USE OF BACILLUS BULGARICUS IN CHEESE STARTERS. 5 
luted at Albert Lea. Minn., the most favorable temperature was 49° C. 
in making Swiss cheese began in the winter of 1910-11 at Albert Lea, 
EXPERIMENTS WITH BACILLUS BULGARICUS STARTERS. 
Our experiments with cultures of Bacillus bulgaricus as a starter 
in making Swiss cheese began in the winter of 1910-11 at Albert Lea, 
Minn. The work was continued at State College, Pa., and finally 
completed in the laboratories at Washington. The milk delivered 
for cheesemaking at Albert Lea was of very poor quality, being very 
gassy, and it was impossible to secure any that was not badly in- 
fected. A long series of experiments in pasteurization had not 
proved entirely successful, and experiments to discover a bacterial 
culture that would prove efficient in suppressing gas-forming bac- 
teria were begun. A number of different cultures of B. bulgaricus 
were used under varying conditions and at all seasons of the year. 
In Table 1 are given the results obtained with B. bulgaricus cul- 
tures that proved efficient in suppressing gas-forming types of bac- 
teria when used in what would probably be considered as reasonable 
amounts of starter ; that is, where the starter was less than 2 per cent 
of the total amount of milk used. The cultures used were obtained 
from different sources. Culture 39a was very active and was the only 
culture of B. bulgaricus used at Albert Lea, Minn. 1 Cultures I S 
and 44H were isolated in the Washington laboratories. 
In the experiments recorded in Tables 1 and 2 all the milk was 
first put into one kettle, where it was thoroughly stirred and then 
divided. As the kettle and all other apparatus used were thoroughly 
cleaned before using, identical conditions in both lots of milk were 
insured. 
Probably every lot of milk used in these experiments was as badly 
contaminated with gas-forming bacteria as the mixed milk would 
be in any commercial Swiss-cheese factory on any day of the year. 
Nevertheless from this milk, by the use of these starters, we were 
enabled to make a perfectly sound cheese that did not develop into 
a " nissler ? ' or " pressler." 
The milk used at the Washington laboratories came from the herd 
owned by the Dairy Division and was almost free from the faults 
common to ordinary factory milk. There may have been no occa- 
sion for using a starter with this milk to suppress gas-forming bac- 
teria. At this time culture 39a, by being carried in the laboratory, 
had lost much of its power to form acid, but was still active enough 
to retain its efficiency in suppressing undesirable gas formers. A 
1 This culture was isolated by Mr. B. J. Davis, of this laboratory, who was in search of 
a strain of high acid-producing bacteria for pure cultures in buttermaking. This culture 
produced 3 por cent of acid in milk, but only 2 per cent in whey. 
