FISHERY IXDUSTRIES OF THE UNITED STATES. 193 7 179 



Park where they were stored in a low temperature refrigerator and 

 analyzed for lactic acid content at regular intervals during the entire 

 period of storage. 



Since this work was not l)egun until late in 1937, w^e are not in a 

 position to report anj^ definite conclusions at this time. However, it 

 was found that fish which were frozen alive, and others which were 

 frozen in rigor, had a lower lactic acid content after storage of 4 

 months than fish packed fresh in ice for 3 days, but still in rigor and 

 then frozen and held in storage for 4 months. Still higher percentages 

 of lactic acid were shown in fish, not kept in ice, but frozen 3 days 

 after death and on which determinations were made after 4 months 

 of storage. It is possible that this study may not only yield another 

 reliable index of decomposition but it may also reveal data which 

 might enable our technologists to develop means of preventing or 

 arresting enzymatic decomposition in fish. 



IDENTIFICATION OF CANNED SALMON 



The utility of a test for identifying canned salmon according to 

 species was discussed in last year's report, and certain data were given 

 which suggested the possibility of identification on the basis of the 

 refractive index and color of the free oil in the can. During the past 

 3'ear our technologists examined oil samples from approximately 

 1,000 cans of salmon which were selected as representative of the 1936 

 season's pack, and found that there was considerable overlapping of 

 the refractive index and color of the oil between the species. This, 

 therefore, precludes the use of this test as an infallible means of iden- 

 tifying canned salmon. 



CHANGES IN THE COMPOSITION OF PINK SALMON {OtlCOrhynchus 



gorbuscha) 



In 1936 the Bureau published Investigational Report No. 33 

 entitled, "Physical and Chemical Changes in the Pink Salmon During 

 the Spawning Migration," by Frederick A. Davidson, Division of 

 Scientific Inquiry of the Bureau, and O. Eugene Shostrom, National 

 Canners Association, Seattle, Wash. Since the pink salmon is one 

 of our most important species of food fish, used almost entirely for 

 canning, our Seattle technological laboratory at the beginning of the 

 salmon season in 1937, and with the assistance of chemically trained 

 personnel supplied bj^ the Works Progress Administration, undertook 

 a further study of individual fish of each sex as to gross t;omposition, 

 such as percentage of fat, ash, protein, moisture, water soluble nitrogen 

 compounds, heat coagulable nitrogen compounds, free amino nitrogen, 

 copper precipitable nitrogen, and phosphotungstic acid prccipitable 

 nitrogen. These analyses for gross composition indicate that while 

 the fat content decreases and moisture content increases, during the 

 course of the spawning season, there is very little if any apparent 

 change in the composition or nature of the protein until the fish 

 reach fresh water. In addition, purified protein material was pre- 

 pared from the samples and reserved for subsequent quantitative 

 measurement of certain essential amino acids. 



