THE SIGNIFICANCE OF YEASTS AND OIDIA IN 
PASTEURIZED BUTTER ; 
F. W. Bouska anp J. C. BRown 
The original object of pasteurization in buttermaking was 
to produce a better immediate flavor by controlling fermenta- 
tions. The aim was to destroy undesirable microorganisms as 
well as microorganisms whose efféct is unknown. By means 
of a pure culture of selected lactic acid bacteria (starters), 
regulated temperatures, and the acid test, the desired flavor 
was to be developed. In more recent times it was discovered 
that pasteurization greatly improved the keeping quality of 
creamery butter made from cream which had soured spontan- 
eously on the farm. A considerable part of American butter 
is now made from such cream. The succession of sweet milk 
by sour cream as a source of creamery butter is a result of 
economic conditions on the farm. Some farmers think that 
the expense of hauling milk to the creamery every day is too 
great. So they skim the milk at home and deliver the cream 
twice a week in the winter and three times a week in the sum- 
mer. The skim milk thus derived has the best feeding value 
because it is warm and sweet. But the cream obtained by this 
farm method is usually sour. It became our lot to design 
methods of making butter from spontaneously soured cream 
and to overcome butter defects that sometimes occur here. 
While our experience, investigations, and results apply prin- 
cipally to sour cream, it will be seen that in some respects a 
general application can be made. 
Butter which has a good flavor when churned but develops 
a bad flavor at low temperatures within one month has poor 
keeping quality. Properly made pasteurized butter scoring 
90 will, in current commerce, remain eatable to the last morsel. 
In cold storage it scores 89 to 90 at the end of seven to ten 
months. We have known churnings of butter to score 90 at 
the end of eighteen months. 
