DAIRY CHEMISTPvY. 



CHAPTER T. 



INTRODUCTORY THE CONSTITUKXTS OF MILK. 



COiN'TENTS — General Composition — Fat— Sugar— Proteins— .Salts — Colour 

 — Reaction — Milk-Sugar — Glucose— Products derived from Milk- 

 Sugar— The Proteins of Milk— Products of Hydrolysis— General 

 Action of Hydrolysis— Mineral Constituents— Other Constituents of 

 Milk— 'Die Gases of Milk— The Fat of Milk— Products of Hydrolysis 

 — Fatty Acids — Other Compounds — Ranciditj'. 



General Composition.— Milk is the normal secretion of the 

 mammary glands of a mammal ; the milk of all mammals has 

 a similar composition, consisting of fat, sugar, protein, mineral 

 constituents, and small quantities of other compounds. The 

 milk of the cow has been studied in greater detail than that 

 of any other animal on account of the extended use of this 

 animal's milk and the products derived from it as human food : 

 the greater portion of this work will, therefore, be devoted to the 

 consideration of the chemical properties of cow's milk, and the 

 expressions " milk," " butter," etc., must be taken as applying 

 to the products derived from the cow, unless described to the 

 contrary. Jluch, however, that is stated with regard to the 

 cow may be taken as applying equally to the milk of other 

 animals ; but our knowledge of the chemical composition of the 

 milk of any animal, except the cow, is very incomplete. Studies, 

 more or less incomplete, have been made of the milk yielded by 

 woman, the goat, the ass, the mare, the gamoose, and the sheep, 

 and analyses, few in number, have been made of the milk of 

 other mammals, both terrestrial and marine. It is probable that 

 there exist wider differences than are yet recognised between 

 the milk yielded by different animals. 



Fat. — The fat in milk is of peculiar and complex composition ; 

 it differs from all other fats in that it contains compound gly- 

 cerides partly built up of fatty acids of low molecular weight. 



