FISHERY INDUSTRIES OF THE UNITED STATES, 1939 2233 
Bacterial enzymes.—The study of this phase of the problem, dealing 
with the effect of bacterial enzymes on the keeping quality of frozen 
fish, has not reached a point where any conclusions can be stated. 
Autolytie proteolytic enzymes —The information thus far assembled 
on this phase of the study indicates that there may be a direct correla- 
tion between the age of the fish; that is, whether the fish is one, two, 
or three or more years old when caught, and the rate of enzyme 
reaction in the flesh. It appears that the enzymes in the older fish 
react more slowly than those in the younger fish and, therefore, the 
older fish can be held in cold storage over considerably longer periods 
of time without appreciable deterioration from this reaction. The 
study has not progressed far enough to confirm this assumption. 
There does, however, appear to be a strong indication that there is a 
correlation between the age of the fish and the period of time frozen 
fish may be kept in good condition in storage. 
TESTS FOR MEASURING DETERIORATION OF FRESH SALMON 
As has been indicated previously, the quality of fresh or preserved 
fishery products is influenced largely by the conditions of handling 
prior to sale or preservation and the effectiveness of the methods of 
preservation used. In order to controi the changes taking place in 
a product as perishable as fresh salmon, and thus improve handling 
or preservative methods which will lead to preparing products of 
higher quality, knowledge of the nature of its deterioration and means 
of measuring the degree of such deterioration quantitatively are 
helpful. 
While several recent publications have suggested tests for measuring 
deterioration in salmon after canning, very little scientific attention 
has been given to development of tests for measuring deterioration of 
salmon while in the fresh condition prior to canning. Accordingly, 
studies of this nature were inaugurated during the past year. The 
preliminary work which is now in progress pertains to the significance 
of bacterial counts, content of ammonia, trimethylamine, volatile 
acids, volatile alcohols, and hydrogen sulfide; and decrease in the 
buffering action of the flesh as indices of deterioration indicative and 
descriptive of the nature of the changes taking place in salmon during 
storage at high temperature, that is, approximately70° F., and at 
low temperature of about 32° F., in ice. At the time this report was 
prepared this work had not progressed sufficiently to permit reporting 
conclusions. 
IDENTIFICATION OF CANNED SALMON 
In previous reports we have discussed briefly the possible use of the 
refractive index of the free oil in canned salmon as an aid in identifying 
the species in the can. Data obtained from a respresentative sampling 
of the entire Pacific coast and Alaska salmon packs for 1936 and 1938 
are summarized in the following table. While it is evident that the 
overlapping of the values for each species precludes the use of refractive 
index of free oil as a positive method for identification, the mean values 
and the standard deviations suggest the utility of the method for 
supplementing existing criteria. No further sampling is contemplated 
for the near future, but as time permits the data at hand will be sub- 
jected to detailed statistical analysis to determine the extent to which 
the method can be used. 
