306 MANUAL OF MILK PRODUCTS 



degree of acidity will usually be shown by an acid test of 0.19 

 to 0.21 per cent, or when the milk coagulates at two and one- 

 half spaces with the Marschall test or in forty-five to sixty 

 seconds with the Monrad test. If the milk is ripened more 

 than this, it is liable to cause trouble in the process of making 

 and the later ripening of the cheese. 

 Coloring the milk. 



Whether or not color should be added will depend on the 

 requirements of the market, the quality of the milk, and the 

 season of the year. Some markets require a cheese of light 

 color, while others desire a highly colored cheese. If it is 

 desirable to increase the natural color of the milk, it may be 

 done by the use of ana to cm butter color, using from \ to 3 oz. 

 to 1000 lb. of milk. Before adding the color to the vat, it 

 should be diluted and then thoroughly mixed through the 

 entire mass of milk. 

 Adding the rennet. 



As soon as the proper degree of acidity has been reached, 

 the rennet extract should be added. This step in the process 

 is usually known as " setting " the milk. Rennet is a substance 

 obtained from the stomach of a calf which is living on milk. 

 The active principle is extracted from the tissue of the stomach 

 and placed on the market in liquid form. The use of rennet 

 in cheese-making is for the purpose of coagulating the casein. 

 Pepsin. 



Commercial pepsin may be used in the place of rennet. This 

 is a preparation made from the stomachs of sheep or hogs, 

 and is usually placed on the market in the form of dry scale- 

 pepsin. This pepsin is used by making a water solution which 

 is then added to the milk in the same manner as rennet. Pepsin 

 does not seem to work in very sw T eet milk as well as does rennet, 

 but for milk which is fairly ripe, its action seems to be entirely 

 satisfactory and produces a cheese equal in quality to that made 

 with rennet extract. 



