Bacteria and Butter- Making. 155 



Changes in germ content. The bacteria that are incor- 

 porated with the butter as it first "comes" undergo a 

 slight increase for the first few days. The duration of this 

 period of increase is dependent largely upon the condition 

 of the butter. If the buttermilk is well worked out of the 

 butter, the increase is slight and lasts for a few days only, 

 while the presence of so nutritious a medium as buttermilk 

 affords conditions much more favorable for the continued 

 growth of the organisms. 



While there may be many varieties in butter when it is 

 fresh, they are very soon reduced in kind as well as num- 

 ber. The lactic acid group of orgariisms disappear quite 

 rapidly; the sppre-bearing species remaining for a some- 

 what longer time. Butter examined after it is several 

 months old is often found to be almost free from germs. 



In the manufacture of butter there is much that is de- 

 pendent upon the mechanical processes of churning, wash- 

 ing, salting and working the product. These processes do 

 not involve any bacteriological principles other than those 

 that are incident to cleanliness. The cream, if ripened 

 properly, will contain such enormous numbers of favorable 

 forms that the access of the few organisms that are derived 

 from the churn, the air, or the water in washing will have 

 little effect, unless the conditions are abnormal. 



Rancid change in butter. Fresh butter has a peculiar 

 aroma that is very desirable and one that enhances the 

 market price, if it can be retained; but this delicate flavor 

 is more or less evanescent, soon disappearing, even in the 

 best makes. While a good butter loses with age some of 

 the peculiar aroma that it possesses when first made, yet a 

 gilt-edged product should retain its good keeping qualities 

 for some length of time. All butters, however, sooner or 



