96 



GRADINC; AND 'I'lvSTING MII.K AND CREAM 



they will reveal themselves by developing small holes in the curd, 

 usually accompanied by a bad odor. 



This test is a very ingenious one for cheese-making. Tn 

 butter-making the Gerber Fermentation Test, or a similar one, 

 is more con\'enient. 



4. Grading Milk by Heating. — This test is not ver}' much 



... y^-i^^ifJiMii-: ■ 



Fig. iS. — Troemner's Kabcock cream-testing scales. 



used in creameries; but in cheese factories the heating of milk in 

 order to ascertain its suitability for cheese-making is practiced 

 to a considerable extent. The heating test, which is in comnn)n 

 use in Canada, consists of heating a small sample of the milk to be 

 tested to 120° F. If it will stand this temperature without coag- 

 ulating, it is considered to be good milk. If it coagulates when 

 heated to this temperature, it is too sour 

 to be used for cheese. 



This heating may l)c considered an 

 acid test. When milk contains about 

 .3 per cent acid, it usuall)- coagulates 

 when heated. It should be borne in 

 mind in this connection that different 

 samples of milk, containing exactly the 

 same amount of acid, do not coagulate at the same tempera- 

 ture. Some samples will coagulate upon heating when contain- 

 ing a little less than .3 per cent acid, while others will not 

 coagulate until more than .3 per cent acid has developed. 



In practice the temperature (120° F.) is not alwaj's closely 



Fig. 19. — Troemner's Bab 

 cock cream-testing scales. 



