Bacteria in Butter- Making. 143 



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 organisms disappear quite 

 rapidly ; the spore-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. 

 This fact is important, for in considering the after 

 -changes in ' ' storage ' ' butter, the relation of these 

 changes to the germ life would naturally be considered. 



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

 pendent upon the mechanical processes of churning, 

 washing, salting, and working the product. These pro- 

 cesses 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. 



144. 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 later undergo a change that render 

 them worthless for table use. This change is usually a 

 rancidity that is observed in all stale products of this 

 class. The cause of this rancid condition in butter has 

 been attributed to the action of living organisms, partic- 

 ularly those that form butyric acid, to the influence of 

 light, of air, etc. 



