CAUSES OF RIPENING CHANGES 369 



protein derivatives. The fact, first discovered by 

 Babcock and Russell, that there is such an enzym 

 has been abundantly confirmed by work done at 

 the New York experiment station and elsewhere. 

 The work done by the discoverers in studying the 

 properties of galactase led them to regard as one 

 of the distinguishing characteristics of this enzym 

 its ability to convert casein and paracasein into 

 simpler proteins and protein derivatives, finally 

 forming ammonia. On the basis of this property, 

 the conclusion was reached by them that galactase 

 is the chief agent in the ripening of cheddar cheese. 

 Work done at the New York experiment station 

 failed to confirm the conclusion that galactase 

 could form ammonia in the case of either milk or 

 cheese. In carrying on the work in New York, 

 cheese was made from milk to which chloroform had 

 been added and the cheese was kept in an atmosphere 

 of chloroform, in order to prevent the action of micro- 

 organisms. The only ripening agents present were, 

 therefore, galactase and the enzym or enzyms of 

 rennet. Cheese, thus made and kept, has de- 

 veloped no ammonia, or possibly slight traces only, 

 even after 24 months. The data on the next page 

 illustrate this fact. 



Stated in a general way, these results show that ( I ) 

 in cheese made and ripened in the presence of chloro- 

 form, the amount of caseoses and peptones is largely in 

 excess of the amount of amino acids; (2) the reverse 

 is true in normal cheese; (3) that ammonia appears 

 in normal cheese much earlier and in larger amounts 

 than in chloroformed cheese, appearing in the latter 

 only after 12 months. About as much ammonia ap- 

 peared in the normal cheese in I month as appeared in 



