58 THE BOOK OF CHEESE 



activity of lactic organisms, which is the usual way. 

 For renneting, the acidity necessary for particular cheeses 

 runs from that of absolutely fresh milk still warm (as 

 in French Brie, Limburger, Swiss, Gorgonzola) through 

 series calling for increase of acidity, hundredth by hun- 

 dredth per cent calculated as lactic acid. This ranges 

 from 0.17 to 0.20 per cent as is variously used in Ameri- 

 can factory Cheddar to about 0.25 to 0.28 per cent as 

 obtained by adding acid in Sammis' method. This 

 method is discussed under the heading " Cheddar Cheese 

 from Pasteurized Milk " (p. 229) since it requires special 

 apparatus and has not thus far been used with other types 

 of cheese. For the development of acidity by the action 

 of bacteria, lactic starter is almost universally used. 

 This may be added in very small quantities and the 

 acidity secured by closely watching its development or 

 by adding starter 'in amount sufficient to obtain the re- 

 quired acidity at once. In either case, the cheese-maker 

 needs to know the rate of action of the culture to in- 

 sure the proper control of the process. The amount of 

 acid already present when the rennet is added affects not 

 only the texture of the curd as first found, but within 

 limits indicates also the rate at which further acidity may 

 be expected to develop. 



A series of experiments in making Roquefort were tabu- 

 lated to show the rate of acidification from various initial 

 points. In the graphs (Fig. 8) the curves for acid de- 

 velopment are parallel after the determination reaches 

 0.30 per cent. These experiments were made at a tem- 

 perature 80 to 84 F. Milk at the lowest acidities tried 

 developed titratable acid very slowly. A period of several 

 hours was required to produce sufficient acid to affect the 

 curd texture. When the acid reached 0.25 per cent by titra- 



