40 



PRCJPERTIES OF MILK 



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

 tion of the bod}' 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 tu some extent. This is facilitated by 



«^ ^ i ,1^ ' {M \. -^rv ^v :■ 



'4# ^ft\ - 





Fig. 6. — Microscopic appearance of milk, showing natural grouping of tlic fat- 

 globules. Single group in circle, highly magnifted. (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 y\merica is not generally heated above 14 s° F. 

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

 subjected to low temj)eralure pasteurization (145° F.) and held 

 at this temperature for twenty to thirty minutes. Under this 

 syste7Ti the disadvantages of high pasteurization are overcome. 



For butter-making purj^oses there are no objections to pas- 

 teurizing cream at a high temperature. The common practice 



