Contamination of Milk. 55 



The third class includes those species that are able to 

 produce deleterious and undesirable flavors in milk and 

 milk products. The abnormal fermentations of milk re- 

 ferred to in the next chapter come under this head. Most 

 of these gain access to the milk through slovenly arid care- 

 less methods of handling. Those species associated with 

 ani mal excreta are particularly dangerous. The number of 

 different kinds that have been found in milk is quite con- 

 siderable, something over 200 species having been described 

 more or less thoroughly. In all probability, however, many 

 of these forms will be found to be identical when they are 

 subjected to a more critical study. 



Direct absorption Of taints. A tainted condition in milk 

 may result from the development of bacteria, acting upon 

 various constituents of the milk, and transforming these in 

 such away as to produce by-products that impair the flavor 

 or appearance of the liquid; or it may be produced by the 

 milk being brought in contact with any odoriferous or 

 aromatic substance, under conditions that permit of the 

 direct absorption of such odors. 



This latter class of taints is entirely independent of bac- 

 terial action, and is largely attributable to the physical 

 property which milk possesses of being able to absorb vola- 

 tile odors, the fat in particular, having a great affinity for 

 many of these substances. This direct absorption may 

 occur before the milk is withdrawn from the animal, or 

 afterwards if exposed to strong odors. 



It is not uncommon for the milk of animals advanced in 

 lactation to have a more or less strongly marked odor and 

 taste; sometimes this is apt to be bitter, at other times 

 salty to the taste. It is a defect that is peculiar to indi- 

 vidual animals and is liable to recur at approximately the 

 same period in lactation. 



