80 BULLETIN 98, U. S. DEPARTMENT OF AGRICULTURE. 
tures of the cream at will, and furthermore mechanical refrigeration 
does away almost entirely with the mold and slop that must neces- 
sarily follow the use of ice. A creamery equipped with a mechanical 
refrigerating plant can at all times, provided the cream is of good 
quality, turn out a uniform grade of butter, regardless of weather 
and temperature changes. 
In the modern creamery refrigeration is employed in connection 
with the processes of pasteurizing, ripening, churning, in the prepa- 
ration of starters, cooling water for washing butter, in cooling 
storage for the finished products, and frequently the raw products. 
In the pasteurization of cream the same methods are employed 
as in the pasteurization of milk, viz, the "flash" and "holder" 
processes. In the " flash" or continuous process of pasteurization 
the cream is heated to a temperature of 160° F. in about 30 seconds 
and is then run over some form of cooler where the temperature is 
lowered to about 65°. From the cooler it is run into the ripening 
vats, where the proper temperature is maintained for 18 to 20 hours, 
at which time the cream has ripened sufficiently for churning. As a 
temperature of 65° is entirely too high for churning, it is lowered by 
running cold water or brine through the coils in the vat or through 
the coils of the cooler, should a cooler be used, and the temperature 
lowered to that necessary for churning. 
In practice, however, the ripening temperature of cream varies 
within wide limits. A ripening temperature that will give good 
results under certain given conditions would, perhaps, give poor 
results under different conditions. Consequently the existing con- 
ditions will to a great extent govern the ripening temperatures. 
When the cream is ripened, cooled, and churned on the same day, 
a higher ripening temperature is of course necessary, while, on the 
other hand, if the cream is ripened overnight, a comparatively low 
temperature is employed. The range of ripening temperatures 
varies from 60° to 80°, but it is believed that between 60° and 70°, 
with an average of 65°, the best results are obtained, as cream held 
at these temperatures does not ripen very rapidly. Consequently 
the desired degree of ripening is approached very slowly and the 
fermentation may be checked quickly when the desired degree of 
acidity is reached, thereby reducing to a minimum the chances of 
getting overripe cream. If, however, the cream is ripened at a high 
temperature there is a great danger of getting overripe cream. 
During the ripening process extreme and rapid changes of tempera- 
ture in the cream should be avoided as much as possible, as the more 
uniform the temperatures are kept the better the results. 
It is believed that the tendency is toward the "holder" process of 
pasteurization for cream and also toward pasteurizing directly in the 
ripening vats. Some types of modern ripening vats are provided 
with spiral coils or disks through which low-temperature water or 
