40 PROPERTIES OF MILK 



nitrogenous constituents in such a way as to aid in the restora- 

 tion of the body of the cream or milk. 



Nearly all dairy laws forbid the addition of any foreign sub- 

 stances to milk or cream. If viscogen is added, Babcock and 

 Russell suggest tha. it be named visco-milk, visco-cream, etc. 

 When the modification is made, no objection can be raised to its 

 legitimate use. 



3. Drives off Gases. When milk is heated, taints and gases of 

 different kinds pass off to some extent. This is facilitated by 



FIG. 6. Microscopic appearance of milk, showing natural grouping of the fat- 

 globules. Single group in circle, highly magnified. (From Bui. 64, Wis.) 



heating and stirring in an open vessel. Many of these gases 

 also escape when milk is aerated and cooled in a pure atmos- 

 phere. 



4. Imparts a Cooked Taste. When milk is heated to 160 F. 

 or above, it assumes a distinctly cooked taste, which makes it 

 disagreeable as a food for many people. On this account, milk 

 for city supply in America is not generally heated above 145 F. 

 In practically all cities where milk is consumed directly, it is 

 subjected to low temperature pasteurization (145 F.) and held 

 at this temperature for twenty to thirty minutes. Under this 

 system the disadvantages of high pasteurization are overcome. 



For butter-making purposes there are no objections to pas- 

 teurizing cream at a high temperature. The common practice 



