DIVISION IV 

 Microbiology of Milk and Milk Products 



CHAPTER I* 

 THE RELATION OF MICROORGANISMS TO MILK 



Importance of Milk as a Food 



Fresh normal milk is one of the most important of human foods. 

 It has a pleasant taste and aroma and is generally liked as a food or 

 drink; but unless properly cared for will not long remain in its normal 

 condition. No article of human diet is more susceptible to undesir- 

 able changes, due to the delicate nature of the milk itself and to the 

 conditions naturally surrounding its production and handling. The 

 injurious changes which commonly occur in milk are of two kinds. 



Absorbed Taints and Odors 



Milk is very quickly affected by odors of any sort. The foreign 

 odor may be absorbed before the milk leaves the udder if the cow has 

 eaten strong feeds, such as cabbage, onions, etc., or it may be absorbed 

 after the milk is drawn from the cow. If milk ii exposed to any 

 strong odor, such as silage or foul air, resulting from lack of ventila- 

 tion in the stable at milking time, these odors will be taken up by the 

 milk with surprising rapidity. If placed in an ice chest with fresh 

 strawberries or pineapple, or foods like cabbage or turnips, the milk 

 will very quickly absorb the odor of these foods. The absorption 

 of any foreign odor gives to milk a decidedly disagreeable taste. This 

 is true even when the odor which is absorbed is pleasant in itself as 

 in the case of strawberries or pineapples. When the "off" flavors are 

 due to absoSrption they are strongest at the outset and become less 



* Prepared by W. A. Stocking with the exception of the paragraphs treating the acid-forming 

 bacteria, prepared by E. G. Hastings. 



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