ABNORMAL CHEESE RIPENING 205 



injured or destroyed by sterilisation. Secondly, the continual 

 supply of pure culture is by no means always an easy matter. 

 Thirdly, the maintenance of a low temperature cellar to pre- 

 vent the rapid multiplication of extraneous bacteria will in some 

 localities be a serious difficulty. These difficulties have, however, 

 not proved insurmountable, and various workers have produced 

 cheese by artificial culture. Adametz, for example, has used one 

 of the peptonising species in this way with some success. Johan- 

 Olsen has made Gammelost cheese by artificial starting v/ith a 

 mould. Edam cheese has also been made in Holland by using, 

 as artificial starter, whey advanced in slimy fermentation. This 

 last is not a pure culture, but a mixture of organisms of which 

 the chief is a micrococcus possessing the power of setting up 

 slimy fermentation. Cheese made in this way ripens in a uniform 

 manner, and irregular taints are less likely to occur. The whole 

 subject is at present, however, only in the experimental stage. 

 What is required is the ideal combination of pure bacterial culture 

 plus enzymes, and this at present seems difficult to obtain.^ 



Abnormal Cheese Ripening* 



Unfortunately, from one cause or another, faulty fermentations 

 and changes are not infrequently set up in cheese. Reference will 

 now be made to the chief of these. 



{a) Inflated cheese (other terms used to describe this condi- 

 tion are '• swelled " cheese, " puffy," " gassy," " blown," or " spongj- " 

 cheese). In this abnormality the substance of the cheese is split 

 up into innumerable cavities and holes containing various gases. 

 Russell has maintained that the real cause of the difficulty is to 

 be traced to the action of certain bacteria that gain access to the 

 milk. Most of these belong, he thinks, to the lactic acid producing 

 bacteria. The cultures form enough acid to curdle the milk, with 

 an abundant evolution of gas. The gas is formed by the decom- 

 position of the milk sugar, and is in most cases CO., and an 

 inflammable gas which is mainly hydrogen. Most gas-producing 

 micro-organisms give also an unpleasant flavour. They do not 

 ferment the casein to any considerable extent. They are readily 

 susceptible to heat: 140'' F. for fifteen minutes is fatal to most 



* Whilst the above chapter was passing through the press, a most useful 

 summary of this subject for the dairy student appeared in a small book by 

 Professor H. W, Conn, entitled Bacteria in Milk and its Products (1903). See 

 pp. 179-250. 



