass Use both white and colored. Boston, Mass A very light color would not du for this market. Chicago, 111 No comment on color. Fond du Lac, Wis A little too light color. Geneva, N. Y No comment on color. Marshfield, AVis No comment on color. Minneapolis, Minn No comment on color. New York, N. Y Color is exactly right. New York, N. Y Should be a trifle higher color. Philadelphia, Pa Have to have white cheese for Philadelphia. Plymouth, Wis No comment on color. Sheboygan, A\'is A good commercial color, but might stand a trifle more color. Sheboygan, Wis No comment on color. St. Louis, Mo No comment on color. Washington, D. C Most of our customers want it colored. Waterloo, Wis No comment on color. Rennet. — The same proportion of rennet is always used in this process, because the milk is alwa3^s in the same condition as to acidity at the time of adding rennet, and always ripens equally fast afterwards. Therefore, ha^^ng once selected the most suitable proportion of remiet, there is no reason for changing it. The use of 2 ounces of ADDING STARTEK, COLOR, AND RENNET. 47 Hanson's or Marschall's rennet per thousand pounds of milk is adopted as the best practice, since this quantity produces visible coagulation in 7 minutes, as shown in Table 2, and the curd is in prime condition for cutting in 25 minutes after adchng rennet. If the rennet extract is weaker than it sliould be, such amounts should be used as will cause coagulation in the time stated. If a larger proportion of rennet than 2 ounces per thousand pounds were used, there would hardly be tijne for tlie milk to become quiet before visible thickening began, and the curd might be damaged and broken through thickening while still in motion. On the other hand, over two years' experience with the method has sliown that there is no need for using a smaller proportion of rennet than 2 ounces. Good cheese can be made with 1 ounce of rennet per thousand pounds of niilk, but the coagulation of the niilk is unnec- essarily slow. As in regular cheese making, great care must be taken not to measure or dilute renn(^t extract in an}- container in whicli there is present the least trace of cheese color, because the cheese color is strongly alkaline, and rennet loses its coagulating power almost instantly when in contact with alkalies. ADDING STARTER, COLOR, AND RENNET TO THE MILK. The temperature of all the mixed milk after pasteurizing is never above 85° and commonly only 70° to 80°. The acidity may be tested, if (k^sired, and should be just 0.25 per cent, or between 0.24 and 0.26 per cent. Three-quarters of a pound of starter per hun- dredweight of jnilk in the vat is added immediately through a liair sieve, stirring the milk. The rake is then put in and the vat stirred, while heating up to 85°. The desu'ed amount of color is stirred in, and always, without exception, the rennet is stirred in last of all. The rennet extract measured out for 5,000 pounds of milk should be diluted in a pailful of water. In adding rennet, hrst stir the milk across the vat the short way, going rapidly from one end of the vat to the other. With the largest-sized vats, two men with rakes may begin at the middle and walk toward the ends while stirring. Then walk back along the vat, adding the diluted rennet from a pail to the milk which is still in vigorous motion, noting on the clock the instant when the rennet first enters the milk. Set down the pail and again stir the milk across the vat the short way, with the rake or rakes, for exactly one minute, in which time the operator should be able to walk up and down the vat three or four times. In this way the smallest as well as the largest vats of milk should be set. Take out the rakes promptly one minute after the rennet entered. Cover the vat at once, and leave undisturbed. No top stirring is necessary or permissible, as the milk begins to thicken almost exactly seven niin- 48 CHEDDAR CHEESE FEOM PASTEURIZED MILK. utes after adding rennet, before there is any visible cream rising. Follow exactly the directions as to temperature, acidity, and propor- tion of rennet every day in the season. CUTTING, STIRRING, AND HEATING THE CURD. The curd formed in this process is always ready to cut exactly 25 minutes after the rennet entered the milk. Therefore as soon as the rennet has been added it is best for the operator to write the entire time schedule, as shown in Table 18, for the rest of the day's work on a paper, or, better, on a blackboard, which can be seen across the room. Some operators may suppose that possibly the curd might be cut a little earlier or later, but experience has shown that the curd is always in a thoroughly satisfactory condition for cutting just 25 minutes after adding rennet. There is therefore no need for repeated testing of the curd with the finger; it is only necessary to keep an eye on the clock, and follow the time schedule. In cutting, begin \\4th the horizontal knife and cut lengthwise of the vat; then use the vertical knife across the vat, cutting alternately toward and away from the operator. Finally cut lengthwise, with the vertical knife. Do not cut the vat more than once in each direc- tion, and try to do the cutting in exactly the same manner every day. The different cuts should not lap, nor should portions of the curd wider than three-eighths of an inch be left uncut between the knives, except in the following case: In cutting next to the sides of the vat, as in the first and last cuts in each direction, hold the knife as close to the metal sides of the vat as possible. If the knife does not appear wide enougli to cut the remaining ciuxl at the last stroke, cut close to the tin and leave a narrow strip of uncut curd, not at the edge of the vat, but between the last cut and the next to the last. This strip will be cut more thoroughly by the knives moving in other directions than if it had been left next the tin. Knives with blades three-eighths of an inch apart are required for this method. Immediately after cutting put the agitator blades in place and start them in motion. The curd obtained in this process is so firm and solid that this can always be done safely. Go around the vat with the hand some time during the next 15 minutes, loosening the curd from the sides, bottom, and corners of the vat. A form of agi- tator which is very satisfactory has one pair of revolving blades which also move up and down the vat, somewhat resembling the motion of the rake. Exactly 15 minutes after cutting turn steam into the jacket of the vat, and raise the temperature gradually during the next 20 minutes — just 19° to 104° — which temperature is maintained until the whey is drawn. BuL. 165, BuHEAu OF Animal Industry. U. S. Dept. of Agriculture. Plate VI MISCELLANEOUS OPERATIONS IN CHEESE MAKING. 49 DRAWING THE WHEY, MATTING, CUTTING, AND TURNING THE CURD. The agitator is left running until about two minutes before the whey is to be drawn, when it is removed, and the curd, after settling a few sec- onds, is ]nished slowly away from the gate with one or two rakes. The whey strainer is placed inside the vat and the hair sieve below the gate in the conductor, the gate being opened at such a time as will permit the whey to be out and the first rack to be put in ])lace at the time given in the schedule. When the whey is nearly all out, the gate end of the vat is lowered gradually, and a few seconds later the curd is pushed down toward the gate, leaving the upper third or half of the vat bottom bare and free from whey. In this process the curd is always sufficiently firmed in the whey so as not to need any stirring in the whey or on the rack. With r(>asonably brisk work the curd can be transferred to the curd cloth on the rack with a curd pail or scoop before it has time to become lumpy on the bottom of the vat. Each pail of curd as it strikes the rack shouUl fall apart loosely and not show the pi'csence of great lumps of curd matted together. Any such lumps should be lightly broken u]) with the hand, and if many lumps ap})ear it indicates lack of skill and quickness. The curd is piled evenly on the rack about 4 or 5 inches thick, and the top is leveled oiT with the hand in the usual manner and cov- ered with a curd cloth. More racks if necessary are put in place and the vat is fuially covered, leaving the curd to drain. The little curd gauge, made of wood, devised during the course of these experiments is a help in getting the layer of curd of the right thiclcness and also gives a good square end to the curd, which makes it easier to cut into blocks of uniform shape. (See PI. VL) Just 15 minutes after the time scheduled for putting in the rack the curd gauge is removed and the cutting of the matted curd into blocks 8 inches square, or G by 12 inches, is begun. The blocks are turned over immediately after cutting, and again turned 15 minutes later. They are then turned once in 10 minutes, and one hour after drawing tlie whey are jiiled two deep, and replied every 10 minutes until milled. In turning and ])iling, care is always used to turn the outer cooler surfaces toward the inside, in order that the entire mass of curd may remain at ])racticall3" uniform temperature throughout, as in ordinary ])ractice. MILLING, SALTING, AND HOOPING THE CURD. Exactly one and a half hours after the whey is drawn the curd is milled. The milled curd is piled along the sides of the vat, so as to drain toward the middle. It is stirred up with the hands from the bottom, turning the ])ile over about once every 10 minutes after milling, so as to cool it somewhat, ])revent matting, and allow free 79994°— Bull. 165—13 i 50 CHEDDAR CHEESE FROM PASTEURIZED MILK. drainage. Little or no white whey ever escapes from the curd after mining or salting when made up by this process, although some clear whey or brine does drain away. One hour after milling salt is thoroughly mixed with the curd at the rate of 2 pounds of salt per hundred of curd, which amounts practically to 2 pounds per thousand of milk in the spring and early summer, and 2\ pounds per thousand of milk in the fall, when the yield of cheese per hundredweight of milk is somewhat greater. The curd is stirred over several times during the next 20 minutes, by which time the salt is all dissolved, and the curd, at a temperature of 82° to 86°, is ready to be hooped. Each hoopful of curd is covered with a cloth and follower as soon as filled, in order to prevent the sur- face of the curd from cooling so far that it might fail to close well in the press. It is of the utmost importance that every cheese should be well closed and develop a perfect rind, free from cracks or other openings. Where openings occur mold is sure to enter during the curing process, and the flavor especially is apt to suffer as a result. PRESSING AND DRESSING THE CHEESE. Throughout the present set of experiments the cheese has been pressed for about an hour, applying pressure with the hand lever only, and at first only sufhcient pressure is used to keep the drippinga running from the hoops. After an hour the cheese is dressed and returned to the press, when continuous pressure is put on and it is left for the night. In bandaging the hoops the usual starched circles are used under the heavy muslin or duck cap cloths, or if it is found that the circles are hard to remove for paraffining they may be left out and the cap cloths left on the cheese until paraffined. The cap cloths, being of heavy cloth, can be stripped off rapidly without tearing and washed; m this way they may be used many times. The next morning it is customary, as in cheese factories generally, to look over the cheese, straighten any bandages which may be faulty, and turn any crooked cheese over in the press, leaving them until noon to straighten. DRYING, PARAFFINING, AND CURING. The cheeses when taken from the press are stenciled with the brand and date of making or a reference number, and placed on shelves in a well-ventilated room to dry on the surface. This room may be as high as 70°. Here they are turned over once a day. The cheese should be paraffined when 5 to 10 days old, or pos- sibly earher. The parafhii should be at 220° F., at least, and better at MISCELLANEOUS OPERATIONS IN CHEESE MAKING. 51 230° to 250° F. The thinnest possible coat of paraffin is the best, and the cheese should be held in the paraflin about 5 secontls and then drawn out and left to drain over the vat, on a rack, until it can be handled. A thin coating of parafFm is flexible and less likely to crack than a thick coating. It is ]>ossible to cure this cheese at any temperature between 34° and 75°. When it is desirable to cure the cheese as fast as possible, a temperature of 75° may be used without injury to the quality. However, at this tem}HM'ature there is considerable shrinkage, and it is necessary to wipe the cheeses occasionally and turn them over to j)revent them from getting moldy and sticking to the shelves. At 45° to 55° the cheese cures well, with little shrinkage and a minimum amount of labor. It also cures well when stored at 34° at the age of 1 week and (levelo)>s little or no mold on the surface, but owing to the extra cost this temperature should only be employed where it is necessary to hold the cluH'se for a considerable length- of time. BRANDIN(J AM) SELLING THE CHEESE. In order that customers may be sure that they are getting genuine pasteurized-milk ch(>es(> when called for, every cheese should be nuirked with the words "Pasteurized cheese" running all round the edge of the checs(\ All persons making cheese ai'cording to the process here described should use such a brand, in order to distinguish this j)roduct from the ordinary Cheddar cheese. A large number can be rapidly mark(Ml with a rubber stamp or by rolling the cheese over rul)ber tyj^c, set in a board, as shown in iigiu'e 2. Narrow strips of wood on each side of the board j)revent the cheese from rolling sitle- wise otr the type. In a new style of pi'oduct ujiiformity is a {|uality which consumers and dealers retpiire. It is reconunended that the maker of this stylo of cheese keep back one cheese from each day's make, when shipping, until the consignment has been accei)ted and ])aid for by the buyer. The sample cheese can then be sent along with the next shipment without i^lugging. If necessary, the cheese can be phigged with a trier, an(l by this means the nuiker will be able to study any faults which may be observed by the buyer and avoid them in the future. Names of leading chees(^ dealers who have already received sample shipments of this make of cheese and found it suitable for their trade may be obtamed from the authors. Where a maker doubts whether the buyer is giving him fair treat- ment, it is recommended that parts of each day's make be sent to two different dealers, whose criticisms, if any are received, can be compared by the maker at the factory. 52 CHEDDAR CHEESE FROM PASTEURIZED MILK, TESTING CHEESE FOR MOISTURE WHEN DRESSED IN THE HOOP. In making cheese by this process, the green cheese was found to differ very Httle in moisture content from day to day, as is shown in Table 19. Exceptmg the first day the cheese was made each day in two vats, and each vat of curd was tested for moisture separately. The determmation of moisture in cheese is not recommended as a part of the daily work in a factory. It is of great value, however, in experimental work, where it is desired to study the effect on their moisture content of different methods of handhng curds, or the effect of different moisture content on the market value or keepmg quahty of cheese. Fig. 2. — Method of markiut; cheese. ]\loisture tests are easUy made. It is ol)jectionable, however, to ])lug a new cheese every day for a moisture test because of the dan- ger of admitting molds, etc., beneath the rind, and it has been found that plugging the green cheese can be entirely avoided by sampling it at the tune it is dressed in the hoop, about one hour after puttmg it to ]n-ess. The trier hole made at this time by turnmg down the bandage and insertmg the trier at the side will close enthely over night in the press, leavuig the rind perfect. Samples of cheese thus taken from the dressed curd and tested for moisture agreed closely in moistiu'e content with samples taken with a trier from the same cheese the next day, after pressmg about twenty hours, as may be seen from Table 19! The moisture tests were all made by heating 10-gram portions of the curtl for at least three hours in the Wisconsm high-pressure INCREASED YIELD OP CHEESE OBTAINED. 53 steam ovon.^ After three or four hours there is practically no further loss of weight from samples of fresh curd in 24 hours' heating. Sam- ples of cured cheese continue to lose weight with continued heating much more noticeably than samples of fresh curd or green cheese. Table 19.— Comparison of moisture determinations made on samples talen luhen cheese was dressed, three-quarters to one hour after pressing, and on samples taken from green cheese, next day, when removed from press. Moisture content when cheese Moisture content. le.xt dav. Date. was dressed. when removed from press" Differ- ence. First. Second. .\verage. First. Second. Average. 1911. Per cent. Per cent. Per cent. Per cenl. Per cent. Per cent. Per cent. .\Uf,'. 15 ■.i7. tv) 37. 40 37. 5i) 37. 95 37. 25 37. ti:) + 0.10 Iti ;is. 50 3S. 70 3S. S) 38. 50 39. 00 3S. 75 + .15 Hi 3S. 50 3S. 90 3S. 70 3S. 05 3S. 51) 3S. 27 - .43 17 39. ()(J 39. 10 39. 35 3S. 50 3S. t) ) 3S. 55 — .SO 17 3.S. . 00 + ..SO 24 44. 25 44. 3) 44. 27 43. 15 43. 3 ) 43. 22 -l.(J5 2.5 39. 55 39. 70 39. ti2 .39. 30 39. 05 39. 4(1 - .l(i 2.') 44. 10 44. 45 44.27 44. 45 44. 95 44. (JJ + ..33 26 3S. 95 39.10 39. 02 3S. SO 39.00 3.S. 9J - .12 2(3 44.30 44. ti!) 44.45 42.80 43.00 42. 90 — 1.55 RESULTS OF TWO YEARS' TRIAL OF THE METHOD. INCREASED YIELD OF CHEESE OBTAINED BY THE NEW PROCESS. APPARATUS ANO METHODS OF STUDY. In the season 1909-1910 it was found that an increased weight of cheese is regularly obtained after ])asteurization as comj)aretl with the weight obtained by the regular factory methods. For the pur- ]K)se of accurately studying the yield of cheese in 1911 two scales were used, one of 5,000 ])ounds' capacity graduated on the beam to one-half pound and one of oOO i)ounds' caj)acity graduated on the beam to one-tenth })Ound. The larger scale was set uj) permanently in one corner of the make room, and a woodcui frame carrying a 300- galion steel receiving vat was placed upon it. The outlet of the vat is of sanitary metal ])i|)ing, suspended by wire to the vat m such a way that the ])ipe and contents are weighed each time \vith the vat. The frame, vat, and pipe w^eighed 487 V pounds when empty. The separate weights and the scale on the beam were carefully tested by use of test weights. The entii-e set of w^eights agreed among them- selves so closely that no difference could be detected in the equilibrium of the beam when one weight was substituted for another in weighing a load. The error in a smgle weighing is not over one-iiutirtcu- of a ' Farringtou, E. H. A creamery method for the determination of water in butter. Wisconsin Agri- (ultural Experiment Station, Bulletin 154. Madison, Sept., 1907. 54 CHEDDAR CHEESE FROM PASTEURIZED MILK. pound with large or small loads. Except when weighmg the lever is kept up, thus relievmg the knife edges from load and wear. The method of using this apparatus is as follows: The vat bemg empty with the ])ipes in place and stopcocks closed, the supply of milk is run into the vat through a conductor and cloth strainer. The strainer and conductor are then removed, the lever is lowered, and the weight of vat and contents determined. It is our habit to balance the scales exactly, giving neither "up" nor ''down" weight. The lever is then raised, and the operator clmibs up tlio ladder on the frame to the riml)oard along the side of the vat. With a dipper he stms the milk continuously and vign'ously for 5 or 10 mmutes, and contuiues stirring while a portion of the milk is being drawn out for use in one of the experimental cheese vats. The vat and the remam- ing milk are then weighed with the same precautions as before, after which another portion of the milk may be tlrawn off for use in another vat in the same manner. Tlic ])rocautions mentioned above seemed sufiicient to insure that the milk used in the two vats — one for ordinary and one for pas- teurized cheese — was thoroughly mixed at the time it was drawn from the receiving vat, and that each lot was weighed accurately with a total possible error of not over one-half a pound in a vat of 200 to 2,000 pounds of milk — an error of one-fortieth to one-fourth of 1 per cent, at most. The other new scale mentioned above is a counter scale gradiuited on the beam to one-tenth of a pound and sensitive to one-twentieth of a pound with any load uj) to 200 poimds. This was used for weighing the cheese throughout the work here described. The set of weights used with this scale agreed among themselves and with the test weights mentioned above in the description of the other scale. With the smaller scale, 20 to 200 pounds of cheese could readily be weighed with an error of not over 0.05 of a pound, or 0.25 per cent, at most. On 6S days durin^ij the season of 1911 the receiving vat of milk was divided into two accurately weighed portions for this ex])er- iment. One of these was pasteurized and made up into cheese by the new method, the other portion was made up into cheese by regidar factory methods. The cheese was 13^ inches in diameter by 4 inches high, the "daisy" size. The green cheese was always weighed as quickly as possible after being removed from the hoops. The daily record of weights of milk used and of cheese obtained, and the per cent of increased yield which resulted from pasteurization, are shown in Table 20. INCEEASED YIELD OF CHEESE OBTAINED. bi> Table 20. — Increased yield of green eheese obtained by the 7iew method from pasteur- ized milk. Pasteurized milk. Raw milk. I'r port ion of St irter used. Gain by Dale made. Yield of Yield of pasteur- clieese cheese ized y, milk. '; Milk (1 reon per liun- Milk Green per hun- s- ir- K use J . cheese. dred- used. eheese. dred- lei iZL aw. weight weiglit d. of milk. of milk. 1911 Pounds. Pounds. Pounds. Pounds. Pounds. Pounds. Per cent. Per ct. Per ct. Feb. Zi 538. 53. 20 9. 89 3S0. 35.40 9.31 6.23 75 00 24 504. 5 51.00 10.11 380.0 36. 60 9.63 4.98 75 00 27 l,02ii.5 108. 20 10.35 600. 57.80 9.63 7.48 75 00 28 800. 82. 20 10.27 400.0 38. 30 9.57 7.31 75 75 Mar. 1 .350. 35.40 10.11 510.0 50.20 9.84 2.75 75 1 50 2 389. 5 39.00 10.01 628.0 59.70 9.51 6.61 75 3 340. 35.00 10.29 522.0 52.30 10. 02 2.79 75 1 .50 7 8.55. 88. 20 10.32 380. 38. 40 10.11 2.08 75 2 (M) S 590. 60. 70 10.29 388. 5 39.30 10. 12 1.68 75 1 50 9 41S.0 42.80 10.24 417.5 41.00 9. 82 4.27 75 1 00 10 442.0 44.70 10.11 700.0 66. 40 9.49 6. 5:3 75 00 13 1,166.0 122.00 10.46 275. 25.70 9. 34 12,00 75 00 14 956.0 10.3.40 10.81 260. 25.80 9. 92 8.97 75 75 15 570.5 .5,8. 10 10. 18 380.0 37.50 9. 87 :3. 14 75 75 K) .531.5 56.90 10.71 359.0 37. 40 10. 42 2.78 75 2 (M) 17 395. 41.20 10.43 396. 39. 80 10. 05 3. 78 75 2 50 20 1,.$44.0 136. 00 10. 12 384. 36. 60 9. 53 6.19 75 00 21 570.0 56. 40 9.89 378. 35. 30 9. 34 5. 89 75 00 22 3ii2. 5 36. 00 9. 93 542.0 51. ,80 9.56 3. .87 75 1 67 .\pr. .5 5S5. ()0. 80 10.39 390. 37. 70 9. 67 7.45 75 75 7 508. 51.15 10.07 339. 5 32. 50 9.57 5.22 75 75 11 549. 55. 00 10. 02 549. 52. 60 9. 58 4.59 75 75 13 364. 35. 70 9.81 364.0 34. ,55 9.49 3. 37 75 75 17 800. 80. 25 10. 03 6(X). 55.50 9.25 8. 43 75 00 IS 720. 71. 15 9.88 540. 49. .80 9.22 7.16 75 00 24 1.254.0 122. .80 9.79 660. 61.90 9.38 4.37 75 75 27 570.0 55. 30 9.70 380. :55. 70 9.39 3. 30 75 75 28 420. 40. 85 9.73 420.0 40.05 9.54 1. 99 75 75 May 2 636. 65. 0.5 10.2:3 424.0 42. 00 9.91 3.2:3 75 75 3 558. 54. 30 9. 73 372.0 35.55 9.56 1.81 75 75 8 1.693.0 1.58. 15 9.34 800. 70. 95 8.87 5. 30 75 75 10 798. 77. (;o 9.72 798.0 73. 70 9.24 5.19 75 75 15 1,. 587.0 161.60 10. 18 800.0 76.90 9.61 5. 93 75 75 17 1.088.5 109. 00 10.01 800.0 76.60 9. 57 4.60 75 75 22 1,223.0 129. 40 10.58 800. 78. 20 9.77 ,8.29 75 75 2.5 851.0 .87. 00 10. 22 800. 78.80 9.85 3.76 75 75 29 1,315.0 138. 60 10. 54 800. SO. 20 10.02 5.29 75 75 June I 798. 83.50 10.46 800.0 83. 10 10. .39 .67 75 75 2 799. 5 82.85 10. 36 800.0 79.50 9.94 4.23 75 75 7 790. 5 79.65 10.07 800.0 76.60 9.57 5.22 75 75 9 800. 82. 30 10.29 800.0 78.15 9.77 5. 32 75 75 13 1,090.0 119. 70 10.98 800.0 80. 20 10.02 9. 58 75 00 15 795. 85.50 10.75 800.0 80.70 10.09 6.54 75 75 16 800. 8.3.45 10. 43 800.0 78. 95 9. .87 5.67 75 75 19 810.0 87.60 10.81 800.0 79. 65 9.96 8.54 75 00 21 798. 5 81.75 10.24 800.0 77.70 9.71 5.46 75 75 26 770.0 ,80.65 10.47 770.0 75.45 9.80 6.84 75 00 27 801.0 83.50 10.42 800.0 79.00 9. 88 5.46 75 75 28 801. 5 85.90 10. 73 SOO. 82.00 10.25 4. 68 75 75 July 3 1,2.34.0 122. 75 9.95 .800. 72. 35 9.04 10. 07 75 00 6 995.0 102. 4.5 10.30 ()60. 66. 10 10. 02 2.79 75 75 8 1.068.0 108. 50 10.16 660. 62. SO 9.52 6.72 75 00 10 1,064.5 107. 30 10.08 800.0 74. 35 9.29 8.50 75 00 11 914.0 93. 50 10.2:3 660.0 63. 6.5 9.64 6.12 75 00 12 873. 93. 15 10.67 800.0 78. 20 9.77 9.21 75 75 24 1,195.0 12.5. 10 10.47 600.0 58.20 9.70 7.94 75 75 26 1,099.0 lis. .32 10.77 190.0 19.32 0.17 5. 90 75 00 Aug. 29 294.5 31.58 10.72 290.0 30.50 10.52 1. 90 75 75 30 344.0 35.82 10.41 340. 34.05 10.01 4.00 75 75 Sept. 1 322. 34.10 10.59 320.0 32.60 10.19 3.92 75 75 5 291.5 31.00 10. 63 292.0 29.65 10.15 4.73 75 75 6 276. 28.95 10.49 275. 27.20 9.89 6.40 75 75 7 286. 5 31. 03 10. 83 286.5 29.48 10.29 5.24 75 75 8 292.0 31.50 10.79 292.0 30.25 10.36 4.14 75 75 20 263. 29.15 11.08 263. 27.80 10.57 4. .82 75 75 22 265.0 29.20 11.02 266.5 28.05 10.52 4.75 75 75 25 748. a3. 90 11.22 250.0 26.40 10.56 6.2.5 75 75 Oct. 2 700. 5 79.25 11.31 420.0 4.5.10 10.74 5.31 75 75 Avera 3 ?e. . 251.0 27.75 11.05 250.0 26.25 10.50 5.24 75 75 10. 7 9.815 5.374 "I" 1 56 CHEDDAR CHEESE FROM PASTEURIZED MILK. It wHl bo noted that every day iii the season there was a greater yield of cheese from the pasteurized milk. From 250 to 1,700 pounds of milk were handled in each vat. The average yield of green cheese from raw milk was 9.815 pounds and from pasteurized milk 10.537 pounds per hundred pounds of milk. The daily increase in yield ranged from 0.6 per cent to 12 per cent, and m 50 cases (72 per cent) lay between 3 and 8 per cent, while the average mcrease in yield by the new process on 69 days was 5.37 per cent.^ On 45 days the same proportion of skim milk starter — three- fourths per cent — was used in both the raw and the pasteurized milk. In the raw milk none ■\\as used on 16 days, and on 8 daj's 1 to 2^ per cent (on the average 1.71 per cent) was used, while in every case the pasteurized milk received three-fourths per cent starter. If the use of starter affects the yield of cheese, the average yield from the pasteurized milk on 16 days was raised about three- fourths per cent, while the average yield from raw milk was raised on 8 days about 1.71 ])er cent. These two effects offset each other in the table, giving a slight advantage to the yield from the raw milk, so that the fmal average figin-e — 5.37 per cent — representing the aver- age gain in yield of green cheese by the new process, is no higher and possibly a trifle lower than it would have been if equal proportions of starter had been used in all cases. Among the 17 cases m Table 20 in which no starter was used m the raw-milk vat, the average gam m the pasteurized-milk vat, usmg three-fourths per cent starter, was 7.48 per cent; and in 8 cases where more than three-fourths per cent starter was used in the raw milk, the average gam in yield in the pasteurizod-milk vat was 3 i)er cent. From this it would appear that the proportion of .starter used does notably afl'ect the yield of cheese, conti-ary to some recent statements.^ SEARCH FOR SYSTEMATIC ERRORS IN EXPERIMENTS ON YIELD OP CHEESE. The presence of systematic errors was carefully guarded against in the daily work on the yield of cheese. Before dividmg the milk from the receivmg vat for use in the two make vats, the milk was first thorouglily stirred for 4 to 10 mmutes, as already stated, and the stir- ring was contmued while the milk was running out. The portion of milk drawn out first was commonly used for making the raw-milk cheese, but sometimes, as on March 8, 9, 10, 17, 21, 22, and April 7, 11, 17, 18, and May 10, the portion drawn first was used for making the past.urized-milk cheese. The average gain m yield through pas- 1 Both the median and the mode lie between 5 and 6 per cent. The mode is the class which occurs with the greatest frequency; the median is the magnitude at the middle of the series from largest to smallest. See "Statistical Methods," by C. B. Davenport, New York, 1899, or •' Principles of Breeding," by E. Daven- port, Boston, 1907, p. 6S4. 2 Van Slyke, Lucius L., and Publow, Charles A. The science and practice of cheese making. New York, 1909. See p. 69. INCREASED YIELD OF CHEESE OBTAINED. 57 teurizatioii on these 11 days was 5.15 i)er cent, so nearly equal to the general avcn^igo of 5.37 ])er cent (see Table 20) as to indicate that the gain in yield is not due to any difference in composition of the milk when divided into two lots. Carefully tested thermometers and the same pair of curd laiives were used in every vat. Usually tlie vat of pasteurized milk was set first with rennet, and the vat of raw milk 5 minutes later. The two vats were placed near each other, and conditions were such tliat one operator could stir them both at once, if desired. On 11 ihiys, April 18, 24, 27, May 8, 10, 15. 17, August 29, 30, Soptem})er 1, and October 2, the rennet was ackled to the raw milk first, and to the ])asteurized milk 5 minutes later. The average gain in yield on {]u\ 11 (hiys was 4.63 per cent, indicating that the order of setting the vats had nothing to do with tlie gain m yield. In order to ascertain what per cent of miavoidable error enters into the measurement of yield of cheese, a special experiment was performed on 34 days. Eacli day, with all of the usiuil precautions, two lots of milk drawn from tlie receiving vat were run through the pasteurizer, one after the other, and made up into cheese in separate vats marked (C) and (D) standing near each other, and handled by the same oper- ator (^Ir. Bruhn). The vats were heated and set exactly 5 minutes a])art by the watch, and the time schedule for each vat was strictly followed m every detail. The same curd knives and thermometer were used in both vats. The pasteurizer and cooler are always rinsed with hot water at the beginnmg of the first run, but are wet with adhering milk at the close of the run just before beginning the second run. Thus the actual weight of milk m the fii'st vat might be slightly less than it shoidd be. To avoid this source of error, the pasteurizer and cooler were allowed to drain each tune into the vat for several minutes (until the stream of milk broke into suigle drops), and then the metal surfaces were carefully rmsed with two measured portions of clean water. Thus the siu'faces of the i)astem'izer and cooler were w^et with w^ater at the beginning of the second nm as well as the fu'st. The milk content of the rinsmg's (see Table 21) was found to be very small and uniform, amounting to about 0.8 of a ])oimd of milk each time, which if it were all lost from one vat but not tlie other would cause a diiference of yield of cheese from a 500-pound lot of milk (as in Table 22) of about 0.16 i)er cent. In order to avoid this source of error entirely, the rinsings from both runs were either thrown away, as on the first 15 days listed in Table 22, or the rinsings after each run were added to the respective vats, as on the last 19 chiys. 58 CHEDDAR CHEESE FROM PASTEURIZED MILK. Table 21. — Milk content of rinsings of pasteurizer and cooler. Date. Weight of rins- ings. Fat content. Estimated weight of cheese in rinsmgs. Estimated \vei'.;h1 of milk in rinsings. Percent. Weight. 1911. Apr. 2.-. (Vat C) 2.5 (Vat D) 2(i(Vat(') 2li(Vat D) Pounds. 2.25 2.25 2.25 2.25 1.25 1.25 1.20 1.20 Pounds. 0. 028 . 028 .027 .027 Pounds. 0.08 .08 .08 .08 Pounds. 0.8 .8 .8 .8 The yield of cheese obtained in diipUcate vats thus handled was never exactly equal and varied on the average for 33 days by 0.585 per cent of the weight of the cheese, as shown in Table 22. The milk in Vat C was drawn first from the receiving vat, and was pasteur- ized and set first in all cases except where otherwise noted. Table 22. — Variation in ijiehl of cheese from duplicate rats of pasteurized milk. Vat C. Ratio of Vat D. Differ- ence in Date. \V('ii,dit Weight Cheese n;ilk \voi':''hts. Weight Weight Chee.se yield of the two vats. of 1, ilk of green per cwt. of milk of green per cwt. u.sed. cheese. of milk. used. cheese. of milk. Ta< TV;/ 1911 Pounds. Pounds. Pounds. C. D. Pounds. Pounds. Pounds. Per cent. Mur. 23 430. 42.50 9. 884 430. 42.55 9. 895 0.11 24 390. 38.80 9. 949 390. 39.10 10. 026 .77 27 375. 3(5. 10 9.627 1,125.0 109. 20 9. 707 .83 28 350. 3(5. (50 10.457 1 21 875. 92.20 10. 537 .76 29 585. 59. 10 10. 102 1| l' 390.0 39.45 10.115 .13 yo 495. 50. 10 10.121 330. 33.50 10. 151 .30 :u .540. 54.20 10. 038 ll 1 360.0 36. 15 10. 042 .04 Apr. 4 5S5. 00. 50 10. 342 ll 1 390.0 40.55 10.397 .53 (i 534. 54.15 10. 140 li 1 35(i. 37.35 10. 491 1 3. 46 1(1 1 , (ISO. 10(5. 30 9. 842 360. .35. 65 9. 903 .(52 12 555. 55.70 10. 036 J I \ 370. 37. 60 10. 162 1.25 14 380. 38. 10 10. 026 380. 38.40 10. 105 .79 19 400. 40. 30 10.075 JOO. 40.60 10. 150 .74 20 370. 3(5. 75 9. 932 1 1.^ 55 .. 55. 40 9. 728 .50 21 380. 37. 00 9.737 1 \\ 570 55. 45 9.728 .09 25 420.0 41.00 9. 762 4:::0. 40. 90 9. 738 .25 2(1 370. 3(5. 20 9. 784 1 \\ 555. 54.35 9.793 .09 May 4 420. 42.10 10. 024 420.0 42.50 10.119 .95 5 531.0 51.40 9. 680 1 .', 1 354. 34.35 9.703 .24 9 408. 40. (55 9. 963 1 1 ', 612. 60.80 9. 935 .28 11 410.0 41.. 50 10. 122 410.0 41.80 10. 195 .72 12 795. 78. 25 9. 843 795.0 79.50 10. 000 1.59 Iti 800. 80. 30 10.037 800. 80. 65 10.081 .44 18 (iOO. 03. 80 10. (533 600. 62.70 10. 450 1.75 19 (iOO. 62.20 10. 367 600. 61.95 10.325 .41 2:-! 000. 04. 00 10. 667 600. 63. 75 10.625 .39 24 012.25 64.35 10.510 612.25 65.15 10.641 1.24 30 600. 61.30 10.217 600. 60.75 10. 125 .91 31 (iOO. 62.10 10.350 600. 62.12 10. 353 .03 Juna C 583. 59. 15 10.146 577. 75 59.15 10. 238 .91 H 000. 61.55 10. 258 600. 61.85 10. 308 .49 14 000. 62.28 10. 380 600. (52. 15 10. 358 .21 17 599. 5 62.71 10. 460 599. 5 63.11 10.527 .(54 20 Average. . (500. 60.30 10. 050 ■ 600. 60.90 10. 150 .99 535. 22 10. 105 536. 37 10. 149 1.585 1 Tlie result for Apr. 6 is omitted in computmg the average because of abnormal conditions. Among the 34 days' results obtained during the season, as shown in Table 22, tlie difference in yield between duplicate vats exceeded 1.75 per cent in only one case. On this day there was unusual diJhculty in the work because of unexpected failure of the supply of DISCUSSION OF VARIATION IN YIELD. 59 water for cooling, and, although the dh-ect cause of the exceptionally liigh figure (3.4(3 per cent) can nob be directly traced, it seems likely that some gross error occurred, whicli was avoided on the other days. Therefore this figure (for April 0) is omitted from the general average. On 28 days (82 per cent of all cases) the variation in yield between du[)licate vats lay below 1 per cent and on 33 days (omitting April G) it a^'eraged 0.584 per cent. For present jiurposes, therefore, it may be considered tliat the figure 5.37 per cent, from Table 20, representing the average increuscnl yield of green cheese obtained through pasteuriza- tion, is correct within 0.58 i)er cent, or about one-ninth of its value. The yield of cheese from ])asteurized milk is thus capable of meas- ui-emont with an average dilFcu'ence between duplicate determina- tions of O.G \)vv cent of the amount determined. This degree of accuracy in manii)ulation is compara])le with liiat attained in many analytical chemical process(\s, in wliich n limit of 1 ])er cent of the amount determined is commonly set as tlie maximum allowable differenci^ between (hiplicativs. The ])rin<'ii)a] cause for the difference of O.GO ])er cent in the yield in making du])li('at(> vals of cheese docs not Yw in the weighing of the milk or cheese, because witli llic seal's eni])loye(l both the milk used and tfu^ chees(^ obtained thei'efi'om could \)o weigiu'd with an (UTor of not over 0.10 ])ei' cent. Tiie ])er cent of difl'ereuce in yield was not reduced when the W(>ight of milk handled was increascul. It appears likely, therefore, that there ar(^ small unavoidable difi'erences caused by the size of the cubes or in th(> mani])ulati()n of the milk and curd which cause an average difference in yield of from 0.50 to O.tiO ])er C(^nt between du])licate ^•ats. An efl'oi't was made so fai- as tini(^ ))erniitted to determine whether any one of several causes was r(>gularly or ejiiefly responsible for this average difference in tlu^ yield. The stirring of the vats was done by hand in all eases when^ the weight of milk in a vat was less than 400 pounds. For ex])eriments with 400 to 800 ])oun(ls of milk in a vat a pair of vats of 800 ])ounds capacity was used. These were stirred with a ])air of wixxIcmi rakes, exactly alike in sha])e and size. Larger c^uantities of milk than 800 pounds were always handled in a vat of 2,400 })ounds ca])aeity in which a two-bladed rotating and oscillating agitator was used instead of the rake. The difference hi yield between duplicate vats could not be traced to the methods of stirring. Thus, on March 27, the agitator-stirred vat (D) gave 0.83 per cent greater yield than the hand-stirred vat (C), but on April 10 the hand-stirred vat (I)) gave 0.62 per cent greater yield than the agitator-stirred vat (C). The average difference on 12 days in yield l)etween du])licate rake-stirred vats was 0.70 per cent, and the average difference in yield between duphcate hand-stirred vats on 19 days was 0.52 per cent. The differences varied slightly whatever method of stirring was employed. 60 CHEDDAR CHEESE FROM PASTEURIZED MILK. Again, handling different amounts of milk did not appear to affect the yield in duplicate vats. On 12 days, using one and one-half to three times as much milk in one vat as in the other, the average differ- ence in yield was 0.40 per cent, which is a little smaller than the average of the other days, showing that the quantity of milk handled by this method does not affect the yield. Since the same results are obtained in a small A^at with 375 pounds of milk as m a large one with 1,125 pounds of milk, it is believed that the general results of this investigation are applicaljle to the largest sized vats of milk used in factories. SHRINKAGE BEFORE PARAFFINING, AND YIELD OF PARAFFINED CHEESE. Since there is always some loss in weight of cheese previous to paraffining, it is of interest to comj-yare the shrinkage of ordinary cheese with that of new-process cheese, and to determine whether there is an increased yield of pasteurized-milk cheese when paraffined corresponding to the increased yield observed in the same cheese when green. This can be done readily from Table 23, which shows the average results for the season and also the range of daily variation. Table 23.- — Comparison of old and new process cheese as to shrinkage before paraffining and yield of paraffined cheese. ShrinkaR ; per 100 pounds of green Yield per 100 Age elieese before pounds of milk. Gain in Date wlien paraflinins;. yield made. par- affined . by new process. Pasteur- ized. Raw. Pasteur- ized. Raw. 1911. Dans. Pounds. Pounds. Pounds. Pounds. Per cent. Feb. 23 It) 5.92 5.23 9.30 8.83 5.32 24 18 5.98 5.05 9.50 9.14 3.94 27 15 5. 32 4.07 9.79 9.18 6. 04 28 14 5.23 4.57 9.74 9.14 6. 51) Mar. 1 13 5. 30 4.88 9.57 9.30 2.24 2 12 5. 20 4.35 9.49 9.09 4.40 3 15 5.71 5.35 9.71 9.48 2.43 7 11 5.21 4.43 9.78 9.06 1.24 8 10 4. 45 4.58 9.83 9.65 1.80 9 9 5. 49 4.82 9. 08 9.35 3.53 10 8 3. .58 3.35 9.75 9.17 0. 32 13 12 5.08 4.28' 9.03 8.95 10. 95 14 11 5. 13 4.20 10. 20 9.50 8.00 15 10 3. 90 3.73 9.78 9. m 2.95 l(i 9 4.22 3. 01 10. 25 10. 04 2.09 17 8 3. 88 ,3.27 10.03 9.72 3.19 20 12 5.37 4.37 9.58 9.11 5.16 21 11 4.42 3.08 9.40 8.99 5.23 22 10 4.72 3.86 9. 46 9.19 2.94 Apr. 5 10 4. 30 3.58 9.94 9.32 6. 65 7 8 4.10 3.85 9.66 9.20 4.00 11 10 5.09 4.56 9.51 9.14 4.05 13 8 4.02 4.05 9.35 9.11 2. 63 17 12 5.11 4.23 9.52 S.80 7.45 18 11 4.85 4.42 9.40 8.81 0. 70 24 12 5.05 4.11 9.30 8.99 3.45 27 9 3. 98 3. 64 9.32 9.05 2.98 28 8 2.82 2. 02 9.45 9.29 1.72 May 2 11 4. 30 3.93 9.79 9.52 2.84 3 10 4. 33 4.08 9.31 9.17 1.53 8 13 4. 52 4.05 8.91 8.40 5.32 10 11 4.19 3.73 9.32 8.89 4.83 15 12 4. 04 4. 36 9.71 9.19 5.65 17 10 4.57 3.98 9.49 9.19 3.26 22 12 4.71 4.09 10.08 9.37 7.57 25 11 4.71 3.93 9.74 9.46 2.96 29 13 4.72 4.37 10.04 9.59 4.09 COMPARISON OF SHRINK Ar4E BY OLD AND NEW PROCESSES. 61 Table 23. — Comparison of old and neiv pmccsa cheese as In shrinhicje before paraffining and yield of paraffined cheese — Continued. Shrinkage per 100 pounds of green Yield per 100 Age cheese before pound.s of milk. (iain in Date when paraffining. yield made. paraf- fiued. by new process. Pasteur- ized. Raw. Pasteur- ized. Raw. 1911. Days. Pounds. Pounds. Pounds. Pounds. Prr cent. Juno 1 10 3.92 3.t;7 10.05 10.01 0.40 2 9 4.22 3.92 9. 93 9. ,'•.5 3. 98 7 7 4.21 3. 66 9. 6(i 9. 22 4.77 9 S 3.80 3. .W 9.90 9. 12 5. 09 13 10 5. 26 4.74 10. 40 9. .'5 8. 90 15 8 4.49 3. 82 10. 18 9. 70 4.95 16 7 4.43 3. 64 9. il7 9.51 4.84 19 12 4. 85 4.27 10. 29 9. 53 7.97 21 10 4.46 4. IS 9. 7S 9.31 5. 05 26 12 4. ,'53 4.17 10. 00 9. 40 6. .38 27 n 4.19 3. SO 9. 99 9. r,i) ,5. 16 2S 10 4.02 3.41 10. :«) 9. 90 4.04 July -i It 4. ,16 3.91 9. 49 8.1.9 9.21 c, 11 4.20 4.01 9.8(i 9. 61 2.(i0 s 9 3.fi4 3.42 9.79 9. 19 6.53 10 10 4. .SO 4.64 9. 60 8. S6 8. 35 11 11 4.46 4.01 9.77 9. 26 5. 51 12 10 4. .54 3. (15 10. 19 9. 42 8.17 Aug. 29 11 4.99 (i.07 10. 18 9. 88 3.14 .30 10 4. 22 4. 05 9. 97 9. 61 3.75 Sept. 1 8 4.14 4. 14 10. 15 9.77 3.89 r^ 13 4.35 4. 05 10.17 9. 74 4.42 6 12 3.82 .3. 49 10.09 9. 54 5.(i5 7 11 3. 49 2. 99 10. 45 9. 98 4.71 8 10 3. 17 2.81 10. 45 10. 07 3.77 20 10 3. SO 3.41 10. 66 10.21 4.41 22 8 3. 43 3.21 10.64 10. 19 4.42 25 Average.. 16 6. 49 5. 87 10.49 9.94 5.53 4. 546 4.078 9. 833 9. 3S8 4.761 In practically every case in Talile 23 tlie pasteurized-milk cheese sliowcd a o;roator slirinkage tliaii the raw-milk clieose durinf? the period before paraffining, which was 7 to 19 days. The average shrinkage of raw-milk cheese before parafhniiig, for all G5 cases, was 4.08 pounds per hundred of green cheese, and for the pasteurized-milk cheese it was 4.55 pounds per hundred, nearly one-eighth greater than the raw. This excess shrinkage is observed whether the cheese was paraffined at 7 or 14 days, as is show^n in the following table, which is a summary of Table 23. Table 24. — Shrinkage of cheese when paraffined at different ages (surnnmrg of Table 2o). Average shrinkage in weight per 100 pounds green cheese. Age when paraffined. Cases av- Excess in i asteurizcd. Pasteur- ized. Raw. Per cent of Days. Number. Pounds. Pounds. Pounds. raw. 7 to 8 11 3. 95 3. .i6 0. 39 11 9 ,■■, 4.31 3. S8 .43 11 10 10 4.35 3. 83 .52 13 11 12 4.52 4.10 .42 11 12 10 4.84 4.17 .67 16 13 to 19 11 5.29 4.78 .51 11 62 CHEDDAR CHEESE FROM PASTEURIZED MILK. On account of this excess shrinkage before paraffining, amounting to about one-half pound per hundred pounds of cheese, the average increased jneld of 5.37 pounds per hundred of milk observed in the pasteurized cheese when green (Table 20) was reduced to 4,76 pounds (see Table 23) by the time the cheese was paraffined. SHRINKAGE AND YIELD OP CURED CHEESE. The further shrmkage and yield of cheese after paraffining was studied: (1) With cheese cured at Madison, Wis., at a temperature of 60° to 75°; (2) with cheese cured at New Orleans, La., and weighed both at New Orleans ^ and Madison; (3) with cheese cured at New Orleans or at Columbus, Ga., and weighed both at Chicago and at IVIadison; (4) with cheese cured in a warm room at Madison; and (5) with cheese put in cold storage at 34° F. at Waterloo, Wis., at difl"er- ent ages after paraffining. So far as possible duplicate cheeses from the same days' make were cured in the different ways stated. These different methods of curing were chosen for study as repre- senting (1) curing conditions at Wisconsin factories; (2), (3), and (4) conditions to which annually large amounts of cheese are subjected when shipped south for sale; and (5) when cured in cold storage as commonly practiced by dealers. The shipments to New Orleans were sent on four dates between April 29 and July 24, 1911. Each shipment consisted of 9 to 25 pasteurized-milk cheeses, and an equal number of raw-milk cheeses for comparison. In order that the cheese stored might be as repre- sentative as possible, each pair represented a different day's make. For each lot of cheese shipped away from Madison for storage, a duplicate lot from the same days' make was kept at Madison. The method of designating these different lots of cheese is shown in Table 25: Tabte 25. — Reference numbers to different lots of cheese stored in 1911. Date made. Cheese Nos. Cured at Madison. Cured at New Or- leans. Cured at New Or- leans and Columbus, Ga. Cured in warm room at Madison. Cured at Waterloo, WLs. Feb. 23 to Apr. 16.... Apr. 24 to May 17 May 22 to June 16 June 19 to July 12.... July 13 to Aug. 21...- 171 to 207 211 to 227 230 to 246 248 to 2G3 264 to 283 lA 2A 3A 4A 5A IB 2B 3B 41? 3C 4C 3D .. 4D 5E In addition to weighing each cheese separately they were also weighed in lots of five, and the close agreement of the weight of a lot 1 The details of the work at New Orleans connected with the storage, weighing, and shipping of the cheese used in this test were handled by Mr. W. J. Bleecker, junior dairyman of the Dairy Division, Bureau of Animal Industry. Thanks are due to Mr. Bleecker for his very careful attention to this work. CURING VAEIOUS LENGTHS OF TIME. 63 of five witli the sum of tlie five separate weii^hts proved the accuracy of the Avei,:j;hiii cheese. Taijh; 2G. — Comparison of yield of raw and paslciirizcd-milk cheese after curing for various lemjths of time at Madison, Wis. Weisht of cured Time cheese per 1(1(1 Dato in.iilp. cured pounds ol uiilk. alter parallin- (!aiu liv izal [)isteur- ioii. ing. Pasteur- ized. Raw. ion. Dai/s. roitrida. Poll mis. Puiinih Per cent. Apr. 24 21 9.27 S. llli 0.31 3. 40 Mar. 20 21) 9. 52 9. (l(i . 40 5. 08 21 2t> 9. 40 S. 94 .40 5.15 22 2ti 9. 37 9. 12 . 25 2.74 20 33 9. 47 S. 09 .48 5. 34 17 32 9. S7 9. ('.3 .24 2.49 16 32 10.(12 9. 9l> .0(1 . (10 15 32 9. liS 9. 3S .30 3. 20 14 32 10. 03 9. 31 .09 7. 3S 13 32 9.72 ,S. NO .92 10.40 2 42 9. 53 9. 30 .17 l.Sl 7 42 9. 57 9. 49 .08 .84 8 42 9.01 9.51 . 10 1.05 9 42 9. 55 9. 29 .20 2.80 10 42 9. t)2 9.09 . 53 5. S3 -Vpr. 17 42 9. 30 S. 73 ..57 0. 54 IS 42 9. 13 8. 04 .49 5. 07 May 1.^. 44 9. 43 S. SO .54 0.07 17 44 9. 15 S. S5 .30 3. 39 June in 44 9. SO S. 94 .92 10. 29 Vi 44 9. 7(1 9.311 .40 4. 30 It; 44 9. (i4 9. (14 .(10 0. 04 Feb. 23 45 9. 12 S. 03 .49 5.07 24 45 9. 2(i S. ;)3 . 33 3.09 27 45 9.51 9. (10 .51 5. 07 2.S 45 9. 49 S. '.19 . 50 5. 50 Mar. 1 45 9. 57 9. OS .49 5. 39 2 45 0.21 S. 94 27 3.02 Apr. 11 50 9. 29 S. 08 .31 3.45 13 50 9. 0(1 S. SO .20 2.20 May 10 50 S. 95 8.51 .44 5.17 June 7 50 9.19 8. 79 .40 4.55 9 50 9.41 8. .58 .83 9.07 64 CHEDDAR CHEESE FROM PASTEURIZED MILK. Table 26.- -Comparison of ijield of raw and pasteurizcd-milk cheese afier curing for various lengths of time at Madison, Wis. — Continued. Weii,'ht of cured Time cheese per lUO Date cured after paraffin- pounds of milk. Gain by jiasteur- made. izalion. ing. Pasteur- ized. Raw. 1911. Days. Pounds. Pounds. Pounds. Per cent. July 3 51 9.06 8. 38 0.67 8.00 6 51 9.35 9.21 .14 1.52 June 1 55 9.59 9.49 .10 1.05 2 55 9 33 8.95 . 38 4.24 May 29 55 9.52 9. 05 .47 5.19 Apr. 25 56 9.62 9.07 .55 6.06- May 2 58 9. 32 9.06 .26 2.87 3 58 8.82 8.66 .16 1.84 Apr. 7 56 9.36 8.89 .47 5.28 May 25 62 9.19 8. 86 ..33 3.72 22 62 9.40 8.74 .66 7. .55 26 61 9.16 8.80 . 31; 4.09 27 61 9 38 8.9.5 .47 5.25 28 61 9.67 9.35 .32 3.42 19 66 9.66 8.90 .76 8.54 21 66 9.16 8.72 .44 5.05 Apr. 28 65 8.97 8.82 .15 1.70 27 65 8.78 8.10 .68 8.40 24 65 9.01 8.68 .33 3. 80 Mar. 10 68 9.10 8. So 25 2 82 21 68 9.15 8. 67 .48 5.53 20 68 9.15 8.74 .41 4.69 Apr. 17 72 9. 03 8.47 .56 6.61 18 72 8.81 8. 34 .47 5.63 Mar. 17 74 9.43 9.28 .15 1.62 16 74 9.72 9. ,55 .17 1.78 15 74 9.34 9. 06 .28 3.09 14 74 9.62 8.99 .63 7.01 14 74 9.37 8.53 .84 9. .84 Apr. 13 80 8.76 8.58 .18 2.09 11 80 8.98 8.74 .24 2.74 7 86 9.09 8.68 .41 4.72 5 8() 9.33 8.88 .45 5.07 Mar. 9 84 9.24 8.94 .,30 3.35 8 84 9.40 9.09 .31 3.41 7 84 9.39 9.13 .26 2.85 ■^ 84 9.24 9.02 .22 2.44 2 87 8.93 8. 64 .29 3. 35 1 87 8.97 8. K5 .12 1.35 Feb. 28 87 9.25 8.71 .54 6.20 27 87 9.28 8.78 .50 5.69 24 87 8.98 8.72 .26 2.98 Mar. 20 98 8.94 8. 62 .32 3.71 21 98 8.95 8.44 .51 6.04 22 98 8.91 8.69 .22 2. .53 17 104 9.20 9. 08 .12 1.32 16 104 9.51 9.35 .16 1.71 15 104 9 12 8.92 .20 2.24 14 104 9.41 8.83 ..58 6. 57 13 104 9.14 8.46 .68 8. 03 9 114 9.02 8.72 .30 3.44 8 114 9.14 8.88 .26 2.93 7 114 9.14 8.93 .21 2.35 3 114 9.06 8.8.5 .21 2.37 2 117 8.80 8.51 .29 3.41 1 117 8.86 8.75 .11 1.25 Feb. 28 117 9.12 8.63 .49 5.67 27 117 9.15 8. 69 .46 5.29 24 Ayerage.. 117 8.79 8.62 .17 1.97 9.289 8.907 .38 4.22 Cheese stored at New Orleans (lots IB to 4B). — Fifty-four days' make represented by 54 raw and 54 pasteurized-milk cheeses were shipped to New Orleans in four lots at different times during the season. These cheeses showed an increased yield for the new-process cheese, as compared with the old, in every case. The average figures for each lot are given in Table 27. CURING VARIOUS LENGTHS OF TIME. 65 Table 27.— Averciffc yield per 100 pound.'? of milk of raw and pasteurizcd-milk cheese cured at New Orleans. Method. Num- her of days' make. Yield 3f cheese per 100 pounds of milk. Lot No. (irecn. Paraf- fined. Ship- ped to New Or- leans. Re- ceived at New Or- leans. Stored one month. Stored two months. Re- ceived at Madi- son. (■Pasteurized 25 25 Pounds. 10.19 9.67 Pounds. 9.69 9.26 Pounds. 9.55 9.16 Pounds. 9.52 9.14 Pounds. 8.85 8.36 Pounds. 8.38 7.85 Pounds. 8.31 7 78 Raw IB Gain, pounds .52 5.37 .43 4.64 .39 4.25 .38 4.16 .49 5.86 .53 6.75 53 Gain, per cent ■ " 6 81 fPasteurized 9 9 9.83 9.45 9.40 9.08 9. .37 9.05 9.26 8.97 8.48 8.12 8 40 Raw 8 01 2B Gain, pounds .38 4 02 ..32 3.52 .32 3.54 .29 3.23 .36 4.43 39 Gain, per cent 4 87 fPasteurized 10 10 10.47 9.93 9.99 9.54 9.92 9.47 9.77 9.34 9 29 9 17 Raw 8. 69 1 8 55 3B Gain, pounds. . ... .54 5.44 .45 4.72 .45 4.75 .43 4.60 .60 ! 6.90 ...' 62 Gain, per cent 7 25 f Pasteurized 10 10 10. .38 9.69 9.92 9.31 9.83 9.24 9.78 9.19 8.94 8.71 Raw 8.28 8. 14 4B Gain, pounds .69 7.12 .61 6.55 ..59 6. .38 .59 6.42 .66 7.97 .57 Gain, per cent 7.00 Pasteurized 54 54 10.22 9.68 9.74 9.29 9.64 9.21 9.57 9.16 8.89 8.37 8.56 Raw 8.03 1-4B Gain, pounds .54 5. 58 .45 4.84 .43 4.67 .41 4.47 .52 6.21 .53 Gain, per cent 6.60 Amono; the four lots in Table 27, and in the siiminar}' at the bottom of the table, it will be seen that the percentage of gain in yield of pasteurized cheese over raw fell otT slowly as the green cheeses were paraffined and shipped, on the average from 5. 58 to 4.47 per cent. After these cheeses had been in storage at New Orleans for one month, the raw-milk cheeses were found to have slirunk more than the pasteurized in the majority of cases, raising the per- centage of gain in average yield of pasteurized cheese to 6.21 per cent. This was also observed in lot IB after the second month of storage, and is confirmed both by the weights taken in New Orleans by Mr. Bleecker and by the weights taken at ]\Iadison. It was expected that the past euri zed-milk cheese, containing slightly more moisture than the raw-milk cheese, would lose more in weight than the latter when stored at high temperatures. It was suri)rising to find that the reverse is true in most cases. The mean daily temperature at New Orleans, as reported by the United States Weather Bureau, varied from 71, the average for April, to 83, the average for June. It is hkely that the temperature of the cheese in the warehouse was somewhat higher than the average figures given above, because the warehouse, although well ventilated, 79994°— Bull. 165"13"^5 66 CHEDDAR CHEESE FROM PASTEURIZED MILK. was necessarily open more or less during the hot days and closed durhig the cool nights. Cheese cured at New Orleans and at Columbus, Ga. (lots 3G and 4^).— Forty cheeses, including 20 pasteurized and 20 raw, were shipped in two shipments for storage in the South through a firm * of cheese dealers in Chicago, who weighed the cheese, both before and after storage for one month. In the first shipment 1 cheese. No. 243-3, was lost in transit, and in the second shipment, 2 cheeses, Nos. 254-1 and 254C1, were damaged so that their weights are not included in the following summary. In the first shipment, according to the Chicago weights, 9 pasteurized-milk cheeses weighed 172^ pounds before storage and 162^ pounds afterwards. The loss, \Q\ pounds, is 5.94 per cent of the original weight. In the same shipment 10 raw-milk cheeses w^eighed 189^ pounds before shipment and 175 pounds afterwards. The loss here, 14^ pounds, is 7.53 per cent of the original w^eight. In the second shijjinent nine pasteurized-milk cheeses weighed 176| pounds before and 159f pounds after storage. The loss, 16f pounds, is 9.49 per cent of the original w^eight of the cheese. In the same shipment nine raw-milk cheeses weighed 161 pounds before and 144f pounds after storage. The loss in this case, 16^ pounds, is 10.09 per cent of the original weight. In both shipments the raw- milk cheese lost a greater per cent of their weight than the pasteurized- milk cheese. On comparing the individual cheeses in pairs, it was found that in most cases the pasteurized-milk cheese lost less than the raw-milk cheese, although in a few cases the reverse was true. The weights taken at Madison on the same lots of cheese gave the figures shown in Table 28, agreeing substantially with the results obtained at Chicago: Table 28. — Average yield per hundred pnund/i of milk o/raiv and pasteurized milk cheese cured in the South. Method. Number of days' make. Weight of cheese per 100 pounds of milk. Lot No. Green. Paraf- fined. Shipped from Madison. Received at Madison. 9 10 Pounds. 10.47 9.93 Pounds. 9.99 Pounds. 9.92 Pounds. 9.24 9.54 9. 4B 8. 68 3C .54 5.44 .45 4.72 .46 4.86 .56 6.44 Pasteurized Raw 9 9 40 10.38 9.69 9.92 9.31 9.84 9.24 8. S3 8.24 .69 7.12 .61 6.55 .60 6.49 .59 Gain percent 7.16 ' We arc indebted to Messrs. Crosby & Meyers for their kind cooperation in this work. CHEESE CUBED IN WARM ROOM. 67 Cheese cured in a warm mom (lots 3D and 4D). — To further test the effect of storage at high temperature 40 cheeses, lots 3D and 4D, were put for 47 days into a warm curing room at Madison where the temperature was hekl at 75° to 85°. Table 29.— Average ijicld per hundred pounds of milk of raw mid pasteurized milk cheese cured in warm room . Method. Number of days' make. Wei.^ht of pheese per 100 pounds of milk. Lot No. Green. Paraf- fined. Put in warm room. Taken out of warm room. f Pa,<;teuri7-eci in 9 Poundx. 10.47 9.93 Poundx. 9.99 9.54 Pound.x. 9.91 9.46 Pound.x. 9. .37 8.88 Raw 3D (Jain, pounds .54 5.44 .45 4.72 .45 4.75 .49 5. 52 Gain, per cent f Pasteurized 9 10 10.38 9.69 9.92 9.31 9.S,i 9.23 9. .33 8.73 Raw 4D Gain, pounds .69 7.12 .61 6.55 .62 6.72 .60 6.87 Gain, per cenl From these resuhs with eight lots of cheese — IB, 2B, 3B, 4B, 3C, 41', 3D, and 4D — it can be stated with certainty that pasteurized-milk chease does not lose more m weight than raw-milk cheese when stored m warm rooms or in the South, after parafTuiing. On the contrary, the pasteurized-milk cheese lost on the average a smaller percentage of weight in warm storage than the raw-milk cheese. At first this fact seemed iiiex])licable, but the reason became clearly apparent from inspection of the cheese kept in the warm curing room at Madison. Within a few days after going mto the warm room the raw-milk cheese became very greasy on the surface, and the grease running on to the shelves and the floor marked the spot where each cheese stood. The pasteurized-milk cheese, standing alongside of them on the same shelves, did not exude grease, or only very slightly in a few cases, and the difference between the greasy raw-milk cheese and the dry surface of the pasteurized-milk cheese was so marked that there was no difiicidty in picking out each kmd by the sense of touch alone. To demonstrate further the difference in this respect, each cheese of the last lot when put into the warm room was placed on a piece of wire gauze in a shallow tin pan, so that the grease running from each cheese could be collected. A very little of the paraihn was scraped from the surface of each cheese by contact with the wire gauze in the bottom of the pan. The total weight of material, practically all paraffin, collected from the 1 pasteurized-milk cheeses weighed 0.13 of a pound, while the material, mostly fat, with a little paraflin and mold, collected from the raw-milk cheeses, weighed 1.92 pounds, which is 1 .2 per cent of the weight of the raw cheese when placed in the store- room. 68 CHEDDAR CHEESE FROM PASTEURIZED MILK. At present we are unable to explain with certainty why the pasteur- ized-milk cheese should lose fat less readUy when stored at 70° to 80° than the raw-milk cheese. Further study will be made of this ])he- nomenon. The purpose of beginning these studies of losses of weight in warm rooms was to determme whether the mcreased yield obtamed by pasteurization would be offset by increased losses in weight when pasteurized-milk cheese are shipped to the South, and it is now fully demonstrated that the pasteurized-milk cheese stored in the South mamtain their advantage as to increased yield. Cheese flaced in cold storage at Waterloo, Wis. (Zoi -5 7i").- -The losses of weight observed in 35 pasteurized-milk cheeses put into cold storage ^ at 34° at different ages are shown in Table 30. The cheese represent seven days' make during July and August, 1911, Table 30. — Shrinkage of pasteurized-milk cheese in cold storage. Date, made. Cheese No. Weight, green. When paraffined. When put into cold storage. When taken out of cold storage. Total s 1 irinkage. Age. Weight. Age. Weight. Age. Weight. 19n. Pounds. Days. Pounds. Days. Pounds. Days. Pounds. Pounds. Per cent. July 19 264-1 20.60 9 19.60 m (') 100 18. 15 2.45 11.89 19 264-2 21.11 1 20.70 1 20.70 100 20. 38 .73 3.45 19 264-3 20.10 7 19.21 7 19.21 100 19.15 .95 4.72 19 264-4 21.07 9 20.05 14 20.04 100 19.85 1.22 5.79 19 264-5 19.89 9 18.90 28 18.70 100 18.28 1.61 8.09 19 264-6 20. 45 9 19.44 41 18. 95 100 18. 65 1.80 8.80 21 265-1 22.49 8 21.60 (2) (') 99 20.10 2.39 10.62 21 265-2 17.98 1 17.58 1 17.58 99 17. 45 ..53 2.94 21 265-3 20.21 7 19.35 7 19.35 99 19.25 .96 4.75 21 265-4 18.86 S 17.98 14 17.92 99 17.75 1.11 5.89 21 265-5 19.58 8 18.68 28 18.42 99 18. 05 1..53 7.81 21 265-6 19.25 8 18.40 28 18. 13 99 17.68 1.57 8.16 21 265-7 19.75 8 18.86 40 18.36 99 18.10 1.65 8.35 25 267-1 20. 82 11 19.86 (2) C') 95 18.50 2.32 11.14 25 267-2 20.29 1 19.95 1 19.95 95 19.80 .49 2.41 25 267-3 19.97 7 19.11 7 19.11 95 18.90 1.07 5.35 25 267-4 21.55 11 20.58 14 20. 58 95 20.38 1.17 5.43 25 267-5 20.23 11 19.25 29 18.98 95 18. 58 1.65 8.15 25 267-6 22.20 11 21.31 43 20. 62 95 20.25 1.95 8.78 27 269-1 18.70 9 17.80 (2) {■") 93 16.45 2.25 12.03 27 269-2 19.88 1 19.45 1 19.45 93 19.20 .68 3.42 27 269-3 19.85 7 19.01 7 19.01 93 18.95 .90 4.53 27 269-4 20.87 9 19.92 14 19.92 93 19.55 1.32 6.32 27 269-5 IS. 80 9 17.91 27 17.60 93 17.22 l.,58 8.40 27 269-6 20.22 9 19.22 41 18.61 93 18.25 1.97 9.74 Aug. 1 272-1 21.91 11 20. 65 m (2) 89 19.00 2.91 13.28 1 272-2 19.78 1 19.30 1 19.30 89 19.05 .73 3.69 1 272-3 19. 40 7 18.55 7 18. 55 89 18.22 1.18 6.08 1 272-4 21.82 11 20.55 14 20.55 89 20.25 1.57 7.19 1 27^5 21.80 11 20.57 29 20. 20 89 19.90 1.90 8.71 1 272-6 21.75 11 20.50- 46 19.75 89 19.50 2.25 10.34 1 276-1 19.90 11 18.63 (2) (') 81 17.20 2.70 13.66 8 276-2 20.42 1 19.98 1 19. 98 81 19.60 .82 4.01 8 276-3 20.44 7 19.50 7 19. .50 81 19.30 1.14 5.57 8 276-4 19.90 11 18.66 15 18. 63 81 18.40 1..50 7. .53 8 276-5 19.70 11 18. 45 28 18.21 81 17.75 1.95 9.89 22 22 283-1 283-2 20.10 19.90 1 19.50 67 67 18.10 19.38 2.00 .52 9.95 2.61 i' "ig.'so' 22 283-3 19.68 8 18.81 8 18.81 67 18.75 .93 4.72 22 283-4 18.80 11 17.90 15 17.70 67 17.40 1.40 7.44 22 283-5 19.84 11 18.84 29 18.62 67 18.45 1.39 7.00 22 283-6 18.65 11 17.62 42 (') 67 16.80 1.85 9.92 .SUMM.'lRY. No. ofch Age whei Average Bese 1 7 day. 1 7 week. 2 weeks. 4 we 7 eks. 6 w 6 eeks. 7 In cellar. 1 stored. total shrinkage, per cen t 3.22 5.10 6.51 8.29 9.29 11.78 1 1 In warehouse at Waterloo, Wis., by courtesy of the Roach & Seeber Co. 2 Cured in cellar. CAUSES OF INCREASED YIELD. 69 Altliough the seven cheeses put into storage at the age of 1 flay showed an average of only 3.22 per cent shrinkage after three months, yet they were not well hroken down and required further curing at 60° to 70° to get rid of their curdy, lumpy texture. The cheese I)araflincd and stored when 1 week old showed an average total shrinkage of 5.10 per cent, and these were found to be thoroughly broken down when taken out of cold storage. This series appears to indicate that the quality of pasteurized-milk cheese is not damaged by placing in cold storage at the age of 1 week, while the shrinkage (5.10 per cent) is about half that of the duplicate cheese, cured in the cellar at Madison (11.78 per cent), as shown at the bottom of the table. THE CAUSES OF THE INCREASED YIELD FROM PASTEURIZED MILK. THE LOSSES OF FAT FROM VAT AND PRESS. The increased yield of green cheese from pasteurized milk, amount- ing to over 5 ])er cent (Table 20), is due partly to the fact that about half of th(^ fat lost in the whey and drippings by the old pi'ocess is retained in the cheese by the new process of making. Also it is found that a little more moisture can safely be incorporated in the new-process cheese without danger of spoiling it, but on the contrary giving it a moist, fat a])pearance wliich consumers generally like. The loss of fat in the whey is caused j)artly by the passage of the cui'd kiiiv(>s through the curd in cutting, at which time a considerable })i-oj)ortion of fat is brushed away from the surface of the curd cubes. J)iu-ing the stirring and heating some further fat globules are lost from the ciu'd cubes, and still further losses occur after milling and during ])ressing. In the new j)rocess of making cheese from pasteur- ized milk the curd is so (irm and elastic (not brittle) at the time of cutting that the loss of fat in the whey averages only about one-half that observed in cheese making b}^ the ordinary process. The average fat content of whey from good clean milk is stated to be 0.30 per cent and from average cheese factory milk 0.36 per cent.* On a great many days during the past two and one-half years the milk supply in the receiving vat has been divided and one half made up by the regular methods and the other half by the new method. The quality and composition of the milk was thus the same in both vats. On the 24 days listed in Table 31 the average fat content of the whey from the i-egular vats was 0.25 per cent and from the pasteurized-milk vats was 0.159 per cent. » Van Slyke and Publow, loc. cit., pp. 1S9, 190. 70 CHEDDAE CHEESE FROM PASTEUEIZED MILK. Table 31. — Comparison of the percentage of fat in whey by new method and by regular method of cheese making. Date. Fat in milk. New method. Regular method. Weight of milk used. Fat in whey when drawn. Weight of milk used. Fat in whey when drawn. 1911. Per ct. Pounds. Per cent. Pounds. Per cent. Aug. 29 4.1 294A 0.14 290 0,17 30 3.6 344' .14 344 .26 Sept. 1 322 .15 320 .20 5 "'4.'6" 29U .17 292 .28 6 3.6 276 .19 276 .32 7 4.1 286^ .18 286i .32 8 292 .16 795 .26 1909. July 21 4.0 200 .15 200 .21 22 3.9 200 .12 200 .20 23 4.0 20(J .15 200 .19 24 4.0 200 .12 200 .22 Aug. 12 3.7 200 .16 200 .26 1908. July 18 4.1 200 .12 200 .22 Oct. 1 4.7 200 .20 200 .30 2 4.5 200 .18 200 .29 7 4.4 200 .14 200 .19 8 4.0 200 .15 200 .25 Sept. 1 4.3 200 .17 200 .32 2 4.2 200 .18 200 . .30 14 4.2 200 .18 200 .24 16 4.0 200 .13 200 .27 17 4.4 200 .19 200 .29 IS 4.4 200 .18 200 .25 19 A verage . . 4.2 200 .17 200 .23 .159 .25 In these cases the small amount of milk handled in each vat per- mitted hand stirring, and neither the rake nor the agitator was used. By tliis means the w^hey fat of the regular-process vats was kept at a lower figure, perhaps, than could have been done with large vats, as handled in a commercial factory using the regular process. On 22 days, using 1,200 to 2,000 pounds of pasteurized milk in each vat, the percentage of fat in the whey at the time of drawing the whey averaged 0.17 per cent, as shown in the following table. In these cases the vats were stirred with an agitator. Table 32. — Fat content of ivhey from pasteurized-milk cheese. Date. Fat in whey two hours after cutting. Weight of mUk handled. Weight of cheese. 1910. Per cent. Pounds. Pounds. May 25 0.14 1,234 139 26 .16 1,322 153 27 .18 1,337 144 June 1 .17 1.578 166 .12 2,061 226 7 .15 1,427 159 8 .14 1,431 158 9 .18 1,360 147 10 .17 1,448 162 CAUSES OF INCREASED YIELD. 71 Table 32. — Fat content of wlmj from pant e.iirized- milk cheese — OouLiuued. Date. Fat in whey two h .ur.-i alter cutting. Weight of milk handleti. Weight of c-hee.se. 1910. Juno 14 10 17 211 21 22 24 ■IS 2y 30 July r, () Average.. PcT cent. 0.21) .20 . .20 .20 . 23 .14 .10 .IS .24 . 14 .17 . US .14 Pounds. l.:i!)s 1,10.") 1,320 1 , ,")SS 1 , 202 1,347 1 . 320 1 , 337 1,277 1,210 1,243 1,242 1,229 Pounds. 148 120 152 170 144 144 139 139 130 130 131 125 134 .17 Most of tlio loss of fat from curd occurs at the moment of eutting, as shown by the tio;ur(>s in Table 33. On 23 (hiys samples of whey were taken chiily from the vat as soon after cutting as it was possible to obtain any clear whey that is, in four to six minutes. The fat content of this whey, sami)le(l five minutes after cutting, tested 0.47 per cent on tlie average of 23 days, Avhile the average test of samples taken from the sanu' vats two hours after cutting was 0.16 {)(>r cent. The average weight of milk handled (hiily in the vat was 1,110 pounds, and the average fat test of the milk was 4 per cent. Table 315. — Fat content of wliey at time ofcutti>i . 1',) 1,011 104 13 .40 .15 907 98 14 .40 . 14 1,045 lOS 15 .50 .12 1,001 100 IS .35 .13 993 103 19 . 55 . 22 900 97 22 .40 .10 lO,) 77 25 .42 . 19 1 , 005 117 20 . 52 .17 940 103 27 ..52 . 10 1,004 109 28 . 57 .15 972 102 29 .4.', . 14 790) 102 May 3 . 05 . 10 1 , 04 1 122 4 .07 . n; 1,0.55 118 . 17 1,119 129 . 50 .20 917 97 10 52 . 10 1 , 2SS 141 11 . .50 . 15 1,285 138 is , 35 .15 1 , 239 137 19 .40 . 14 1,180 130 23 .25 . 12 2, 477 208 24 Average.. .45 .19 1,454 154 .47 .16 1,110 119.8 72 CHEDDAR CHEESE FROM PASTEURIZED MILK. The reason for the decrease in percentage of fat in whey at two hours after cutting is tliat there was httle fat lost from the curd during the time the whey was being expelled, so that the fat lost from the curd cubes at the moment of cutting was diluted about 0.47 divided by 0.16 = 3 times by the water expelled from the curd during the two-hour period. Losses of fat after drawing the whey. — On several days the whey drippings from the pasteurized-milk curd, from the time the curd was all on the rack up to the time when it was taken from the press, were collected, weighed, and tested for fat. From this could be cal- culated the weight of fat lost in the drippings, as shown in Tables 34, 35, and 36: Table 3i.- Loss of fat in drippings in 2 hours new process is about 1.6 per cent of the weifrht of the cheese, as sliovvn in the following sumjnary of the ])rec(>(ling tables : 'J'Aiii.K 'M. —Total losses of fat in making W pounds of cheese from pasteurized milk. Whey when drawn Drippings from curd before inilhng. . . . Drippings from curd in vat after miUin; Drippings from press Total Total, weiglit. Fat content. Pounds. Per cent. Pound. 87.4 0. It; 0. 1400 2.01 .08 .0010 .31 1.00 .0051 .33 3.40 .115 90. 05 .1583 Lo.ss of fat from cheese. Per cell!. 1.400 .OJii .051 1.58o The average total loss of fat from 100 pouiuls of milk handled by the new process of clieese making is seen to be on the average 0.158 l)oiinds of fat, or a little less than 4 })er cent of the total fat content of milk containing 4 per cent fat. The loss of fat from 100 j)oiinds of milk in ordinary cJieese making under average factory coiulitions has been found to amount to 0..38 of a ])ound of fat, or 0.36 per cent of fat in the whey, or 9 ])er cent of the total fat content of the milk.' It wdll be seen from these figures that the loss of fat is reduced to less than one-half by the new process of cheese making. It might be expected from tliis statement that each day's make of pasteurized- milk cheese tested by the Babcock test would show a higher percentage of fat than the sani(> day's raw-milk cheese. In Table 38, however, it is seen that in 15 cases out of 21 the pasteurized-milk cheese tested lower in fat (0.65 per cent lower on the average) than the raw-milk cheese. THE INCREASED MOISTURE CONTENT OF PASTEURIZED-MILK CHEESE. Tliis is due to the fact that there is an increased content of moisture as well as of fat in the new-])rocess cheese, and in most cases the in- crease of moisture is m-eater than the increase of fat. On this Van Slyke and Publow, loc. eit., p. 189. CHEDDAE CHEESE FROM PASTEURIZED MILK. account the moisture content of pasteurized cheese listed in the table below is greater than that of the raw-milk cheese in 29 cases out of 33, and the average percentage was 1.68 greater. The cheeses listed in the table were the same as those in Table 26, and the testing for fat and moisture was done immediately after the last weights had been taken for the determination of yield and shruikage. The samples of cheese weighed into the Babcock test bottles were rapidly dissolved in a mixture of hot water and sul- phuric acid, as suggested by one of us in a previous paper.' Table 38. — Comparison of the fat and moisture content of raw and pasteurized milk cheese cured at Madison. Date. Moisture content of cheese. Fat content of cheese. Pasteur- ized. Kaw. Ditt'erence. Pasteur- ized. Raw. Dilference. 1911. Feb. 24 27 28 Mar. 1 •> 3 8 9 10 13 14 15 Ui 17 20 21 22 Apr. 5 7 11 13 17 18 24 27 28 May 2 3 8 10 15 17 Average. . Per ct. 30.50 33.55 32.52 32. 55 31.00 31.05 31.90 32. 37 32. 77 32. 45 33. 15 33.51 31.02 33. 40 34. 15 32. 72 32.90 34. 00 34.10 34. 52 32.90 31.78 33.47 33.55 32.28 31.80 34.17 32.03 31.02 32. 87 31.05 33. 47 31.87 Per ct. 30. 15 30.15 30.05 31.25 30.75 31.47 29.75 30. 17 31.32 31.45 30.00 31.95 30.90 30. S7 33. 22 31.58 30.10 32.20 32. 25 31.92 31.97 30.17 31. 55 30.15 32. 68 32.70 33.22 31.25 30.87 31.05 30. 45 32.25 32.58 + Perct. 0.35 3.40 2.47 1.30 .85 -Per ct. Per ct. 38.86 Per ct. 39.10 —Perct. 0.24 + Per ct. 0.42 2.15 2.20 1.45 1.00 3. 15 1.56 .72 2.53 .93 1.14 2.80 1.80 1.85 2. 00 .93 1.01 1.92 3.40 37.44 37.99 38.01 38. 10 38.16 38.04 . 72 !l7 57 38. 28 38.01 38.01 38.36 38. 39 37.97 .08 !o4 36.93 36. 56 37.09 36.85 . 16 .29 36.84 36.81 38.22 39.18 38.64 37.93 39. 55 40.68 37. 97 39.28 37.97 38.10 37. 02 37.94 39.95 38.86 38.66 39. 08 40.68 41.43 39. 06 39.27 38. 06 37.67 . 18 1.13 1.73 .40 .90 .32 .02 1. 15 1.13 .75 1.09 .95 1.38 .15 1.82 1.20 1.22 .01 .69 .71 .43 32. 69 31.28 1.68 .61 38.21 38.59 .65 .26 The combined effect upon the percentage composition of cheese caused by increasing both the fat and moisture content is shown in the following example : Ten pounds of raw-milk cheese of the same average percentage composition as in Table 38, as shown at I, below, would contain the weights of fat, moisture, and casein, etc., shown at II. If by pas- teurization the fat content of the cheese is increased about 4 })er cent of itself, and the moisture content is increased about 12^ per cent of itself, there will be obtained 10.54 pounds of pasteurized-milk cheese 1 Sammis, J. L. The determination of fat in cheese by the Babcock test. Engineering Chemistry, vol. 1, no. 8, p. 604. Easton, Pa., -Vug., 1909. Journal of Industrial and QUALITY OF PASTEURIZED-MILK CHEESE. 75 as shown at III instead of 10 pounds of raw-milk cheese, a theoretical gain of 5.4 per cent in the >-ield of cheese. (The actual gani shown in Table 20 was 5.37 per cent.) The percentage composition of this ])asteurized cheese will be as shown at IV, which agi'ees closely with tlie average conij)()sition of tJie pasteurized-milk cheese shown at the bottom of Table 38. I- 11. III. IV. Fat 38.59 per cent. 3.859 pounds+0. 154 pounds=4.013 pounda. 38.07 per cent- MuLsture. . 31.28 per cent. 3.128 pounds f 0.391 pounds=3.519 pounds. 33.37 per cent. Casein, etc. 30.13 per cent. 3.013 pounds-)- .... pouuds=3.013 pounds. 28.57 per cent. 100.00 per cent. 10.000 pounds. 10.545 pounds. 100.00 per cent. The increased moisture content of pasteurized-milk cheese made by this process is due to the effect of pasteui'ization on the properties of curd, as stated on page 25. THE QUALITY OF PASTEURIZED-MILK CHEESE, SCORES AND CRITICISMS OP I'A.STEURIZED AND R.VW MILK CHEESE. The milk supply u.sed at Madison is no better than the average cheese-factory milk. Sunday's milk is delivered on Monday tlu-ough- out the year and is therefore inferior to that of the other days. Cheese from every day's make dining the season was scored by two judges, Mr. U. S. Bacr, assistant dairy and food commissioner of the State of Wisconsin, and Mr. A. T. Bruhn, junior dairyman. United States De})artinent of Agriculture, who during the past year have scored the cheese sent to the monthly scoring exhibition, conducted by the Wisconsin Experiment Station. The judges worked independently and pinned their scor(vsheets to each cheese without knowing even the immbers of the cheese, which were turned toward the wall. Their scores show close agreement with each other in most cases and leave no doubt as to the relative quality of the cheese scored. After linishing about 20 of the cheeses, they turned them around and added the cheese numbers to the sheets. In general, a score of 92 or above indicates that the cheese is of good quality and salable at full market ]jrice. A cheese scored l)ek)W 92 is likely to be cut in price in a dull market. Tallies 39 to 46 show the .scores of both judges as well as the average scones, which latter are used in the discu.ssion. Raw-milk cheese is in all (lases indicated by the letter C attached to the serial number. CHEESE CURED AT MADISON AT NORMAL TEMPER.\TURB. Lots lA, 2A, SA, and 4^.— These lots include 53 pairs of cheese cured in the cellar at Madison. The temperature of the curing room showed daily about 3° to 5° ditference between maxmuim and mini- mum and ranged from 60° to 73° from February to July, 1911. By opening the windows at night only, it was kept at 60" to 70" from July to October. 76 CHEDDAR CHEESE FROM PASTEURIZED MILK. The scores of the 53 pairs of cheese are as shown in Table 39. The average score of all the pasteurized-milk cheese is 92.75 and of the raw-milk cheese 89.09. Table 39. — iScores of 53 pairs of raw and pasteurized cheese {lots lA, 2 A, SA, and 4A) cured at Madison. LOTS lA AND 2A, SCORED JULY 17, IQU. Tem- Scored by U. S. Baer. Scored by A. T. Bruhn. Average pera- ture of Date Cheese curing room sa. m. made. No.i Fla- vor. Tex- ture. Total. Flavor. Tex- ture. Total. Flavor. Tex- ture. Total. °F. 1911. Feb. 24 172 41.0 26.0 92.0 40.0 20.5 91.5 40.50 20.25 91.75 24 1720 37.0 27.0 89.0 38.0 27.0 90.0 37.50 27.00 89.50 27 173 43.0 28.5 96.5 42.5 28.0 95.5 42.75 28.25 96.00 27 173C 38.0 27.0 90.0 40.0 27.0 92.0 39.00 27.00 91.00 28 174 41.0 27.0 93.0 41.0 27.5 93.5 41.00 27.25 93.25 28 1740 39.0 26.0 90.0 39.0 26.5 90.5 39.00 26.25 90.25 Mar. 1 175 41.0 27.0 93.0 40.0 26.0 91.0 40.50 20.50 92.00 1 1750 40.0 26.0 91.0 40.0 26.5 91.5 40.00 20.25 91.25 2 170 40.0 28.0 93.0 41.0 27.0 93.0 40.50 27.50 93.00 2 17C0 37.0 27.0 89.0 39.0 27.0 91.0 38.00 27.00 90.00 3 177 40.0 27.0 92.0 40.0 26.5 91.5 40.00 26.75 91.75 3 1770 38.0 26.0 89.0 38.0 26.0 89.0 38.00 26.00 89.00 7 178 40.0 26.0 91.0 40.0 27.0 92.0 40.00 26.50 91.50 ( 1780 38.0 27.0 90.0 39.0 27.0 91.0 38.50 27.00 90.50 8 179 40.0 27.0 92.0 41.0 27.5 93.5 40.50 27.25 92.75 8 1790 35.0 26.0 86.0 38.0 26.0 89.0 36.50 26.00 87.50 9 180 41.0 26.0 92.0 41.0 27.0 93.0 41.00 26.50 92.50 9 ISOO 39.0 26.0 90.0 40.5 26.5 92.0 39.75 26.25 91.00 11) 181 41.0 26.0 92.0 42.0 27.0 94.0 41.50 26. 50 93.00 10 1810 38.0 27.0 90.0 39.0 20.5 90.5 38.50 26.75 90.25 13 182 40.0 27.0 92. 41.0 27.0 93.0 40.50 27.00 92.50 13 182(; 41.0 26.0 92.0 40.0 27.0 92.0 40.50 26. 50 92.00 14 183 40.0 26.0 91.0 40.0 26.5 91.5 40.00 26. 25 91.25 14 1830 40.0 27.0 92.0 40.0 26.5 91.5 40.00 26. 75 91.75 15 184 40.0 26.0 91.0 41.0 27.0 93.0 40.50 26.50 92.00 15 1S40 40.0 27.0 92.0 41.5 27.0 93.5 40. 75 27.00 92.75 (iO 10 1S5 40.0 26.0 91.0 41.5 27.0 93.5 40.75 26.50 92. 25 10 1S50 35.0 26.0 86.0 41.0 27.0 93.0 38.00 26.50 89.50 02 17 180 42.0 28.0 95.0 41.0 26.5 92.5 41.50 27.25 93. 75 17 ISOO 41.0 28.0 94.0 41.0 27.0 93.0 41.00 27.50 93.50 03 20 187 43.0 27.0 95.0 41.0 26.0 92.0 42.00 26.50 93.50 20 1870 35.0 25.0 85.0 39.0 26.5 90.5 37.00 25.75 87.75 00 21 188 43.0 28.0 96.0 41.0 27.0 93.0 42.00 27.50 94. 50 21 1880 38.0 26.0 89.0 40.0 27.0 92.0 39. 00 26.50 90.50 00 22 189 43.0 27.0 95.0 42.0 28.0 95.0 42.50 27.50 95.00 99 1890 39.0 27.0 91.0 40.0 27.0 92.0 39.50 27.00 91.50 02 Apr. 5 198 43.0 27.0 95.0 42.0 28.0 95.0 42.50 27.50 95.00 5 1980 41.0 27.0 93.0 41.5 28.0 94.5 41.25 27.50 93. 75 7 200 42.0 27.0 94.0 42.0 27.0 94.0 42.00 27.00 94.00 04 7 200O 35.0 25.0 .8.5.0 40.0 20.0 91.0 37.50 25. 50 88.00 11 202 42.0 26.0 93.0 42.5 27.0 94.5 42.25 26. 50 93.75 11 2020 39.0 26.0 90.0 40.0 27.0 92.0 39.50 26. 50 91.00 13 204 41.0 27.0 93.0 42.0 28.0 95.0 41.50 27.50 94.00 13 204O 39.0 26.0 90.0 40.0 27.0 92.0 39.50 26. 50 91.00 17 200 41.0 27.0 93.0 41.0 27.0 93.0 41.00 27.00 93.00 17 200O 40.0 25.0 90.0 38.0 25.0 87.0 39.00 25.00 88.50 IS 207 43.0 20. 94.0 41.5 27.0 93.5 42. 25 20. .50 93.75 IS 207O 42.0 25.0 92.0 40.0 25.0 90.0 41.00 25.00 91.00 24 211 43.0 20.0 94.0 42.0 27.0 94.0 42.50 26. 50 94.00 24 2110 .39.0 25.0 89.0 39.0 27.0 91.0 39.00 26.00 90.00 27 214 40.0 25.0 90.0 42.5 27.0 94.5 41.25 20. 00 92. 25 27 2140 37.0 24.0 86.0 37.0 26.0 88.0 37.00 25.00 87.00 28 215 42.0 27.0 94.0 42.0 27.0 94.0 42.00 27.00 94.00 (iO 28 2150 37.0 25.0 87.0 38.0 26.0 89.0 37.50 25.50 88. 00 May 2 210 41.0 20,0 92.0 40.5 26.0 91.5 40.75 26. 00 91.75 AS 9 210O 37.0 25.0 87.0 .38. 26.0 89.0 37.50 25.50 88.00 3 217 42.0 28.0 95.0 41.5 27.0 93.5 41.75 27.50 94.25 (;2 3 2170 37.0 25.0 87.0 40.0 26.0 91.0 38.50 25.50 .89. 00 S 220 41.0 27.0 93.0 42.0 27.0 94.0 41.50 27. 00 93. 50 02 s 2200 34.0 25.0 84.0 39.0 25.0 89.0 30. 50 25.00 86.50 10 222 40.0 25.0 90.0 40.0 27.0 92.0 40.00 26.00 91.00 03 10 2220 37.0 25.0 87.0 40.0 20.0 91.0 38.50 25.50 89.00 1.1 225 40.0 20.0 91.0 42.0 28.0 95.0 41.00 27.00 93. 00 04 15 2250 38.0 26.0 89.0 39.0 27.0 91.0 38. 50 20. 50 90.00 17 227 41.0 20.0 92.0 41.0 27.0 93.0 41.00 26. 50 92. 50 07 17 2270 35.0 24.0 84.0 37.0 25.0 87.0 36.00 24.50 85.50 'C" in this column indicates raw-milk cheese. QUALITY OF PASTEURIZED-MILK CHEESE. 77 Table 39.— Scores of 53 pairs of raw and pasteurized cheese (lots lA, 2 A. 3 A. and 4 A) cured at Madison — Continued. LOT 3a, scored august 14, 1911. Tem- pera- ture of curing reom 8 a. m. Pale made. Cheese No.i Scored by U. S. Baer. , Scored by A. T. Briihn. Average. Fla- vor. Te.v- ture . Total. Flavor. Tex- ture. Total. Flavor. Tex- ture. Total. 'F. 67 66" 66' 66" 66" 76' 6S' 66' 66 1911. Mav 22 22 2.5 2.5 29 29 June 1 1 2 2 7 7 9 9 13 13 15 15 16 16 230 230C 233 2.33C 234 234C 237 237C 238 238C 240 240C 242 242C 243 2430 245 2450 246 2460 43.0 40.0 41.0 .38.0 42.0 39.0 42.0 35.0 40.0 37.0 40.0 33.0 39.0 39.0 40.0 .38. 41.0 37.0 40.0 40.0 27.0 26.0 25.0 25.0 27.0 25.0 27.0 25.0 26.0 26.0 27.0 25.0 27.0 26.0 27.0 25.0 27.0 26.0 27.0 26.0 a5.o 91.0 91.0 88.0 94.0 89.0 94.0 85.0 91.0 88.0 92.0 83.0 91.0 90.0 92.0 88. 93.0 88.0 92.0 91.0 41.5 37.0 41.0 36. 42.0 .37.0 41.0 38.0 41.0 37.0 41.0 37.0 41.5 .38.0 41.0 .38.0 41.5 40.0 40.0 39.0 26.5 25.0 26.0 25.0 27.0 25.0 26.5 26.0 26.5 25. 5 26.0 26.0 26.0 26.0 26.0 25.0 27.0 26. 26. 27.0 93.0 87.0 92.0 86.0 94.0 87.0 92.5 89.0 92.5 87.5 92.0 88.0 92.5 89.0 92.0 88.0 93.5 91.0 91.0 91.0 42.25 38.50 41.00 37. 00 42.00 38.00 41.50 36. 50 40.50 37.00 40. 50 35.00 40.25 38.50 40.50 38. 00 41.25 23. .50 40.00 39.50 26.75 25.50 25.50 25.00 27.00 25.00 26.75 25.00 26. 2,5 25.75 26. ,50 25., 50 26. .50 26.00 26. 50 25. 00 27. 00 26. 00 26. 50 26.50 94.00 89.00 91.50 87.00 94.00 S8.00 93. 25 87.00 91.75 87.75 92.00 85., 50 91.75 89.50 92. 00 SS.OO 93. 25 89.. 50 91.. 50 91.00 LOT 4A, scored SEPTEMBER 18, 1911. 68 June 19 19 68 21 21 70 26 26 70 27 27 70 28 28 72 July 3 3 72 8 8 73 10 10 73 11 11 72 V2 ]9 248 2480 250 2500 253 2530 254 254C 255 2.550 258 2580 260 260C^ 261 2610 262 2620 263 2630 42.0 40.5 40.0 37.0 37.0 35.0 41.0 3/.0 41.0 35.0 40.0 35.0 41.0 37.0 40.0 ,38. 41.0 37.0 40.0 35.0 27.0 94.0 42.0 27.0 94.0 42.00 27.00 94.00 26. 91.5 40.0 26.5 91.5 40.25 26. 25 91.. 50 26.0 91.0 41.0 26. 5 02.5 40. 50 26. 25 91.75 25.0 87.0 .38. 2,5.0 88. ,37.50 25.00 87.. 50 25.0 87.0 ,39.0 25.0 89.0 38.00 25.00 88. 00 2,5.0 85.0 ,35. 26. 86.0 35.00 25.. 50 85.50 27.0 93.0 41.0 27.0 93.0 41.00 27.00 93.00 26.0 88. ,37.0 26.0 88.0 37.00 26.00 88. 00 27.0 93.0 41.0 27.0 93.0 41.00 27.00 93.00 25.0 85.0 37.0 25. 5 87.5 36.00 25.25 86. 25 27.0 92.0 40.5 26.5 92.0 40.25 26.75 92.00 2.5.0 85.0 35.0 25.0 8,5.0 35.00 25.00 85.00 27.0 93.0 41.0 26.5 92.5 41.00 26.75 92. 75 2,5.0 87.0 36.0 25.0 86.0 36. 50 25.00 86. .50 25.0 90.0 ,39. 5 26.0 90.5 39. 75 25., 50 90.25 27.0 90.0 ,38.0 27.0 90.0 38. 00 27.00 90.00 27.0 93.0 41.0 26.5 92.5 41.00 26.75 92.75 26.0 88.0 37.0 25.5 87. 5 37.00 25.75 87.75 26.0 91.0 40.0 26.0 91.0 40.00 26.00 91.00 26.0 86.0 35.0 26.0 86.0 35.00 26.00 86.00 ' "0'" in this column indicates raw-milk cheese. In 51 cases out of the 53 in the table the pasteiirized-milk cheese received a hio:her averacje total score than the raw-milk cheese; but in two cases the i-aw-milk cheese scored one-fourth to one- half a point hit^her (Xos. 183 and 184). In the 51 cases just mentioned the differences in total score between pasteurized and raw milk cheese ranged from one-fourth of a j-yoint to 7 points and averaged 3.82 points. In four-fifths of these cas-^s the difference in the score was over 2 points. In 49 of the 53 raw-milk cheeses the average score was below 92, while 39 of the 53 pasteurized-milk cheeses scored 92 or above. The distribution of the scores in each case is most clearly shown in figure 3. 78 CHEDDAR CHEESE FROM PASTEURIZED MILK. PA{STEUP/ZEO-M/LK CHESTSE >•: ••• •••• •• It can readily be seen from figure 3 that 94 per cent (50 out of 53) of the pasteurized cheese scores lie between 91 and 95, a range of 4 points, wliile the same proportion (94 per cent) of the raw-milk cheese scores are quite uniformly distributed between 85 and 92, a range of 7 points. The variation in (piality of j)roduct from day to day is thus reduced nearly one -half by the new process. In scoring all of these cheeses the color and make-up were al- ways marked per- fect, and the cheeses were marked oft' only on flavor and texture. It is of in- terest therefore to consider the flavor and texture scores separately, in addition to the discussion of total scores given above. The average flavor score for all of the pasteurized cheese is 41.05 and for the raw-milk cheese 38.13. In 50 cases out of 53 the pas- teurized-milk cheese has a higher average flavor score than the raw, in 2 cases the scores are ec^ual, and in 1 case the pasteurized cheese is one-fourth point less than the raw. In the 50 cases RAW-M/L/< CMETESE: ! : i« as 86 87 ee 89 90 9/ 9a 93 9^ 9S 96 Fig. 3. — Distribution of total scores of pasteurized and raw miiic clieese. P/iSr£U/?/2r£D''/^/^/t' CHeBSS •••• • • • {• ••• •• ••• just mentioned the difference in the fla- vor score between the two makes of cheese ranged from 0.50 to 5.50 points, averaging 3.1 points. The difference was equal to or greater than 1.25 points in 47 out of the 50 cases, showing that the improvement in flavor through pas- teurization was not only unquestionable, but also consistent. In 51 out of the 53 cases the pasteurized-milk cheese scored 40 or above for flavor, while 45 out of the 53 raw-milk cheese scored below 40 for flavor. Figure 4 shows that 94 per cent (50 out of 53) of the pasteurized cheese flavor scores lie between 40 and 42|^, a range of 2\ points; while the raw-milk cheese flavor scores are cjuite evenly distributed ; : : • • • • • • : : i : • • • •••••••• 36 37 33 39 ^W -^ ^2 43 Fig. 4.— Distribution of flavor scores of pasteurized and raw milk cheese. PASriEUR/Z£:D-M/L/CCH££S£\ • • • t • • • • • •••••• • •••••• /^AW-M/LH' CH£ES£ • : : : : : : : 3 2-? 2S 26 27 CHEESE CURED IX THE SOUTH. 79 over a raiifje of 5 ])oints (from l^f) to 40 or 41). The raiitjje of vuiia- tion is thus twice as orroat in the raw as it is in the pasteurized, show- ing that the (hiily variation of flavor is reducetl about one-lialf by the new })ro('ess. The averag<' texture seoi-es show also some advantage for the new- process cheese. The averag<' texture score on all of the pasteurized- milk cheese was 26.70, and on the raw-milk cheese 25. OB. In 40 cases out of 53 the pasteurized che(>se scored liiglier than the raw, in five cases the scores were equal, and in 8 cas(>s the pasteurized cheese scored 0.25 to 1.5 points (average 0.59 point) Iowcm- than the raw. Among the 40 cases just mentioned, tlu^ difrerences in t(\xture score between the two makes ranged from 0.25 to 2 points, and averaged 1.09 points. Figure 5 shows that 90 per cent (48 out of 53) of the pasteurized- milk cheese texture scores lie between 26 and 27.50. a range of 1.50 points; wliile 94 per cent (50 out of 53) of the raw-milk cheese scores are quite evenly distributed l)etween 25 and 27, a range of 2 points, a distinct advantage^ in favor of the new })rocess, both as to quality and uniformity of texture. CHEESE CUKEl) IN THE SOUTH. Lot 75.— Foui- lots of cheese, lots IB, 2B, 3B, and 4B, were sliipped to New Orleans for storage, the first lot for two months and the other three for one month. Lot IB consisted of 25 pairs of cheese wliich were made on 25 days between February 23 and April 18, at Madison, and sliipped to New Orleans April 29, arriving May 9. They were stored theie until July 3, and then shipped back to Madison where they were scored sepa- rately on July 17, 1911, by Messrs. U. S. Baer and A. T. Brulm. The temperatures at New Orleans given below are taken from the United States Weather Bureau monthly meteorological sunnnaries. The average daily mean for May was 75.8°, with temperature on different days varying from 60 to 96. For June the average daily mean was 83^2°, with temperature on different days varying from 70 to 98. The quality of both the raw an(l pasteurized cheese after returning from New ()rleans was very poor, as shown by the scores of the judges and by letters from dealers to whom they were afterwards sold at a Fig. 0. — Distrituition of toxture scores of pasteurizod and raw milk clU'OSO. 80 CHEDDAR CHEESE FROM PASTEURIZED MILK. reduced price. The average score of the 25 pasteurized-milk cheeses was 85.10 and of the 25 raw-milk cheeses 83.34, a difference of 1.76 points. In 17 cases out of 25 the pasteurized-milk cheese scored higher, in 3 cases equal to, and in 5 cases less than the raw-milk cheese. (See Table 40.) The highest average score given to any cheese in the lot was 90.5 and the lowest 78.50. The scores are shown in Table 40. Table 40. — Scores of 25 pairs of raw and pasteurized cheeses {lot IB) cured for two months at Neiv Orleans. Total Total AveraKe total Date made. Cheese No.' score (U. S. score (A.T. Baer). Bruhn). score. 1911. Feb. 23 171 82 SO 81 23 1710 87 87 S7 24 172 83 79 SI 24 172C 8.5 81 S3 27 173 87 90 SS.5 27 173C 8.5 86 8,5.5 28 174 90 S.5 87.5 28 174C 83 8.5 84 Mar. 1 175 86 S7 86. 5 1 1750 83 84 83.5 2 176 86 88 87 2 1760 83 84 83.5 3 177 88 84 86 3 1770 88 8.5 86.5 7 178 86 86 86 7 1780 86 8.5 8,5.5 S 179 91 90 90.5 8 1790 85 S3 S4 9 ISO 86 SS 87 9 ISOO a5 8,5 85 10 ISl 90 SS 89 JO 1810 85 8,5 85 13 182 SO SO 80 13 1820 80 SO 80 14 183 79 79 79 14 1830 87 84 &5.5 15 184 8,5 84 84.5 15 1840 8.5 82 83.5 16 185 85 89 87 16 1850 85 S.5 85 17 186 80 80 SO 17 1860 80 80 80 20 187 79 80 79.5 20 1870 79 80 79.5 21 188 77 80 78.5 21 1880 80 80 80 22 189 86 83 84.5 22 1890 80 80 SO Apr. 5 198 92 89 90.5 5 1980 89 81 85 7 200 86 87 86.5 7 200O 82 85 8.3.5 202 85 88 86.5 2020 83 84 8.3.5 204 89 87 88 204O 84 84 84 206 89 86 87.5 206O 83 81 82 18 207 85 86 8,5.5 18 207O 83 84 83.5 i <' C" in this column indicates raw-milk cheese. CHEESE CURED IX THE SOUTH. 81 It can be seen that storage lor so long a period as Uvo months in New Orleans, at. such teraperatnres, can not be i)racticed with either raw or pasteurized cheese without great loss of quahty; and that of the two lots, the pasteurized was somewhat the better when taken out of storage. On account of the unmarketable quahty of both lots of cheese when scored it appears unnecessary to give the detailed score and criticisms as to flavor and texture. Lots 2B, SB, and 4B. — These lots were stored at New Orleans for one month each during parts of June, July, August, and Sei)teml)er, 1911 . The mean daily tempera tm-e during this jx'riod averaged 83.2° for June, 80.2° for July, 81 .8° for August, and 82.6° for September. In lot 2B the 9 pasteurized-milk cheeses received an average total scoi-e of 90.44, and the raw-milk cheese of 85.56. The pasteurized was better in every case, and on the av(M'age 4.88 ])oints better. PASrEU/?/ZEO-M/L/< CHEESE^ X • • • : : • : ::::;•::: • * • • ••• • • RA{A/-A7/L/< CHEESE • • • • • • • •• ••• • • • • • • • • • • • • • 77 78 79 80 81 82 83 8f 85 86 87 88 89 90 91 92 93 l''!i;. ii.--l)i.stril.)Uliiiii of tcital scores of pastctiriziMl and raw milk clict'sc. In lot 3B the 10 piisteurized-milk cheeses scored the highest in every case, the average being 7.7 i)oints higher. The average score of the pasteurized was 90.30, and of the raw 82.60. In lot 4B the 10 pasteurized-milk cheeses scored th(>, highest in every case but one, and averaged 85.62, while the 10 raw-milk cheeses averaged 82.10, a difference of 3.52 points. From the results shown in Tables 40 and 41 and in ligure 6, it is clear that after storage in the South the pasteurized-milk cheese came out better in quality than the raw-milk cheese made from the same milk. It is not intended to suggest that cheese could be shipped to the Southern States with the exi)ress intention of storing it for one month before it is sold, but it is clear that during the few days or Weeks necessarily elapsing after market cheese reaches its destination in the South and before it is eaten, the pasteurized-milk cheese is less likely to undergo serious deterioration than the raw-milk cheese. 79994°— Bull. 165—13 tj 82 CHEDDAR CHEESE FROM PASTEURIZED MILK. Table 42. — Scores of 29 pairs of raw and pasteurized cheeses {lots JB, 3B, and 4B) cured for one month at New Orleans. LOT 2B, SCORED JULY 17, 1911, AT MADISON. Date made. Mean tempera- ture at New Orleans. Cheese No.i Total score (U.S. Baer). Total score (A. T. Bruhn). Averas;e total score. 1911. Apr. 24 24 27 27 28 28 May 2 2 3 3 :^ in in 15 15 17 17 'F. 46 211 2110 214 2140 215 215C 216 2160 217 2170 220 220O 222 2220 225 2250 227 2270 90 8.5 92 85 93 85 90 85 91 8.5 90 85 92 88 89 87 92 86 88 86 90 86 90 84 88 86 89 8.5 87 58 , 94 87 91 85 92 85 89 85.5 91 &5.5 91.5 84.5 89 8,5.5 90.0 8,5 88,5 85 93 87.5 90 86 92 85.5 CO 55 66 m 71 73 76 76 LOT 3B, SCORED AUG. 14, 1911, AT MADISON. May 22 22 25 25 29 29 June 1 1 2 2 7 9 9 13 13 15 15 16 16 78 230 2.300 233 2330 234 2340 237 2370 238 2380 240 2400 242 2420 243 2430 245 2450 246 2461' 89 83 90 79 91 S3 91 SO 91 8.5 92 80 93 82 92 86 90 87 89 86 SS 84 88 80 99 82 90 81 90 82 89 79 92,5 SI 90,5 85 91 85 89 S2 88.5 83. 5 89 79.5 90. 5 82. 5 90. 5 .80. 5 90.5 83. 5 90. 5 79.5 92. 75 SI. 5 91.25 ,8,5. 5 90.5 86 89 84 82 S4 '.86 8j 8 i 87 88 88 86 LOT 4B, SCORED SEPT. 18, 1911, AT MADISON. June 19 19 21 21 26 26 27 27 28 28 Julv 3 3 8 8 10 10 11 11 12 12 76 248 2480 250 2500 2.53 2530 2,54 2540 255 2550 258 2580 260 260O 261 2610 262 2620 263 2630 88,5 83 81 85 87 87 89 76 80 78 8.5 82 88 86 62 79 90 a5 87 80 87 8.5 82 8,5 88 85 89 78 80 S>i 85 88 83 80 78 89 8,5 86 80 87,75 84 81.5 85 87.5 86 89 77 80 77.5 .85.5 83.5 88 84.5 81 78.5 89.5 85 86.5 80 74 80 82 80 82 79 82 82 79 » "0" indicates raw-milk cheese. CHEESE CURED IN THE SOUTH. 83 Lots 30 and J^C. — These two additional lots were stored for one month in the South and subsequently scored at Madison. In lot 3C the 10 pasteurized cheeses averaged 91 and the 10 raw-milk cheeses 84.85, as shown in Table 42. In every case the pasteurized cheese scored higher than the raw. In Lot 4C, the 10 pasteurized averaged 87.82 in total score, and the 10 raw-milk cheeses, 85.07, and in every case but one the pasteurized scored higher than the raw. All but two of these 40 cheeses scored below 92 and most of them were unsalable at full ])rice, after storage as described. The temperature inside of the storage warehouse was not recorded. Table 42. — Scores of 20 pairs of raw and pasteurized milk cheese (lots SC and 4C) stored one month in the South and scored at Madison. LOT 3c, STORED ONE MONTH AT COLUMBUS, GA., AND SCORKD AT MADISON, AUG. 14, IQU. Date made. Cheese No.' Total spore (O. s. Baer). Total score (A.T. Bruhn). Averagp total score. 19U. Apr. 22 2.'!0 00 90 90 22 ZiOr S7 8ti Sf>. 5 25 233 90 89J 89. 75 25 2330 85 84 84. 5 29 234 94 94 94 29 2340 91 87 89 JUTIP 1 237 92 89 90. a 1 237(^ 85 83 84 2 238 90 91 iK). 5 2 2380 84 S5 84. 5 7 240 92 91 91.5 7 240O 78 79 78.5 9 242 91 93 92 9 2420 85 87 86 1.3 243 Lost.. Lost. Lost. 1.-? 24M • S5 S2 83.5 15 245 91 90 i»0. 5 15 245(': 89 84 86. 5 16 246 ('se fi'om cacli day's juake was ke])t at Madison (hiring the entire ])erio(l. Table 44. — Scores of pasteurized and raw mill: cheese (lot -'{E) put into cold storage at different ayes and scored Oct. ,iO, 1911. Scored bv U. S. Scoied bv A. T. 1 Age when stored. Baer. Hruhn. Average score. i Date iiiiide. Chease No.' Tex- ture. Te.x- ture. Flavor. Total. Flavor. Total. Flavor. Tex- ture. Total. 19n. July 20 20 264. 1 264.2 42. 00 41.00 28.00 26. 50 95. 00 92. .50 42. .50 40. .W 27. 00 27. 00 94. 50 92. 50 42. 25 40.75 27.50 26. 75 94.75 92. 50 1 day — 20 264. W 1 week . . 40. (K) 26. 00 91 . 00 40. 50 27. 00 92. 50 40. 25 26. 50 91.75 20 264.4 2 weeks. 41.00 28. 00 94. 00 41.00 27. .50 93. 50 41.00 27. 75 93. 75 20 264. 5 4 weeks. 41.00 2S. (H) 94. 00 42. 00 28. 00 95. 00 41., 50 28. 00 94. 50 20 264.6 6 weeks. 41.00 2.S. 00 94.00 42. 00 27.50 94.50 41. 50 27.75 94. 25 20 21 265. 1 265. 2 41. 00 40.00 27. (H) 27. 00 93. 00 92. 00 41.00 41.00 26. ,50 26. 50 92. 50 92.50 41.00 40.50 2(i. 75 26. 75 92. 75 92. 25 "idayV.".. 21 265. 3 1 week . . 42. 00 28.00 95. 00 42.00 28. (X) 95. 00 42.00 28. 00 95. 00 21 265. 4 2 weeks. 40. 00 27.00 92. 00 40. 00 27.00 92.00 40. (X) 27. 00 92. 00 21 265. 5 4 weeks. 4(1 00 27.00 92. 00 40. 00 27. 00 92.00 40.00 27.00 92.00 21 265. 6 4 weeks. 40. 00 27. 00 92. 00 41.00 27. 00 93.00 40. .50 27.00 92. 50 25 265.7 6 weeks. 41.00 28. 00 94. 00 42. 00 27.00 94.00 41., 50 27. 50 94.00 25 25 267. 1 2t)7. 2 41.00 40. 00 28. IX) 26. 00 94.00 91.00 42.00 40. 00 27. 00 26. 00 94.00 91.00 41.. 50 40. 00 27. 50 26. 00 94. 00 91.00 1 day 25 267. 3 1 week . . 41. 50 27. 00 93. 00 41.50 27. 50 94. (X) 41.. 50 27. 25 93. 75 25 267. 4 2 weeks. 40. 00 27. 00 92.00 41.00 27. 00 93. 00 40. 50 27.00 92.50 25 267.5 4 weeks. 41.00 27. 00 93. 00 40. 50 27. 00 92. 50 40. 75 27.00 92.75 25 267.6 6 weeks. 42. 00 27.00 94.00 42. 00 27. .50 94.50 42. 00 27. 25 94.25 25 267('l 36. 00 26.00 87.00 36. 00 26. 50 87. .50 36. 00 26.25 87.25 25 267C2 i (iay 38. no 27.00 90. 00 39. 00 27.00 91. 00 38. 50 27. 00 90.50 25 267('3 2 weeks. 38. 00 27.00 90. 00 38. 50 27.00 90.50 3S. 25 27.00 90. 25 27 27 269.1 269. 2 40. 00 40. 00 27. 00 27. 00 92. 00 92.00 41.00 40. 50 26.50 26. .50 92.50 92.00 40.50 40. 25 26.75 26. 75 92. 25 92.00 1 day — 27 269. 3 1 week . . 40. 00 27.00 92. 00 40. 50 26.50 92. 00 40. 25 26.75 92.00 27 269.4 2 weeks. 41.00 27. 00 93. 00 40. 00 26,50 91.50 40. 50 20. 75 92. 25 27 269.5 4 weeks. 41.00 27.00 93. 00 42.00 27. 00 94.00 41. .50 27. 00 93. 50 27 269.6 6 weeks. 42. 50 28.00 95. 50 42. 50 27.50 95. 00 42.50 27.75 95.25 27 269C1 2 weeks. 34.00 23. 00 82.00 32.00 25. (X) 82. 00 33. (X) 24. (K) 82. 00 Aug. 1 1 272.1 272.2 35. 00 36.00 23. 00 25.00 83.00 86.00 36. 00 36.00 25. 00 25. 00 86.00 86.00 35.50 36.00 24. 00 25. 00 84. ,50 86.00 1 day — 1 272.3 1 week.. 37. 00 25. 00 87. 00 .39. 00 24.00 8.S.0O 38.00 24. 50 87. 50 1 272.4 2 weeks. 38.00 2.5.00 88.00 38.00 25.00 88.00 38.00 25. 00 88. 00 1 272.5 4 weeks. 35. 00 25.00 85.00 36. 00 24.00 85.00 35. .50 24. 50 85. 00 1 272.6 6 weeks. 37. 00 24. 50 86. 50 38. 00 25.00 88.00 37.50 24. 75 87. 25 8 S 276.1 276. 2 37.00 40. 00 25. 00 26.00 87. 00 91.00 39. 00 40. 00 26. 00 26. 00 90.00 91.00 38.00 40. 00 25.50 20.00 88. .50 91.00 1 day — 8 276.3 1 week.. 40. 00 25. 00 90. 00 39. 50 25. 50 90.00 .39. 75 25. 25 90. 00 8 276.4 2 weeks. 40.00 24.00 89. 00 39. 00 25. 00 89.00 39.50 24. 50 89.00 8 276.5 4 weeks. 40. 00 27.00 92. 00 39. 50 26. 50 91.00 39.75 26.75 91. 50 22 22 283. 1 283. 2 41.00 40.00 27.00 26.00 93.00 91 . 00 41.. 50 40. ha 26. .50 26.00 93.00 91.50 41.25 40.25 26. 75 26. 00 93.00 91.25 1 day 22 283.3 1 week.. 42.00 27.00 94. 00 41.00 27.00 93. 00 41.50 27.00 93.50 22 283. 4 2 weeks. 40.50 27.00 92.50 41.00 26. 50 92.50 40.75 26. 75 92.00 22 283.5 4 weeks. 42.00 27.00 94.00 41. 50 27.00 93. 50 41.75 27. 00 93.50 22 283. 6 42.00 27.00 94.00 42.00 2(). 50 93. 50 42.00 26. 75 93.75 > "C" in this column indicates raw-milk cheese. 86 CHEDDAK CHEESE FROM PASTEURIZED MILK. In every case the pasteurized-milk oheese put into cold storage at the age of one day was criticized by the judges as being flat, low, and not developed in flavor, and the texture was described as curdy, new, not broken down, not cured, etc. They received an average score of 90.84, as shown in Table 44. The cheeses put into cold storage at the age of one week received an average score of 91.93. They were found to be weU cured, and they had less mold on the surface (practically none), both when put into storage and when taken out, than any of the later lots. The cheeses put into storage at two weeks, four weeks, and six weeks of age were given average scores of 91.36, 91.82, and 91.46, respectively, while those kept at Madison for the entire period scored 91.39. So far as this short series indicates, there is no objection to putting pasteurized-milk cheese into storage at 34°, at the age of one week, immediately after paraffining. It was planned, however, to make a more extensive trial of the use of cold storage for pasteurized-milk cheese during the season of 1912. EXCEPTIONAL DIFFERENCES BETWEEN THE RAW AND PASTEURIZED MILK CHEESE. It is of interest to coUect in one pkice all of the cases recorded in the tables where the pasteurized-milk cheese was scored lower than the raw, in order if possible to locate the cause for such difi^erence. Table 45. — Summary of cases in which raw-milk cheese scored higher than pasteurized. LotslA,2A,3A,4A. LotslB,2B,3B,4B. Lots 30, 40. Lot? 3D, 4D. Cheese No.i Total Score. Cheese No.' Total Score. Cheese No.' Total Score. Oheese No.' Total Score. 171 2 171C 172 2 172C 177 « 177C 183 2 1830 184 1840 188 2 1880 250 2 250O 261 2610 81.00 87.00 81.00 83.00 86.00 86.50 79.00 85.50 84.50 83.50 78.50 80.00 81.50 85.00 81.00 78.50 172 172C 177 177C 183 2 183C 184 2 184C 188 188C 250 250C 261 2610 91.75 89. 51) 91.75 89.00 91.25 91.75 92.00 92.75 94.50 90.50 91.75 87.50 90.25 90.00 250 250C 261 2 2610 88.00 85.00 83. 50 86.50 250 250C 261 2 2610 86.00 85.50 85.00 88.00 • "0" indicates raw-milk cheese. « These are the cases in which the raw-milk cheese scored higher than the pasteurized. of duplicate cheese in the other lots are given for comparison. The other scores The fact that pasteurized and raw cheese from the same milk may occasionally score exactly alike or nearly alike would appear to indi- cate that where the milk supply is excellent the quality of cheese pro- duced is not improved by the new process. With so small a differ- ence in score as half a point, occurring in No. 184 in lot A and No. DISCUSSION OF CHEESE SCORES. 87 177 in lot B, it is doubtful whether there was any difference between the two cheeses which could be ascribed with certainty to the effect of the pasteurization process. The most adverse criticism on the process that can be based upon the 10 cases tabulated above is the following: It is entu-ely possible that some harmful bacteria or thou- cnzyms which arc occasionally present in dirty milk may not be destroyed by the pasteurization process and that such infections damage the quality of pasteurized- milk cheese as well as raw^-milk cheese. In this year's work it has been noticed that on a few occasions when the raw milk was very ripe the quality of cheese produced, even after j)asteurization, was not so good as from milk of fairly good quality. For example: The poorest pasteurized-milk cheese in Table 45 is No. 201, and the milk used for making this was of 0.28 i)er cent acidity before pasteurization. In Table 44, showing the scores of cheese shipped to cold storage, Nos. 272 and 276 are the poorest in quality and these were made from milk which titrated 0.275 and 0.31 per cent acidity, res})ectively, before pasteurization. Of course such milk should not be accepted at any cheese factory. No claim is made that the pasteiu'ization process is a cure for all the troubles of the cheese factory, or that it reduces the responsibility resting on factory patrons to improve the sanitary quality of their milk. It would, in fact, be most unfoi'tunate if any process coidd be used for making cheese, or any other article of food, which would relieve the milk producer or the factory man of the necessity for cleanliness. SUMMARY OF DISCUSSION OF SCORES, The scores of lots IB, 2B, 3B, and 4B, 3C and 4C, and 8D and 4D all show that cheese, either raw or pasteurized, stored for one or two months at about 80° are often seriously injured, so as to be unsalable at the ruling market price. The pasteurized cheese came out of such storage better in quality than the raw-milk cheese in about 90 per cent of all the cases observed. It is clear that pasteurized-milk cheese is better suited to stand exposure to high temperature than raw-milk cheese. This fact may find useful application in two ways: Wliile it is never advisable to store market cheese for any great length of time in the South, yet several days or weeks may often elapse before cheese shi])ped South is finally sold to the consumer, and it appears that })asteurized-milk cheese shoidd stand this ex- posure with less damage in quality thair raw-milk cheese. It is likely, too, that ])asteurized-milk cheese can be cured at ordinary curing-room temperatures below 70° in Wisconsin without the use of ice or mechanical refrigeration, thus avoiding part of the expense for cold storage. The quality of the 53 raw-milk cheeses in lots lA, 2A, 3A, and 4A, cured at 60° to 73° at Madison, is represented by the 88 CHEDDAR CHEESE FROM PASTEURIZED MILK. average total score of 89.09, and would no doubt have been greatly improved if the cheese had been cured in cold storage. In 51 cases out of 53 the pasteurized-milk cheese in these lots scored higher than the raw, on the average 3.8 points higher, the average total score of the pasteurized being 92.75 points, which indicates that cold storage for the pasteurized cheese was not necessary. In a short series of cheese placed in cold storage at 34° F. at dif- ferent ages, it was found that those stored at the age of one day were curdy and uncured at the age of three months, wliile those placed in storage at the age of one week were free from this fault and scored as high, even a little higher, and showed less mold on the surface than those put in storage when older than one week. From this it appears that pasteurized-milk cheese can be safely put in cold storage at the age of one week immediately after i)araffining. It was planned to try cold storage with both raw and pasteurized-milk cheese during 1912. THE DEMAND FOR PASTEURIZED-MILK CHEESE. One of the objects of the work during 1909, 1910, and 1911 was to sell the cheese to consumers as widely as possible, and learn whether it would meet with favor and continued demand. It' was felt neces- saiy thus to establish its suitability for the market before recom- mending cheese makers to take up the new process. The amount of pasteurized-milk cheese sold each year was limited by the output of the factory, it being impossible to secure a larger supi)ly of milk. Much more cheese could have been sold to the same purchaseis, and doubtless to others, if we had had the cheese to sell. In nearly all cases the cheese was sold at the current price ruling on the Plymouth cheese board, f. o. b. Madison without discount. During 1910, 4,815^ pounds of pasteurized-milk cheese valued at $711.16 were sold to 19 representative grocery stores, hotels, restaurants, and delicatessen stores in Madison, Wis, The total number of such sales was 137 during the season. Nearly every purchaser reordered it several times, and three of the leading retailers reordered it 15, 20, and 49 times, respectively, during the season. The average price paid for all of tliis cheese was 14f cents per pound. During 1909, 1910, and 1911, 41 shipments of pasteur- ized-milk cheese weighing 10,126 pounds in all and valued at $1,382.93 were sent to 27 leading cheese dealers, including a few retail stores, at New York, Boston, Philadelphia, Chicago, St. Louis, IVIinneapolis, and San Francisco, and at various Wisconsin points outside of Madison, including Plymouth, Sheboygan, Fond du Lac, Marshfield, Richland Center, Waterloo, and Milwaukee. Samples of the cheese were also shipped to experiment station workers in the leading dairy States for an examination. EXTRA COST OF PASTEURIZED-MILK CHEESE. 89 OPINIONS OP PURCHASERS. No written opinions were asked from dealers in Madison handling the pasteurized-milk cheese, neither were they urged to purchase a second time. The university se sold readily for the ruling market prices and often above. Very few dealers offered any objections to them and several wislu^d to buy them regularly. A good many wer(^ sold throughout tlu^ South by dealers. In general, the cheese passed through the market without excituig special comment, selling for full price and giving satisfaction. They were not labeled or marked except with a number for purposes of identification. Th(>re appears to be no reason why ])asteurized- milk cheese can not be sold regularly in any market with entire satisfaction, exce])tiiig possibly to the limited trade that demands very high-flavored cheese. OUTLINE OF THE NEW METHOD. In the method liere described a ))ri7U'iple is ap|)lied to the cheese- making process which has already been found useful in many other lines of manufacture, namely: The raw material, milk, is first treated by a preparatory process to bring it into uniform coniUtion before it enters the manufacturing process proper. Material of uniform quaUty thus prepared is made up into the finished product b}^ a uniform routine process without daily variations of the time schedule or other details, and the product is more uniform in quality, has better keeping quahties, etc., than the product obtained by the older process. The difficulties met with, liitherto in making American Clieddar cheese from pasteurized milk are: First. That heated milk coagulates poorly with rennet; and Second. The curd when obtained does not expel moisture pre- cisely as a raw-milk curd does, and this effect is more marked the 94 CHEDDAR CHEESE FROM PASTEURIZED MILK. higher the temperature of pasteurization. The quahty and behavior of pasteurized-milk curd suggest that it lacks the acid which is normally produced in raw-milk curds by the action of bacteria on milk sugar. The first of these difficulties, but not the second, can be over- come by adding calcium-chlorid solution to pasteurized milk. This method has been tried experimentally, but is not recommended for use in American cheese factories. Both difficulties, however, are over- come by adding an acid, preferably hydrochloric, to the pasteurized milk. Hydrocliloric acid is normally present in the human stomach during the process of digestion in larger proportions than that added to milk in this process of cheese making. Further, 95 per cent of the added acid passes out of the cheese with the whey during the process of manufacture. On tliis account no objection can be made on sanitary grounds to the use of this acid in the manner and for the purposes described. Among different lots of cheese, part of wliich was made with hydrochloric acid and part with calcium chlorid added to portions of the same milk after pasteurization, those made with acid were found to be more uniform in moisture content and superior both in flavor and texture to those made with calcium chlorid. The losses of fat in the whey are reduced by the use of the acid. Pasteuriza- tion and acidulation of milk for cheese making appear to be com- plementary processes. ITsed together they furnish a means for bringing milk daily into uniform condition both as to acidity and bacterial content for cheese-making purposes. The acidulation of milk with hydrochloric acid after pasteuriza- tion is accomphshed without difficulty or danger of curdhng by running a small stream of the acid, of normal concentration, into the cooled milk as it flows from the continuous pasteurizer into the cheese vat. One pound of normal-strength acid is sufficient to raise 100 pounds of milk from 0.16 per cent to 0.25 per cent acidity (calculated as per cent of lactic acid). The amount of acid needed each day to bring the milk up to 0.25 per cent acidity is read from a table or calculated from the weight of the milk and its acidity, determined by the use of Manns's acid test (titration with tenth- normal sodium hydrate and phenolphthalein). The preparation of standard-strength acid in carboy lots for tliis work and the acidula- tion of milk present no great difficulty to anyone who is able to handle Manns's acid test correctly. After the milk is pasteurized and acidulated three-fourths per cent of first-class starter is added and the vat is heated to 85°. It is set with, rennet, using 2 ounces of rennet per thousand pounds of milk, so that the milk begins to curdle in 7 minutes and is cut with three-eighth inch knives in 25 minutes. All portions of the OUTLINE OF THE NEW METHOD. 95 work after addinj^: rennet are carried out in an unvarying routine manner, according to a fixed- time schedule every day. As soon as the rennet has been added the cheese maker is able to calculate the exact time of day wlien each of the succeeding operations should be performed, and the work of making the cheese is thus simplified and systematized. It is possible that the routine process here de- scribed maybe varied somowliat with advantage at different factories. For example, some experienced cheese makers may prefer to mat the curds on the bottom of the vat instead of on racks or may find the use of the "curd gauge" unnecessary, and local conditions may be found in {hfl"erent factories making other adjustments of details desirable. However, the experience already had with the process indi- cates that the routine of daily operations found suitable at any fac- tory can be practiced there throughout the season without variation. It is the intention to give the new process a tliorougli trial in different cheese factc^-ies in various localities to test its applica- bility to different milk supplies before recommending it for general use by cheese makers. These trials will show whether new diffi- culties may arise wliich were not encountered heretofore. Cheese makers are therefore advised to await the publication of results of further trials of tlie method by the writers before undertaking to use the new process at their factories. The extra cost of making pasteurized-milk cheese is being studied with a view to finding out accurately what the net profit is in making this clieese compared with the regular process. The new process sliould interest the farmer because of tlie increased yield and the avoidance of the usual losses in yield and quality of cheese due to defective milk. It should interest the cheese maker because the process of making is systematized to such a degree that it is conducted upon a fixed-time schedule for all operations. It should interest the dealer because the cheese is more uniform in quahty and there is less need for cold storage in curing. Finally, the cheese should interest the consumer, because it is more uniform in flavor than most of the cheese to be found on retail counters and because it is made from pasteurized milk and is therefore a more sanitary product than ordinary American cheese made from raw milk. ADDITIONAL COPIES of this publication S\- may be procured from the SuPERfNTEND- ENT OF Documents, Government Printing OfRce. Washington, D. C, at 15 cents per copy f ^- LIBRftRY OF CONGRESS 000 891 643 3