108 REPORT OF THE SECRETARY OF COMMERCE 



mercial method of " floating." One difficulty encountered in the 

 storage of frozen mackerel is the tendency of the oil or fat in the 

 fish to become rancid, thereby making the mackerel unfit for use- 

 Obviously, the intensity of rancidity is dependent upon the per- 

 centage of oil in the fish, which percentage is subject to considerable 

 seasonal fluctuation, the maximum percentage occuring in August. 

 Studies are being made to prevent or minimize this difficulty. A 

 process was developed for smoking mackerel which produced a high 

 quality product. This process has promise of commercial applica- 

 tion and should be of aid in expanding the market for mackerel dur- 

 ing periods of unusual abundance. Other studies revealed that losses 

 of food value through leaching would be prevented if fish are cov- 

 ered with waterproof wrappers when packed in ice for shipment. 

 Progress was made in developing a practical method for determining 

 the relative freshness of cod, pollock, and mackerel under commer- 

 cial conditions. A pamphlet was issued containing practical and 

 tested methods for canning some species of fish in the home. 



Bacteriological investigations. — Bacteriology plays a role in nearly 

 all technological investigations of fishery products in that the various 

 experimental products or methods are under bacteriological control. 

 For instance, bacteriological examinations were made of the experi- 

 mental packs of fish canned by the Bureau to determine which 

 processes produced sterility, on the keeping quality of fresh mackerel 

 packed in ice, in determining the preservative value of smoke, and 

 on the tests developed for determining the relative freshness of fish. 

 In addition, special bacteriological investigations were conducted for 

 the development of disinfectants for sponges in household use and for 

 determining the effect of antiseptics in ice on the keeping quality of 

 iresh haddock when packed in such ice for temporary preservation. 



Preservation of fishery hy products. — The value of the Bureau's 

 investigations in the field of fishery waste utilization has been very 

 apparent during the past year. Studies with respect to the utiliza- 

 tion of salmon cannery waste have demonstrated that valuable 

 vitamin-active oils and a high quality edible oil can be recovered 

 from this type of material by proper methods of preparation. The 

 vitamin oils have been proved as desirable sources of fat soluble vita- 

 mins for poultry feeding and also as a new and reasonable source 

 of these vitamins for human nutrition. The edible salmon oil may be 

 added to canned salmon to improve both the nutritive value and 

 appearance of the pack. Definite commercial application has been 

 made of the results of the above study with advantage. 



Studies on the manufacture of fish meal have demonstrated the 

 possibility of producing materials of higher quality, and the funda- 

 mental information ol)tained in the course of these investigations 

 has contributed much to a better understanding of the value of fish 

 meals in animal feeding. 



By investigation of the oil contained in swordfish livers, the Bu- 

 reau discovered the richest known natural source of both vitamins 

 A and D, and as a result of this work the fishing industry is obtain- 

 ing additional revenue from the sale of livers which were formerly 

 discarded. Swordfish-liver oils can be prepared that contain as high 

 as 300,000 U. S. P. vitamin A imits and 9,500 U. S. P. vitamin D 



