CHEESE 229 



organisms, and so be able to control the ripening, for we shall then be 

 able to introduce starters into the cream or curds and take steps to 

 ensure the predominance of the right bacteria. 



As a matter of fact, steps in this direction have been taken, as Lloyd 

 states that in the case of Cheddar cheese, Bacillus acidi lactici alone is 

 necessary, the other bacteria tending more or less to hinder the process. 

 In preparing this cheese, therefore, a "starter" composed of a pure 

 culture of Bacillus acidi lactici is added to the milk in order that it 

 may be present in abundance in the ripening cheese. This microbe 

 can not only convert milk sugar into lactic acid, but can also dissolve 

 the casein of milk, changing it into soluble substances, provided that 

 the acidity (produced by lactic acid) be removed by the addition of a 

 neutralising substance like chalk. Another fact that has came to light 

 is that green mould (Penicillium glaucum) which so often attacks 

 bread, preserves, etc., is one of the chief agents in the ripening of 

 Roquefort cheese, in the preparation of which green mould is scraped 

 off bread and added to the curds. In the same way the flavour and 

 colour of G-orgonzola are also largely due to species of Penicillium. 

 whilst other moulds are encouraged to grow upon the surfaces of 

 soft cheeses such as Brie cheese, It is therefore obvious that each kind 

 of cheese will have ripening organisms peculiar to it. In most cheeses 

 the discovery of the ripening organisms is a difficult matter, as can be 

 seen by the fact that one investigator has obtained 80 different species 

 in the samples examined by him. All attempts to ripen cheese by 

 means of any one organism have hitherto been unsuccessful, though 

 good results have lately been obtained by using a combination of 

 organisms. 



Defects of Cheese. As so many bacteria can gain access to the milk, 

 to the curds, and to the crude cheese, it is not surprising that serious 

 defects are by no means uncommon in the ripening of cheese. A 

 common defect is the formation of large holes throughout the cheese, 

 making it porous, shapeless, and worthless. This is due to excessive 

 multiplication of one of the gas-producing bacteria. At least twenty- 

 five species are known that have this power of causing abnormal 

 swelling in cheese. It does not follow, however, that their presence 

 is always harmful — harm arises only where they multiply extensively. 

 The abnormal swelling may be due to the absence of cleanliness in 

 handling the milk, or to the use of milk from diseased udders. The 

 presence of acid and salt appear to inhibit the activity of these bacteria, 

 and of course the employment of a starter still further handicaps 

 them. 



