June 15,1914 
Flavor of Cheddar Cheese 
187 
was more likely to bring about this condition. When variety “c” was 
used, the cheese was almost certain to be ruined by the acid before it was 
a month old. This variety was isolated only once from the 21 normal 
raw-milk cheeses which have been studied with reference to the varieties; 
and then there were present less than 500,000 bacteria per gram of cheese. 
B. casei, c, has been isolated, however, from three raw-milk cheeses which 
had a sour taste rather than the Cheddar flavor. Therefore this variety 
can not be regarded as a necessary organism in normal ripening. It is 
likely that it never occurs in large numbers in the young cheese without 
causing injury. B. casei , varieties “a” and “b,” are about equally distrib¬ 
uted in normal Cheddar cheese, where they usually occur together and per¬ 
form an active part in the ripening changes. It has been noted that the 
B. casei groups develop gradually in the pasteurized-milk cheese, as they 
do in the raw-milk cheese, although usually more slowly. The introduc¬ 
tion of this group as a starter, however, resulting in abnormally large 
numbers of B. casei in the early ripening period, is detrimental to the 
cheese. 
In subsequent series of experiments with pasteurized-milk cheese 
this group of organisms was never added to the starter. 
influence; of bacterium lactis acidi upon flavor production 
When Bacterium lactis acidi , a or b, is used for a starter in pure 
culture in pasteurized-milk cheese, an acid taste is produced which 
is characteristic of the ordinary pasteurized-milk cheese made with the 
use of a commercial starter. No suggestion of a Cheddar flavor is ever 
obtained. If B. lactis acidi , d, is added to the milk, there is almost 
always produced a peculiar flavor, which, as it intensifies with continued 
ripening, becomes decidedly bitter. Out of 14 experimental cheeses in 
which 0.75 per cent, the ordinary quantity used for a starter, of a 
pure culture of this variety was used or in which a mixture of several 
pure cultures was used with B . lactis acidi , d, in large proportions, the 
unpleasant flavor has developed some time between the fourth and 
fourteenth weeks. Usually the cheese becomes bitter by the time it 
is 2 months old. In only one instance has the bitterness failed to develop 
befor'e the fourteenth week. The figures in Tables VIII and IX show 
that B. lactis acidi , d, was isolated from normal raw-milk cheese with 
sufficient frequency that it may be concluded that it is always present 
in this type of cheese in large numbers. It no doubt contributes to the 
characteristic Cheddar flavor under the conditions obtaining in a normal 
cheese. But it is certain that a large amount of this variety is not 
suitable for use in the starter for pasteurized-milk cheese. 
INFLUENCE OF THE COCCUS GROUPS IN THE PRODUCTION OF FLAVOR 
From the frequency of occurrence of all four varieties of the strepto¬ 
cocci in normal Cheddar cheese in percentages ranging as high as 50, 
as shown in Tables VIII and IX, it is most certain that this group is 
