GB507742A - Method of treating fish livers and products obtained thereby - Google Patents

Abstract

507,742. Extracting fish liver oils. BROOKES, N. E. (Gorton-Pew Fisheries Co., Ltd.) Dec. 19, 1938, No. 36916. [Class 91] Oil is extracted from fish livers by treating the preferably comminuted livers with an alkaline buffer solution to give a mixture of pH value of 8À5 to 12À5 whereby the tissue is dissolved, whereupon the liberated oil is separated from the aqueous part. Alkaline buffer substances specified are, tri-sodium or potassium phosphate, borax, sodium tetraborate, or ammonium hydroxide. Dilute alkali metal hydroxide solutions and alkali salts which hydrolyse to form insoluble precipitates, such as sodium silicate, are excluded. Free alkali may be present with the alkali salts. Fish livers, fresh or thawed if received frozen, pass to a cutter 2 and are comminuted. The resulting mass is conveyed to a tank 5 to which ammonia solution of 26 to 28‹ BÚ is admitted. The charge is diluted with water and heated by open steam jets or a coil 7, to about 170‹ C. A small amount of salt may be added. The agitated mixture passes to a centrifuge 14, provided with a byepass pipe and relief valve 24. The aqueous liquid is discharged through a pipe 22, and the separated oil through a pipe 16 into a tank 17, where it is washed with water containing a fruit acid such as citric acid to neutralise traces of ammonia. The mixture is again separated in a centrifuge 18, and the wet oil is discharged into a tank 26 where a desiccant, such as anhydrous sodium sulphate, is added. The oil is again separated in a high speed centrifuge 21. Livers from cod, halibut, sword fish, tuna, shark, or whiting may be treated.