As the fermentation takes place, different odors will be noticed in different jars. In ten to twelve hours the jar should be finally examined for odors and the curd taken out and cut to examine it for gas pockets. By this means, bad flavors and gas in the cheese can be traced to their sources.
43. The sediment test.—The presence of solid material or dirt in the milk is always accompanied by bacterial contamination. By means of the sediment test, the amount of solid material can be determined. The test consists of filtering the milk through a layer of cotton; the foreign material is left on the cotton filter. Various devices for filtering the milk have been
Fig. 5.—A single sediment tester. manufactured. (Figs. 4 and 5.) In order to be able to compare the filters from the different dairy-men's milk, the same amount of each patron's milk is filtered, usually about a pint. These tests are usually made once or twice a month at the factory and the filters placed on a card where the dairy-men can see them. Much improvement in the quality of the milk has been accomplished by the use of the sediment test. The purpose of this test may be and often is defeated by the use of efficient strainers. Milk produced in an unclean way may be rendered nearly free from sediment if carefully strained. It must be remembered that the strainer takes out only the undissolved substances and that bacteria and soluble materials which constitute a very large part of the filth pass through with the milk.
CHAPTER III
COAGULATING MATERIALS
At the present time, two substances are used to coagulate milk for cheese-making,—rennet extract and commercial pepsin.[20] Many substances will coagulate milk, such as acids and other chemicals. Enzymes in certain plants will also coagulate it.