BACTERIA IN BUTTER-MAKING. 249 



less numerous than in butter, and the oleo is, on the whole, 

 less likely to distribute infectious diseases than ordinary butter, 

 inasmuch as the chance for contamination is much less, and 

 the treatment is more likely to destroy the bacteria. 



But, although the oleo products thus made resemble butter 

 in appearance, they do not resemble it in taste, and the oleo 

 factories are therefore forced to use some special method of 

 imparting to their product a flavor as closely as possible like 

 the butter which they are trying to imitate. To do this they 

 depend upon the very same flavors as those found in butter 

 and obtained from a similar source. Their method of procur- 

 ing them is very simple. A certain amount of whole milk, 

 skim milk or cream (varying according to the quality desired 

 in the product) is placed in a large vat or in cans, and allowed 

 to sour. Ordinarily the milk is allowed to sour normally. 

 It is simply placed in a warm temperature where the lactic 

 bacteria grow rapidly, and the milk sours readily enough. 

 After the milk has properly soured, or ripened, it is placed in 

 the mixing vat with a quantity of the melted oils, generally in 

 the proportion of about one part of milk to four of the oils. 

 The whole is then thoroughly mixed by violent agitation and 

 drawn off into the cold brine. As it hardens the milk is held 

 with the fats and thus becomes a part of the final product. In- 

 asmuch as the milk has developed a flavor in its souring, just 

 as cream does during its ripening, this flavor is imparted to the 

 oleo product, and the final result is a mass of fats with the flavor 

 of butter more or less prominently developed. 



It is, of course, clear that this flavor in the oleo products is 

 due to exactly the same factors which we have found in the 

 production of butter flavor. The oleo-maker fully under- 

 stands that his flavors are due to the action of bacteria, and he 

 uses the best means at his disposal to favor their growth. 

 Ordinarily he allows his milk to sour by normal lactic fermen- 

 tation. In some factories, in recent years, the oleo-maker has 

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