USE OF BACILLUS BULGARICUS IN CHEESE STARTERS. 6 
cheese is cooked at a comparatively high temperature, 126° to 13G° 
F., and is cooled very gradually while the cheese is in press. This 
treatment checks temporarily the growth of most species of bacteria, 
including the lactic-acid bacteria, which are used for starters in the 
making of butter and Cheddar cheese. 
The Bacillus bulgaricus group of bacteria has the qualifications 
which apparently fit in with the manufacturing process of Swiss 
cheese. Investigators have found a wide variation in the tempera- 
tures at which different varieties will grow and in the amount and 
rapidity of acid formation. The presence of this group of bacteria 
in the rennet preparations was first recognized by Freudenreich and 
Jensen, 1 who studied it and named it Bacillus casei s. They came to 
the conclusion that it was largely responsible for the normal ripen- 
ing of the cheese, but Jensen apparently receded from this position 
a few years afterwards, though he still advocated the use of B. casei e 
in the preparation of rennet for the purpose of suppressing the 
growth of undesirable bacteria in the rennet solution. He has been 
supported in this by many of the European authorities, and pure 
cultures of B. bulgaricus have been furnished extensively to makers 
of Swiss cheese for this purpose. 
Peter and Held, 2 in discussing the sources of infection causing 
troubles with Swiss cheese and the influence of the rennet solution on 
the cheese, suggested the possibility of the cultures in the rennet sup- 
pressing undesirable gas-forming types of bacteria in the cheese. 
Gratz, 3 in some laboratory tests, found that a culture of Bacillus 
bulgaricus inhibited the growth of bacteria of the coli-aerogenes 
group in milk held at a temperature of 40° C. (101° F.). 
Burri, 4 in discussing the relative merits of commercial acid and 
pure cultures of Bacillus bulgaricus in making up the whey rennet 
solution, points out that B. bulgaricus suppressed the growth of gas- 
forming bacteria in the whey rennet. 
Thoni 5 showed the influence of B. bulgaricus in making good 
rennet. He reported some experiments in which rennet containing 
B. bulgaricus made good cheese, while cheese made with the natural 
rennet without this bacillus was gassy, evidently because the gas- 
producing bacteria made a very heavy growth in the rennet. 
1 Freudenreich, Edward von, and Jensen, Orla. Die Bedeutung der Milchsaurefer- 
mente fur die Bildung von Eiweisszersetzungsprodukten in Eminenthalerkasen, nebst 
einigen Bemerkungen tiber die Reifungsvorgange. Landwirtschaftliches Jahrbuch der 
Schweiz, vol. 13, p. 169-197. Bern, 1899. 
- Peter, A., and Held, J. Praktische Anleitung zur Fabrikation und Behandlung des 
Emmentalerkases. Second edition. Bern, 1910. 
3 Gratz, Otto. Studien iiber die Antibiose zwischen Bacterium casei e and den Bak- 
terien der Coli-Aerogenes-Gruppe. Zeitscbrift fiir Garungsphysiologie allgemeine, land- 
wirtschaftliche und tecbniscbe Mykologie, vol. 1, no. 3, p. 256-281. Berlin, June, 1912. 
4 Burri, Robert, Reinkulturen oder Siiuremischung beim Labansatz? Molkerei 
Zeitung, vol. 22, no. 33, p. 387-389. Berlin, 1912. 
5 Thoni, Johannes. Bakteriologische studien iiber Labinagen und Lab. Ein Beitrag zur 
Kenntnis der Bereitung des Kasereilabes. Landwirtschaftliches. Jahrbuch der Schweiz, 
vol. 20. p. 181-242. Bern, 1906. 
