TESTS USED IN CHEESE-MAKING 429 



used stands for o.oi per cent of acidity equivalent to 

 lactic test (Testing Milk, etc., pp. 103-105). 



Testing acidity of whey. — Whey is tested in the 

 same manner as milk. The sample of whey tested 

 should be free from all curd particles, since curd has 

 some power to neutralize alkali (Testing Milk, etc., 

 pp. 109-110). 



Testing acidity of cheese. — An extract of a 

 weighed amount of cheese is made and this extract 

 is tested for acidity in the usual way (Testing Milk, 

 etc., p. no). 



Special precautions in making acidity tests. — 

 In carrying out tests for acidity, certain points of the 

 operation must be kept carefully in mind. 



(i) The material tested must be thoroughly mixed 

 before taking a sample. 



(2) The water used in preparing the alkali solu- 

 tion should be neutral, soft and clean. Distilled water 

 is best. 



(3) Alkaline tablets must be kept dry. 



(4) The alkali solution, whichever form is used, 

 must be kept from contact with air as much as pos- 

 sible to prevent change of strength. 



(5) Prepare fresh solution of alkaline tablets for 

 best results. 



(6) Make tests only in a good light. 



QUICK TEST FOR ACIDITY OF MILK 



It is often desirable to ascertain quickly whether 

 milk or cream contains more or less than 0.2 or 0.3 

 per cent of acid. This can be done by the following 

 method : An alkali solution is prepared by dissolving 

 in an 8-ounce bottle 2 alkali tablets for each ounce 



