Issu U. S. DEPARTMENT OF AGRICULI 9 BUREAU OF ANIMAL INDUSTRY. BULLETIN 11 I -) - m* A. D. MELVIN, CHIEF OF BUREAU. = IE INFLUENCE OF ACIDITY OF CREAM ON THE FLAVOR OF BUTTER. BY L. A. ROGERS, Bacteriologist, Dairy Division, AND C. E. GRAY, Formerly Chemist, Dairy Division. WERSl'iY OF CAUR. LOS ANGELES SEP 23 1952 WASHINGTON: GOVERNMENT PRINTING OFFICE. 1909. LIBRARY R M Issued Junr 10, 1909. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY. BULLHTIN 114. A. D. MELVIN, CHIEF OF BUREAU. THE INFLUENCE OF ACIDITY OF CREAM ON THE FLAVOR OF BUTTER. BY L. A. ROGERS, Bacteriologist , Dairy Division, AND C. E. GRAY, " Formerly Chemist, Dairy Division . WASHINGTON: GOVERNMENT PRINTING OFFICE. 1909. THE BUREAU OF ANIMAL INDUSTRY. Chief: A. D. MELVIN. Assistant Chief: A. M. FARRINGTON. Chief Cleric: CHARLES C. CARROLL. Biochemic Division: M. DORSET, chief; JAMES A. EMERY, assistant chief. Dairy Division: B. H. RAWL, chief. Inspection Division: RICE P. STEDDOM, chief; MORRIS WOODEN, R. A. RAMSAY, and ALBERT E. BEHNKE, associate chiefs. Pathological Division: JOHN R. MOHLER, chief; HENRY J. WASHBURN, assistant chief, Quarantine Division: RICHARD W. HICKMAN, chief. Zoological Division: B. H. RANSOM, chief. Experiment Station: E. C. SCHROEDER, superintendent; W. E. COTTON, assistant. Animal Husbandman: GEORGE M. ROMMEL. Editor: JAMES M. PICKENS. LETTER OF TRANSM1TTAL. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY, Washington, D. C., March 29, 1909. SIR: I have the honor to transmit herewith, with the recommenda- tion that it be published as a bulletin of this Bureau, a paper entitled "The Influence of Acidity of Cream on the Flavor of Butter," by L. A. Rogers and C. E. Gray. The deterioration in quality and the development of objectionable flavors in butter kept in cold storage cause considerable loss to the trade, and the causes and nature of these changes have not been understood. The Dairy Division of this Bureau has been making a study of these problems during the past three years, and the present paper reports investigations in which quantities of butter were made from cream of varying degrees of acidity and stored at different tem- peratures. It is believed that the results will be of practical value to the butter manufacturers of the country. The authors wish to express their appreciation of the services of the various persons whose cooperation has made this work possible. They are especially indebted to the director and members of the staff of the University of Wisconsin Agricultural Experiment Station, who kindly allowed the use of their creamery and laboratories for part of the work. They are also under obligations to the manager of the creamery at Bloomer, Wis., and to the several persons who kindly scored the butter. Respectfully, A. D. MELVIN, Chief of Bureau. Hon. JAMES WILSON, Secretary of Agriculture. 3 CONTENTS. Page. Introduction 7 Experiments with butter made from (.-ream with varying acidity Discussion of results 11 Determinations of bacteria in the butter J 2 Possible action of enzymes in deteriorating high-acid butter 1~> Influence of lactic acid on flavor of butter 17 Result of producing acidity with other acids than lactic arid 17 The manufacture of commercial butter from sweet cream 18 Conclusions... 21 THE INFLUENCE OF ACIDITY OF CREAM ON THE FLAVOR OF BUTTER. INTRODUCTION. Although much has been written about butter, there is yet very little known about the changes taking place in its chemical composi- tion, the relation of these changes to the changes in flavor, the causes which produce them, or the factors which control their progress. It becomes necessary, therefore, to work out one by one the various conditions which cause or control the changes in the composition and flavor of butter. The difficulty of controlling conditions exactly and at the same time making normal butter renders it hard to determine the part played by any one factor. However, it is only by limiting the variations so far as the circumstances will permit to one factor that any definite conclusions can be reached. A factor in the manufacture of butter, the variations of which can be controlled, is the acidity developed in the cream. This factor has long been recognized as important in determining the flavor of butter and as having a decided influence on the constancy with which butter retains its desirable flavors in storage. It is generally taught by instructors and writers on dairy subjects that to produce good butter it is necessary to develop a certain amount of acid in the cream. The reason for this is twofold first, to develop a desirable flavor, and, second, to improve the keeping quality by suppressing the undesirable bacteria. McKay and Larsen" state that in the ripening of cream the lactic-acid bacteria suppress other bacteria which, if carried into the butter, would produce undesirable, changes. It is recognized, however, that if the fermentation is carried too far the keeping quality of the butter is injured. McKay and Larsen also state that in overripened cream undesirable bacteria may gain the ascendency and cause deterioration of the butter. Michels 6 states: It has been found that butter with the best keeping quality is obtained from well- ripened cream. It is true, however, that butter made from cream that has been ripened a little too far will possess very poor keeping quality. An acidity of 0.5 per cent should be placed as the limit when good keeping quality is desired. "George L. McKay and ('. Larsen. Principles and Practice of Butter-making. P. 194. 1906. b John Michels. Creamery Butter Makine. P. 70. J904. 8 INFLUENCE OF ACIDITY ON FLAVOR OF BUTTER. These statements by recognized authorities may be taken as an expression of the opinion of instructors, investigators, and butter- -makers in general. This opinion seems to be based, not on the results of actual experiment, but on experience in buttermaking. The little experimental evidence available on this question is conflicting and inconclusive. Patrick, Leighton, and Bisbee, and Patrick, Leighton, and Heileman 6 concluded that butter made from sweet cream retained its flavor better than butter made from sour cream. The opposite conclusion was reached by Dean. c Unpasteurized cream was evidently used in these experiments. The Dairy Division of the Bureau of Animal Industry therefore planned to include in a general investigation of the changes in storage butter a scientific and carefully controlled study of the influence of the acidity of the cream on the keeping quality of the butter in order to determine, if possible, the proper conditions under which butter intended for storage should be made. Obviously, results obtained from pasteurized cream could not properly be applied to butter made from unpasteurized cream, and vice versa. Therefore the investi- gation was planned to include butter made from both pasteurized and unpasteurized cream with varying degrees of acidity. EXPERIMENTS WITH BUTTER MADE FROM CREAM WITH VARYING ACIDITY. The first lot of butter in this investigation was made in the creamery of the University of Wisconsin dairy school at Madison in the summer of 1906. Owing to the fact that it was necessary to obtain part of the cream from another creamery it was impossible to control conditions as exactly as was desired, since in some cases the ripening developed more than had been planned. The entire lot of cream was mixed; one half the quantity was pasteurized in a Farrington pasteurizer at 180 F.; the other half was not pasteurized. After the pasteurization of the first half the two lots of cream were treated in the same way. One-fourth of each lot was cooled and then churned as soon as possible. To the remaining cream was added 14 per cent of the starter in use at the creamery. One-third of this lot was cooled and churned as soon as possible. The remaining cream was allowed to ripen to about 0.45 per cent, d a G. E. Patrick, F. A. Leighton, and D. B. Bisbee. Sweet versus Sour Cream Butter. Iowa Agricultural Experiment Station, Bulletin 18, pp. 478-487. 1892. &G. E. Patrick, F. A. Leighton, and W. H. Heileman. Sweet versus Ripened Cream Butter. Iowa Agricultural Experiment Station, Bulletin 21, pp. 788-791. 1893. cH. H. Dean. Experiments in Creaming and Butter Making. Ontario Agricul- tural College and Experimental Farms, Twenty-first Annual Report (for 1895), pp. 60-66. Toronto, 1896. d In this paper acidity is expressed as per cent of lactic acid. BUTTER MADE FROM CREAM WITH VARYING ACIDITY. 9 when it was divided, one half cooled ami churned, and the other half allowed to stand forty-eight hours after separation. The mode of procedure may be illustrated by the following diagram : Mixed cream. Unpaste;irized. Pasteurized. I I I I I I Xostirter, Starter, Starter. Starter, No starter, Starter, starter. Starter, not not ripened over- not not ripened over- ripened, ripened. normally. ripened. ripened. ripened. normally. ripened. The acidity of the overripened cream developed very little above that of the normally ripened cream. The acidity of the overripened pasteurized cream at time of churning was 0.52 per cent. The acidity of the corresponding unpasteurized cream was 0.47 per cent. The salt and moisture contents were controlled as closely as possible and showed no variations which could be expected to influence the results, except in the case of the unpasteurized cream churned without starter. In this case the salt was 1.81 per cent. The butter, which will be designated as Lot I, was packed in 20-pound tubs and held seven days in the creamery refrigerator, when it was scored by Mr. J. G. Moore and then shipped by refrigerator freight to the cold-storage rooms in Chicago. Two tubs of each lot were stored at temperatures of 32 , 10, and 10 F. The storage rooms were held at these tempera- tures with very little variation. In the following summer a quantity of butter (Lot II) was made at Albert Lea, Minn., by the same method. This butter was made from milk received in the creamery in one day. Half of this cream was pasteurized in a regenerative Jensen pasteurizer at 1 70 F. The various lots were churned at the following acidities: Vnpastexirized: 1'ereent. No starter 0. 13 Starter added 37 Ripened 51 Overripened 86 Pasteurized: No starter 13 Starter added 16 Normally ripened 51 Overripened . 6S The starter used in this cream was not very active and the acidity developed slowly in the pasteurized cream: otherwise this butter could be taken as representative of butter made under normal com- mercial conditions. The butter was packed in sealed 10-pound tin cans and stored, as was the Madison butter, at 32, 10, and 10 F. The butter of Lot I was scored after six months in storage by Messrs. Credicott, Smarzo, KiefFer, and White, and after nine months by the 80396 Bui. 11409 2 10 INFLUENCE OF ACIDITY ON FLAVOR OF BUTTEE. three first named. Each man scored independently and without knowledge of the history of the butter. The average scores of the Madison butter were as follows : TABLE 1. Average scores of butter of Lot I. Storage Method. temper- ature. Score when fresh. Score aftersix months' storage. Score after nine months' storage. Unpasteurized: " F. [ -10 No starter, no ripening { 10 > 92 f 90.6 \ 9 1 91.3 91.6 32 -10 Starter, no ripening . . < 10 1 I 93.5 1 87 f 89. 5 < 90 86.6 90 92 II 32 [ -10 Starter normal ripening < 10 1 I 96 1 86.5 f 91 < 90 86 91.3 91 32 -10 Starter, overripening. < 10 1 92 [ 86.5 [ 90. 05 < 90.2 85.3 92.6 No tub. I 32 Pasteurized: f -10 No starter, no ripening < 10 1 1 97 I 87.2 ( 91.3 < 91.3 87.5 92.3 92 32 f -10 Starter, no ripening . < 10 96.5 I 90.6 ( 91. 18 i 91.37 89.3 92 92 32 -10 Starter, normal ripening < 10 95 I "88.3 89 I 87.5 89 91.8 90.3 32 f -10 Starter, overripening < 10 92.5 [ 85.6 85.5 < 85.1 84 90.3 84.3 ' I 32 I .81. 75 82 The butter of Lot II stored at 10 F. was scored after four months by Mr. Credicott, and all the butter was scored after eight months by Messrs. Kieffer and Smarzo. In the latter scoring a number of grades with a definite score were arranged and the packages grouped accord- ingly. In all cases a separate package was used for each scoring. TABLE 2. Average scores of butter of Lot II. Method. Storage temper- : Score after ature. four months. Score after six months. Unpasteurized: No starter churned sweet F. 1 -10 90. Cheesy. Fishy. Fishy. Curdy, cheesy. Curdy, very poor. Curdy, very poor. Curdy, cheesy. Curdy, very poor. Curdv. verv poor. 10 i 90. Ranc 32 id 90. Starter not ripened . . . 87. r -10 90. 10 90. Kane I 32 id 90. Starter 90. 10 90. 10 90. Cold storage 82. 32 . . 82. Starter overripened . . -10 84. 10 89. Bad 82. Pasteurized: No starter churned sweet 82. f -10 . .. 92. 1 10 92.5 90. Starter, not ripened 32 91. 10 91. 10 92 ' 91. Starter, normal ripening 32 91. -10 91. 10 91. Cold 32 storage 91. 90. Starter, overripentd -10 8-1. 10 88. Bad. .. 82. 32 L .. 82. DISCUSSION OF RESULTS. 11 A third lot of butter (Lot III) was made, as before, from one lot of cream, one-half of which was pasteurized at 180 F. After taking out one-fourth of each half to be churned sweet, 15 per cent of starter was added. The different portions of this lot of cream were churned at the following acidities: Unpasteurized cream: INT cent. No starter 0. 18 Starter added 32 Ripened 54 Overripened (it Pasteurized cream: No starter JG Starter added 32 Ripened 59 Overripened 70 This butter was packed in sealed tin cans. One can from each lot was sent to New York, where it was scored when twenty days old by Mr. Kieffer. The remainder was stored at 10 F. and was again scored by Mr. Kieffer at the end of five months. The scores are shown in the following table: TABLE 3. Scores of h utter in Lot III. Method. Twenty days old. After five months' storage at 10 F. Unpasteurizcd: No starter Starter added '90. Ripened 88. Oily i so. Very fishy. Overripened 85 88. Pasteurized: No starter ! 915 91. Starter added 9f> (to. Ripened : 90. Slight metallic.... 87. Overripened 87. Metallic 87. DISCUSSION OF RESULTS. The score of the fresh butter of Lot I immediately before it went into storage indicates that while there were some differences all of the butter was at least fairly good, while the average of the scores made after the butter had been in storage shows marked differences in a few cases. The comments of the scorers show that the butter made from unripened unpasteurized cream always developed a cheesy or rancid flavor. The butter made from ripened cream, both pasteurized and unpasteurized, developed cold-storage, fishy, and other flavors typical of storage butter. In all cases the overripe butter showed marked deterioration. The butter made from pasteurized cream without starter usually retained its flavor with little or no change. Even at 32 F., where all the ripened butter showed decided changes, the sweet -cream butter deteriorated very little. The score of the sweet-cream butter in the Madison lot was decreased bv a "woodv" 12 INFLUENCE OF ACIDITY ON FLAVOE OF BUTTER. or "fruity" flavor which was noticeable at the top and sides of the package. In the opinion of the judges, this flavor was due to some extraneous cause. The difference between butter made from pasteurized sweet cream and that from ripened cream, both pasteurized and unpasteurized, became very marked after holding in a warm room for a short time. Butter made from pasteurized cream with starter added, after the so-called Le Clair or Credicott method, retained its fresh flavor better than the ripened-cream butter, but was not quite equal in keeping quality to that made from sweet pasteurized cream. In making deductions from results obtained by the usual method of scoring butter, allowance must be made for certain variations due to the sense of taste, which is not adapted to expression in mathematical terms. However, after making allowance for the personal tastes and variations that can not be avoided in butter scoring, it is evident from the results shown in the tables that some factor having a deleterious influence on the butter was developed with the ripening of the cream. The action of this factor is especially evident in the cream allowed to stand beyond the usual ripening period, although it is not necessarily accompanied by a marked increase in acidity, as is shown by the overripened butter of Lot I. In determining what this deleterious factor is, it should be remembered that these changes took place at temperatures of 20 and even 40 degrees below the freezing point. We know that a comparatively high acidity was developed in the cream from which this butter was made, but there is also the possi- bility that other influences having little connection with the acid may have developed to affect the flavor of the butter. The direct action of bacteria in causing changes at these temper- atures is obviously excluded, but an indirect action may be found in the possibility that enzymes are secreted in the cream by bacteria and that these enzymes are able to act even at the low temperatures at which this butter was stored. DETERMINATIONS OF BACTERIA IN THE BUTTER. Qualitative and quantitative determinations of the bacteria in the cream and butter were made according to the following methods: Gelatin, and in some cases both gelatin and agar, plates were made of the cream at the various stages of the ripening. All media used con- tained 2 per cent lactose and were corrected to a reaction of +0.2 Fuller's scale, with the exception of plates made from Lot III, in which the reaction was +1.0. Anaerobic plates showed no bacteria not present on the ordinary aerobic plates. In making plates from the butter, samples of 5 to 10 grams each were taken, with proper precau- tions to prevent contamination, from five or six different places in each tub. The samples were melted at 40 C., and after thorough DETERMINATIONS OF BACTERIA IN THE BUTTER. 13 mixing, 5 grams of each were weighed into flasks containing 500 c. c. of sterile water. These flasks were held in a water bath until the tem- perature reached 40 C. anil were shaken vigorously to insure a thor- ough distribution of the bacteria. Plates with varying dilutions were made in the usual way. The results of the bacterial determinations are given in Table 4 for the Lot I butter, in Table 5 for the Lot II butter, and in Table 6 for the Lot III butter. TABLE 4. Bacteria in butter of Lot I. Method. Initial temped' number. *t*'\ After six months' storage. After nine months' storage. Unpasteurized cream: F. ( -10 8,983,000 \ 10 2.300,000 2,360. 000 3,090.000 | 32 -10 2.893,000 { 10 1,195.000 872. 500 730 000 816.000 906. 1X10 351,000 1 32 -10 3.924,000 * 10 531,000 1,257,7.50 1 107 500 : 02, ooo 949,000 1 O' l ii 000 Overripened 32 -10 9,825,000 I 10 349.825 24, 727,. 500 1,470, 166 2I1.000 1,187,00(3 No butter. Pasteurized cream: Churned sweet . . 1 32 !| -10 386,166 \ 10 554,000 146,625 134,166 124,000 49,000 106.214 Starter added 32 | -10 2,800,000 < 10 6, 870, 000 855. 7.50 245,2.50 . 174.000 ; 20, ooo 102.000 Normal ripening 32 ( -10 945,000 < 10 305,000 110,000 275.000 253.000 10,. 500 6,600 Overripened 32 -10 1,956,000 i 10 265.000 67,. 500 300, 166 32,876 11,800 16, 100 1 32 24,500 8,100 TABI.K 5. Bacteria in cream and but'rr of Lot II. Method. burning. *> IT storage. Not pasteurized: No starter 66, 100, 000 11,900,000 ] -10 10 490,000 365, 000 Starter added < 553,. 500, (KX) 12,800 000 | 32 -10 10 i 53, 000 726,000 133, (XXI Normal ripening 779,000,000 4,260,000 ] 32 -10 10 64,000 376, (XX) 297, (XX) 32 10 106,000 Overripened 620,000,000 10 13, (XX) Pasteurized: No starter 27000 491 500 < 32 -10 10 5,000 28, (XX) 32 Starter added . 85 7.50 000 86 000 < -10 10 90,000 Normal ripening 7ft 1,000, 000 13,650,000 < 32 -10 10 241, (XX) 38! .IXX) 4.50, (XX) Overripened . 880 000 000 38 400 000 | 32 -10 10 35.600 172.000 1 KX) 000 32 23,000 14 INFLUENCE OF ACIDITY ON FLAVOE OF BUTTER. TABLE 6. Bacteria in cream and butter of Lot III. Method. Bacteria per cubic centi- meter in cream at time of churning. Bacteria per grain in fresh butter. Bacteria per gram in butter after stor- age at 10 F. Total. Liqueflers. Total. Lique- fiers. Total. Lique- flers. Unpasteurized: No starter. . 43,800,000 226,000,000 258,500,000 362, 500, 000 195, 500 162,500,000 1,000,000,000 526,000,000 1,750,000 540, 000 75,000 40,000 13,300 None. None. None. 3,755,000 7,233,000 12,766,000 3,136,000 88,500 10,300,000 11,520,000 24,666,000 161,000 94,000 None. None. 20,000 3,000 None. None. 610,000 563,000 469,500 87,000 a 1,344, 000 2,275,000 278,500 420,000 85,000 1,000 None. 2,000 56,000 1,500 400 None. Starter added Ripened Overripened Pasteurized: No starter Starter added Ripened Overripened . a Development of O'idium lactis and Bacterium lactis aerogenes. There is, of course, always the possibility that bacteriological meth- ods do not show true bacteriological conditions. Assuming that the gelatin plates gave a correct indication of the nature and number of the bacteria present, there is little in the results in the Lot I butter to connect the bacteria in any direct way with the changes in the butter. The unpasteurized cream contained a total of 9,000,000 bac- teria per cubic centimeter, of which 300,000 were of the liquefying type. There was an increase for a short time of the liquefying bac- teria, but these were soon suppressed by the lactic-acid bacteria. When the maximum development was reached the lactic bacteria decreased slowly. There was, however, no apparent growth of any other kind of bacteria. The freshly pasteurized cream contained 1,192 bacteria. There was a small increase of nonlactic bacteria, but this was soon checked by the lactic bacteria, and the subsequent development agreed with that observed in the unpasteurized cream. The cream from which Lot II was made contained 66,100,000 bac- teria per cubic centimeter, which were reduced by pasteurization to 27,000. In the unpasteurized cream the lactic-acid bacteria soon gained the ascendency and suppressed all other kinds. There was a considerable development of bacteria of the aerogenes type in the normally ripened pasteurized cream, but these were suppressed in the overripe cream by the lactic-acid bacteria. Otherwise the plates showed no bacteria which could be expected to influence the flavor. The bacteria in the cream of Lot III followed the same general course. There was no appreciable growth of gas-forming bacteria in this cream, but in the overripened unpasteurized cream there was a small development of O'idium lactis. Ten days elapsed after this but- ter was taken from storage before it was received at the laboratory. During this time it was doubtless held at temperatures within the thermal growth limits of ordinary bacteria. There w T as a distinct increase of bacteria in the pasteurized sweet-cream butter in which DETERIORATION POSSIBLY DUE TO ENZYMES. 15 the two inhibiting factors, acid and salt, were low. This bacterial growth may have been responsible for the deterioration of this butter. In all the butter stored at 10 and 10 F. there was a gradual decrease in the total bacteria. This was usually slightly more rapid at the higher temperature, but this difference in the rate of decrease was sometimes obscured by errors, due largely to the diiliculty of securing a representative sample. At 32 F. this decrease was usu- ally much more pronounced than at the lower temperatures. In several cases, however, there was an actual increase confined chiefly. if not entirely, to the torula group of yeasts. In one package the development was sufficient to make an actual increase in the total number of bacteria, which in the ordinary technique includes yeasts as well as bacteria. Usually the growth of yeasts was so much less than the decrease in bacteria that the total number showed a decrease. It has been demonstrated that some members of this group of yeasts may cause a decomposition of butterfat. a In some cases the change in the flavor of the butter stored at 32 F. might be accounted for by this development of yeasts, but in others in which there was an equal deterioration there was no appreciable increase of yeasts or bacteria. The inference should not be drawn that the writers exclude the action of bacteria as a factor in causing changes taking place in butter. It is undoubtedly true that not only the flavor of the fresh butter but the change in flavor after the butter is made may be influenced by the bacterial growth in the cream, and under certain conditions bacteria and yeasts may grow in the butter itself. The uniform deterioration of the high-acid butter at the lower tempera- tures, however, could not be accounted for in this way. POSSIBLE ACTION OF ENZYMES IN DETERIORATING HIGH-ACID BTTTER. A plausible explanation of the changes may be found in the possible production of enzymes by the lactic-acid bacteria, which if carried into the butter would continue to act, as has been previously sug- gested, even at the lower temperatures at which it was stored. It is doubtful if enzymes are excreted by the lactic-acid bacteria, but it is well established that all cells contain enzymes which rapidl\ T bring about the destruction of the cell after its death. Even the minute amounts of the decomposition products of the bacterial cells might affect the flavor of butter. Moreover, it is possible that enzymes not normally excreted are liberated by the natural death and dis- integration of the cell. This is at least a possibility that can not be disregarded. n L. A. Rogers. Studies upon the Keeping Qualities of Butter. I. Canned Butter. United States Department of Agriculture, Bureau of Animal Industry, Bulletin 57. 16 INFLUENCE OF ACIDITY ON FLAVOR OF BUTTER. The situation in the unpasteurized cream is complicated by the possible action of the enzymes of the milk, which include proteolytic, lipolytic, and oxidizing enzymes, but these enzymes would be destroyed by the pasteurization of the cream, which, as we have seen, did not prevent the deterioration. If, as suggested, enzymes are liberated in any way by the lactic-acid bacteria, butter made from cream heated sufficiently after ripening to destroy the enzymes should not change at temperatures low enough to prevent the growth of bacteria and other organisms. In Table 7 are given the results of an experiment in which 10 per cent of starter was added to sour hand-separated cream, the mixture pasteurized at once at 180 F., cooled properly, and churned. One-half of this cream was pasteurized, starter added, and allowed to ripen over night. TABLE 7. Showing changes in butter made from cream pasteurized after ripening. Score after one Storage Score Score Method. week tempera- after two after five (before ture. months. months. storage). a. Sour hand-separator cream, 10 per cent starter added, pas- teurized at 180 F., cooled, and churned. 1 93 | -10 10 32 83.7 84.7 82.7 84.2 84.0 85.0 6. Half of a. Pasteurized at 180 F., 10 per cent starter added, ripened over night, cooled, and churned. | 92 -10 10 1 32 83.2 83.7 S3. 7 83.5 83.5 84.0 When these lots of butter went into storage one week after making, they scored 93 and 92, respectively. In two months both lots had developed, regardless of storage temperature, a rank, fishy flavor. All 'enzymes would be nearly if not quite destroyed by the tempera- ture to which this cream was exposed. To assume that this marked change in flavor was caused by the development of bacteria would be contrary to our experience with other butter. These results have been duplicated many times in the course of other investigations. One lot of butter was made in our experimental creamery in Albert Lea in the following way: The fresh cream was pasteurized at 170 F. To this was added 20 per cent of starter, and one-fourth was cooled and churned at once (designated as a). Another fourth w r as ripened overnight to an acidity of 0.41 per cent (6). The remainder was allowed to stand forty-eight hours. At this time the acidity was 0.59 per cent. Half of this remainder was properly cooled and churned (c), and the remaining fourth heated in a vat at 158 F. for ten minutes, after which it was cooled and churned (d). These butters were examined by numbers only when they went into storage one week after making, and again after four and one-half months of INFLUENCE OF LACTIC ACID. 17 storage at a temperature of 10 F. The results of the examination are given below: TABLE 8. Changes in butter made from cream pasteurized ufier ripening. Portion and method. o. Starter added 6. Ripened c. Overripened d. Overripened and heated. Acidity. Result afier one week. Per cent. Perfectly good. 0. 41 Very nice butter; good aroma . 59 Unclean . 59 Extremely unclean Score after four and one-half months storage at 10 F. 92. Tallowy. 92. Tallowy. Slight storage. 91. Stale-water flavor. 87. Old, tallow, rancid, grease. It is apparent that the deleterious effect of high acidity was not duo to any organism, enzyme, or other substance which can be destroyed by heat. It is evident, then, that some by-product of bacterial growth, unaffected by heat, had a marked influence on the flavor of the butter. It is probable that this was a by-product of the lactic- acid bacteria and that the by-product was lactic acid itself. INFLUENCE OF LACTIC ACID ON FLAVOR OF BUTTER. A number of experiments have been made to determine the influ- ence of acidity developed in the cream by the addition of lactic acid. These have invariably given results similar to those shown in Table 9. In securing the results shown in this table one-third of a lot of pasteurized cream was cooled and churned at once (). To the re- mainder were added small portions of chemically pure lactic acid until it showed an acidity of 0.36 per cent. Half of this was cooled and churned on the following morning (&). The acidity of the remaining .third was increased to 0.41 per cent, cooled, held over- night, and churned the next day (c). The butter remained in the creamery refrigerator two weeks, when it was examined by num- bers only, and snipped to storage at 10 F. It was examined again after three and a half months in storage with the following results: TABLE 9. Influence of lactic acid on the flavor of butter. Portion and method. Acidity. Condition after two weeks. Score after three and one-half months in storage at 10 F. Per cent. 099 Good 9H 5. Sweet. 6. Lactic acid added c. Lactic acid added... . 300 .444 Oily, unclean oilv, decomposed fat... 89. Sweet, fruity. 87. Sweet, oilv. RESULT OF PRODUCING ACIDITY WITH OTHER ACIDS THAN LACTIC ACID. Similar results have been obtained with butter made from cream acidified with acid other than lactic acid. These butters wen 1 made in the following manner: Sweet cream sufficient to make three 1 churn- 18 INFLUENCE OF ACIDITY ON FLAVOR OF BUTTER. ings was pasteurized in a continuous pasteurizer at 170 F. One- third was cooled and churned at once (a). To the remaining two- thirds acid was added slowly until the acidity expressed as lactic acid equaled about 0.22 per cent. This portion was divided and one-half cooled (b). The remaining portion was acidified to about 0.4 per cent and cooled (c). Portions Z> and c were churned on the following day. Lot 1 was acidified with lactic acid, lot 2 with acetic acid, and lot 3 with hydrochloric acid. There was a slight development of bacteria in these creams, which was evidently checked by the higher acidity. The greater part of the bacteria present were of the lactic-acid type, or had no appre- ciable effect on milk. This butter was packed in sealed cans and a few days after making was shipped to storage and was examined by Mr. Credicott when about 15 days old. The results are given in Table 10. TABLE 10. Showing the influence of different acids on the flavor of butter. Lot. Acid added. Acidity of cream. Score after fifteen days. 1 None... Per cent. 0.144 88 Trifle unclean and very greasy. 1 b Lactic .216 88 Do. 1 c. do.... .432 8fi Fishy and greasy. 2a 26 None Acetic... .126 .216 90. 87 Trifle oily, body weak and greasy. Very greasy, and rancid on fishy order. 2c do .350 S-l Very flshv and greasy. 3o 36 None Hydrochloric . .126 .225 90. 90 Clean but greasy. Trifle unclean and oily. 3c do .450 84 Very fishy, greasy. This table shows that this action is not peculiar to lactic acid or even to organic acids. It would appear, therefore, that the acidity of the cream has a direct influence on the changes in the butter. This is, of course, usually complicated by the influence of other factors, many of which are still undetermined. Just what action the acid has and what parts of the butter are changed to bring about the undesired flavors we are not prepared to say at this time, but investigations are in progress which it is hoped will throw some light on the complex chemical changes controlling the flavor of butter. THE MANUFACTURE OF COMMERCIAL. BUTTER FROM SWEET CREAM. To the person interested in the application of these results to practice it is obvious that butter which market conditions require to be held for any length of time should be made with as little acid as possible. This is especially true of butter held for several months in cold storage and butter canned for use on shipboard or for export to tropical countries. While the object of this investigation was to determine the causes of change in butter, the results allow some com- COMMERCIAL BUTTER FROM SWEET CREAM. 19 parisons to be made of the commercial value of the different methods of butter making. The deterioration in storage of butter made from overripened cream is well known, and this investigation has shown clearly that butter made from cream ripened according to the usual creamery practice changes much more than butter made with a low acidity. A number of trials were made to determine if adding sufficient starter to cream to improve the flavor of the butter would seriously impair the keeping quality. The keeping quality of butter made from sweet pasteurized cream is compared in the next table with that of butter made with starter. The scores given in this table are the average scores of six lots of butter made in the creamery at Bloomer, Wis. The cream from which this butter was made was pasteurized in a Farrington pasteur- izer at temperatures varying from 155 to 175 F. The lot was divided, a large starter added to one-half, and each portion cooled and churned at once. In a few cases one-half was ripened, but this butter was so much poorer than the sweet-cream butter that it was not stored. The scorers were Messrs. Kieffer, Smarzo, Credicott, and White : TABLE 11. Showing relative keeping quality of butter made from pasteurized sweet sweet cream with starter added, and normally ripened cream. cream, Average Average O WJI U^t Lot an. Sweet cream 1 1 91.5 93.0 3-2 92.2 91.5 I 10 92. 1 93. 56. Starter added 10 90. 9 92. 1 1 32 88. Sli. [ -10 91.3 93.'. 6 a. Sweet cream 10 90.6 91.5 1 32 89. 6 92. 2 -10 91. 93. 66. Starter added ) 10 90. 8 92. 7 1 32 87. 3 89. 3 20 INFLUENCE OF ACIDITY ON FLAVOR OF BUTTER. The foregoing table is summarized in Table 12, which gives the average of the scores of the six lots of sweet-cream butter and of the five lots of butter made from sweet cream with starter: TABLE 12. Showing average scores of butter made from pasteurized sweet cream and sweet cream with starter added. Method. Storage tempera- ture. Average score after four months. Average score after eight months. Sweet cream (six lots) "F. \ -10 10 91.28 91 03 92.81 92 45 Starter added (five lots) ... 32 -10 10 90.32 91.64 91 26 90.73 93.16 92 68 I 32 88.38 88.72 The foregoing table shows that at the two lower temperatures there was little or no advantage in the sweet-cream butter over that with the starter, but at 32 F. there was a decided difference in favor of the sweet-cream butter. Butter has been made under commercial conditions by this method in large quantities, and when sold after several months in storage was considered highly satisfactory. In the work described in the foregoing pages we have given little attention to sweet-cream butter for immediate consumption. We have, however, a number of scores of fresh butter, most of which are comparisons of butter made from pasteurized sweet cream with and without starter added. In three lots sent to the New York market the butter made from cream with starter added was scored from 1 to 2| points higher than the sweet-cream butter. On the other hand, in eight lots of butter sent to the Fox River Butter Company the average -score of the sweet- cream butter was 93.7, against 93.3 for the butter with starter. The difference in favor of the sweet-cream butter was greater in the butter eight or ten days old at the time of scoring, while in the butter scored immediately after making the highest score was given to the butter with starter. In four lots in which sweet-cream butter was compared with butter made from cream ripened in the normal manner, the former received an average score of 94 against 91.2 for the ripened-cream butter. The difference between the scores given the butter sent to New York and that sent to the Fox River Butter Company may be explained by the demand of the market and the personal tastes of the scorers. The New York market calls for a butter with a decided flavor, and the mild sweet-cream butter consequently received a low scbre. The scorer at the Fox River Butter Company, on the other hand, gives a good score to a butter free from any objectionable flavors. The scores of these lots are given in Table 13: CONCLUSIONS. 21 TABLE 13. Scores of fresh butter made from pasteurized sweet cream, siccct (ream vith starter added, and cream ripened normally. Fox OW York 'V,;';; r r Lot ami method. (Kieffen , any scon 1 . a. Sweet cream in 6. Starter added U4 a. Sweet cream '.rj. .", in 6. Starter added