62 HE TYPES OF MILK BACTERIA. 



the odor comes directly from the co.w, the milk being at the 

 moment of secretion filled with volatile products which give 

 rise to these flavors. Such tastes and flavors in milk are, 

 however, not very common and associated with only a few 

 strongly flavored foods. The animal or the cowy odor, 

 already referred to, is one which has been in general re- 

 garded as due to volatile products directly transferred from 

 the animal to the milk at the moment of secretion. It ap- 

 pears, however, that this animal odor is chiefly due to con- 

 taminations and is primarily caused by manure. The soiled 

 boots and clothing of the farmer have the same odor. Milk 

 which is produced in a clean dairy, under the exceptional 

 precaution already mentioned, does not show these animal 

 odors. They may be largely, if not wholly, prevented by 

 sufficient care in the dairy. 



Flavors due to Micro organisms. --Aside from these tastes 

 and odors there are others which are due to the development 

 of bacteria in the milk. There is little difficulty in determin- 

 ing whether a particular taste in milk is due to the growth 

 of bacteria in the milk or to products derived directly from 

 the cow and probably due to her food. Odors which are due 

 to volatile products transmitted from the animal to the milk, 

 like the garlic flavor, are strongest in the fresh milk. The 

 milk when drawn shows these flavors developed at their 

 height and, if the milk is kept for a few hours, the tendency 

 will be toward a reduction of the flavors rather than their 

 increase. On the other hand, the odors and flavors, or any 

 chemical change which occurs in milk as the result of a 

 growth of bacteria, will never be found in the freshly drawn 

 milk, but will appear later, being slight at first and continu- 

 ing to increase hour by hour as the bacteria have a chance to 

 multiply and produce their action. 



In giving an account of the common milk bacteria it must 

 always be recognized that no statements will apply to all 

 localities. Certain species are common in some places which 



