202 ECONOMIC BACTERIA IN MILK AND MILK PRODUCTS 



common to all members of the group is the production of lactic 

 acid fermentation. At present it is impossible to say that ripening 

 of cheese is solely due to lactic acid species, but there is no doubt 

 that they play an important part in the ripening, and form more than 

 95 per cent, of all organisms present during the ripening process. 

 When the cheese is partially ripened the species begins to decline. 



(2) The casein - digesting bacteria probably assist in the 

 peptonising process of breaking down the curd, but do not take 

 much, if any, part in flavouring. 



(3) The gas-producing bacteria give to cheese its honeycombed 

 appearance. 



(4) A miscellaneous group of organisms occurring in the milk at 

 the outset of cheese-making, or as intruders from air, rennet, or the 

 various utensils employed in cheese-making, also appear in cheese. 

 In this group are included those "disease" organisms which set 

 up abnormal ripening, and which yet cannot be classified under 

 the three previous heads.^ 



In addition to bacteria, moulds, and possibly yeasts, should be 

 added as agents in the ripening process, particularly of soft 

 cheeses. Conn divides the soft cheeses into three classes accord- 

 ing to the relation of bacteria and moulds respectively : {a) soft 

 cheeses in which bacteria alone are concerned in the ripening, the 

 cheeses ripening from the outside (Limburger cheese, Backstein, 

 etc.) ; {b) soft cheeses in which moulds contribute to the ripening, 

 the moulds growing on the surface and extending to the interior 

 (Brie, Camembert, and others) ; {c) soft cheeses in which moulds 

 play an important part in ripening, and grow throughout the 

 entire mass. These latter include the Roquefort, Gorgonzola, and 

 Stilton cheeses. In imitations of these cheeses the curd is inoculated 

 on the outside, and planted on the inside with mould spores, and in 

 some cases the process of ripening is facilitated by piercing the 

 cheese with special appliances in order to admit of the entrance 

 of oxygen into the interior, to enable the moulds to grow. After 

 inoculation the cheese is placed under suitable conditions of 

 temperature and moisture. These moulds grow rapidly, and soon 



' One of the classifications of cheese fermentation bacteria suggested in 

 1896 was as follows : — Sour milk and cheese fermentation bacteria .• (i) Bacillus 

 acidi lactici of Hueppe ; (2) Bacillus acidi lactici of Grotenfeld ; (3) Bacillus 

 lacticus of von Giinther and Thierfelder ; (4) Bacillus acidi lactici of Marp- 

 mann ; (5) Bacillus acidi lactici of Peters ; (6) Bacillus No. 19 of Adametz ; 

 (7) Bacillus pallescens of Henrici ; (8) Bacillus Schafferi of Freudenreich ; 

 (9) Bacilli a, b, and c of Guillebeau. 



