368 CHEESE 



group of bacteria such as species of Tyrothrix and 

 allied spore-producing kinds were the chief cause of 

 ripening, it would be expected that they would be more 

 abundant in a ripened cheese than in one which has 

 undergone little change, but this is not the case. They 

 are never abundant in cheese at any time, and are 

 generally absent altogether in Cheddar and other hard 

 cheeses a few months old : even when added in large 

 numbers to the curd they fail to increase, and die out 

 usually before any sign of ripening can be detected. 



() The view that the lactic bacteria are the chief 

 agents in the ripening of cheese was strongly supported 

 by Freudenreich, and many of his pupils still maintain 

 this opinion. The common lactic bacteria are by far the 

 most abundant organisms met with in cheese of all kinds, 

 and in the early stages of the ripening comprise more than 

 95 per cent, of the total bacteria present. Weinzirl 

 found that of the total bacteria present in Cheddar 

 cheese about 74 per cent, were lactic forms near Strepto- 

 coccus lacticus and 22 per cent, allied to Bs. acidi lactici 

 (Hiippe), leaving only 3 or 4 per cent, for all the other 

 species, and similar results have been obtained by 

 Percival and Mason in Stilton cheeses. The lactic 

 bacteria uphold their supremacy almost to the end of 

 the ripening period, and in practice it is found that 

 cheeses which contain large numbers of these organisms 

 are much superior in quality to those in which fewer are 

 found. Cheese made from milk from which they are 

 absent always ripens slowly and abnormally, whereas 

 when a culture or " starter " of lactic acid bacteria is 

 added such milk will produce a good cheese. 



In hard cheeses, where the organisms other than 

 lactic bacteria are in the early stages in greater pro- 



