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Home and Farm Food Preservation
Chapter XVIII - Milk Products

The manufacture of condensed milk, dried milk, cheese, and butter constitutes a series of very important dairy industries. A full discussion and description of these industries would be entirely outside the scope of this book. In the following pages only that material is taken up which will be of most interest and value to those desiring to preserve moderate amounts of butter or who desire to make a small amount of cheese or who wish to pasteurize milk in a small way. No attempt or claim is made to give a description of commercial installations or practices.

108. Sterilization and Pasteurization of Milk.

(a) Sterilization. Enormous quantities of canned milk are used. Commercial factories concentrate milk before canning and sterilization. This must be done in a vacuum evaporator and cannot be carried out on a small scale. Milk may be sterilized in sealed cans under steam pressure at ten pounds' pressure for forty minutes or for one hour at 212 F. on each of three successive days. Milk is exceedingly difficult to sterilize because of the spore-bearing bacteria present. There is, however, very little need of sterilizing milk in the household because it is usually not necessary to keep it more than two or three days. Pasteurization is, however, useful.

(b) Pasteurization of Milk in the Household. Milk heated to 140 to 160 F. will keep much longer than unheated milk. Heating to this temperature kills many of the bacteria and so weakens those not killed that their growth is very much slowed up.

Pasteurization may be accomplished in bottles or in open pots. If carried out in bottles the bottles should be scalded before filling. The filled bottles should be sealed with sterilized corks. They may be heated in a pot of water with bottles completely immersed until the water reaches 150 F. Maintain at this temperature for twenty minutes. Remove and cool. A thermometer must be inserted in the water to test the temperature.

The milk may also be pasteurized by heating in a pot to 145 F. at which temperature it is maintained for twenty-five minutes. A double boiler is best. Pour into scalded jars or bottles. For practical purposes milk may be pasteurized by heating in a pot to the simmering point or by "scalding "; that is, heating to boiling. This is often necessary for the keeping of milk in hot weather.

Pasteurized milk will keep considerably longer than the unpasteurized, and will not contain living typhoid or tuberculosis bacteria. Where there is any suspicion that milk may be infected with disease organisms it should be pasteurized; or if a thermometer is not available it should be heated to boiling ("scalded ") before use.

109. Storage of Butter. Butter may be kept very satisfactorily in cold storage, but this is rarely available on the farm. The most practical method for farm use is preservation by salting. Butter should be kept cool, excluded from the air and away from the light. The spoiling of butter is brought about by the formation of fatty acids from the butter fat and the decomposition of the proteins and sugar in the buttermilk left in the butter. These changes are largely bacterial in nature, although partly a simple chemical change. Exclusion of air lessens the tendency for decomposition by bacteria.

Preservation by salt may be accomplished by adding from one-half to one pound of salt to each ten pounds of butter. The salt is worked in thoroughly. The butter is packed tightly in crocks and covered with salt.

Butter may also be preserved by adding one-fourth to one half a pound of salt to each ten pounds of butter and then storing the salt in a saturated brine (three and one- half pounds of salt per gallon of water). This is the usual household method. Such butter should be "freshened" by working in cold water before use.

Butter contains casein and buttermilk which tend to decompose. These can be removed by heating the butter in boiling water a short time. The casein is coagulated and falls to the bottom of the pot. The melted fat may be skimmed or poured off without mixing any water with it. It is then poured in dry jars, allowed to cool, and is sealed with paraffin. The butter is stored until it is to be used and keeps well in this form. It must be salted before it is used.

110. Cheese.

(a) "Cottage" Cheese. The only cheese that may be made satisfactorily without special experience and training is "cottage" cheese or "schmier kase." Formerly this product was made only in the home. In recent years, however, it has been made in large quantities for sale in delicatessens, restaurants, and cafeterias.

Skim milk is ordinarily used. It must be clean and of good quality. The first step is the formation of the curd. This is ordinarily accomplished by permitting the milk to sour naturally or by addition of a starter of lactic acid bacteria. It may also be accomplished by the addition of rennet, as in the making of hard cheese, but this produces rather a tough curd. Seventy degrees Fahrenheit is considered the best temperature for souring of the milk.

The curdled milk must next be heated to coagulate the curd. This should not be carried out at too high a temperature, or the curd will be tough and dry. The milk should be heated slowly to about 100 F., i. e., blood temperature or a little higher and kept at this temperature until the curd seems firm and the whey clear. About half an hour's heating at this temperature will be sufficient.

The Curd is then drained through a cheesecloth for several hours. It is then broken up with a wooden potato masher or with the hand. About one ounce (one tablespoonful) of salt is added to each five pounds of curd. Other flavorings, such as finely chopped pimento, or black pepper, or various spices may also be added. "Pimento" cottage cheese is especially popular in California. If a rich flavor is desired, cream or melted butter is added and worked into the cheese.

Cottage cheese must be used within three or four days. after it is made and is best when fresh. It does not ripen and improve with age in the way that other cheese does.

(b) Cheddar Cheese. This is the most common type of American cheese. It is made from whole milk. It cannot be made very successfully without considerable experience.

The first step is the souring of the milk to .2% acid. This is done by the addition of a starter of lactic bacteria and must be carefully watched by a chemical determination of the acid.

Rennet is then added. This is a substance obtained from the lining of calves' stomachs. It may be purchased also under the name of junket tablets. Rennet coagulates or curdles the casein. The curd is cut into cubes and left until the acid reaches 1%. It is then salted, pressed, and left to ripen.

The ripening process is a very complex one brought about by bacterial and enzyme action. Lactic acid is formed from the milk sugar left in the curd; the casein or curd is softened and partially decomposed and the butter fat undergoes partial decomposition. Most of these changes are brought about by bacteria occurring in the milk.

(c) Other Types of Cheese. There are numerous other types of cheese. Space will not permit their discussion here. Bulletin 146 of the Bureau of Animal Industry of the United States Department of Agriculture gives good descriptions of the various types. This bulletin may be obtained free of charge by writing to the United States Department of Agriculture, Washington, D. C. It is not recommended that the making of cheese (except cottage cheese) be undertaken on the farm unless in a small experimental way and with the personal advice and supervision of some one experienced in cheese making. Recipes for cottage cheese and gouda cheese will be found in Part III.

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