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 



