CHAPTER III. 



PROPERTIES OF MILK. 



Color. — The color of normal milk ranges between bluish 

 white and golden yellow, according to breeds, foods, and sea- 

 sons of the year. The milk yielded by Jersey cows generally 

 is more yellow, due chiefly to the larger amount of fat which 

 it contains. Holstein cows yield milk of a whiter color. Foods 

 such as grass and certain roots (mangles and carrots) have 

 the power of giving to milk a higher color. As has been pre- 

 viously mentioned, the coloring substance in milk has been 

 named lactochrome, and so far as known is associated with 

 the palmitin fat. 



Flavor. — Milk has a sweet flavor, and a faint odor. Fresh 

 milk has a pecuUar cowy taste and odor, which pass off when 

 exposed to the air. The flavor is affected by foods and con- 

 ditions of the cow, as mentioned under " Abnormal Milk." 



Opacity of Milk. — Milk is opaque, except when seen in 

 very thin layers; then it is slightly transparent. The opacity 

 of milk is due to the presence of the fat and nitrogenous mat- 

 ter. When these substances are filtered away on a fine clay 

 filter (the Chamberland), the filtrate which passes through 

 is clear and transparent. It has been maintained that the 

 fat in milk is the chief cause of its opacity, and that the per- 

 centage of fat could be determined according to the degree 

 of opacity and transparency of milk with an instrument named 

 pioscope; but it was soon found out that the size of the 

 fat-globules, as well as the number, had considerable influence 

 upon the degree of opacity of milk. For that reason, this 

 method of determining the amount of fat in milk was not 



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