128 METHODS OF ANALYSIS. 



It' the sample is a full cream cheese a Babcock cream bottle is employed. 



The contents of the beaker, after cooling, are transferred to the test bottle 

 as follows: Add to the beaker about half of the 17.6 cc of sulphuric acid 

 usually employed in this test, stir with a rod, and pour carefully into the bottle, 

 using the remainder of the acid in two portions for washing out the beaker. 

 Finally proceed as in the Babcock test for milk. Multiply the fat reading by 

 18 and divide by the weight of the sample to obtain the per cent of fat 



6. Acidity. Provisional. 



To 10 grams of finely divided cheese add water at the temperature of 40 C. 

 until the volume equals 105 cc; agitate vigorously and filter. Titrate 25 cc 

 portions of the filtrate with standard sodium hydroxid, preferably tenth-normal, 

 using phenolphthalein as indicator. Express amount of acid as lactic. 



7. Separation of Fat for Examination. Provisional. 



(a) METHOD I ALKALINE EXTRACTION METHOD. 



Cut about 300 grams of the cheese into fragments the size of a pea. Treat 

 with 700 cc of potassium hydroxid (50 grams per liter) at 20 C. in a large 

 wide-necked flask, and promote the solution of casein by vigorous shaking. 

 In from five to ten minutes the casein will be dissolved and the fat will come to 

 the surface in lumps. Collect the lumps of fat into as large a mass as possible 

 by gently shaking. Pour cold water into the flask until the fat is driven up 

 into the neck and remove it by means of a spoon. Wash the fat thus obtained 

 with as little water as will remove the residue of the lye which it may contain. 

 Experience has shown that the fat is not perceptibly attacked by the lye in 

 this treatment By this method the fat is practically all separated in a short 

 time and is then easily prepared for chemical analysis by filtering and drying 

 as directed in the oflScial method, page 124. 



(b) METHOD II ACID EXTRACTION METHOD. 



Grind the cheese by passing it through a meat-cutting machine. Transfer 

 it to a large flask and pour warm water upon it using 1 cc for every gram of 

 cheese. Shake thoroughly and add sulphuric acid (sp. gr. 1.82 to 1.S25) 

 slowly and in small quantities, shaking after each addition of acid. The total 

 amount of acid used should be the same as the amount of water used. Remove 

 the fat, which separates after standing a few minutes, by means of a sepa- 

 ratory funnel, wash it free from acid, filter, and dry. 



8. Examination of the Fat. 

 Proceed as directed under " XIX. Edible Oils and Fats," page 129. 



