204 Report of the Chemical Department of the 



may exert a retarding- influence upon the action of pepsin and 

 rennet. Alallitano^ makes the statement that the action of pepsin 

 is considerably diminished by chloroform. The difference noted 

 in our work may be due to the greater amount of acid present 

 in the experiment in Table \'. However, both sets of experi- 

 ments practically agree in showing small formation of amides 

 and entire absence of ammonia. 



EXPERIMENTS IN MAKING CHEESE FROM PASTEURIZED MILK WITH 



" STARTER." 



For the purpose of comparison, it was regarded as desirable 

 to have some cheeses made from pasteurized milk. The cheeses 

 in experiments 52 and 53 were made for this purpose. We 

 pasteurized 135 pounds of milk at 85° C. (185° F.), cooled it to 

 29° C. (84° F.), passed carbon dioxide gas through it for half 

 an hour, introduced 4.5 pounds of a specially prepared lactic 

 acid " starter," added Hansen's rennet-extract at the rate of 2.5 

 ounces for 1,000 pounds of milk, and then carried on the opera- 

 tion of cheese-making in the usual way. The curd was divided 

 into two equal parts and one part, unsalted, was made into 

 cheese No. 52, while the other portion, salted at the usual rate, 

 was made into No. 53. Both cheeses were ripened at a tempera- 

 ture of 15.5° C. (60° F.). 



As factors active in causing proteolytic changes, we had in 

 the cheeses made in these two experiments (i) acid, (2) rennet- 

 enzyme and (3) such micro-organisms as happened to be intro- 

 duced with the " starter " and from the air of the room. As 

 compared with a normal cheese, there were no milk-enzymes 

 present and the biological factor would be expected to be con- 

 siderably less marked. In comparison with the cheeses made in 

 experiments 44 to 51, we had in 52 and 53 no chloroform, a 

 difference that meant absence of a biological factor in the former 

 case. In 52 and 53 the acid was furnished by a " starter," while 

 in the other experiments artificial acid was added. In Table \T 

 we give the results of chemical analysis made when the cheese 

 was fresh from press and when 9 months old. The detailed 

 analyses are given in the Appendix. 



^ Ann. Inst. Pasteur, 16:853 (1902). 



