MILK PRODUCTS 331 



typical cheese, e.g. Cheddar, is prepared, may be summed up 

 in a few words. 



Lactic fermentation is initiated by means of a " starter." 

 This may consist either of a pure culture or, more commonly, 

 of some sour milk which, of course, contains large numbers 

 of the necessary bacteria. The milk is kept at a suitable 

 temperature, to promote the change, until it is found on 

 testing with standard alkali solution that a sufficient amount 

 of lactic acid has been formed. 



The temperature is then raised to a suitable point usually 

 about 87 F. and rennet is added to coagulate the milk 

 (p. 75). An experienced cheesemaker can tell from the 

 condition of the coagulum when the action of the rennet is 

 sufficiently advanced. The curd is then broken up, and 

 manipulated until it reaches the proper condition, and the 

 whey is drawn off. The temperature effects at this stage are 

 very important. The curd is ground and salted, put into 

 moulds and pressed. The product is then known as green 

 cheese, and must be kept till it is ripe. 



When rennet is added to milk, the caseous matter alone 

 is coagulated, but some of the ash constituents remain in 

 association with it. The fat which, of course, is not in 

 solution, undergoes no change, but is carried down mechani- 

 cally. The albumin and globulin, together with the milk 

 sugar, and the lactic acid formed from it, remain in solution. 

 Practically the whole of these compounds, the small pro- 

 portion of fat which escapes when the curd is broken up, and 

 the remainder of the ash are, therefore, found in the whey. 



A gallon of milk (10 Ibs.) yields roughly, on the average, 

 about i Ib. of cheese of the Cheddar type, 8f Ibs. of whey, and 

 about J Ib. of water is lost by evaporation during the -process. 

 Calculating from these figures and the composition of the 

 products, the distribution of the solids is found to be as shown 

 below. 



