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 
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