150 NORMAL MILK : ITS ADULTERATIONS, ETC. 



CHAPTER III. 



NORMAL MILK : ITS ADULTERATIONS AND ALTERATIONS, 

 AND THEIR DETECTIONS. 



Contents. — Chemical Composition of Milk — Colostrum — Limits and 

 Standards of Milk — Adulterations of Milk — Preservatives — The 

 Action of Heat on Milk — Sterilised Milk — Condensed Milk — 

 The Action of Cold on Milk. 



The Chemical Composition of Milk— Average Composition.— 



The milk of the cow has, on the average, the following composi- 

 tion (deduced from about 280,000 analyses made within the last 

 seventeen years in the Laboratory of the Aylesbury Dairy Com- 

 pany, Limited) : — 



It is essentially an aqueous solution of milk-sugar, albumin, 

 and certain salts, holding in suspension globules of fat and, in 

 a state of semi-solution, casein, together with mineral matter. 

 Small quantities of other substances are also found, which have 

 been referred to (Chap. I.). 



When evaporated, a residue is left, which is known as the 

 solids of milk ; these are empirically divided into fat and solids 

 not fat. It was first pointed out by Wanklyn that the solids not 

 fat in milk show comparatively small variations. Though this 

 rule is by no means absolute, it is to a great extent borne out in 

 practice, especially in dealing with the mixed milk of several 

 cows. 



Limits and Variations. — The following are the maximum 

 and minimum percentages which have come under the author's 

 notice ; the highest fat is recorded by Bannister, the highest 

 and lowest solids not fat and the lowest fat were observed in the 

 Aylesbury Dairy Company's Laboratory : — 



Fat. Solids not Fat. 



Per cent. Per cent. 



Maximum, .... 12-52 10-60 



Minimum, .... 1-04 4-90 



