116 U. S. BUREAU OF FISHERIES 



of oily fish. The primary objects of the study were to obtain (1) data 

 concerning the possibihty of reducing pressing losses as a result of 

 cooking methods, (2) data which could be used to guide press opera- 

 tion, and (3) data which could be used as a basis for press design. In 

 order to determine this, tests were made on (a) the efi'ect of the amount 

 of cooking on extraction, (b) the effect of cooking fish by direct and 

 indirect steam heat on oil extraction, solids lost in press liquors, color 

 of oil and acidity of the oil, (c) the effect of the intensity of pressure on 

 extraction and solids loss, (d) the effect of the rate of pressure increase 

 on extraction and solids loss, (e) the effect of time on extraction, (/) 

 the eft'ect of aperture size on extraction and solids loss, (g) the effect 

 of the thickness of press cake on extraction, and {h) the effect of pre- 

 liminary drainage on extraction. Although the experimental work 

 has been concluded the data have not been sufficiently analyzed to 

 permit definite conclusions to be published at the present writing. 



REDUCTION OF NONOILY FISH WASTE 



Knowledge obtained in past researches by the bureau on the effect 

 of methods of manufacture on the nutritive value of fishery by- 

 products has given impetus to the bureau's study of efficient utilization 

 of the waste incident to the North Atlantic ground fishery and the 

 waste accumulated in the preparation of these fish for market as 

 packaged products. During the past year a program has been worked 

 out which will involve an exhaustive and detailed study of this subject. 

 The investigative work outlined has been designed to determine the 

 relation of: (1) Temperature, (2) method of applying heat, (3) kind 

 of heating medium, (4) length of contact with the heating medium, 

 and (5) particle size upon the quality of the products and the efficiency 

 of the process. Both chemical and biochemical studies will be carried 

 on in connection with the engineering studies, and products for both 

 human and animal consumption will be investigated. The investiga- 

 tion will also include a continuation of the bureau's study of the utiliza- 

 tion of trawler waste. 



In past studies on this subject, efforts have been made to adapt 

 equipment designed for other purposes to fit the requirements for fish 

 meal and fish flour manufacture. Although the studies indicated cer- 

 tain improvements the final results were never completely satisfac- 

 tory. It is believed, therefore, that in determining the relation of 

 certain principles of reduction and the chemistry of the material to 

 the quality of the final product manufactured, more intelligent prog- 

 ress will result. This work is contemplated for the Gloucester tech- 

 nological laboratory of the bureau. 



THE IODINE NUMBER OF HADDOCK LIVER OIL 



According to the Pharmacopoeia of the United States, cod-liver oil 

 is specified as being obtained fr»m the fresh livers of the cod, Qadus 

 morrhua Linnasus and of other species of Gadus. The latter state- 

 ment was evidently meant to include fish of species related to the cods, 

 such as haddock, cusk, hake, and pollock. Even though this concep- 

 tion of the definition is generally accepted the specifications on iodine 

 value have raised a question of importance to the ground-fish industry. 

 Some samples of haddock liver oil have shown an iodine value of over 

 180, which is the maximum prescribed by the Pharmacopoeia. 



