348 MILK AND DAIRY PRODUCTS 



by adding artificial lactic acid bacteria cultures. Butter 

 contains about 84 per cent, of fat, 13 per cent, of water, and 

 about 3 per cent, of lactose, albumin, and sodium chloride, 

 the latter having been added to improve the flavor and also 

 to serve as a preservative. Since it is possible to produce 

 butter which contains considerable water and thus sell an 

 adulterated product, it is not permitted in the United States 

 for butter to contain more than 16 per cent, of water. 



Butter frequently becomes rancid, a condition which is 

 due probably to the action of bacteria, molds, light, and oxy- 

 gen. This combination of factors results in the hydrolysis 

 of fat, which sets free some of the fatty acids, one of them 

 at least, butyric, being volatile, and some of them oxidizing 

 to aldehvdes. 



Oleomargarine. — At this point it may be well to mention 

 one of the principal butter substitutes, which is a perfectly 

 nutritious article of food, but which not being butter should 

 not be sold as such. It is manufactured from beef fat by 

 rendering the latter and allowing the resultant product to 

 stand at a low temperature for some time, when part of the 

 solid fats crystallize. The soft mass is now subjected to 

 pressure, and a liquid oil consisting of olein and palmitin 

 principally are pressed out. This "oleo oil" is worked up 

 by itself or with lard, cottonseed oil, cocoanut and other 

 oils. It is then churned with milk, sometimes with a little 

 butter, after which it is worked and salted. 



249. Cheese. — This is one of the oldest articles of food, 

 being used 1000 years B. C, and still retaining its popularity 

 as a nutritious article of diet. It consists essentially of the 

 casein from milk with considerable fat entangled with it 

 and some water, lactose, and inorganic salts. The solid 

 product is submitted to seasoning and ripening processes 

 which favorably affect its composition and flavor. Ordinary 

 American cheese contains about 34.4 per cent, water, 26.4 

 per cent, protein, 32.7 per cent, fat, 2.9 per cent, lactose, 

 and 3.6 per cent. ash. 



Cheddar, or American cheese, is the commonest form of this 

 food. It is made by first ripening the milk with an artificial 

 starter until it contains a small amount of lactic acid. Then 



