day ooo 8 I a | Rew Dork State College of Agriculture At Cornell Anibersity Dthaca, N. VD. Library ee ee Zs. A HANDBOOK FOR DAIRYMEN THE RELATION OF TEMPERATURE, HUMIDITY AND PRESSURE TO DAIRY OPERATIONS A HANDBOOK FOR DAIRYMEN By WALTER W. FISK, M.S. IN AGR. Professor of Dairy Industry, New York State College of Agriculture, Cornell University FOXBORO, MASS. THE FOXBORO CO., Inc. Neponset AVENUE A Copyright, 1922 By Tue Foxsoro Co., Inc. First Edition, July, 1922 THE UNIVERSITY PRESS, CAMBRIDGE, U.S. a. FOREWORD , I SHE object of this book is to provide authorita- tive and up-to-date information on the relation of temperature, humidity and pressure to the manufacture of dairy products. Because of his professional standing and wide ex- perience with every phase of the dairy industry, Professor Walter W. Fisk, of Cornell University, was asked to prepare the material. Professor Fisk is in no way connected with The Foxboro Co., Inc., and no restriction of any kind was imposed upon him. He was at liberty to write what he wished. Each branch of the dairy industry has been analyzed from the standpoint of tempera- ture, humidity and pressure, and discussed in the light of the best practices of the most successful dairymen. No theories that have not proved to be commercially practical are presented. The result is an unbiased, authoritative treatise on some of the most significant phases of dairy operation. With the hope that we have contributed to dairy improvement and progress this book is dedicated to the dairy industry. THE FOXBORO CO., INC. July 1, 1922 Chapter II. Ii. IV. VI. VI. VITI. IX. TABLE OF CONTENTS INTRODUCTION BacTERIOLOGY Butrer Maxine MILK AND CREAM Ick CREAM CONDENSED AND EvAapPorRATED MILK . Mirk PowpER CHEESE CaskEIN aND Mink SUGAR Ture Power PLANT Page 19 26 39 48 56 59 65 . 67 ee. itt Salt ae Tew VITAL Volley - ISU GO SA YOUIO CIID FULPACooe JO VOU ASuL puord Ay CHAPTER I INTRODUCTION Ir is only recently that the importance of tempera- ture, pressure and humidity in relation to milk handling has been fully realized. Authorities are now agreed that the successful manufacture, han- dling and storage of milk and milk products of prime quality depend upon the knowledge and the careful regulation of these factors. Cleanliness is not to be minimized, but it is taken for granted in this dis- cussion that every right-thinking dairyman has the welfare of his community enough at heart to use the utmost care in keeping his plant clean and sanitary. Our aim is to give to the manufacturer, superin- tendent and operator certain suggestions regarding the relation of temperature, humidity and pressure to dairy operations, which will not only enable him to raise the standard of his product and eliminate needless wastes, but in the end will be of assistance to the whole industry. Temperature has two influences on dairy opera- tions: it regulates the growth of micro-organisms, and it has a physical effect on certain operations and on the quality of the finished product. The Influence of Temperature on the Growth of Micro-Organisms. Every dairyman knows that in milk and milk products there are many micro-organisms: bacteria, yeasts and molds. Because these are really tiny plants, their growth depends upon a readily avail- able food supply and proper temperature. Milk and 2 A Handbook for Dairymen milk products furnish their food, but high tempera- ture will kill them and low temperature will retard their growth. Professor W. A. Stocking in an interesting ex- periment shows the effect of temperature on the development of bacteria in milk. A sample of milk was thoroughly mixed and divided into six equal parts. The six bottles were placed in water at dif- ferent temperatures for twelve hours, at which time the germ content of each lot was determined. The bottles were then all placed together in a tempera- ture of 70° F. and allowed to remain until they curdled. As each sample curdled, the time was re- corded. Results show what may happen easily in milk which is allowed to stand overnight without thorough cooling. Effect of Different Temperatures, Maintained for Twelve Hours, on the Growth of Bacteria and on the Keeping Quality of Milk I ll Kept at 45 degrees Kept at 50 degrees Number of bacteria, 9300 Number of bacteria, 18,000 Curdled in 75 hours Curdled in 72 hours Ill IV Kept at 55 degrees Kept at 60 degrees Number of bacteria, 38,000 Number of bacteria, 453,000 Curdled in 49 hours Curdled in 43 hours Vv VI Kept at 70 degrees Kept at 80 degrees Number of bacteria, 8,800,000 Number of bacteria, 55,300,000 Curdled in 32 hours Curdled in 28 hours In cheese and butter making, the growth of cer- tain types of organisms, especially the lactic acid type, is essential. In other dairy operations, such as the handling of market or fluid milk, condensed milk and evaporated milk, the growth of organisms invariably causes the product to spoil. Introduction 3 All dairymen and milk producers probably make use of these facts, and the most successful cool the milk as soon as it is drawn from the cow. Regard- less of how clean the milk may be produced, there is certain to be some micro-organisms in it. Of course some of these are beneficial and others are harmful, but as the producer cannot distinguish between them, the development of all should be retarded by cooling and holding cold. The Influence of Temperature on the Quality of the Finished Product. The quality of the finished product is judged by its flavor, body, texture and appearance. Flavor is affected by bacterial growth, and this growth in turn is regulated by the temperature. A high temperature will cause a bad or undesirable flavor. A low temperature may cause a lack of flavor. The body and texture and appearance are deter- mined by the moisture content and the process of manufacture. Both are largely regulated by tem- perature. For example, if cheese is heated too high, it will be dry, hard and crumbly, while ice cream that is not frozen sufficiently will be watery and grainy. The churning of cream into butter depends upon the correct churning temperature. If the cream is too warm, the butter will be too soft and will have a very poor body; if too cold, it will not : churn at all, or very slowly. The successful manufacturer must make a prod- uct that is uniform from day to day. Uniformity depends upon many factors, but the important one, as will be pointed out in detail later, is that of the correct temperature. 4 A Handbook for Dairymen The Influence of Temperature on the Storage of Dairy Products. The keeping quality of milk or milk products de- pends largely upon a uniform holding temperature. If the temperature is allowed to go too high or to fluctuate from day to day, the product will not keep as long as when held constantly at the proper temperature. When butter and cheese are held in a refrigerator and the temperature rises, they not only deteriorate in flavor and body and texture, but molds grow rapidly and injure the quality. Bad flavors and poor body and texture in practically all dairy prod- ucts quickly develop under poor storage conditions. Many losses can be positively attributed to im- proper storage temperatures. For example: The writer knows of one case in which an ice-cream manufacturer lost his entire business because of the poor quality of his ice cream. The ice cream was of good quality when it left the freezer, but be- came grainy and icy during the hardening process, due to uneven and, at times, too high a temperature. Another case of loss is that of the storage of butter. A thousand tubs of butter were held in a storage which occasionally became too warm and damp so that molds rapidly grew. In this case, each tub had to be stripped and the mold scraped off. The butter sold at a loss of ten cents a pound, or about six dollars a tub, because of the moldy flavor. A loss of six thousand dollars could have been avoided if only a very small fraction of that sum had been invested in a recording thermometer. There is no definite length of time that a product may be held in storage without deteriorating. Time of deterioration depends upon the quality of the product when put in and the temperature of Introduction 5 storage. Whenever the temperature rises during storage, if conditions are right, it gives the lactic acid-forming bacteria a chance to develop. This is especially true of fluid or liquid milk and unsweetened condensed milk. These products sour quickly in a refrigerator that is not held at a uniform cold temperature. The Influence of Humidity on Dairy Products. Humidity is most important in the ripening of cheese, the manufacture of milk powder and the storage of products not hermetically sealed. The correct humidity is necessary for the proper func- tioning of the ripening agent during cheese curing. If the humidity is too low, there will be too much evaporation, which will cause unnecessary losses. If too high and accompanied by the correct tempera- ture, molds will grow and spoil the product. If the humidity is too high, it is impossible to make good milk powder after certain processes. The Influence of Pressure on Dairy Products. It is very necessary to have a constant steam pressure for the successful operation of many ma- chines. For example: the centrifugal separator. If there is not sufficient steam pressure, the efficiency of the machine is reduced. It is also important to have different materials put through machines at a given pressure. For example: ice cream mixed through the homogenizer. If the pressure is reduced, the in- tended results are not accomplished. The important subject of power-plant efficiency will be discussed in a separate chapter. As stated above, the quality and salability of dairy products depend upon a careful regulation of temperature, pressure and humidity. Manufactur- 6 A Handbook for Dairymen ing and storage losses can be traced directly to a lack of knowledge, or to inadequate means of controlling these factors. Savings can be made in formerly wasted materials, steam and water. Losses can be turned into profits. The vital relationship of temperature, pressure and humidity to each dairy product will be discussed in the following chapters. View of one of six temperature-control boards with recording thermometers for incubation rooms in Pathological Division, Bureau of Animal Industry, U.S. Dept. of Agriculture. Foxboro Ther- mometers of the continuous seven-day type are used. CHAPTER II BACTERIOLOGY Tue control of temperature within close limits is very important in laboratories where bacteriological investigations of the micro-organisms of dairy prod- ucts are conducted. In many instances the success in the maintenance of cultures depends upon the ability continuously to maintain a constant tem- perature. : The micro-organisms of dairy products are grown on various food materials known as media. To se- cure the proper temperature for growth they are usually placed in an insulated box known as an in- cubator, and the temperature is regulated by an electric thermostat, fan and ice. Each incubator is usually fitted with a seven-day recording thermometer. The recording elements are mounted on the wall outside of the incubator and the capillary tube passes through the wall, the bulb being located near the top and in the center of the incubator. The charts taken from the recorder are examined and any variations in temperature be- yond the prescribed limits are noted, with the time at which the variations occurred. The value of a continuous temperature record in the process of incubating cultures lies in the fact that such records not only show the temperature at all times throughout the period of incubation, but they are dated and can be filed for reference. It is thus possible to determine with accuracy the tem- perature maintained in the incubating process on any previous date. 10 A Handbook for Dairymen If the temperature in the incubator is too low, the growth of the organism will be very slow, or it will not grow at all. Also if the temperature is too high, the organism may not grow. In either case if it does grow, it will not give a strong type and contaminations are likely to appear. Starter. A practical application of bacteriology to dairy operations is the preparation of starter.* The lactic acid starter used in the making of butter and cheese is the most common. Other starters are the molds of Camembert and Roquefort cheese, Bulgari- cus for Swiss cheese, the eye-forming culture for Swiss cheese, and the starter for ripening cream for Hebrew trade. The Lactic Acid Starter. Since cultures must be prepared by a bacteriolo- gist, commercial laboratories have developed a large business in their production, usually under trade- marked names. Some of these cultures represent races of lactic bacteria cultivated and cared for efficiently, hence uniformly valuable over long periods of time. Others, carelessly produced, are worthless, or even a peril to the user. The organisms are usually shipped in small quantities in bottles of liquid or powder, or in cap- sules of uniform size. The contents may be either the culture medium upon which the organisms grew, or an inert substance designed merely to hold the bacteria in active form. In either solid or liquid form, the producer of the culture should guarantee its activity up to a plainly stated date. *Starter is a culture of desired organisms in a living or active state. Bacteriology i It is the problem of the cheese or butter maker first to keep the organisms pure, and second to in- crease them to such numbers and in such an active condition that they are commercially useful. The common practice is to allow them to develop in some material, usually whole milk or skimmed milk, or even dissolved milk powder. The manufacturer’s directions apply to average conditions and must be varied to suit the individual case. The directions should state the amount of milk necessary for the first inoculation, usually one or two quarts. Suggestions for Selecting Starter Milk. As the flavor of the starter will be the same as that of the milk from which it is made, great care should be used in its selection. The following sug- gestions are offered to aid in this selection: only clean-flavored sweet milk, free from undesirable micro-organisms, should be used. Choose the morn- ing milk because the bacteria have not had much chance to develop. In no case should mixed milk be used, as this eliminates all opportunity for selection. Choose the milk from a producer who maintains high standards and whose milk is usually in good condition. The quality of the milk can be deter- mined by the fermentation test. Pasteurization. Pasteurization kills most of the micro-organisms in the milk and makes a clean seed-bed for the pure culture. The temperature of pasteurization recom- mended for starter making differs with the author- ity. A temperature of 180° F. for thirty minutes or longer seems to be very satisfactory because under 12 A Handbook for Dairymen these conditions nearly all the micro-organisms are killed. The small amount of milk needed for starter making may be pasteurized by placing the container in water heated to the desired temperature. A very satisfactory arrangement is to cut off a barrel and place a steam pipe in it. Two or three extra bottles should be prepared, as some of them may be broken. Fill the bottles about two-thirds full so that there will be room enough for the mother starter and for later examination. To avoid pos- sible contamination, it is desirable not to have the milk or starter touch the cover. It is a good plan when pasteurizing to have one bottle of water as a check. Test the temperature for all the bottles by inserting a thermometer in the bottle filled with water. Never put a thermometer in the starter bottles. Uniform temperature may be obtained by shaking. Cleanliness. A successful starter can only be made if all uten- sils coming in contact with the milk are sterile. Keep the covers on the containers at all times. Don’t put thermometers into the bottles. When examining the starter, pour it out—vnever dip into it. If the cover is removed from the container, put it in a sterile place. It is easy to spoil the culture if the cover becomes contaminated. Glass fruit jars, or quart milk bottles, or tin containers may be used for starter making. The first two are more easily cleaned and their content is always visible, but they break easily. The tin con- tainer does not break, but it is hard to keep clean and the chance for contamination is exceedingly great. Bacteriology 13 Adding the Culture. After being pasteurized, the milk should be cooled to a temperature of 80° F.— a suitable temperature for the development of the lactic acid-forming or- ganisms. The commercial or pure culture is added to the milk and mixed thoroughly by shaking the bottle. The shaking should be repeated four or five times every fifteen or twenty minutes. The milk should be placed in a room or incubator with a tem- perature as near 80° F. as possible. A uniform temperature is necessary for the growth of the or- ganisms. The bacteria in the pure culture are more or less dormant, so that this higher temperature is necessary to stimulate their activity. The milk should be coagulated in eighteen to twenty-four hours, depending largely on the uniformity of the temperature maintained in the incubator. “Mother” Starter, or Startoline. The thickened sour milk obtained by inoculating the sweet pasteurized milk with the pure culture of lactic acid-forming bacteria is known as “ Mother” starter, or Startoline. Its physical properties, odor and taste should be examined carefully. Sometimes the first few inoculations from a new culture will show signs of gas, but ordinarily this will quickly disappear and have no injurious effect on the starter. It should have a clean .sour-cream odor and be smooth, thick and creamy, entirely free from lumps, whey, and gas pockets. This starter may have an objectionable flavor, due to the media in which the organisms were growing when shipped. In such cases it is necessary to carry one or two propagations to overcome the flavor, to enliven the micro-organisms and to secure the quantity desired. 14 A Handbook for Dairymen A Foxboro Recording Thermometer installed on the exterior of a bacteriological cold storage vault. The tube connecting the bulb passes through the wall. Permanent records of the exact temperature are thus maintained and unnecessary open- ing of the door to the vault is climinated. The Second Day's Propagation. For the second day, the milk for the starter is selected as on the first day. It is pasteurized, and this time is cooled to 70° F. because the organisms have become more active, and hence do not require so high a temperature to grow. Instead of inocu- lating with powder, as was done the first day, the mother starter already prepared is thoroughly mixed with the milk. Only a very small amount is required, perhaps a tablespoonful to a quart bottle. Since this starter may have the flavor of the media used in the laboratory culture, it may be necessary that it be carried one or two days more to eliminate it. After the flavor has become normal, the mother starter is ready for use. Bacteriology 15 Preparation of Larger Amounts of Starter. Determine the quantity of starter required, select the milk as carefully as before, pasteurize, cool and add the mother starter. The milk should be pasteurized at a temperature of 180° F. for thirty minutes if possible. A good incubation temperature is 60° to 65° F. However, this temperature may be varied so that the starter will be ready at a given time —the’higher the tem- perature the less time is required to ripen the starter. Pasteurization and incubation can be carried on in a starter can or a milk can. The former requires mechanical power to operate the agitator. The latter may be used where mechanical power is not available, and the milk and starter is stirred by hand. This kind of apparatus is more often used in cheese factories. Amount of Mother Starter to Use. Use the mother starter prepared the day before. The amount depends upon the following factors: 1. Temperature of milk when mother starter is added. 2. Average temperature at which the milk will be kept during the ripening period. 3. Time allowed for the starter to ripen before it is used. 4. Vigor and acidity of the mother starter added. The amount of starter may vary from 0.5 per cent to 10 per cent, depending upon the above conditions. Some operators prefer to add the mother starter while the milk is at a temperature of about 90° F., before it has been cooled to the incubating tempera- 16 A Handbook for Dairymen ture. This reduces the amount of mother starter necessary. If an even incubating temperature can be main- tained, less mother starter is needed than if the temperature goes down. If the ripening period is short, it will require a larger amount of mother starter. If the starter has a low acidity or weak body, indicating that the or- ganisms are of low vitality, more will be required. The starter, when ready for use, may or may not be coagulated. A good idea of the quality of the starter may be gained by the condition of the coagulation. It should be jelly- or custard-like, close and smooth, entirely free from gas pockets, and should not be wheyed off. When broken up, the starter should be of a smooth, creamy texture and entirely free from lumpiness or wateriness. It should have a slightly pronounced acid aroma. The flavor should be clean, mildly acid and free from all undesirable taste. Bulgaricus Starter. The Bacillus Bulgaricus Starter for Swiss cheese is carried in about the same way as the lactic acid starter, except that whey is a more desirable medium than milk. This organism requires a temperature of 100° F. for growth. The growing of the molds for Camembert and Roquefort cheese is somewhat similar, except that Camembert is aérobic and grows on the outside of the cheese, while the Roquefort is anaérobic and grows on the inside of the cheese. The Camembert mold may be grown on a media of whey agar or on sterile crackers. It grows spores more rapidly when held at a temperature of 60° to 70° F. It should also be kept very moist. The Roquefort molds grow best Bacteriology 17 when inoculated into a fresh loaf of bread that has been paraffined as it comes from the oven. As soon as cooled, it is ready for inoculation. This can be done by drawing the mold spores with sterile water into a sterile pipette and then forcing them into the bread. The loaf should be sealed and held at a temperature of 60° to 70° F. Experiments are now being conducted on the eye- forming culture for Swiss cheese. The fact is known that such a culture exists, but definite information is lacking as to its preparation and handling. Commercial Buttermilk. Commercial buttermilk is the term applied to lactic acid starter used for drinking. It is often sold as buttermilk or prepared buttermilk, and under many trade names, such as Lactic Culture, Bulgazoon and the like. It is made in the same way as any starter up to the time it begins to coagulate. As soon as it is coagulated and before the coagula- tion becomes too hard it must be broken up. If allowed to become too hard, the buttermilk will be lumpy and will whey off very rapidly —a great ob- jection to it. As soon as coagulated the starter should be churned. The flavor is improved if 10 or 15 per cent of sweet whole milk is added and churned with the starter. As soon as churned, it should be placed in a ripener or other suitable con- tainer and rapidly cooled to 40°-50° F. and held at this temperature. If allowed to warm up and cool again, it will whey off much more rapidly. As soon as cooled it is ready for consumption. It may be sold in bulk in 40-quart cans or put up in various- sized milk bottles. Commercial buttermilk should have a desirable mild acid flavor, a smooth, creamy body and texture, and should not have free whey. TROD ‘OOSTOURL LT uRrg “Mae CT BIGCTUN]O,) out ye SdoZlanoysed ANOF uo S1oJOULOU LOY LT, SUIP1OOY OLOQXOW jo UOLZETPLLYSUL uy CHAPTER III BUTTER MAKING Tue A B C’s of butter making are separating the cream from the milk, preparing the cream for churn- ing or ripening, churning, packing and _ storing; five simple steps full of pitfalls for the unwary. What are the precautions to be taken? How can losses be avoided? How can savings be made by the proper regulation of temperature and pressure? After studying the manufacturing methods of many of the most successful butter makers of the country, a few of the factors which enable the butter maker to manufacture consistently a uniform product of high quality will be set forth. Separating the Cream. If the cream separator is working efficiently there should not be more than .01 to .02 per cent of fat left in the skimmed milk. The efficiency of the ma- chine depends upon the following factors: 1. Temperature of milk being separated. If the separator is set up properly, temperature is the factor which is most likely to affect the ef- ficiency of the machine. If the temperature is below 85°-100° F. the separator will not re- move all the fat. 2. Speed of the separator. If belt driven, keep the belt tight. If turbine driven, the proper speed can be insured by placing a pressure gauge in the steam line. It must be remem- bered that if the separator is not operated at the specified speed, it will not skim clean. 3. Rate of flow of milk. Operate the separator to 20 A Handbook for Dairymen capacity and keep the feed cup filled to the level indicated by the maker. 4. Percentage of fat in the cream. Sometimes a cream rich in fat will not be skimmed clean. Butter makers differ as to the desirable fat con- tent but a cream testing 30-35 per cent fat will give satisfactory results. The separator will not always deliver cream containing exactly the same percentage of fat, even if the cream screw is adjusted properly. If an exact percentage of fat is desired, it can only be secured by stand- ardizing. (For method of standardizing, see page 31.) 5. Amount of slime in bowl. Most butter makers install a pre-heater to heat the milk to the proper separating temperature. It is desirable to connect a recording thermometer to the pre-heater. This gives the operator an accurate working guide and the management a check on operating conditions. Pasteurization. There is no “best practice” in regard to pasteur- ization. There are pro-pasteurizers and those who are against it. Those that favor pasteurization base their judgment on the fact that it eliminates the possibility of disease and that it usually im- proves the flavor of the butter. A temperature of 145° F. for thirty minutes has proved to be very satisfactory. However, if cream is pasteurized at too high a temperature, the butter is likely to have a cooked flavor. After pasteurization the cream should be cooled to the ripening temperature of 60° to 75° F. Preparing the Cream for Churning — Ripening. Good judgment of the butter maker and the taste of the consumer usually determine the method of Butter Making Q1 preparing the cream for churning. The various methods of preparation are as follows: 1. The cream may be pasteurized, if sweet, held cold and churned sweet. 2. Pasteurized, starter added and churned. 3. Neutralized and not pasteurized, starter added and churned. 4. Neutralized, pasteurized, starter added and churned. Sweet cream should be pasteurized before churn- ing, or there will be a large fat loss in the but- ter-milk. Cream that is churned sweet makes a milder-flavored butter and keeps better in storage. Amount of Starter. No definite rule can be stated as to the amount of starter to add, as it will vary from 1 to 380 per cent. The proper amount depends upon the length of time the cream is ripened, the ripening temperature, the acidity of the starter and the acidity desired in the cream at the time of churning. The amount of acid or degree of ripeness is determined largely by the amount of fat in the cream. The more fat the less acid is required. The cream when ready to churn should have 0.3 to 0.65 per cent acidity. There is no definite time when the starter is added. Some butter makers prefer to add it when the cream is partially cooled, usually from 75° to 90° F. The cream must be cooled below the tem- perature at which the lactic acid organisms are killed before the starter is added or its effect will be lost. Others prefer to add it after the cream is partially cooled. Lumps of starter cause white specks in the butter. Therefore, the starter should be strained. 22 A Handbook for Dairymen After being ripened the cream should be cooled to the churning temperature or slightly below and held for at least three or four hours. This allows the fat globules to congeal. It is obvious that successful ripening and pas- teurization hinge upon the careful regulation and control of temperature while the cream is in the coil- ripening vat. Even the experienced operator should have an accurate guide at this critical stage. Re- gardless of the size of the creamery, it has been proved that the installation of a recording ther- mometer not only helps to standardize the quality of the product, but points the way to savings worth many times the cost of the instrument. Churning. If the butter is to be colored, it is desirable to add the coloring to the cream either just before or im- mediately after placing the cream in the churn. Some makers prefer to add the color to the salt. However, it is difficult to obtain a uniform color by this method. The amount of color to use varies from 1 to 3 ounces per 100 pounds of fat. Churning time is determined by the temperature of the cream. The churning temperature varies from 48° to 65° F. according to the season of the year, being lower in summer than in winter, If churned too warm, the butter will come very quickly and will be too soft. If too cold, it will come very slowly and the granules will not gather easily. The butter should be churned until the granules are about the size of kernels of wheat. This should require thirty to sixty minutes. After the buttermilk is drawn off, the butter should be washed with water at the same temperature as the buttermilk. If the butter is very soft, colder Butter Making 23 water may be used to make it firm. It is advisable to wash the butter in two waters to remove any re- maining buttermilk. The churn should be given several revolutions in each water. Butter may be marketed either with or without salt, That without salt is known as sweet butter, and is demanded especially by the Hebrew trade. The amount of salt to add varies from 1.5 to 5 per cent, depending upon the taste of the consumer. It is advisable to add the salt while the butter is yet in the granular condition. Working distributes the salt evenly, presses out the free buttermilk, gives the butter a solid body, the desired texture or grain and a uniform color, and also incorporates the moisture. If worked too much the butter will be greasy or salvy and the texture injured. If not worked enough, the color will not be uniform and the body will not be solid. The increase of the butter over the butter fat is due to the incorporation of moisture and is known as over-run. It is the aim of every butter maker to secure as large an over-run as possible. The legal limit of moisture is 15.99 per cent. The incorporation of the moisture should be studied in relation to the following factors: Temperature of cream and wash water. Amount of cream in churn. Percentage of fat in cream. Amount of working. Pasteurized or raw cream. Degree of ripeness of cream. Churning butter in wash water. Working butter in wash water. The secret of moisture control lies in regulating the churning temperature and in adjusting the Q4 A Handbook for Datrymen working process according to the firmness of the butter as determined by the chemical, physical and mechanical properties of the butter fat, and in the constant use of a reliable moisture test. This shows the vital relation of temperature to over-run. In many plants the cost of manufacture, marketing and profits must come from the over-run because the fat is paid for at the same price per pound as the butter. As a large percentage of butter is made during the short season when there is a large production of milk, it has to be held to supply the demand during the rest of the year. Quality is maintained by storing the butter in very cold refrigerators — 0° F. or below. If the quality of the butter is to be maintained, the temperature of the refrigerator must not fluctuate. The refrigerator should be equipped with a recording thermometer with the re- cording element located on the outside. This saves opening the door to observe the temperature, and also gives a record of the temperature. It is es- pecially desirable if butter is stored for some one else. Then, if it deteriorates in storage, the oper- ator can produce his records of the temperature, which at once show whether the deterioration is due to temperature or to some other cause. The value of such an installation was pointed out in Chapter I. Whey Butter. Whey, or the liquid portion of the milk left after cheese making, contains a small amount of fat. The amount varies with the variety of cheese made, usually from .8 to .8 per cent. Special separators have been devised to separate this fat from the whey. Cream rich in fat (60 to 75 per cent) is desirable. Butter Making 25 This cream should be reduced with milk to the cor- rect percentage for churning. It may be made into butter the same as any cream. It is best to pasteur- ize it and add a larger percentage of starter. Be- cause the whey naturally contains the softer fats, whey butter is apt to be soft-bodied. For this reason, it should be churned at as low a temperature as possible. If the milk from which the whey is obtained was of good quality, the cream separated as soon as the whey was drawn and the directions above followed, whey butter should be of good quality. CHAPTER IV MILK AND CREAM Ir has been estimated that the total annual produc- tion of milk in the United States is valued at approximately two billion dollars. Of this huge amount 45.7 per cent is consumed as fluid or whole milk. In brief, these figures show the tremendous importance of this one branch of the dairy industry. Market milk not only is of importance from the standpoint of its production value, but it has be- come a vital factor in the life and well-being of every community. Boards of Health in a great many localities enforce stringent regulations in re- gard to the source of the milk supply and the pasteurization of the milk. But progressive dairy- men exercise greater care than is even prescribed by the Boards of Health. In the last analysis the successful handling of market milk depends upon the’ careful regulation of temperature. The growth of bacteria, pasteuriza- tion, storage and the efficient operation of the plant are all influenced by temperature. The dairyman knows that temperature influences these processes, but is that knowledge accurate and is it used to make his business more profitable? As one superin- tendent of a large Boston dairy said: “ Until I kept a record of temperatures, a careless employee, in the Pasteurizing Department alone, could waste his wages in steam and water several times a day.” Pre-Heating and Clarifying. As the milk is delivered to the dairy at a lower temperature than is required for proper handling View of the pre-heater and clarifier at the Turner Centre System, Somerville, Mass. The Foxboro Long Distance Dial Type Indicating Thermometer inserted is commonly used on pre-heaters. (often 40° F. in winter time) a pre-heater is usually necessary. The heating may be accomplished by running the cold milk counter-current to hot water, or by other methods. A temperature of 85° to 100° F. has proved satisfactory for the subsequent process of clarifying. It is almost necessary to in- stall a recording thermometer on the pre-heater in order to save heat and to prevent the milk from scorching. The centrifugal clarifier strains the milk at any temperature, but works more efficiently when the milk is heated 85° to 100° F. The clarifier removes the dirt, pus cells, blood corpuscles, ete., without separating the whole milk and aérates the milk, which improves its flavor. The machine may be belt or turbine driven, and if the latter a pressure reg- ulator in the steam line will insure a uniform pres- sure. The clarifier will not operate efficiently unless it is run at the prescribed speed. 28 A Handbook for Dairymen Pasteurization. There are two general methods of pasteurization, —the Holding and the Flash methods. A more recent development is the pasteurization of the milk after it has been bottled. However, this method is not used so generally as the first two. The Flash Method: The milk or cream is heated to a temperature of 170° to 180° F. for an instant, and then cooled. Unless great care is exercised the high temperature is likely to impart a cooked flavor to the product. The Holding Method: The milk is heated to a temperature of 142° to 145° F. and held at this temperature for thirty minutes. Bottle | Method: After the milk is packaged, it is placed in a large container and heated by live steam. Although the application is different, the principle of pas- teurization is the same as has been described above. The bottles are cooled by running cold water into the container. It is claimed that this method of pasteurization is more efficient because there is little or no chance for the milk to be contaminated. Pasteurization is the critical : a ial b stage in the handling of market Re milk. Temperatures in the pas- theBottle Method i of Pasteurizing. teurizer should be known and care- s fully regulated at all times. Ewen the most experi- enced operator cannot be so efficient or so vigilant as a recording thermometer or a temperature con- Milk and Cream 29 Installation of Foxboro Recording Thermometers on Burrell continuous pasteurizer at the Turner Centre System, Somer- ville, Mass. The arrows indicate the location of the ther- mometer bulbs. troller-recorder. The only way a superintendent can check the efficiency of his plant is to keep a record of the operations involving temperature. The regu- lations set down by most Boards of Health require that a record be kept each day showing the tempera- ture at which the cream or milk is heated and the time it was held at this temperature. Three thousand dollars were saved the first year by one medium-sized dairy after four recording thermometers and two temperature controllers were installed in the Pasteurizing Department. The in- stallation paid for itsclf during the first two weeks of operation. Cooling After pasteurization, the milk should be cooled rapidly with as little contamination as possible, to a 30 A Handbook for Dairymen Installation of Foxboro Recording Thermometers{on coolers at the Turner Centre System, Somerville, Mass. Arrows show where thermometer bulbs are connected to the coolers. temperature of about 40° F. At this temperature the growth of any organisms which may have sur- vived pasteurization is very slow. The ease of clean- ing the cooling device should not be overlooked. The nilk may be cooled by running it counter-cur- rent to cold water, or by other equally effective methods. A recording thermometer should be used as a check on the efficiency of the cooler. The milk is often held in large glass-lined holding tanks until it can be packaged. The tanks are equipped with brine pipes for cooling and an agitator to keep the cream evenly distributed throughout the milk. The operator will find a recording ther- mometer a great aid in maintaining a uniform cool temperature in the tanks. If the milk or cream warms up, it is very likely to sour. As it is customary to prepare the milk and cream Milk and Cream 31 one day and to deliver it the next, it is necessary to refrigerate the milk for several hours. The refrig- erator temperature should be held uniformly at 40° F. and the milk should not be allowed to freeze. Here, too, the only practical precaution for the dairyman is a recording thermometer. With the recording elements on the outside of the refrigerator, the temperature may be observed and maintained uniformly without the loss otherwise incurred by frequent opening of the door for temperature observation. Standardizing Milk and Cream. To satisfy the consumer, cream or milk containing the same percentage of fat should be sold every day. Because a separator will not deliver cream testing the same percentage of fat every day the cream must be standardized. Standardizing milk or cream consists of raising or lowering the fat content to a fixed standard. In standardization, there are two classes of prob- lems involved: first, a certain fixed amount of milk is to be made up or a certain amount of standardized milk is desired. Second, a certain amount of milk or cream is to be used and enough of another product added to make the mixture test a certain percentage of fat. In the latter case the amount of the mixture is indefinite. The original method of computing problems in standardization is long and difficult, but a scheme has been devised that is simple. The method is as follows: Draw a rectangle and place in the center of it the percentage of fat desired. Place at the left-hand corners of the rectangle the percentage of fat in 32 A Handbook for Dairymen the materials to be mixed. Subtract the number in the center from the larger number at the left of the rectangle. Place the remainder on the diagonally opposite right-hand corner of the rectangle. Sub- tract the smaller number on the left-hand corner from the number in the center and place the re- mainder on the diagonally opposite right-hand corner of the rectangle. The two numbers on the right-hand corners of the rectangle represent the number of pounds of ma- terial required. If these two numbers are added, they will express the number of pounds of the mix- ture, which will contain a percentage of fat expressed by the number in the center of the rectangle. In each case the number on the right-hand corner cor- responds in fat test to the number on the left-hand corner directly opposite. Problem. How many pounds of 40 per cent cream and 8 per cent milk must be mixed to make milk testing 5 per cent? Using the diagram as described, the following result is obtained: 3 35 40 2 This means that if 2 pounds of 40 per cent cream are mixed with 85 pounds of 38 per cent milk, the re- Milk and Cream 33 sult will be a 37-pound mixture testing 5 per cent. — Answer. Problem. How many pounds of 28 per cent cream and 8 per cent milk will be required to make 500 pounds of a mixture testing 4 per cent? In this problem a definite number of pounds of the mixture is required. 3 24 28 1 According to the diagram, 1 pound of 28 per cent cream is required to every 24 pounds of 3 per cent milk to make a mixture testing 4 per cent. This would make 25 pounds of the mixture, but 500 pounds is the amount desired. In other words, the number of pounds desired is 20 times larger than the number of pounds on hand (500 25 = 20). The amounts must be kept in the proportion of 1:24. Therefore, in order to get 500 pounds of mixture, it is necessary to multiply both the 1 and the 24 by 20. This would give a result of 20 pounds of 28 per cent cream and 480 pounds of 8 per cent milk, which mixed will equal 500 pounds of 4 per cent milk. — Answer, 34 A Handbook for Datrymen This problem may also be worked by simple pro- portion: 1: 25 :: x : 500 25x = 1 500 25x = 500 x = 20, number of pounds of 28 per cent cream there will be in the 500-pound mixture. — Answer. If there are 20 pounds of 28 per cent cream in the 500-pound mixture, the remainder will necessarily be 8 per cent milk. Therefore, 500 —20 = 480, number of pounds of 3 per cent milk. — Answer. The number of pounds of 3 per cent milk can be found directly by simple proportion: 24 : 25 :: x : 500 25x == 24 X 500 = 12,000 x = 480, number of pounds of 8 per cent milk. — Answer. Proof. In working problems in standardization, it is al- ways wise to prove the answer and check for mis- takes. According to the conditions of the problem, there would be 500 pounds of 4 per cent milk. This amount of milk would contain 20 pounds of fat (500 X .04= 20). According to the results the 480 pounds of 3 per cent milk would contain 14.4 pounds of fat (480 K .08—14.4). The 20 pounds of 28 per cent cream would contain 5.6 pounds of fat (20 X .28=—5.6). 14.4 + 5.6 = 20 Since the 500 pounds contain 20 pounds of fat and the materials of which the 500 pounds is made Milk and Cream 35 up furnish the 20 pounds of fat, the answer is correct, Problem. How many pounds of 3 per cent milk must be mixed with 150 pounds of 28 per cent cream to make a mixture testing 4 per cent? In this problem the number of pounds to be made up is not definitely known. Foxboro Automatic Temperature Recorder-Controller in- stalled on a flash pasteurizer at Schlosser Bros. Creamery, Plymouth, Indiana. This one instrument does the work of both controller and recorder. The chart shown is a facsimile of an actual chart from this instrument. The heavy lines show how close the temperature was held within the allow- able limits. The momentary high and low temperatures were caused by the cream supply being changed from one fore-warmer to another. 36 A Handbook for Dairymen Working the problem by the rectangle method (see page 32), 1 part of 28 per cent cream is re- quired for 24 parts of 8 per cent milk. According to the terms of the problems, 150 pounds of 28 per cent cream must be used, and the 3 per cent milk must be increased 150 times. This would give 150 pounds of 28 per cent cream (1 X 150), and 3600 pounds of 8 per cent (150 K 24— 38600), making in all 83750 pounds (150 + 8600 = 8750) of a 4 per cent mixture. This problem may also be worked by simple pro- portion: 24:1 :: x : 150 x — 8600, the number of pounds of 3 per cent milk required. Proof. The 8750 pounds of 4 per cent milk will contain 150 pounds of fat (8750 X .04—= 150). If the 150 pounds of 28 per cent cream and 8600 pounds of 3 per cent milk furnished 150 pounds of fat, the problem is correct. 3600 X .08 = 108, number of pounds of fat in milk. 150 X .28 = 42, number of pounds of fat in cream. 108 + 42 —150, number of pounds of fat in mixture. — Answer. Milk and Cream 37 Specific Gravity and Weight of Milk and Cream at a Temperature of 68° F. A Weight of Per cent of fat ee oe ee OKUM ic gees Gain ecae -025 1.037 8.6295 Milk .......0........ 3 1.034 8.6045 MME cis asec tend 3 Soa 3.5 1.033 8.5962 MUIK: i Scie antes ceca ca 4 1.032 8.5879 Mil Res 2 see ia eds 5 1.031 8.5796 IMU ee cart, eet coe aten 6 1.030 8.5713 Mixed Milk, Cream... 10 1.025 8.5297 Mixed Milk, Cream... 15 1.018 8.4714 Cream 6.54 sie ene as 18 1.015 8.4564 Cream ............... 20 1.013 8.4298 Cream............... 22 1.011 8.4182 Cream............... 25 1.008 8.3882 Cream : so. ee es 28 1.006 8.3715 Cream... oye e ee ews 30 1.004 8.3549 Cream............... 32 1.002 8.3383 Cream..iiccis ccc ecds 35 .999 8.3133 Cream asec os cock stews 38 997 8.2966 Gr@aMi os oes de ce ielonve 40 995 8.2800 ‘ainjzeioduis} sulIg JO plOdsaI SNnonuUTUOD JUSULULIEd B SoAtZ JOJQWOMIIY} SUIpIOIaY “SSVI ‘][LAIOMIOG “WoyskG oiyUaT) JOUINT, ey] Ye Woor SUIZIIIF OY} JO JOLIN] UT CHAPTER V ICE CREAM No milk product varies so much in quality as ice cream. This is largely due to the fact that the federal standard which requires that a vanilla mix- ture contain 14 per cent of fat and a fruit or nut mixture 12 per cent is not enforced. In many states ice cream may be sold either very low or very high both in fat and in milk solids not fat depend- ing upon the amount the manufacturer wishes to spend for materials. Many concerns make an ice cream containing 8 to 10 per cent of fat and 30 to 35 per cent of total solids. The common milk products used in ice cream are cream, whole milk, skimmed milk, whole or skimmed condensed milk, whole or skimmed powdered milk and butter. The Importance of Refrigeration. One of the most essential parts of an ice-cream plant is its refrigerator. Because the demand for ice cream fluctuates with weather conditions, manu- facturers must carry a sufficient amount of raw materials to meet any emergency. These raw prod- ucts should be kept in a refrigerator at a uniform temperature and as near freezing as possible — but not frozen. Without such a refrigerator manufac- turers either run short of raw materials and cannot supply a sudden demand that would mean a large increase in profits, or certain of the raw products spoil before they are manufactured. Sour ice cream 40 A Handbook for Dairymen is more often due to faulty refrigeration of raw materials than to anything else. Many ice-cream plants have a fruit storage room. This is similar to the storage for raw-milk products and in many cases is a small refrigerator partitioned off from the larger one. Fruits should never be - allowed to freeze. Pasteurization of Milk Products. Some manufacturers pasteurize their milk prod- ucts while others do not—there is no uniform practice. It is a known fact that pasteurization reduces the viscosity, so that after being pasteur- ized the product must be held for some time to regain its viscosity. As will be pointed out later, the viscosity is very important in relation to swell. Products should be pasteurized at as low a tempera- ture as possible, not above 145° F., to prevent a cooked flavor. Any of the milk or cream pasteur- izers may be used. Basic Recipes for Ice Cream. Here are two basic recipes which make ten gallons of ice cream: No. 1. Without condensed milk. 40 lbs. cream. 4 oz. gelatine in 4 lbs. water. 8 lbs. sugar. Flavoring. The percentage of fat in the cream governs the percentage of fat in the ice cream. No. 2. With condensed milk. 30 lbs. cream. 4 oz. gelatine in 10 Ibs. condensed milk. 4 lbs. of water. 7 lbs. sugar. Flavoring. Either whole or skimmed condensed milk may be used. Plain condensed is preferable to sweetened Ice Cream 41 condensed milk. Again, the percentage of fat in the cream may be varied to give the ice cream the de- sired percentage of fat. For standardization see page 81. The percen- tage of fat in the mix is figured by dividing the total pounds of fat by the total weight of the materials in the mix. (The “mix” is the unfrozen ice cream.) Milk powder is either used to make milk or to bring up the percentage of milk solids not fats or in place of the condensed milk, or the cream or milk may be made by mixing the various milk products mentioned above. Machines for Mixing Materials. The mixing process can be accomplished by two types of machines. One is the type in which the materials are forced through very small holes or slots by centrifugal force. It is known as an emulsi- fier. The other, in which the material is forced be- tween a valve and its seat by a piston pump, or through a very small opening between porcelain discs by a piston pump, is known as a viscolizer and homogenizer. Viscolizers and homogenizers are much more powerful than the emulsifiers and break up the fat globules so finely that the cream can never be rechurned. Many ice-cream makers run the whole mix through these machines, which increases the viscosity which in turn increases the swell. Mixing. Opinions differ as to the correct temperature at which the materials should be emulsified. Some manufacturers prefer to pasteurize and then emul- sify at the same temperature. A temperature of 120° to 180° F. is satisfactory. The materials must be kept thoroughly mixed or else the fat rapidly separates and comes to the top. This mix- 42 A Handbook for Dairymen ing may be accomplished by supplying the machine with the materials from a revolving coil or by an agitator in the supply tank. When butter is used, it should be cut into small pieces and then melted in the milk or water. Directly from the emulsifier, the material must be cooled as near 40° F. as possible, or the fat may separate. The preparation of materials to be viscolized or homogenized is the same as stated above. By means of an adjusting screw, the pressure under which the material passes through the machine can be regu- lated. The pressure may vary from 2000 to 8000 pounds. The only objection to these machines is that inferior products can be made to appear better than they really are. This is especially true of but- ter. Homogenizers may also be used on market or fluid cream, causing it to appear much richer than it really is. The next step in the preparation of the mix is the adding of the correct amount of sugar. If an ice-cream powder is used it must be thoroughly mixed with the sugar. Gelatine is added to prevent the separation of water crystals that cause ice cream to be grainy or icy. There are several ways to prepare the gelatine. The following method gives good results: To eight quarts of cold water add one pound of gelatine, or in that ratio, then mix the gelatine and water and let it stand twenty or thirty minutes. In this length of time the gelatine and water mixture will be rather thick. It should then be heated in a water bath to 165°-170° F, While at this temperature it should be added slowly to the mix which is being agitated. The whole mix or each individual freezer can now be flavored. Ice Cream 43 Showing Properties of Solution of Salt (Siebly)* (Chloride of Sodium) Per cent | Pounds salt} Degrees or Weight Specific Freezing of salt | per gallon ome | per gallon gravity Specific | point by weight | of solution io | at 89°F, |at 39°F. 4°C. eat F. 1 | 0.084 4 | 8.40 | 1.007 0.992 | 30.5 2 0.169 8 846 | 1.015 | 0.984 | 29.5 25 9.212 10 8.50 1.019 0.980 28.6 8 | 0.956 12 | 853 | 1.088 | 0.976 | 27.8 3.5 9.300 14 | 8.56 1.026 0.972 27.1 4 | 0.844 16 | 8.59 1.030 0.968 | 26.6 5 | 0.433 | 20 8.65 1.037 | 0.960 | 25.2 6 | 0593 | 24 | 872 | 1.045 | 0.946 | 28.9 7 0.617 | 2 8.78 1.053 | 0.982 22.5 8 | 0.708 82 | 8.85 1.061 | 0.919 | 21.2 9 0.802 36 ~=.5 «8.91 , 1.068 | 0.905 | 19.9 10 | 0.897 40 8.97 | 1.076 | 0.892 | 18.7 12 1.092 48 | 9.10 1.091 | 0.874 16.0 15 1.389 60 | 9.26 1.115 0.855 | 12.2 20 1.928 80 9.64 1.155 | 0.829 | 6.1 24 | 2376 | 96 9.90 1.187 0.795 | 12 25 | 2.488 | 100 9.97 1.196 | 0.783 | 0.5 26 2.610 104, 10.04 1.204 | 0.771 (—1.1 | | | Properties of Solution of Chloride of Calcium (Siebly)* Ber cent Spec eat Soule avi ee 1 0.996 | 1.009 $1 5 0.964 | 1.043 27.5 10 0.896 1.087 22 15 0.860 1.134 15 60 0.834 1.182 5 a5 0.790° | 1.984 8 * From Larsen & White’s “Dairy Technology,” by courtesy of the authors. Ageing the Mix. It is desirable, after the mix has been prepared, age” it by allowing it to stand. Ageing blends to 6c 44 A Handbook for Dairymen View of hardening room at the Turner Centre System, Somer- ville, Mass. It is very important that the temperature be kept even if quality is to be maintained. the flavors and increases the viscosity. It is usually done in large, insulated brine circulating coil tanks, equipped with recording thermometers. The one great danger of ageing is that the mix is likely to sour. Souring is determined entirely by tempera- ture. If the mix sours, it is practically a loss. It may be neutralized but it never makes a product of as high a grade. If cream is aged and sours while age- ing, it can be churned into butter, providing it has not been homogenized. For this reason many man- ufacturers prefer to age the cream rather than the whole mix. The temperature at which the mix enters the freezer is an important factor in relation to both quality and swell. The mix should enter the freezer as near 40° F. as possible. This helps to eliminate the danger of churning and of producing an_ ice cream of greasy texture. Ice Cream 45 How to Freeze Ice Cream. The freezer has a dasher with scrapers revolving in the center and a jacket around the outside in which cold brine is circulated. The rate of flow of the brine is determined by the pump, and after it is once regulated should be constant. The temperature of the brine may vary within wide ranges, though the best results are obtained when it is from +6° to-+10° F. Temperature is an extremely im- portant factor in connection with the making of ice cream. If the brine is too warm the cream will churn instead of freeze, and there will be chunks of butter in the ice cream. If the brine is too cold, the ice cream freezes too fast and then it is difficult, if not impossible, to obtain the swell. Care in freezing is of the utmost importance be- cause it affects both the quality of the ice cream and the swell. If the desired swell is not obtained, the business will be a failure. The rate or time to freeze depends upon the following factors: Temperature of brine. Rate of flow of brine. Temperature of materials when put into freezer. Materials in mix. Speed of the freezer. go gp The first three factors show the important part that temperature plays in the freezing process. It should take from 12 to 20 minutes to freeze a batch of good ice cream. By “swell” is meant the increase in volume of the ice cream over the mix. This increase is due to the incorporation of the air. The factors affecting swell may be divided into two general classes: kind and preparation of materials used and method of freezing. 46 A Handbook for Dairymen Certain combinations of these factors increase the swell, while other combinations decrease it. To obtain swell: 1. Have viscous milk and cream. 2. Age the milk and cream or mix. 3. If pasteurized milk and cream are used, age until viscous. 4, The cream and milk or whole mix should be homogenized or emulsified. 5. Condensed milk in the mix aids in obtaining swell. 6. The mix should contain at least 30 per cent of total solids. The dasher should run at the required speed. Mix should enter freezer as near 40° F. as possible. 9. There should be a sufficient supply of brine from +6° F. to 110° F. 10. The cream should be whipped for a moderate time in the freezer. 11. The mix should fill the freezer half full. 12. It should require 12 to 20 minutes to freeze. 13. The ice cream should not be below 27° F. when drawn from the freezer. os The converse of these conditions will cause a de- crease in the amount of swell. If not enough swell is obtained in freezing, the ice cream will be soggy and heavy, and if too much swell is obtained the ice cream will be fluffy and inclined to be grainy.