FREEZING THE MIX 153 



well-insulated tank, and the brine is kept cold by a coil of 

 ammonia pipes. 



Speed of Dasher. — The speed of the dasher must be 

 such that the cream will be uniformly frozen, and be well 

 whipped during the freezing process. If the cream is put 

 into the freezer at a temperature under 40° F., it will be 

 quickly frozen, and the freezer should be run at its maximum 

 speed during the entire time. If the temperature of the 

 cream is 50° F. or above, in order to avoid churning, the 

 freezer should be run at slow speed at first, until the mix 

 is brought down close to the freezing point; then the 

 machine can be brought to full speed and the freezing 

 completed. If it is impossible to run the freezer at low 

 speed, then, intermittent freezing may be practiced. If 

 this latter is resorted to, no salt should be added, at first, to 

 the ice around the freezing can. The mixing of salt would 

 cause the can to freeze fast, and the part of the cream next 

 to the can would freeze solid, thus forming icy cream. 



In the vertical batch freezers, the dasher commonly 

 makes 90 to 100 revolutions per minute, and the can, re- 

 volving in the opposite direction, makes the same number 

 of revolutions, the result being equivalent to from 180 to 

 200 revolutions per minute. 



Freezing Period. — The time required for freezing is 

 dependent upon (i) the temperature of the mix when put 

 into the freezer, (2) the freezing mixture (size of pieces 

 of ice and proportion of salt), and (3), to a limited extent, 

 the composition of the mix. The composition and spe- 

 cific gravity of the mix are nearly constant for the same 

 class of product, so that the maker must depend upon 

 regulating the two other factors to control the duration of 

 the freezing period. This latter cannot be varied widely 

 without impairmg the texture of the product. 



