GB633953A - Improvements in or relating to the production of oil from oil-bearing protein material of animal origin - Google Patents

Abstract

Oil from animal materials, particularly fish meat and livers, is preserved during storage of the raw materials prior to its extraction therefrom, by forming an aqueous mixture of the fresh raw material together with an alcohol, the concentration of the alcohol being not more than 12 per cent nor less than 3 per cent by weight of the mixture, storing the mixture until substantial digestion of the material has taken place, and finally recovering the oil from the mixture. The alcohol of the specified concentration permits the protein splitting and the accompanying proteolytic digestion of the tissues by the proteases to proceed unhindered thereby releasing the oil therefrom, but inhibits the fat-splitting action of the lipases which normally hydrolyse the oil to form free fatty acids with resulting dark colour &c. of the products. Any usual alcohol, including butyl and amyl alcohols, may be used, but ethyl and isopropyl alcohols are preferred. Alcohols of 6 to 12 per cent concentration on the above basis also inhibit bacterial decomposition; this is much less with alcohols of 3 to 6 per cent concentration which should therefore preferably include a small proportion of a suitable water-soluble germicide. The germicides specified comprise any free fatty acid up to capric acid, particularly acetic and propionic acids, borax, sodium benzoate, sodium salicylate, bromphenolic acid, chlor-acetic acid and sodium arsenate. The aqueous alcohol-raw material mixtures preferably contain an acid reacting material, which may be the germicide, to shift the pH of the solutions toward the acid side so as to promote the tissue digestion. After digestion is complete, such as by storage on board ship until the oil recovery is conveniently made, the upper oil phase is separated from the lower aqueous phase by decantation, siphoning, centrifuging, &c. The usual refining of the oil with sodium hydroxide, water washing, &c. may follow.