FISHERY INDUSTRIES OF THE UNITED STATES, 1929 711 



find application in all by-products industries where similar materials 

 are handled and the wet process of reduction is considered most 

 advisable. In addition, the menhaden industry is perhaps in most 

 need of assistance because of the recent decrease in the annual amount 

 of raw material taken. For instance, in 1922 the peak catch amounted 

 to 1,212,450,069 fish while in 1929 the catch barely exceeded 600,000,- 

 000 fish. The factories representiiiii; the industry were designed and 

 first operated during periods of bountiful fishing. With an abundant 

 supply of fish on hand, little attention was given to the efficiency of 

 the process. Now, however, the same factories must operate on 

 smaller quantities of fish and losses fornu^rly unnoticed are becoming 

 of considerable economic importance. If by technical improvements 

 in the process used the losses now encountered could be reduced, the 

 amount of material obtained from the supply of raw material at hand 

 would necessarily be increased and additional income made available. 

 This, then, has been one of the auns of the bureau's investigation. 



Another point receiving consideration has been the quality of the 

 finished product. Recent development in animal-nutrition studies 

 indicate that products of marine origin have very desirable feeding 

 qualities because they contain valuable proteins, minerals, and 

 vitamins. Formerly the dried scrap produced was marketed entirely 

 as a fertilizer material. It is essential that the quality of the product 

 receive attention because a material produced for fertilizer purposes 

 without consideration of preserving the components of nutritional 

 value is very unlikely to possess the full feeding value of which it is 

 capable. 



The studies with respect to the reduction process show at least two 

 important opportunities for improvement. They are (1 ) the handling 

 and separation of press liquors, and (2) the drying of the pressed 

 fish. The data obtained show that the press liquors contain approxi- 

 mately 22 per cent of the total flesh of the original material. Of this, 

 about 17 per cent is dissolved proteins and about 5 per cent is 

 suspended material. At the present time all dissolved material is dis- 

 carded and only about one-third of the suspended material is recov- 

 ered. The data further disclosed that only about 90 per cent of the 

 oil in the press liquors is recovered as first grade oil, about 2 per cent 

 is absolutely lost and the remaining 8 per cent is recovered in such a 

 manner that it has lost approximately half its value. 



Several methods of reducing the above losses were studied. Theo- 

 retically, all solids now lost in the press liquors would be saved by 

 dry rendering. In this process the raw fish are cooked and dried in 

 one operation in a steam-jacketed batch dryer. Tests with such 

 equipment indicate that menhaden do not react satisfactorily to this 

 type of reduction. Even though the process was carried on under 

 considerably reduced pressure, a dark oil of high acid content resulted. 

 For this reason, further test work was confined to recovery methods 

 adaptable to the present wet process. Tests with a simple rotary 

 screen indicated that over 80 per cent of the suspended material could 

 be recovered. This would amount to an increase of approximately 2 

 per cent of the total amount of scrap produced. Data obtained on 

 the amount of liquors and the content of dissolved materials present 

 indicated that this material could be recovered at a profit in suitable 

 evaporating equipment. Tests with mechanical separators also 

 showed that the present oil loss could be reduced and the final quality 



