USE OP BACILLUS BULGARICUS IN CHEESE STARTERS. 5 



latecl 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 per cent of acid in milk, but only 2 per cent in whey. 



