1916] DAIRY FARMING DAIRYING. 177 



Bacterial studies of Camembert cheese, W. M. Esten and Christie J. Mason 

 (Connecticut Storrs Sta. Bui. 83 (1915), pp. 103-111). — In bacterial examina- 

 tions of Camembert clieese from many different sources it was found that the 

 highest numbers of bacteria were usually found about the third day, after 

 wliich the numbers decreased, and most rapidly between the seventh and 

 eleventh days. With fluctuations the numbers decreased gradually until the 

 cheeses were ripe. In the majority of cases 99 per cent or more of the bac- 

 teria in the interior of the cheese were of the lactic acid type. The propor- 

 tion of liquefying types was small, especially where a starter was used, as 

 was generally done. 



In a comparison of the types of Bacterium lactis acidi found in European 

 and American cheeses, the European form made somewhat larger colonies in 

 litmus lactose gelatin plates and grew on the surface, while the American form 

 was always found below the surface. The European form grew more abund- 

 antly on agar slants and in bouillon. Milk soured with cultures of the two 

 forms developed no noticeable difference in flavor or odor either when first 

 curdled or when kept for four weeks at the temperature used for ripening 

 cheese. Cheeses made -with starters of these two types showed no real dif- 

 ference in flavor. 



Practically every cheese tested showed the presence of yeasts. They were 

 most abundant on the surface, but were uniformly found in the curd. Rarely 

 the numbers reached several millions per gram, but in most cases there were 

 only a few thousands per gram, the highest numbers being usually foimd be- 

 tween the fourteenth and twenty-first days. Several different species were 

 found, the most common being an acid producer which in litmus lactose gelatin 

 resembled B. lactis (crogenes. Several cases of gassy cheese were apparently 

 due to yeasts. Some of the yeasts from cheese produced in milk an acid, 

 others an alkaline reaction ; some peptonized milk. Those tested were able 

 to develop in the absence of air, but not so rapidly as in aerobic conditions. 

 They were not greatly restrained by amounts of salt as large as are present 

 in cheese. 



The acidity of 10 samples ranged from 1.67 to 3.2 per cent. The presence 

 of Bacillus bulgaricus was ascertained, but it is stated that it is doubtful if 

 this organism has any decided influence on the ripening of Camembert, since 

 it grows best at from 44 to 45° C. and only very slowly at the lower tempera- 

 tures, from 10 to 15°, at which Camembert ripens. As Camembert ripens 

 within five weeks it is also very doubtful if B. hulgaricus could develop sufli- 

 ciently in that time to affect the flavor. 



Tests showed only one-ninth as many bacteria under anaerobic as under 

 aerobic conditions, and in tests of the slime only one-fortieth as many. No 

 species were found in anaerobic cultures which were not present in the 

 aerobic. 



Bacterial counts were made from the slime of cheeses of different origin. 

 The surface slime contained a great number of different types of organisms. 

 However, it is thought that they contribute but little to the production of 

 flavor. 



Tests conducted with Roquefort cheese gave results very similar to those 

 given for Camembert. The lactic acid bacillus, B. lactis acidi, was always 

 found in nearly pure cultures and other species did not appear uniformly 

 enough to suggest any special importance in ripening the cheese. Yeasts were 

 present in four out of the five important brands examined. B. bulgaricus is 

 probably almost always present in Roquefort cheese. Tests of acidity showed 

 a range of from 1.64 to 4.95 per cent. B. hulgaricus was also found in other 



