522 MANUAL OF MILK PRODUCTS 



than the same butter would have been had the cream remained 

 cold for some six hours immediately prior to churning. The 

 same law holds true in ice cream making. A better bodied 

 goods may be made when the fat has been cooled for a sufficient 

 length of time to allow thorough hardening. The most eco- 

 nomical and efficient method of holding or cooling milk or cream 

 with ice is to set the filled cans into a well-insulated tank of 

 water in which the ice is floating. In this way the maximum 

 of cooling effect is obtained from the ice, and the cream or milk 

 is cooled much more quickly than would be the case if it were 

 set into a room, even though the air were of the same tempera- 

 ture as the water. Furthermore, this pre-cooling of the cream 

 enables the maker to freeze his goods in a short space of time 

 without cooling it too rapidly (see p. 537). This feature is 

 especially valuable where several batches must be run through 

 the same freezer in quick succession. It also has the final 

 advantage of practically guaranteeing that no crumbs of butter 

 will be formed in the freezer, for all of the agitation of the 

 cream will have taken place at a temperature far below the 

 churning point. 

 Keeping cream sweet. 



A can of cream or milk set into cold water will cool many 

 times more rapidly than it will if set into a dry air refrigerator, 

 even though the air and water were kept at the same tempera- 

 ture. This is due to the fact that water is a much better con- 

 ductor of heat than is air and that the heat-carrying capacity 

 of the mass which is able to come into contact with the can is 

 immensely greater in the case of water ; in fact the amount of 

 heat required to be absorbed from the article being cooled in 

 order to raise the temperature of water one degree is 445 times 

 greater than the amount of heat required to raise the tempera- 

 ture of the same volume of air one degree. Or, in other words, 

 one cubic foot of water will absorb 445 times as much heat 

 from the can of cream as will one cubic foot of air for each 



