RIPEXIXi:! OF CHEESE. 373 



Lactic acid bacteria, whicli rapidly multiply, and produce 

 acid, which inhibits the action of other bacteria. 



A special mould, Penicillium Camemhertii, which secretes an 

 alkaline substance, and a peptonising enzyme ; the latter diffuses 

 into the curd, and produces the texture of the cheese. 



Oidium lactis, which gives the cheese its characteristic flavour. 



For Roquefort cheese the only organisms necessary are lactic 

 acid bacteria and the Penicillium Roquejorti ; the latter reduces 

 the acidity, digests the curd, and produces the characteristic 

 flavour. 



The Roquefort Penicillium is also found on Stilton, Gorgon- 

 zola, and other cheeses. The common green mould, Penicillium 

 glaiwum, does not appear to play any part in cheese ripening. 



Role of Enzymes. — Duclaux has recognised this, and 

 attributes the ripening of cheese to enzymes (called by him 

 " diastases ") secreted by various organisms to which he gives 

 the name lyrothrix ; the enzyme would remain and be active 

 after the organisms had died off. 



Babcock and Russell have shown that milk itself contains a 

 peptonising enzyme. By treating milk with a quantity of an 

 antiseptic, such as chloroform, to check all microbial action, 

 they found that a digestion of the proteins was still going on. 

 They have isolated the enzyme from milk, and, finally, have 

 prepared cheeses, which have been ripened under aseptic con- 

 ditions. Though perfectly sterile, these cheeses show that the 

 proteins are converted into albumoses, peptones, and amino- 

 compounds in the same manner as in normal cheeses. 



Babcock and Russell conclude that the action of the natural 

 enzyme of milk is the chief factor in the manufacture of cheese, 

 and consider that Freudenreich and Lloyd have been misled. 



The true part played by micro-organisms in cheese is probably 

 the production of compounds in small quantities Avhich give the 

 characteristic flavours to the cheese. 



The Analysis of Cheese. 



A complete analysis of cheese includes determinations of the 

 water, fat, ash, salt, proteins, primary products of ripening (as 

 albumoses and peptones), secondary products of ripening (such as 

 amino-compounds, ammonia, and nitrates), and lactic and fatty 

 acids ; also, when present, milk-sugar. Few, however, of these 

 determinations can be made with accuracy, though results which 

 are of great utility can readily be obtained. In addition to the 

 determinations mentioned, the fat may be examined as to its 

 genuineness, and the proteins as to their digestibility. 



