196 BUTTER-MAKING. 
the desired characteristic flavor of good butter, yet we know 
that these flavoring substances are direct products, or accompani- 
ments, of the development of lactic acid. 
Cream ripened at a low temperature does not sour very 
rapidly; the germs do not grow at a very rapid rate. The 
desired degree of acidity is approached very slowly, and as a re- 
sult the fermentation may be checked almost at once when 
the desired degree of acidity has been reached, and the chance 
for getting overripened cream is reduced to its minimum. 
If the cream is ripened at a high temperature, there is greater 
danger of getting overripened cream. 
Extreme and rapid changes of temperature should be avoided 
as much as possible. The more uniform the temperature can 
be kept, if suitable for proper ripening, the better the results. 
Accordingly, the ripening-vats used in this country are practi- 
cally all jacketed, which permits the operator to regulate at 
will the temperature of the water in the jacket surrounding the 
cream. 
Amount of Starter to Add to Cream.—The amount of 
starter to add to cream will vary according to the temperature 
of the cream, and to the length of time required for ripening. 
If cream is to be ripened quickly, then a large starter should 
be added. Good results can be obtained by adding starter to 
the extent of 50% of the cream to be ripened. This much, 
however, is usually not satisfactory, as it so reduces the thick- 
ness of the cream as to render it more difficult to churn. It 
increases the amount of serum which will form the buttermilk 
when churned. The more buttermilk, the greater will be the 
loss of fat in churning. On this account it is desirable not to 
add any more starter than will give cream a proper thickness 
(from 30% to 35% fat) and at the same time supply enough 
desirable germs to gain the upper hand of, and to suppress the 
undesirable germs already present. 
It is important to skim the cream thick enough to permit 
the use of an amount of starter equal to from 8% to 20% of 
the cream to be ripened. This, under average conditions, will 
