1 94 BACTERIA IN BUTTER AND OLEOMARGARINE. 
is now largely prevented by a prohibitive tax on colored oleomarga- 
rine. The bacteria normally present in oleo products are commonly 
much less numerous than in butter, and the oleomargarine is, on 
the whole, less likely to distribute infectious diseases 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 mixture is 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. Ordi- 
narily he allows his milk to sour by normal lactic fermentation. 
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. 
