200 THE ANALYSIS OF MILK PRODUCTS. 



Corrections for Solids not Fat in Sour Milks, When it is desired 

 to ascertain from the analysis of a sour milk the original com- 

 position of the sample, the following constituents should be 

 determined ; fat and solids not fat by the maceration method, 

 alcohol, ammonia, acidity, and aldehyde figure of the milk, 

 volatile acidity by the Government Laboratory method, and 

 aldehyde figure of the neutralised solution obtained in this 

 method. If the volatile acidity is high, the proportions of 

 butyric, propionic, and acetic acids should be determined by 

 Duclaux's method. The solids not fat should be mixed with 

 10 c.c. of hot water, and the acidity or alkalinity and aldehyde 

 figure determined. 



The following corrections should be made : 



Alcohol Correction. 



1. For each 184 parts of alcohol add on 342 parts, or the 

 difference between 1 and the specific gravity of the distillate 

 multiplied by 977 and by the weight of the distillate (or volume 

 in c.c.), and divided by the weight of milk taken. 



Volatile Acid Corrections. 



2. For each 60 parts of acetic acid add on 25-5 parts. 



3. For each 74 parts of propionic acid add on 68-5 parts. 



4. For each 88 parts of butyric acid add on 87-5 parts. 



Ammonia Correction. 



5. For each part of ammonia add on 5-2 parts. 



Lactic Acid Correction. 



6. For each part of lactic acid subtract 0-05 part.' 



Aldehyde Correction. 



7. For each degree of difference between the aldehyde figure of 

 the neutralised solution obtained in the volatile acid estimation 

 and that of the solids not fat subtract 0-0026 per cent. 



Amino-Acid Correction. 



8: For each degree of aldehyde figure of the neutralised solu- 

 tion obtained in the volatile acid estimation above 20 subtract 

 0-0018 per cent. (This is rarely required.) 



Loss of Butyric Acid. 



9. Subtract the acidity of the solids not fat from the difference 

 between the aldehyde figures of the volatile acid solution, and 

 of the solids not fat ; multiply the figure thus obtained by 0-0088, 

 and add it to the solids not fat. 



By this system of corrections the author and Miller have 

 found that the solids not fat deduced from the analysis of sour 



