88 CHEMICAL EXAMINATION 



Skim Milk. The usual methods of milk analysis may be 

 applied. 



Condensed Milk. About 30 grms. of milk are weighed out 

 and, after boiling with 50 c.cms. of water, the solution is cooled 

 and made up to 100 c.cms. The methods of analysis described 

 above under milk may then be applied, .but longer extraction 

 should be given if the Adams process is used for the estimation 

 of the fat. 



In sweetened samples the cane sugar is determined by sub- 

 tracting the sum of the fat, lactose, proteids, and ash, from the 

 total solids. 



Enzymes 



Although the presence of enzymes in milk has been an 

 established fact for many years, it is only comparatively recently 

 that the origin of these ferments has been seriously considered. 

 The nature and characteristics of these bodies suggests that 

 they are derived from the blood and the results of various 

 experimenters show that they are largely associated with the 

 cells invariably found in milk samples. Whilst the greater 

 portion of the enzyme activity of milk is anchored to the cells 

 and may, consequently, be removed by filtration, there is also 

 present a smaller quantity of extra cellular activity. This is 

 not surprising when the rapid metabolic changes taking place 

 during the secretion of milk are considered. Certain enzymes, 

 such as Schardinger's reductase, occur in amounts which vary 

 directly with the fat content and, unless, this enzym.e is almost 

 entirely extra cellular, the cells should also vary somewhat with 

 the fat content. Although various hypotheses have been ad- 

 vanced as to the effect of enzymes in milk, the author believes 

 that too much importance has been attached to the qualitative 

 and too little to the quantitative tests for these substances. 

 The amylase content of normal milk is equivalent to about 0.4 

 grm. of starch per 100 c.cms. of milk per hour. The catalase 

 in 100 c.cms. liberates from hydrogen peroxide 10 c.cms. or 

 0.014 grm. of oxygen in two hours, whilst Babcock and Russell's 



