USE OF BACILLUS BULGARICUS IN CHEESE STARTERS. 3 



cheese is cooked at a comparatively high temperature, 126° to 136° 

 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 s 

 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. (104° 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 Emmenthalerkasen, nebst 

 einigen Bemerkungen iiber die Reifungsvorgange. Landwirtschaftliches Jahrbuch der 

 Schweiz, vol. 13, p. 169-197. Bern, 1899. 



2 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 und den Bak- 

 terien der Coli-Aerogenes-Gruppe. Zeitschrift fur Garungsphysiologie allgemeine, land- 

 wirtschaftliche und technische 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 Labmagen und Lab. Ein Beitrag zur 

 Kenntnis der Bereitung des Kasereilabes. Landwirtschaftliches Jahrbuch der Schweiz, 

 vol. 20, p. 181-242. Bern, 1906. 



