FISHERY INDUSTRIES OF THE UNITED STATES, 193 7 183 



purpose of obtaining further data on their composition. The studies 

 inchided the estimation of the percentages of saturated and un- 

 saturated fatty acids and their mean molecular weights. These data 

 are being included with the former data in report form. 



In certain localities in Alaska the problem of utilizing salmon 

 cannery trimmings is primarily one of how to overcome the seemingly 

 prohibitive situation of having a season of operation of not more than 

 30 days during the year. One means of accomplishing this would 

 be to broaden the scope of operations to include other types of fish 

 which are available over a longer period of time which would permit a 

 byproducts plant to operate over a longer season. In this connection 

 our technologists began studies on the utility of other fishery materials 

 which might be available for supplementmg the supply of salmon 

 cannery waste. An examination of samples of atkafish, said to be 

 abundant in the Bristol Bay area, indicated these fish would yield at 

 least 30 gallons of oil per ton of raw material and the resultant meal 

 would contain over 70 percent protein. Except for color, the prop- 

 erties of atkafish oil were quite similar to those for red salmon oil. 

 Greater attention might also be given to the utility of these fish as a 

 source of human food. 



Since beginning our investigations on the utilization of salmon 

 cannery waste, definite progress has been made by the salmon-canning 

 industry toward more complete use of the waste. A certain degree of 

 this progress can be attributed to the advisory service being supplied 

 by the Bureau's technologists on the basis of their investigational work. 



FISH-LIVER OIL STUDIES 



Methods of extraction. — Because of the sustained interest in fish 

 livers as sources of highly potent vitamin active oils, the Bureau has 

 continued to give considerable attention to developing methods for 

 the more economical extraction of oil from these livers. 



In last year's report reference was made to the development of a 

 simple method of oil extraction which had been demonstrated to be 

 applicable to halibut and "lingcod" livers. This involved a special 

 mechanical disintegration of the liver, conversion of the liver tissue 

 into a soluble and nonheat coagulable condition, and separation of the 

 oil from the solution by centrifuging. An application for a public 

 service patent on the method is on file at the United States Patent 

 Office. 



During the past year the above method of extraction was found to 

 give satisfactory results with swordfish livers but was not directly 

 applicable with uniform success to domestic tuna livers. This is 

 because the tuna livers are normally of very low oil content and the 

 active lipolytic action in the liver during the period required to bring 

 the catch to port results in there being only a very small quantity 

 of neutral glyceride oil available for recovery. This difficulty, how- 

 ever, can be overcome by mixing a quantity of foreign oil with the 

 livers prior to subjecting them to the extraction process. Experi- 

 ments on salmon livers and salmon waste during 1933 had demon- 

 strated the vitamin solvent action of fish oil and the experiments on 

 tuna livers during the past year demonstrated the increased efficiency 

 when using the foreign oil in connection with the process developed 

 for halibut livers. The method is applicable for producing oils 



