Apr. 22,i9i8 Streptococci Concerned in Cheese Ripening 247 



lesser acidity. In color and texture it was noticeably more like a raw- 

 milk cheese after about two months of ripening. Samples were sub- 

 mitted to several persons, who agreed that the experimentally inoculated 

 cheese was preferable to the control. The third cheese was made in the 

 same way, but had starters of Streptococcus X and 5. kefir in addition 

 to the S. lacticus starter. After two months' ripening it was unquestion- 

 ably the best cheese of the three. In fact, a Cheddar cheese can rarely 

 be obtained in market altogether as pleasing as this cheese because the 

 undesirable organisms in milk when it comes to the factory commonly 

 give to cheese "unclean" flavors. In the pasteurized-milk cheese all 

 undesirable organisms have been destroyed, and in the case of the cheese 

 in question, a part, at least, of the flora necessary for developing the 

 delicate flavors typical of a Cheddar cheese made from raw milk had 

 been restored. For a few weeks during the third and fourth months of 

 ripening the flavor of the one inoculated with cheese streptococci did 

 not compare so favorably with that inoculated with 5. lacticus alone. 

 After four months' ripening at about 23° C. the cheeses were placed in 

 a refrigerator where the temperature varied from 12° to 15° C. When 

 they were seven months old the cheese inoculated with Streptococcus X 

 and S. kefir was pronounced by experts to be a good Cheddar cheese, 

 with the typical flavor highly developed, whereas the control cheese 

 inoculated with 5. lacticus alone had a mild, rather pleasing flavor, which 

 did not in any way resemble Cheddar. 



In the last series of experiments 10 cheeses were made. One control 

 was made of raw milk with a starter of S. lacticus, three were made of 

 pasteurized milk with a starter of S. lacticus, to serve also as controls; 

 and six were made of pasteurized milk with a starter of 5. lacticus and 

 of cheese streptococci. Three strains of cheese streptococci were used in 

 these experiments ; one of Streptococcus X, one of S. kefir, and one whose 

 characteristics did not conform to either of these species; it is not 

 described in this paper because it is an odd strain in the collection 

 of cheese streptococci. Its beneficial effect when inoculated into 

 pasteurized-milk cheese merits for it further study and a determination 

 of its frequency in dairy products. At the time of this writing the 

 cheeses have been ripening for six weeks at a temperature of from 13° 

 to 15° C. The raw-milk cheese is unquestionably the poorest of the 

 lot. There are many small gas holes in it, and the flavor is unclean. 

 It was made during very hot weather, and the milk was poor in quality, 

 as is usually the case under such conditions of temperature. All three 

 of the cheeses made of pasteurized milk and inoculated with 5. lacticus 

 are good in texture, and have the clean, acid flavor typical of cheeses 

 made in this way. All three strains of cheese streptococci, when 

 inoculated singly or in various combinations, improved the flavor of 

 the cheese as compared with the controls. The acid flavor characteristic 

 of the control pasteurized-milk cheese is lacking; instead there is a mild 



