, ,

Ice , creamied cottage cheese and the small percentage in cottage cheese . for the manufacture of cheese is placed promptly in milk cans and cooled, usually in a tank in cold, run- ning water or by running it over a George P. Sanders^ cooler. It is delivered early in the morn- Donald H. Wiliiams ing, while still sweet, to the cheese fac- tory. There it is graded and weighed, inferior lots arc rejected, samples ari^ taken for content and fre- Of an annual production of about quently for quality tests, and then it is J 20 billion pounds of milk on farms in pumped or flows to a receiving tank. the , about 54 billion For most kinds of cheese, including pounds, or slightly more than 45 pcr- Cheddar, the milk should be pasteur- ccnt, is utilized in the production of ized—heated to 161° F., or slightly four kinds of -product foods— higher for at least 15 seconds, or to at cheese, butter (including farm-made least 143° for not less than 30 minutes, butter), , and sherbet. and then cooled. im- proves the average grade of cheese and THE PRINCIPAL TYPES of cheese makes it more uniform in quality and manufactured^ with approximate pro- composition, as research by this De- duction in million pounds in 1949, are : partment has demonstrated, and also (including Cheddar) kills any harmful or undesirable micro- from whole milk, 935; Swiss, 81; organisms that might be present. , 54; Italian varieties, 55] Standards of identity for various brick and Munster, 30; blue mold, 8; kinds of cheese, applying to cheese in Limburger, 7; Neufchatel, 4; and other interstate commerce, have been issued types, 24. The total cheese production, by the Federal Food and Drug Admin- exclusive of cottage cheese, in 1949 was istration. Among other requirements, about 1,200 million pounds. About 9.5 the standards specify that the milk and percent of the total milk supply is used cream used in making cottage, pot, in manufacturing these types of cheese. baker's, and cream —the so- In addition, approximately 280 mil- called soft, unripened types—is to be lion pounds of cottage is ])astcurizcd. For most of the various produced annually, in the manufacture ripened cheeses, the standards specify of which approximately 1,770 million that if the milk is not jjasteurized the pounds of skim milk, equal to nearly cheese is to be cured for a stated length 1.5 percent of the total milk supply, is of time. For example, utilized. A large proportion of the curd made from is cured for not is used in manufacturing annually less than 60 days at a temperature not some 287 million pounds of creamed less than 35° F. Many of the States cottage cheese. It is estimated that \5.5 have similar regulations. The pasteuri- million pounds of butterfat, in the zation requirements were adopted as form of 78 million pounds of cream a safeguard to }DrCvent the possible testing about 20 percent , is utilized transmission of disease-producing mi- in manufacturing this quantity of cot- cro-organisms to humans. Some kinds tage cheese, including the fat in of cheese, such, as Swiss, are not yet be- 683 684 1950-1951 YEARBOOK OF AGRICULTURE ing made generally from pasteurized , which coagulates it to form the milk; hence for these a definite curing cheese curd. period is required, which in most cases After the curd has formed, it is cut is little or not longer than the curing into pieces, stirn^d, and warmed gradu- period customarily used. ally. When the curd is sufiñciently firm, A so-called phosphatase test, which the is removed. The volume of is used to detect underpasteurization Vv'hey is usually 86 to 90 percent of the or the presence of raw milk in pasteur- volume of milk. Whey obtained from ized milk, cheese, and other dairy Cheddar cheese contains 0.3 to 0.35 products, has been developed in the percent of fat; that obtained from division of Dairy Products Research Swiss cheese, as much as 0.7 percent. Laboratories of the Department ( San- The whey is separated, and the w^hey ders-Sager test). The test has been cream thus obtained is used in making adopted as an official method for use butter. The utilization of the fat-free in enforcement of the pasteurization whey, which contains nearly one-half requirements. as much solids as the original milk, is The milk for Swiss cheese is always described in the preceding chapter. clarified—that is, it is run through a After draining, the curd may be high-speed centrifugal clarifier, which salted. It is placed in hoops or forms, removes dust and other particles and which usually are lined \vith cloth, greatly improves the eye formation. and is put under pressure, usually The milk then is pumped through o\Trnight. Some types, such as cottage a pipe to the cheese vat or kettle. Most and cream cheese, are not pressed but vats are rectangular, and Cheddar vats merely allowed to drain in cloths, and may each hold as much as 10,000 hence contain a relatively large amount pounds of milk. Swiss cheese is made of moisture. Some hard cheeses, such in round copper kettles holding as as Swiss, are not salted during the much as 3,000 pounds. The vat or draining and firming stage, but are kettle is made with a steam jacket for immersed later in salt brine. heating the mijk. Milk for some kinds The cheese is cured on shelves, and of cheese may be standardized : that is, kept clean, in special curing rooms. a small proportion of the fat is re- The temperature is usually between moved as cream to adjust the composi- 45^ and 60° F., and the relative hu- tion of the cheese uniformly. For Swiss midity is regulated. After curing, the cheese, about 10 percent of the fat is cheese may be stored at a lower tem- removed. In some States, such removal perature, as low as 35° F. At least 3 of fat from milk used in making Ched- months is required generally for cur- dar cheese is prohibited by law. The ing, and some types, such as the very cream removed in standardizing is hard Italian cheeses, require more either sold as market cream or churned than a year. into butter. No two of the principal varieties of The temperature of the milk in the cheese are made by the same method. vat or kettle is adjusted to a point in The details of setting, cutting the curd, the range of 86"^ to 91'' F., and a bac- stirring, heating, draining, pressing, terial culture, known as a starter, is salting, and curing, as well as the ad- added. The starter for most kinds of justment of the composition of the milk cheese is a mixed culture containing and the use of bacterial starters, vary several types of harmless bacteria, for different types of cheese. The varia- which produce lactic acid from the tions in the process are regulated lactose and also aid in the ripening or strictly by the manufacturers in accord- curing process. For Swiss cheese, two ance with the art that has been found or sometimes three separate cultures most favorable for producing the char- are added. The milk may be allowed acteristics and quality peculiar to each to ripen, and then it is set with kind of cheese. CHEESE, BUTTER, ICE CREAM, SHERBET 685 Small quantities of cheese are made milk is produced when the cream is on farms from cows' milk. On some separated; is produced in farms cheese is made from ' milk, the churning process. Skim milk pro- chiefly for use in the home. However, duced on the farm is fed to poultry, by far the greater proportion is made calves, and hogs, and that produced in in factories. Five thousand pounds of creameries is utilized in concentrated milk a day, or approximately 500 forms. The lower grade of buttermilk, pounds of cheese, is considered a min- which is obtained from neutralized imum quantity for profitable produc- sour cream, is used for animal feed. tion for sale. Buttermilk of good quality, produced The kinds of cheese that are still be- in churning sweet cream, may be ing made in limited quantities on farms either condensed or dried, and is for home use are mostly hard, ripened utilized in preparing food. cheese of the Cheddar or American Cream gathered from many pro- type, and soft, unripcned cheese of the ducers is frequently high in acidity. cottage type. Directions for making The pasteurization of sour cream for these cheeses, as w^ell as other kinds, butter fnaking first requires partial re- can be obtained by writing to the Bu- duction of the acidity. Neutralization reau of Dairy Industry. is accomplished by the addition of alka- line compounds, containing either lime CREAM FROM 33.9 billion pounds of or soda, to the cream before pasteuri- milk was used in 1949 in the manufac- zation, which makes it possible to pas- ture of 1,695 million pounds of butter teurize the cream without coagulation in the United States, including 1,412 in the pasteurizer. The practice of neu- million pounds made in creameries and tralization is discouraged. It is a proce- 283 million pounds on farms. dure for using low-grade sour cream Milk to be used in the manufacture in making butter, and such butter often of creamery butter may be separated is inferior. It is better to use only high- into cream and skim milk on the farm quality cream. and the cream delivered to the cream- The process- or renovated-butter in- ery, or the whole milk may be deliv- dustry, which at one time produced as ered to the creamery and separated much as 50 million pounds annually, there. The latter practice is becoming depends largely on low-grade farm but- more common. The cream is tested ter as a source of raw material. With to determine the butterfat content. the decline in production of farm- Cream for churning contains usually made butter, the process-butter indus- between 30 and 35 percent of fat. The try has declined until now only 1 mil- cream is pasteurized, cooled, and aged lion to 2 million pounds is produced to solidify the butterfat, and then annually. In 1950, only three factories churned under carefully controlled were bonded to manufacture process temperature conditions. When the butter. The enactment of Public Law particles of butter have gathered to 427 in 1946, and the regulations pro- the proper size, the buttermilk is drawn mulgated pursuant thereto early in from the churn. The butter is w^ashed 1947, yjlaced the manufacture of proc- with water, salted, and worked in the ess butter under rigid inspection by the churn to insure thorough distribution Department of Agriculture. Since that of salt and moisture, as well as the de- time, such butter is being made only sired body and texture. Then the but- under the continuous inspection of the ter is removed and printed or packaged Department. in . Federal standards require Process butter is made by melting the that butter contain at least 80 percent farm butter received as raw material, fat. clarifying the butter oil, reemulsifying Thus two byproducts are obtained the oil with whole or skim milk, and in the manufacture of butter. Skim churning this mixture of "reconsti- 686 1950-1951 YEARBOOK OF AGRICULTURE tutcd cream" in the conventional utilized in making butter by the con- manner. ventional churning method. However, The invention of continuous butter- a continuous, mechanical method of making equipment is the outstanding making butter would meet the need for recent technical development in butter more efficient production and im- making. P'undamcntally, the continu- proved sanitation in the handling of ous method of making butter involves butter during manufacture. breaking the natural fat emulsion in The butter industry has a stabilizing cream to yieild a butterfat concentrate, effect on the dairy industry as a whole. which is then standardized with salt Because it utilizes surplus milk in times and water and crystallizxd by chilling. of greatest production, it acts as a bal- Among several designs of equipment ance wheel. When the supply of fluid developed for continuous butter mak- milk is low, milk is diverted from the ing, tw^o, patented by American firms, butter industry into channels where it are being used to a limited extent com- is needed more. mercially. The two processes arc being The skim milk and buttermilk pro- investigated experimentally with a duced as by]:)roducts by creameries arc view toward further improvement. returned to farms for use as feed for In one jjrocess, cream is converted livestock ; or, if of suitable quality and to butter by first homogenizing a quantity, they can be processed for hu- highly concentrated or "plastic" cream^ man consumption. Both skim milk and which contains 75 to 80 percent of but- buttermilk are us(^d in the manufacture terfat. The treatment breaks the {emul- of ice cream. Butter itself, when un- sion, and the free fat. or butter oil, saltcd, is also used to furnish part of separates readily from the serum. The the butterfat for ice cream. serum is removed, salt and water are Although modern (Tcanieries have mixed with the oil to give it the com- largely supplanted the farm manufac- position of butter, and the mixture is ture of butter, there is no difficulty^ chilled rapidly. During the final or after some experience, in making but- chilling stagCj the solidified product is ter of good equality in the home. The worked to produce the desired body cream is separated from the milk, pref- a.nd texture, and extruded for subse- erably with a cream separator, but any» quent packaging. one having only a few cow^s can use In the other process, the cream is gravity-se]:)arated cream. The milk or heated and at the same time agitated cream should be pasteurized, not only violently to break the emulsion. The for the sake of keeping quality, but butter oil set free by agitation and heat also because pasteurization is a safe- is separated, pasteurized, and stand- guard against the possibility, however ardized to the correct composition remote, that the milk contains micro- with salt and water. The mixture is organisms that might cause sickness. crystallized by cooling and worked to Churns of various sizes for use in the the consistency of butter, as in the first home are available on the market. Di- process. rections for making and storing butter Variable composition and imperfect in thci home can be obtained from the body and texture are principal defects Bureau of Dairy Industry. in butter made by some of the continu- ous methods. Apparently it is difficult ABOUT O.Iî BILLION POUNDS of milk to develop, by mechanical means, a v/as used in the manufacture of 557 process that will produce the perfection million gallons of ice cream in the of body that has been attained in the United States in 1949. About 157 mil- older art of churning. An important lion pounds of milk was used in the objection also is the possibility of the manufacture of 39 million gallons of use of large quantities of undergrade, milk sherbet and ice milk. About 80 poor-quality cream that would not be million pounds of milk was used in the CHEESE, BUTTER, ICE CREAM, SHERBET 687 manufacture of 7.1 million gallons of Stabilizing materials, usually colloi- frosted , frozen custard, dal in nature, are added to the mix and other frozen dairy products. during its preparation in order to pio- Ice cream usually contains from 8 to ducc a smooth body and texture. They 16 percent of butterfat, from 9 to 11 retard the formation of large ice crys- percent of milk-solids-not-fat (lactose, tals. Some stabilizers in common use protein, and salts), from 14 to 16 yoer- are gelatin, sodium alginate, Irish cent of sugar, from 0.15 to 0.5 percent moss, locust bean and karaya gums, of stabilizer, and sometimes from 0.2 psyllium seed husks, citrus and apple to 0,5 percent of egg yolk. The total pectin, and c(41ulose gum. solids range from 36 to 41 percent. Besides its function in partly freezing The components of milk sherbet arc the niix. the freezer also whips air into essentially the same as those of ice it, and thus increases the volume of the cream, but they are present in much ice cream. The increase is known as different proportions. Individual man- overrun, and may frequently be as ufacturers have their own formulas, much as 100 percent. Thus, a gallon and therefore sherbets vary considtn*- of mix weighing 9.2 pounds will yield ably in composition. A typical sherbet, 2 gallons of ice cream weighing 4.6 however, may contain from 25 to 35 pounds a gallon when the overrun is percent of sugar, from 2 to 5 percent 100 percent. of milk solids, from 0.3 to 0,7 percent Because ice-cream mix contains a of stabilizer, and flavoring material. somewhat greater percentage of milk- Sherbet may contain buttcrfat as well solids-not-fat and a much greater per- as milk - solids - not - fat—constituents centage of fat than does milk, it is that add to the nutritive value and in- necessary to use concentrated dair\^ crease the refreshing properties. Water products in preparing the mix. The ices dilTer from sherbets in that the ices usual components are cream, which contain no solids derived from milk. contains the fat in concentrated form, Th(i first step in the manufacture of and condensed or dried skim milk, ice cream is the preparation of the \vhich contains the solids-not-fat in mix. It is customary to combine with concentrated form. Other dairy prod- the dairy ingredients such nondairy ucts used in making ice cream include products as stabilizer, sugar, and water, frozen cream, plastic cream, unsalted in the connect proportions to provide butter, condensed whole milk, sweet- the desired percentages of buttcrfat, ened condensed whole milk, dried milk-solids-not-fat, sugar stabilizer, and whole milk, sweetened condensed skim water. Usually part oï the water of the milk, and concentrated buttermilk. mix is provided in the dairy products themselves. The mix is pasteurized im- CHEESE WHEY has been used experi- mediately after it is made up, usually mentally, in research in this Depart- in an insulated, vat-type pasteurizer, in ment, to furnish a small proportion of which the entire batch is heated to a the milk solids in ice cream and to re- pasteurizing temperature and held for place conventional milk solids in sher- 30 minutes. The heating conditions bet. The w^hey was prepared both as customarily are prescribed by local reg- plain condensed whey and as sweet- ulatory authorities. Following pasteuri- ened condensed w^hey. It w^is found zation, the mix is homogenized, cooled, that concentrated whey in either of and pumped to a storage tank. Subse- these forms can bc^ used to furnish all quently, flavoring materials are added of the milk solids in sherbet. It cannot and the mix is frozen in an ice-cream be used to furnish more than a siTiall freezer as it is needed. The semifrozen proportion of the solids in ice cream, ice cream that flows from the freezer however, because its solids consist is placed in containers for sub-zero mainly of lactose and the presence of hardening and storage. excessive lactose in ice cream mav 688 19 5 0-1951 YEARBOOK OF AGRICULTURE cause the development of the defect until it contains 70 percent total solids. known as sandincss. The concentrate is cooled and kept at The use of sweet-cream buttermilk 50° F. for 20 hours, during which time to furnish the milk-solids-not-fat in ice m.ost of the lactose crystallizes out of cream is another development in the solution. Afterward the crystallized utilization of surplus dairy byproducts. lactose is removed by means of a Experimental work carried out by this ccntiifuge or by a filter press. Department has shown that sweet- The resulting ice-cream mix was cream buttermilk of good quality, in prepared wâth 11 to 13 percent of milk- concentrated form, can be used in ico solids-not-fat instead of the usual 9 to cream mix to supply part or all of the 11 percent. The nûx, in which the m.ilk-solids-not-fat rec^uired in the concentration of lactose was reduced formula. The buttermilk solids im- by use of this *'low-lac" milk, had im- prove the quality of the ice cream by l^roved body and texture and with- imparting a pronounced creaminess stood adverse handling conditions not ordinarily obtained with conven- without developing sandincss. Such tional milk-solids-not-fat. In addition, processing makes it possible to incoi^po- it was found that the buttermilk solids rate increased amounts of food solids improve the whipping ability of the in ice cream—improving the product mix, making it easier to incorporate the • without increasing the lactose content. desired amount of air during in^^zing. A few large-scale manufacturers of Although the supply of suitable butter- ice cream use the high-temperature milk is limited to the areas of the coun- short-time method of pasteurization try that produce sweet-cream butter, instead of the lower-temperature vat buttermilk can be concentrated with method, which takes more time and cane sugar for preservation and eco- requires more floor space. In the newer nomical shipment to other areas where method, the mix is heated at a tem- there is a demand for it in the produc- perature higher than that ordinarily tion of ice cream. used in the holding or vat method, and Too great a concentration of lactose it is held at the higher temperature in ice cream frequently produces the for only a few seconds. defect of sandiness, which is caused by Research workers are studying the the crystallization of lactose from the problems of hc^at-treating the ice-cream supersaturated solution in which it mix as w^ell as its various components, normally exists in hardened ice cream. particularly the milk-solids-not-fat. En- This factor is not important in sherbet, gineers of the Department of Agricul- as sherbet contains enough water to ture recently d(\signed and obtained a hold all the lactose in solution. jDublic-service patent on a high-tem- In an effort to increase the utiliza- perature heating device or pasteurizer tion of dairy products in food and at that can be used to attain heating ex- tlie same time to increase the milk- posures over a wide temperature range solids-not-fat content of ice cream, the and that can be used for heat-treating Dairy Products Research Laboratories the milk-solids-not-fat part of the mix. of the Department developed a modi- Recent exjjeriments in the Bureau fied, concentrated form of sknn milk of Dairy Industry indicate the jDossi- from which part of the lactose was re- bility of improving the body and tex- moved by a special process. About 65 ture of ice cream by use of this special percent of the lactose of skim milk is heat-treating equipment. Earlier in- removed, lowering the lactose content vestigations indicated that extremely from about 5 percent to less than 2 rapid, short-time heating of fresh milk percent. In the process, 5.9 pounds of to a temperature higher than boiling cane sugar is added to 100 pounds of causes changes in the milk that may be skim milk, and the mixture is concen- used to advantage in some dairy-manu- trated (evaporated) under vacuum facturing processes. I'herc is a possi- CHEESE, BUTTER, ICE CREAM, SHERBET 689 bility that, in condensed skim milk that the smoothness of body, condensed by has bi^cn exposed to a high temperature evaporation of water in a vacuum pan under carefully controlled conditions, to approximately the concentration of the milk proteins have a tendency to a normal mix, and then spray-dried. hold more water in a "bound" condi- It requires only the addition of water, tion without meanwhile becoming de- or water and ilavor, according to di- natured or heat-coagulated. If further rections on the package, and then alter- research proves this to be true, the nate whipping and freezing in the principle may have useful application home refrigerator. in the manufacture of ice cream, be- The continuous freezer is a relatively cause the mix may be stabilized in part recent technical development in icc- by the increased water-binding prop- cn^am equipment. The mix is partly erty of the milk proteins. With an in- frozen as it passes continuously through crease in bound water, there would be the machine and is collected in cans or less free water present. Since appar- cartons and transferred to a low-t(^m- ently only free water forms ice, there perature room—a so-called hardening should be fewer ice cr\'stals in the room. New developments in packaging frozen ice cream, and its body should have made it possible to fill packages be smoother. entirely automatically, on a produc- There are indications also that spe- tion-line basis, as the semifrozen ice cial heat treatment of the constituents cream flows from the continuous may have other favorable effects on freezer. Continuous freezing and me- the properties of the mix. For exam^ple, chanical packaging save time and la- heat treatments used in forewarming bor, eliminate much of the handling raw^ skim milk have been found to alter required with the batch freezer, and the viscosity of the sweetened con- minimize contamination. densed skim milk made from it, which Ice cream is one of the most popular is used commonly in ice cream. of the dairy-product foods that can be For use with the high-temperature made easily on the farm where milk heater, Department engineers have de- and cream are produced and where ice signed and developed also a simple, is available. An ice-cream freezer is the magnetic flow-diversion valve—an only mechanical equipment required. electrical device that automatically Formulas for preparing the mix are controls the heating exposure precisely. available by writing to the Bureau of Limited quantities of concentrated Dairy Industry. (condensed) ice-cream mix are being made commercially and sold for use in GEORGE P. SANDERS is a chemist in the home. A common brand is a semi- the division of Dairy Products Re- solid paste, which is sold in small cans search Laboratories in the Bureau of or screw-top jars and requires only the Dairy Industry. He received his bache- addition of water and flavoring mate- lor's and master's decrees at the rial before whipping and freezing in University of and his doc- the household refrigerator. Concen- tor's de<^ree at American Lhiiversity. trated ice-cream mix, like sweetened He joined the Department's research condens(?d milk, is preserved with staff in 1926. He has made a larfie sugar. The mixes sold commercially are number of contributions and published prepared like the usual mixes w'c have numerous scientific papers on the described. chemistry of milk and cheese. Dried ice-cream mix, in the form of DONALD H. WILLIAMS is a dairy powder, a new product, is sold in one manuf act urinal technologist in the di- form in 5-ounce paper cartons. The vision of Dairy Products Research mix is prepared in the usual way from Laboratories in the Bureau of Dairy unconcentratcd dairy products, and it Industry. He was graduated from the is pasteurized, homogenized to increase University of Maryland in 1938.