HACTERIA IN CHEESE-MAKING. 265 



most common one is called " inflated cheese " or "swflledcfeese" 

 It is characterized by the development of large amounts of 

 gas in the cheese during the ripening. The accumulating gas 

 causes the cheese to become swollen and filled with cavities. 

 The amount of the swelling and the size of the holes are by 

 no means constant. The trouble may be so slight as hardly to 

 affect the cheese, or so marked as to ruin it completely. The 

 holes may be a few great cavities, or they may be very numer- 

 ous, minute holes. That the phenomenon is due to the growth 

 of bacteria has been proved by a number of experiments. It 

 does not appear that any single species produces the phe- 

 nomenon, but quite a number of bacteria may 

 be concerned in it. Several experimenters 

 have inoculated cheeses with various species of 

 gas-forming bacteria. (Fig. 33.) The cheese 

 always becomes more or less swollen in the 

 ripening and develops the cavities. There are 

 many ordinary dairy bacteria which produce A bacillus causing 

 an abundance of gas in their growth in milk, 



Shaffer i). 



and almost any one of these, if present in un- 

 due quantity in the milk, is likely to produce so much gas in 

 the cheese as to give rise to this abnormal ripening. 



There is no type of abnormal ripening which produces so 

 much trouble in cheese-making as this, and various devices 

 have been suggested for remedying it. One method is by the 

 use of salt, which partly prevents the undue growth of these 

 organisms. One of the most practical suggestions is a quick 

 but effective test of samples of the milk to be used in the 

 cheese-making. The essence of this method is to take sam- 

 ples of milk from different patrons, especially if the milk is in 

 the slightest degree suspicious, and place each in a small vial 

 of a proper form. The milk is then kept at a temperature of 

 about 90 F., and, if gas-forming bacteria are present in abund- 

 ance, they will soon make their presence known by numerous 



