26 THE BOOK OF CHEESE 



below that at which the bacteria grow and multiply 

 rapidly, it will retard their development. In general, 

 all milk should be cooled to 50 F. or below. In cooling 

 the milk, it should not be exposed to dust or odors. One 

 of the best methods of cooling is to set the can containing 

 the milk into a tub of cold running water, and then stir. 

 If running water is not available, cold well-water * may be 

 used, but the water should be changed several times. 

 If the milk is not stirred during the cooling process, it 

 will not cool so rapidly, because the layer of milk next 

 the can will become cold and act as an insulator to the 

 remainder in the center of the can. 



One way to destroy many of the bacteria in milk is by 

 pasteurization. This consists in heating the milk to 

 such a degree that the bacteria are killed, and then quickly 

 cooling it. After pasteurization, the milk is so changed 

 that some kinds of cheese cannot be made successfully. 



42. Fermentation test. When a cheese-maker is 

 having trouble with gas in his cheese, or bad flavors, he 

 can generally locate the source of difficulty. This can 

 be done by making a small amount of cheese from each 

 patron's milk, called a fermentation test. 2 Pint or 

 quart fruit jars or milk bottles make suitable containers. 

 They should be thoroughly washed and scalded, to be 

 sure they are clean and sterile, and then covered to pre- 

 vent contamination. As the milk is delivered to the 

 factory, a sample is taken of each patron's milk. The best 

 way to secure the sample is to dip the sterile jar in the 

 can of milk as delivered and fill two-thirds full of milk. 



^uddick, J. A., and G. H. Barr, The cooling of milk for 

 cheese making, Ottawa t)ept. of Agr. Bui. 22, 1910. 



2 Wis. Exp. Sta. Kept. 1895, pages 14-150, Fermentation 

 test for gas-producing bacteria in milk. This is commonly 

 called the Wisconsin curd test. 



