56 Dairy Bacteriology. 



ried on at a temperature lower than that of the milk, it 

 results in more or less rapid cooling. 



In earlier times, aeration was generally recommended 

 and practiced, especially in connection with the cheese 

 industry, but carefully controlled experiments fail to 

 show that the process exerts any material influence on 

 the rate of germ development. If it is carried out in 

 an atmosphere more or less charged with bacteria, as in 

 the barn or stable, it is more than likely to add to the 

 bacterial content of the milk. While to some extent 

 odors may be eliminated by the process, the custom is not 

 followed so generally now as it used to be some years 

 ago. 



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 a way, as to produce by-products that im- 

 pair 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 absorpton of such odors. 



This latter class of taints is entirely independent of 

 bacterial action, and is largely attributable to the phys- 

 ical property which milk possesses of absorbing volatile 

 odors. 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 is withdrawn from the animal, or afterwards if exposed 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 ta.ste ; sometimes it is apt to be bitter, at other 

 times salty to the taste. It is a defect that is peculiar to 

 individual animals, and is liable to recur at approxi- 

 mately the same period in lactation. The peculiar 



