362 SCIENCE AND PRACTICE OF CHEESE-MAKING 



milk is cooled and, in order to prevent bacterial action, 

 treated with chloroform before being made into 

 cheese. The heating of the milk to the stated tem- 

 perature diminishes the readiness and completeness 

 with which the rennet-extract coagulates milk-casein; 

 but the power af prompt coagulation by rennet can 

 be restored by addition of calcium chlorid or carbon 

 dioxid gas or any ordinary acid or acid salt. In thus 

 eliminating other factors otf cheese-ripening than ren- 

 net-enzym, we necessarily produce conditions that 

 do not exist in normal cheese-making, such as (i) 

 heated milk, (2) absence of milk-enzyms, (3) absence 

 of enzym-forming or acid-producing micro-organisms, 

 and (4) the addition of calcium chlorid or carbon 

 dioxid or lactic acid. Several experiments were car- 

 ried on at the New York experiment station under 

 the foregoing conditions and, in the table following, 

 we give some of the results of this work. Lactic acid, 

 when used, was added to form 0.2 per cent of the milk. 



PEPTIC ACTION OF RENNET IN CHEESE WITH AND 

 WITHOUT ACID 



In studying this table, we can readily observe the 

 following indications : 



