Bacteria and Cheese Making. 177 



The most successful method of preventing trouble 

 with gassy milk in cheese making is to eliminate unde- 

 sirable milk by frequent testing of the supply of the 

 different patrons by means of the Wisconsin curd test. 



Not only gas-forming bacteria may be the cause of 

 gassy cheese, but the lactose-fermenting yeasts may cause 

 similar trouble. If these are abundant in the milk, a 

 considerable part of the sugar may be fermented by 

 them, in which case, carbon dioxide gas is abundantly 

 formed. The cheese thus rendered gassy will present 

 the same appearance to the eye as where the gas is formed 

 by bacteria, but will have a different flavor. The odor 

 of alcohol may be evident, and if most of the sugar has 

 been fermented by the yeast, the acidity of the cheese 

 may not be sufficient for the pepsin to exert its digestive 

 action. 



Milk containing many gas-forming bacteria occurs 

 most frequently in summer. It is claimed by some that 

 the milk of cattle pastured on low lands is more likely 

 to contain the gas-forming organisms than that from 

 cattle running on higher lands. If this is true, it must 

 be due to the bacterial content of the soil ; the udders of 

 the animals become soiled as they lie on the ground, and 

 during the milking, the dust finds its way into the pail. 

 Many cheese makers think that the milk from an animal 

 suffering from a garget may be the cause of the huffing 

 of cheese. This belief is undoubtedly well founded, as 

 some of the bacteria known to be the cause of garget are 

 gas-forming. 



Bitter cheese. In a previous chapter the bitter fer- 

 mentation of milk has been discussed. If milk contain- 

 ing large numbers of such organisms is made into cheese, 

 the bitterness is very likely to be noted in it. Cheese 



12 



