426 SCIENCE AND PRACTICE OF CHEESE-MAKING 



(5) Mix milk and acid thoroughly as soon as acid 

 is added. 



(6) Mix a second time after a short interval. 



(7) Make sure that the tester runs at the right 

 speed and does not jar. 



(8) Use only clean, soft water in filling bottles. 



(9) Read bottles before they cool and at about 

 130 F. 



( 10) To guard against mistakes, read each test 

 twice. 



Testing whey for fat. The test is conducted in 

 the usual way, except that special bottles having small 

 necks for more accurate reading are used and less acid 

 is generally sufficient (Testing Milk, etc., pp. 81- 

 83). 



Testing curd and cheese. Care must be taken in 

 sampling. The weighed sample (8 to 10 grams) is 

 treated in the test-bottle with about 10 cc. of wate'r 

 (65-7O F.), after which the acid (17.6 cc.) is added 

 and the test completed in the usual way (Testing Milk, 

 etc., pp. 83-85). The acid should be added carefully, 

 about i cc. at a time, mixing the acid and water by 

 shaking after each addition. After all the acid has 

 been thus added, shake the whole vigorously until the 

 cheese is completely disintegrated. 



TEST FOR ACIDITY 



Fresh milk contains substances (casein and acid 

 phosphates) which neutralize alkali and in this respect 

 behave like acids. The amount of this acidity is ap- 

 proximately equivalent to o.io per cent. Amounts of 

 acid above this figure are usually due to the action of 

 lactic acid that has been formed bv the bacterial decom- 



