isEw York Agricultural ExpMiment Station. 167 



I. INTRODUCTION. 



Fermentation, or the breaking down of complex organic com- 

 pounds into simpler ones, was first looked upon as a purely 

 chemical process. Later it was studied from the standpoint 

 of germ life and now we are coming to see that most of the work 

 of fermentation is accomplished by the action of unorganized 

 ferments commonl\i called enzymes. Enzymes are chemical sub- 

 stances, without life, capable of causing deep-seated changes in 

 certain substances, the enzymes themselyes undergoing little or 

 no change. They are produced by the activity of plant or animal 

 cells. 



As we shall see, Cheddar cheese as ordinarily manufactured, 

 contains enzymes derived from three sources — (1) bacteria, (2) 

 milk glands of cows and (3) rennet. 



During the past three years, in which we have constantly been 

 working upon the problem of cheese ripening, it has been our 

 hope to determine what proportion of the casein decomposition 

 in normal cheese can be justly ascribed to the activity of 

 enzymes. A direct determination under normal conditions is 

 rendered impossible by the continued activity of germ life 

 within the cheese mass. A separation of the activities of the 

 various groups of enzymes is also rendered difficult under 

 ordinary circumstances, owing to the intimate way in which the 

 enzymes are mingled during the process of manufacture. 



Work on these lines is going forward under more satisfactory 

 conditions than before and this report is to be considered only 

 as a record of a portion of the data secured. 



The difficulties attending an investigation of this kind have 

 been reduced to a minimum by the convenient location of all the 

 departments and supplies concerned in the work. Our bac- 

 teriological laboratory, cheese-curing rooms and dairy are in one 

 building, while the chemical laboratory and the cattle barns are 

 only a few rods distant. 



In making the cheese used in our investigation, we have had 

 the valuable assistance of Mr. George A. Smith, Dairy Expert, 



