154 Dairy Bacteriology. 



water is ready for use. It has been shown that the cost 

 of treating an impure water is more than covered by the 

 increased returns from the product. 



A pure and healthful water supply should be one of 

 the essential things of every dairy, creamery, and cheese 

 factory, not only for the sake of the quality of the prod- 

 uct, but also to avoid contamination of products with 

 disease-producing bacteria, 



Bacteria in butter. The germ content of butter will 

 depend on the type of cream. Sweet-cream butter con- 

 tains but few bacteria. In sour-cream butter the con- 

 tent in bacteria will be greatly increased, especially as 

 to lactic organisms. Often, it may amount to several 

 millions of organisms per gram. The germ content of 

 butter is said to be greater on the outside of a package 

 than within the mass, due doubtless to the free access 

 of air, thus favoring the growth of the aerobic forms. 



The composition of normal butter does npt favor the 

 growth of the majority of kinds of bacteria that are con- 

 tained in it: The washing process removes much of the 

 material suitable as food for the bacteria, such as sugar 

 and albumen. If considerable butter milk is left in the 

 butter, the growth of bacteria will be quite rapid, at 

 first, but does not continue for any considerable length 

 of time. The addition of salt also tends to restrain the 

 growth of most kinds of bacteria. 



Butter is at its best when it is perfectly fresh. De- 

 terioration begins within a short time and the rapidity 

 with which the changes go on is dependent on the tem- 

 perature at which the butter is stored. The tempera- 

 ture of the butter rooms in the large cold storage plants 

 is kept below F. The butter in such rooms will de- 

 teriorate very slowly, but on removal from the cold 



