1 84 MILK 



The amount of total solids in milk may vary from 

 II to 14 per cent, the average value being about 12-3. 



If the temperature during the heating be much 

 above 100° C, there is a danger of a slight decomposi- 

 tion of the milk sugar occurring. 



Fat. 



The fat (butter-fat) existing in milk is a mixture of various 

 glycerides of ten or more different fatty acids, among which are 

 butyric, caproic, caprylic, capric, lauric, stearic, oleic, etc. It 

 is probable that the glycerides are largely mixed tri-glycerides, 

 that is to say, consist of two or three different acid radicles 

 combined with one glyceryl group thus — 



CH2 . OOC . C3H7 (radicle of butyric acid). 



I 

 CH.OOC.C5H11 ( „ caproic „ ). 



I 

 CH2.00C.C9Hi9( „ capric „ ). 



The fat is present in milk in the form of microscopic globules, 

 present as an emulsion, and the globules are separate and do 

 not run together except as the result of shaking or other violent 

 mechanical treatment (churning) (p. 196). 



The quantity of fat in milk is liable to considerable fluctuations, 

 depending on the breed of cow (Jersey cows give the richest milk), 

 individuality, period of lactation, frequency of milkings, and in 

 separate milkings the values may vary between i and 8 per cent. 

 With the mixed milk of a number of different cows, however, the 

 percentage is nearly always between 2-5 and 4-5. Owing to the fact 

 that the value of milk largely depends upon the percentage of fat 

 it contains, and owing to the easy removal of part of the fat or 

 dilution of the milk with water, it is usual for most countries to 

 fix a legal minimum (in England, 3-0 per cent.) for the percentage 

 of fat. Milk falling below this minimum is regarded as having 

 been skimmed or diluted, unless it can be proved to be the un- 

 treated and unadulterated product of cows, in which case the 

 prosecution is not proceeded with. The actual determination of 

 the percentage of fat in milk is naturally, therefore, an operation 

 of the greatest importance. 



