PROPERTIES OF MILK. 41 



cooled quickly, the cooked taste can be greatly reduced and 

 almost entirely avoided. Where heating or pasteurization 

 of cream has been adopted, as in some creameries, the pre- 

 vention of this cooked flavor in the butter is of vital importance. 

 The reason why this cooked flavor forms in milk when 

 heated is not well understood. It is supposed to be due to 

 the effect which heat has upon the nitrogeneous constituents 

 of milk. 



5. Precipitates Albuminoid and Ash Constituents. — When 

 milk is heated, there is a tendency for the soluble salts and a 

 portion of the albuminoids to be thrown down, or changed into 

 an insoluble form. 



The higher the milk is heated, the greater is this tendency. 

 By subjecting a sample of milk in a flask to intense heat, and then 

 allowing it to stand, a fine white sediment will be deposited on 

 the bottom. This is believed to be minerals precipitated from 

 the milk. 



When milk has been heated to about 170° F., and cooled, 

 rennet is unable to precipitate the curd in a normal way. The 

 curd resulting from adding rennet to pasteurized milk is floccu- 

 lent in nature. It does not assume that smooth and even 

 texture that curd from raw milk has when precipitated with 

 rennet. This abnormal behavior of pasteurized milk towards 

 rennet can be reestablished by adding a small quantity of 

 calcium chloride (CaCl). Whether this would effect the 

 quality of cheese materially has not yet been determined 

 definitely. According to G. Fascetti,* if pasteurized milk is 

 used for cheese-making, the cheese ripens more slowly than 

 when made from raw milk. The same investigator also claims 

 that a larger quantity of cheese is obtained per 100 parts of milk 

 when pasteurized milk is used. 



6. Destroys Properties of Enzymes. — As was mentioned in 

 the composition of milk there is a substance normal to milk 

 named galactase. This is an enzyme. By heating milk to 



* Exper. Sta. Record, Vol. 15, Xo. 10, 1904. 



