12 



BULLETIN" 282, U. S. DEPARTMENT OF AGRICULTURE. 



A graphic representation of the acid values is given in figure 3. 

 From this figure it will be seen that after the first year of storage the 

 acid value of the soft resins diminished in the sulphured hops and 

 gradually increased in the unsulphured hops. The rise in acid value 

 of the soft resins of the sulphured hops during the first year in cold 

 storage was probably due to the rearrangement that was taking place 

 in these resins; although esters were formed during this period the 

 esterification did not proceed as rapidly as in the following years, 

 with a consequent rise hi free-acid value. During the first year of 

 open storage the acid value of the soft resins of the sulphured hops 

 remained about the same and then gradually decreased at a rate 

 proportionate to that of the sulphured hops in cold storage. The 

 formation of esters was slow during the first year of storage and rapid 



during the next two 

 years, reaching a 

 slightly higher value 

 at the end of the 

 third year than in the 

 corresponding sam- 

 ple in cold storage. 



T h e unsulphured 

 hops in cold storage 

 yielded soft resins 

 whose acid value 

 constantly increased 

 throughout the pe- 

 riod of storage. The 

 ester value for these 

 soft resins decreased 

 during the first year, then gradually increased dming the second 

 year, and very rapidly during the third year of storage. In open 

 storage the acid value in the unsulphured hops was slightly less at the 

 end of the first year than in the corresponding original sample. The 

 ester value (fig. 4) remained almost constant, indicating that there 

 was little change in these values during the first year of storage. 

 From this point the acid values from the unsulphured hops increased 

 gradually, until at the end of the third year of storage about the 

 same degree of acidity was reached. 



The increase in acidity was, however, most marked in the unsul- 

 phured hops in open storage. The ester values for the soft resins of 

 the unsulphured hops increased after the first year of storage and 

 was most rapid in the cold-storage samples. 



The acid value of the soft resins from sulphured hops in both cold 

 and open storage gradually diminished at approximately the same 

 rate after one year of storage. The corresponding ester values in- 



Fig. 3. 



^£*#S //V STORAGE 



•Acid-value curves of the soft resins in sulphured and unsul- 

 phured hops in cold and in open storage. 



