BACTERIA IN OLEOMARGINE PRODUCTS. 193 



development of butyric acid and frequently by a considerable 

 change in the consistency of the butter. It finally becomes strongly 

 rancid and tallowy, totally ruined for use. The cause of this 

 rancidity has been difficult to determine, apparently because a 

 variety of factors contribute to it. It is probably due, in part, to 

 chemical fermentation, produced by enzymes in the milk, and in 

 part to the growth of bacteria. The rancidity is much more likely 

 to occur if the butter is exposed to the light, and it develops more 

 readily in warm than in cold temperatures. At temperatures below 

 freezing rancidity does not occur. If butter is, therefore, kept 

 cool and in large masses, it may be held for a long time without 

 the appearance of any very noticeably strong flavor. In the end, 

 however, the rancidity is sure to appear. To what extent bacteria 

 are concerned in this change we do not yet know, although most 

 investigators have concluded that they are prominently concerned 

 in the phenomenon. Rancidity may certainly be looked upon as 

 a fermentation change, and the only method the dairyman has of 

 controlling it is by cool temperatures, by packing the butter in large 

 masses, by paraffining the butter tubs, and by keeping it from the 

 light. It may be delayed by pasteurizing the cream and by using 

 pasteurized water for washing, facts that show its close relation to 

 bacteria. Fortunately, it is a matter of no very great importance, 

 because butter can be kept without difficulty for some months, and 

 it is almost always possible to market it before it has spoiled. 



BACTERIA IN OLEOMARGARINE PRODUCTS. 



The materials out of which oleomargarine is made are chiefly 

 stearin, lard, cottonseed oil, and other oils. These are warmed to 

 the melting-point, are thoroughly mixed, and then drawn off into 

 cold brine, which chills the oils into a hard mass. The process 

 is certainly a useful method of utilizing quantities of oils which 

 would otherwise be waste products. It makes a * wholesome, 

 digestible food, which could have no objection raised against it 

 if it could only be sold upon its own merits, instead of under the 

 false guise of butter. In order to make the product the more 

 resemble butter, it has been customary to color it; but this practice 



