THE MILK IN ITS RELATION TO CHEESE 11 



are certain kinds of cheese, such as Ricotte, made by the 

 recovery of albumin by heating. 



15. Ash. The ash or mineral constituents make up 

 about 0.7 per cent of cow's milk. This total includes 

 very small amounts of a great many substances. The 

 exact form of some of the substances is still unknown. 

 Of these salts, the calcium or lime and phosphorus salts 

 are most important in cheese-making. They are par- 

 tially or completely precipitated by pasteurization. 

 After such precipitation rennet fails to act * or acts very 

 slowly ; hence pasteurized milk cannot be used for making 

 rennet cheese unlesfe the lost salts are replaced, or the 

 condition of the casein is changed by the addition of some 

 substance, before curdling is attempted. 



16. Enzymes. Milk also contains enzymes. These 

 are chemical ferments secreted by the udder. They have 

 the power to produce changes in organic compounds with- 

 out themselves undergoing any change. Minute amounts 

 of several enzymes are found in milk as follows : Diastase, 

 galactase, lipase, catalase, peroxidase and reductase. 

 Just what part they play in cheese-making is not definitely 

 known. 



17. The flavor of feeds eaten by the cow. Unde- 

 sirable flavors in the milk are due many times to the use 

 of feed with very pronounced flavors. The most common 

 of these feeds are onions, garlic, turnips, cabbage, de- 

 cayed ensilage, various weeds and the like. These un- 

 desirable flavors reach the milk because the substances 

 are volatile and are able to pass through the tissues of 

 the animal. While feed containing these flavors is being 

 digested, these volatile substances are not only present 



1 Sammis, J. L., and A. T. Bruhn, The manufacture of cheese 

 from pasteurized milk, Wis. Exp. Sta. Research Bui. 27, 1912. 



