BUTTERMILK AND CHEESE. 369 



It is seen from the figures quoted above that the analysis of 

 butter which has been kept for any length of time is a matter of 

 considerable difficulty. Though in butter fat the volatile acids 

 do not show any diminution, but rather an increase (due pos- 

 sibly to the oxidation of the glycerol), in butter the reverse is 

 usually the case. It is by no means improbable that, besides 

 the solubility of these in the water contained in the butter, a 

 portion is destroyed by the action of micro-organisms. The 

 most reliable datum would seem to be the determination of the 

 volatile acids on the butter itself without separation of the fat, 

 subsequent determination of the fat, and calculation of the 

 Reichert figure on the actual fat present. The potash absorption 

 does not appear to undergo much change. 



The phytosteryl acetate test may be applied to rancid butters. 



Buttermilk. It is sometimes asserted that a certain amount 

 of water (20 or 25 per cent.) is allowed to be added to milk or 

 cream for churning purposes. This view, however, appears to 

 be quite incorrect ; the addition of " breaking " water does not 

 appear to be recognised by any statute, and if buttermilk is to be 

 sold there is no reason why it should contain any added water. 

 It is probable, however, that should a sample of buttermilk 

 taken under the Sale of Food and Drugs Acts be found to con- 

 tain a small percentage of added water, the Public Analyst 

 would advise his authority that it is a custom to add water 

 during churning, and a prosecution for the addition of small 

 percentages is improbable. 



Adulteration of Cheese. The only forms of adulteration of 

 any importance consist in the substitution of skim milk cheese 

 for whole milk cheese, or milk cheese for cream cheese, and the 

 addition of fat not derived from milk to skim milk before making 

 it into cheese. 



The former adulteration is detected by the estimation of 

 fat and total nitrogen. In a whole milk cheese the ratio 



; r on varies from 1 to 1 -5 ; in a skim milk 



total nitrogen X 6-39 



cheese it is usually less than 1 . 



Another method consists in calculation of the composition of 

 the original milk (or cream) ; the author has found that the 

 following calculation gives a very fair approximation to the 

 composition of the milk or cream from which the cheese was 

 prepared. 



Multiply the percentage of proteins by 354, add the percentage 

 of fat, and divide 103 times the percentage of fat by the figure 

 thus obtained ; to the resulting figure add 0-25, and the sum 

 will be a close approximation to the percentage of fat in the 



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