Contamination of Milk, 57 



Absorption of odors after milking:. If milk is brought in 

 contact with strong odors after being drawn from the ani- 

 mal, it will absorb them readily, as in the barn, where fre- 

 quently it is exposed to the odor of manure and other 

 fermenting organic matter. 



It has long been a popular belief that milk evolves 

 odors and cannot absorb them so long as it is warmer than 

 the surrounding air, but from experimental evidence, the 

 writer 1 has definitely shown that the direct absorption of 

 odors takes place much more rapidly when the milk is 

 warm than when cold, although under either condition, 

 it absorbs volatile substances with considerable avidity. 

 In this test fresh milk was exposed to an atmosphere im- 

 pregnated with odors of various essential oils and other 

 odor-bearing substances. Under these conditions, the cooler 

 milk was tainted very much less than the milk at body 

 temperature even where the period of exposure was brief. 

 It is therefore evident that an exposure in the cow barn 

 where the volatile emanations from the animals themselves 

 and their excreta taint the air will often result in the ab- 

 sorption of these odors by the milk to such an extent as 

 to seriously affect the flavor. 



The custom of straining the milk in the barn has long 

 been deprecated as inconsistent with proper dairy prac- 

 tice, and in the light of the above experiments, an additional 

 reason is evident why this should not be done. 



Even after milk is thoroughly cooled, it may absorb 

 odors as seen where the same is stored in a refrigerator 

 with certain fruits, meats, fish, etc. 



Distinguishing bacterial from non-bacterial taints. In 



perfectly fresh milk, it is relatively easy to distinguish be- 



* Russell, 15 Kept. Wis. Expt. Stat. 1898, p. 104. 



