248 Journal of Agricultural Research voi. xiii, no. 4 



and more delicate flavor, unanimously preferred to the acid flavor by 

 the four cheese experts to whom the samples were submitted. The curd 

 is also more broken down in several of the cheeses inoculated with cheese 

 streptococci, which indicates a more rapid ripening. 



The experiments have shown that the cheese streptococci improve the 

 flavor of cheese made of pasteurized milk according to the Cheddar 

 process. The cheeses were made on an experimental scale, where there 

 was every facility for handling the pure cultures, but it is hoped that 

 practical methods may be devised whereby any manufacturer can make 

 use of these pure cultures in his factory. 



Sammis and Bruhn {18) worked out the method by which cheese of 

 the Cheddar type can be manufactured from pasteurized milk, and they 

 pointed out the advantages of pasteurizing the milk for making that 

 kind of cheese. They sent to city markets great quantities of their 

 cheese which had been inoculated with 5. lacticus alone. From the 

 reports of the dealers they conclude : 



There appears to be no reason why pasteurized-milk cheese cannot be sold regularly 

 in any market, with entire satisfaction, excepting possibly, to the limited trade that 

 demands very high flavored cheese. 



The experiments recorded in this paper show that the pasteurized- 

 milk cheese may not only be improved in flavor by inoculation with a 

 starter of cheese streptococci, but also the time of curing may be 

 shortened, an important consideration with the cheese manufacturer. 

 When the makers of Cheddar cheese recognize the advantages of pasteur- 

 izing the milk, there is no reason why a practical method may not be 

 developed by which any manufacturer could make a choice of the strain 

 of streptococcus or the combination of streptococci which would give a 

 flavor he desires, and by using it constantly under uniform conditions 

 the whole output of a factory could be made to develop its own "trade" 

 flavor. 



As a result of this and earlier {8) work, it may be concluded that the 

 cheese streptococci are essential factors in normal Cheddar cheese ripen- 

 ing. A few fundamental biochemical reactions have been determined 

 but not enough is known of these streptococci to explain fully the chem- 

 ical processes they may be responsible for in the cheese ripening. A 

 few facts are suggestive, however, of the part the several types of strep- 

 tococci may play in the Cheddar cheese ripening. The formation of 

 large quantities of acetic acid in milk cultures by Streptococcus X and 

 S. kefir suggests that these organisms may be responsible for the produc- 

 tion of alcohols and esters, substances which, according to Suzuki, Hast- 

 ings, and Hart (20) give flavors to Cheddar cheese. They found that 

 acetic acid formed 90 per cent of the acids obtained by the saponification 

 of the esters and the oxidation of the alcohols of their "flavor solution" 

 from ripe Cheddar cheese. As yet it is unknown whether the acetic acid 

 is formed simultaneously with the lactic acid in the decomposition of the 



