148 MODERN METHODS OF TESTING MILK 



solutions and the large amount of material used (50 

 cc.) is not only inconvenient and time-wasting but 

 calls for the use of larger amounts of alkali than are 

 necessary. It is much better to use not more than a 

 9-gram sample and then the reading can be made 

 direct ; each cubic centimeter of solution representing 

 o.i per cent, of lactic acid, or, if a 17.6 cc. sample is 

 used, the reading is divided by 2. 



TESTING THE ACIDITY OF WHEY 



Whey may be tested by any of the methods de- 

 scribed. Owing to the comparatively low acidity of 

 whey in the operation of cheese-making, it is desirable 

 either to have the alkali dilute ( i cc. of alkali equal to 

 .01 per cent, acid), or else to take twice as much whey 

 for testing as in the case of cream, the final results 

 being corrected by dividing by 2. The whey should 

 be free from particles of curd, since curd has the 

 power of neutralizing alkali to some extent. The per- 

 centage of acid in milk can be used as a guide in 

 ripening the milk before adding rennet, in the rate of 

 heating (cooking) the curd, in the regulation of the 

 piling of the curd, in the time of milling, etc. 



TESTING THE ACIDITY OF CHEESE 



From a sample of cheese, prepared in the manner 

 described on page 108, weigh 9 grams and to this 

 add water at a temperature of 100 to 110 F. until 

 the volume equals 90 to 100 cc. Agitate vigorously 

 and filter. To the filtrate add alkali solution, each 

 cubic centimeter of which equals .01 per cent, of lac- 

 tic acid, carrying out the test as with milk, cream, etc. 



