CHAPTER XL 



THE DAIRY. 



Milk. — Its constituents — Conditions affecting its richness— Influence 

 of breed. Curdling. — The action of bacteria. Cream. — The fat 

 globules — Modes of raising cream — Composition of cream — 

 Ripening of cream. Skim and Separated Milk. — Its composition 

 under various conditions. Butter. — The operation of churning — 

 Return for milk used — Composition of butter. Butter Milk. — 

 Its composition. Cheese. — Rennet — Operation of cheese-making — 

 Ripening of cheese — Composition of cheese. 'Whey. — Its com 

 position. Annatto. — Its nature and use. Necessity for Cleanliness. 



Milk. — The general composition of colostrum and 

 of ordinary cows' milk has been already given on 

 p. 170. 



The milk from a herd of dairy cows has generally a 

 specific gravity between 1*030 and 1'04:0. The solids 

 other than fat tend to raise the specific gravity, while 

 the fat tends to lower it. As cream may be removed 

 and water added without altering the specific gravity, 

 no safe conclusion as to the quality of milk can be 

 based on this indication. 



The albuminoids of milk are chiefly composed of 

 two constituents, casein^ and albumin. Casein is 

 coagulated by the addition of acids, or by rennet, but 

 not by boiling. Albumin is not coagulated by rennet, 

 or by most acids, but is coagulated by heat. In colos- 

 trum albumin largely preponderates, so that the milk 



' Some writers call the original, unpreoipitated albuminoid in the 

 milk, caseinogen. 



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