XV. 



MILK AND MILK PRODUCTS' 



341 



palatable nitrogenous bodies, consisting probably of peptones and 

 albumoses. Exactly how these changes are brought about is still 

 a matter of uncertainty. 



Freudenreich l asserts that the lactic bacteria are able to decom- 

 pose casein and thinks that these organisms play the most important 

 part in the ripening of cheese. This view has been supported by the 

 investigations of Lloyd 2 and Campbell. 3 On the other hand, Babcock 

 and Russell announced, in 1897, the discovery of a proteolytic enzyme 

 or unorganised ferment, to which they have given the name, galactase, 

 and to which they ascribe the chief share in the ripening of cheese. 

 This enzyme is present in the milk of all animals, possesses the power 

 of peptonising casein, and in many respects resembles trypsin, the 

 enzyme of the pancreatic juice. It is more active in alkaline than in 

 acid solutions. By its action on casein, there are formed albumoses, 

 peptones, amides and ammonia. 4 Freudenreich has repeated and 

 confirmed Babcock and Russell's experiments. G He finds that formalin 

 or a temperature of 75 weakens the action of galactase. 



Duclaux, as long ago as 1880, 6 ascribed the ripening of cheese to 

 changes in the casein produced by enzymes, but the latter were thought 

 by him to be produced by the life-processes of micro-organisms. It 

 seems probable that this view is also true so far as some of the changes 

 in cheese are concerned. 



The following are analyses of several varieties of cheese quoted by 

 Wiley ' : 



The above analyses are of the type usually made, but are not 

 satisfactory, inasmuch as they do not differentiate between the various 

 nitrogenous compounds present, some of which are almost valueless as 

 food. Recently, attempts have been made to get more detailed results. 8 

 As an example, Stutzer gives the results of his investigation of the 

 nitrogenous constituents of Camembert and of Swiss cheeses as fol- 

 lows ; the total nitrogen in each was distributed thus : 



1 Landw. Jahr. der Schweiz, 1897 ; also 1898, 279. 



2 Board of Agriculture, Report on Cheddar cheese -making, 1899. 



3 Trans. High, and Agric. Soc. Scotland, 1898. 



4 Jour. Chem. Soc., 1900, Abstracts, ii. 712. "' Ibid. 

 G Ibid., 1882, Abstracts, 436. 



7 Agricultural Analyses, Vol. Ill, 524. 



8 Stutzer, Jour. Chem. Soc., 1896, Abstracts, ii. 683. 



