Bacteria in the Cheese Industry. 169 



European forms that have been isolated, and has found 

 nineteen bacterial species (five cocci, fourteen bacilli) 

 and eight varieties of yeast-like fungi that are gas-pro- 

 ducing organisms. 



If pasteurized milk is seeded with a pure culture of 

 any of these gas-forming organisms and made into 

 cheese, an intense fermentation is always to be noted. 

 This often appears in the curd, sometimes even before 

 the whey is drawn. The cheese when taken from the 



%^:PSw 



FIG. 34. " Gassy" cheese. The milk from which this cheese was made was 

 first pasteurized, and then infected with a gas-generating bacillus. Note not 

 only the " spongy " texture, but the distorted form. 



press develops gas rapidly, causing it to swell and a cross 

 section of it at this stage will show a spongy structure. 

 If the cheese is left intact, the fermentation may progress 

 to such an extent that the pressure of the contained gas 

 will cause the rind to split open. This fermentation does 

 not last for more than a few days; then the swelled 

 cheese sinks as the gas slowly diffuses throughout its 

 mass, but the flavor of the product is generally impaired. 



