BUREAU OF FISHERIES XIX 



and passing the liquors through a pressure filter, the oil and water 

 emulsion is broken and all suspended and about one-third of the 

 dissolved solids may be recovered. Furthermore, such treatment 

 may be expected to give a greater oil recovery. 



It was demonstrated that the type of flame drier used at present 

 in the industry causes a loss of over 10 per cent of the monetary 

 value of the scrap dried, and that the use of steam tube driers will 

 reduce the present loss in monetary value of dried scrap by over 50 

 per cent. In addition to this advantage, preliminary feeding tests 

 indicated that steam-dried menhaden meal has greater nutritional 

 value than the flame-dried product. Another important discovery 

 was the fact that storing of oil in open tanks at the factory causes 

 an increase in the free fatty acid content of the oil. 



Special studies have been made of the effect of different methods 

 of manufacture on the quality and nutritive value of the finished 

 products. It has been shown that the intrinsic value of both fish 

 meal and fish oil can be greatly improved through changes in manu- 

 facturing methods. Heat and oxidation, both in intensity and dur- 

 ation, are the great destroyers of the nutritional value of foods and 

 feedstuffs. Therefore, any food manufacturing process Avhich min- 

 imizes the destructive effect of heat and oxidation contributes 

 greatly to the quality and nutritive value of the manufactured pro- 

 duct in question. 



NET PRESERVATION 



Net preservation studies dealt with trap nets and gill nets. 

 Chemicals of the antioxidant class and bactericides were found to 

 be valuable materials, in general, for treating nets. The proper 

 handling of nets and preservative treatments, including the appli- 

 cation of preservatives to nets, was studied in order to cut down 

 labor cost and to minimize fire risk. 



So many factors enter into the problem of prolonging the life of 

 nets that these investigations have been pursued along four general 

 lines of study as follows: (1) Development of chemical preserva- 

 tives, (2) method of application of chemicals to textiles, (3) differ- 

 ences in deterioration by localities, and (4) yearly variability of 

 deterioration in one locality. 



NUTRITIVE VALUE OF MARINE PRODUCTS 



Marine products represent an important food supply. These 

 products are, generally speaking, rich in vitamins, and minerals in 

 quantity and variety. 



Cooperative research with the Bureau of Chemistry and Soils, 

 U. S. Department of Agriculture, on fish oils, fish meals, fish 

 flour, and oysters has been continued. Chemical and spectro- 

 graphic analyses of the mineral elements in fish and shellfish meals 

 and kelp meals have been conducted at Johns Hopkins University. 

 A plan of cooperative research in the laboratories of the South 

 Carolina Food Research Commission at Charleston, S. C, has been 

 initiated in which a study is being made of the mineral content of 

 oysters with^ relation to the prevention and cure of nutritional 

 anemia. Various other cooperative tests with Federal and State agri- 



