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 anormal 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 materiaily 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, No. 10, 1904. 
