238 PRACTICAL DAIRY BACTERIOLOGY 



common practice of leaving the cheese in a fairly cool room 

 to ripen at normal temperatures has produced a fairly rapid 

 ripening, giving a more or less strong cheese of the type that 

 has been common on the market. In the last few years, how- 

 ever, experiments have been undertaken to determine the effect 

 of ripening at lower temperatures. The results have been 

 highly satisfactory, for it is found that if the cheeses are placed 

 in ripening rooms at temperatures below 56, though ripening 

 goes on much more slowly, it is more uniform, more satisfac- 

 tory, and there is a noticeable improvement in the product. The 

 use of low temperatures for ripening is quite new, but has ex- 

 tended rapidly, and at the present time a large amount of cheese 

 is thus ripened. 



DEFECTS IN HARD CHEESES 



Most of the defects which injure a cheese, sometimes com- 

 pletely destroying it, are due to the growth within it of undesir- 

 able organisms. There is quite a variety of these, some of 

 which are rare, some of which are fairly common, and some 

 of which cause immense losses to cheese makers the world 

 over. The most important we will briefly consider. 



Gassy or Swelled Cheese. The phenomenon spoken of as 

 gassy or swelled cheese is perhaps the most common of cheese 

 faults. It is due to the development inside of the curd of a 

 considerable quantity of gas, which fills it full of holes and 

 causes it to swell and lose its shape. Sometimes the holes 

 are extremely numerous and small, and sometimes they are 

 fewer but of larger size ; and, in any case, they are un- 

 desirable. The abundance of the gas produced varies greatly. 

 Even good cheeses are apt to show some gas holes, but the 

 amount is so small it does no especial injury to the cheese. 

 Sometimes the gas is so abundant as to cause the cheese to 

 burst, in which case it is, of course, completely ruined. Between 

 these extremes are all kinds of intermediate grades. In some 



