DIVISION IV 



MICROBIOLOGY OF MILK AND MILK PRODUCTS 



CHAPTER I* 



THE RELATION OF MICROORGANISMS TO MILK 



CHARACTER OF MILK 



The ideal milk is that which reaches the consumer in as nearly as 

 possible the condition in which it leaves the udder of the healthy cow. 



The factors which determine the quality of commercial milk may be 

 stated as follows: (a) Food value, (b) flavor and odor, (c) keeping 

 quality, (d) cleanliness, (e) healthfulness. With the exception of the 

 first, all of these qualities are in part or wholly dependent upon the 

 microbial content of the milk. 



Fresh normal milk has a pleasant taste and aroma and is gener- 

 ally 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 undesirable changes, due to the delicate nature 

 of the milk itself and to the conditions naturally surrounding its pro- 

 duction 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 is exposed to any 



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

 bacteria, prepare4 by E. G. Hastings. 



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