Page:The story of milk.djvu/79

 while air is whipped into the cream by the rapid motion of the beater. A great variety of excellent freezers of this kind for hand or for power are on the market which answer the purpose for making ice cream at home or at the ice cream parlor.

Coarse-grained salt and crushed ice, mixed in the proportion of 1 part salt to 4 parts of ice, are constantly filled into the space surrounding the ice cream can, and the brine produced by the melting of the mixture is gradually drawn off from the tub. In a good freezer the operation should not take over fifteen minutes. When the cream is frozen to a soft mush, stop the beater and scrape down the hard particles which may have accumulated on the sides of the can, add any ingredients which may be better incorporated at this stage than mixed into the original material, such as crushed fruit or preserves, and finish the freezing without carrying it too far.

Remove the beater, stir the cream which should still be soft enough to handle, and pack in ice with only a little salt. Or the cream may be transferred from the freezer can to the shipping can and packed in it. If bricks are wanted the soft cream is packed in molds of the desired shape and size and buried in the freezing mixture to harden.

In modern ice cream factories Brine Freezers are generally used. In a Refrigerator Plant intensely low temperatures are produced by the vaporizing of compressed ammonia or carbonic acid in an ice machine, and brine circulating in iron pipes is cooled by such medium and may, in turn, cool the air in the Cold Storage room, or the cream in the freezer, or pure water in metal boxes for the manufacture of Artificial Ice.