BACTERIA IN OLEOMARGARINE PRODUCTS 209 
than ordinary butter, inasmuch as the chance for contamination is 
less. 
But, although the oleo products thus made resemble butter in 
appearance, they do not resemble it in taste, and the 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 obtain them from a similar 
source. 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. After the 
milk has properly soured, or ripened, it is placed in the mixing 
vat with a quantity of melted oils, generally in the proportion of 
about one part of milk to four parts of the oils. When this mix- 
ture 1s hardened by the cold brine, the milk is held with fats, and 
thus becomes a part of the final product. Inasmuch 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 clear that this flavor is due to exactly the same factors as 
those which produce the butter flavor. The oleo-maker fully 
understands 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 fermenta- 
tion. In some factories, in recent years, he has not been satisfied 
to depend upon such a method, but has come to use, more and 
more largely, pure cultures of bacteria in order to introduce 
greater regularity in the process. In some oleo factories, indeed, 
so fully aware have the makers been of the extreme significance 
of this matter of proper bacteria to the successful manufacture 
of oleo products, that they have actually built and furnished 
bacteriological laboratories and employed bacteriologists to keep 
constant guard over these factors in the oleo-making. 
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