176 Dairy Bacteriology. 



of ferments, but yet sufficiently distinct to be separated 

 from trypsin. Jensen 1 has also shown that the addition of 

 pancreatic extracts to cheese accelerated the formation of 

 soluble nitrogenous products. 



The action of galactase in milk and cheese has been con- 

 firmed by Freudenreich 2 and Jensen, 8 as well as by Ameri- 

 can investigators, and this euzym is now quite generally 

 accepted as the cause of the decomposition of the casein. 

 Freudenreich admits that it plays a role in converting the 

 casein into albumose and peptones, but that the lactic-acid 

 bacteria are chiefly responsible for the further decomposi- 

 tion of the nitrogen to amid form. 



Failure before to recognize the presence of galactase in 

 milk is attributable t0 the fact that all attempts to secure 

 sterile milk had been made by heating the same, in which 

 case galactase was necessarily destroyed. A brief exposure 

 at 176 F. is sufficient to destroy its activity, and even an 

 exposure at lower temperatures weakens its action consider- 

 ably, especially if the reaction of the medium is acid. This 

 undoubtedly explains the contradictory results obtained in 

 the ripening of cheese from pasteurized milk, such cheese 

 occasionally breaking down in an abnormal manner. 



The results mentioned on page 172, in which cheese failed 

 to ripen when treated with disinfectants, experiments 

 which were supposed at that time to be the foundation of 

 the bacterial theory of casein digestion are now explica- 

 ble on an entirely different basis. In these cases the casein 

 was not peptonized, because these strong disinfectants de- 

 stroyed the activity of the enzyms as well as the bacteria. 



Jensen, Cent f. Bact. II Abt., 3:752. 



Freudenreich, Cent, f . Bakt., It Abt., 1900, 6:882. 



Jensen, Ibid., 1900, 0:734. 



