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 m 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 in 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. 
The unsulphured 
hops in cold storage 
ylelded soft resins 
whose acid value 
constantly mcreased 
pote | | throughout the pe- 
7 2 3 é 
YEARS IN STORAGE riod of storage. The 
Fig. 3.—Acid-value curves of the soft resins in sulphured ana unsul- ester valye for these 
phured hops in cold and in open storage. 
ACID VALUE 

soft resins decreased 
during the first year, then gradually increased during 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 
sradually, 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- 
