194 Report of the Chemical Department of the 



chloride in 500 cc. of water, and we used 2.5 cc, of this solution 

 for each kilogram of milk. Carbon dioxide was used in place 

 of calcium chloride in experiments 48 to 51. In using this, we 

 passed a vigorous stream of the gas through the milk for about 

 30 minutes previous to adding rennet. After several trials, we 

 found that calcium chloride and carbon dioxide, used in the 

 manner described, enabled the rennet-extract to coagulate the 

 milk completely in 20 to 30 minutes. Hansen's rennet-extract 

 was used at the rate of 2.5 liquid ounces for 1,000 pounds of 

 milk (about i part of rennet-extract to 600 parts of milk by 

 weight). In those experiments in which we compared the effect 

 of the presence and absence of salt, a double portion of milk 

 was generally used and the operation of cheese-making was 

 carried on as usual to the point of salting, when the curd was 

 divided into two approximately equal parts, one portion not 

 being salted and the other portion receiving salt at the rate of 

 2 pounds of salt for 1,000 pounds of milk. 



The cheeses were taken from the press and at once put under 

 air-tight vessels in an atmosphere of chloroform, where they 

 were kept during the period covered by our study. For addi- 

 tional details regarding the use of chloroform in cheese-making 

 and cheese-ripening, see Bulletin No. 203, page 327. 



The first series of experiments included 44 to 47. In these 

 calcium chloride was used to restore the coagulability of the 

 milk. Lactic acid was added in 45 and 46 and omitted in the 

 others. wSalt was added in 46 and 47 and omitted in 44 and 45. 

 In all cases the milk was heated and treated with chloroform. 



After a month, it was noticed that there was little indication 

 of proteolytic change, and it was thought possible that the 

 presence of calcium chloride might retard the action of the 

 rennet-enzyme. It was then decided to repeat the experiments, 

 using carbon dioxide in place of calcium chloride, and this second 

 series included experiments 48 to 51. 



In experiments 52 and 53, the milk was pasteurized at 85° C. 

 (185° F.), carbon dioxide was added and the acid was furnished 

 by a " starter," as in normal cheese-making. No chloroform 

 was used. In 53 salt was used and omitted in 52. 



