RELATION OF BACTERIA TO DAIRY PRODUCTS 549 



The dairy utensils. 



If the milk pails, strainer cloths, and other utensils with 

 which the milk comes in contact are thoroughly cleaned and 

 sterilized by the use of boiling water or steam, there will be 

 practically no contamination from this source, but it has been 

 found, under ordinary dairy conditions, that the utensils are 

 frequently not well sterilized, and constitute one of the most 

 important sources of contamination to the milk. This is 

 especially true if the rinse water is allowed to stand in the pails 

 and cans instead of their being thoroughly dried. The abso- 

 lute importance of thoroughly sterilizing either with boiling 

 water or steam, and the immediate drying of the utensils, can- 

 not be too strongly emphasized, nor their importance over- 

 estimated in controlling the germ-content of milk. 



Development of bacteria in milk 



After all reasonable care has been exercised in the care of 

 the utensils and the production of the milk, it will contain a 

 certain number of bacteria, and the quality of the product will 

 depend on this initial contamination and its later development. 



Fresh milk exercises a certain amount of germicidal influence 

 over the bacteria in it. The degree of germicidal action varies 

 in the milk of different cows, and its strength and duration will 

 depend on the temperature at which the milk is held. The 

 influence of this action in milk is well shown by the table 1 

 on the following page. 



Following this germicidal period, there is a more or less rapid 

 development of the bacteria in the milk, the rate of increase 

 depending primarily on the temperature at which the milk is 

 held. During this period the lactic acid producing organisms 

 (Bad. lactis acidi) grow very rapidly, and under normal condi- 

 tions greatly outnumber the other species present, so that by 



1 Cornell Bulletin No. 197. O. F. Hunziker. 



