魚油の酸敗に關する研究

Abstract

I. Changes of the Characteristics of Oil during the Process of Drying and Storing Sardine. The fatty oils of the samples obtained in the course of drying and subsequent storing of sardine, were examined by extraction with ether, acetone, ethyl acetate, and acetic acid res-pectively. Thus, the author concluded that the diminution of the quantity of extractablematter should have been caused by an autoxidation followed by polymerisation of oil. More-over, a suggestion was given, that the autoxy-polymerisation product might have different solubilities for above solvents, depending on the grades of oxidation or polymerisation. The ethyl acetate extracted the neutral oil more rapidly than the other solvents did, but the oxi-dation product of oil was hardly extracted, though easily by glacial acetic acid. Analysis of ether-extracted oil showerd with lapse of storing time of sardine, that the acetyl value, refractive index and acid value increase, while the iodine value decreases, and that the colour darkens and also it becomes viscous. The content of free acid quickly increases during drying process, where much moisture still remains in sardine, and it seems that acrolein is produced which is presumably influenced by exposure to light, and that finally, the volatile decomposition gradually takes place with the progress of oxidation. II. Changes of the Components of Oil during the Process of Drying and Storing Sardine. The fatty acids obtained from the ether-extracted oils, which were described in the pre-vious paper, gave considerable amount of brownish substances which were insoluble in ether and petroleum-ether respectively, while extremely pale fatty acid was obtained from each pet-roleum-ether-soluble portion. Therefore, it was suggested that the darkening of the ether-extracted oil was mainly due to these insoluble matters which might be the oxidation product of oil. The petroleum-ether-soluble fatty acids were then separated into solid and liquid acids respectively, and from the latter, the respective bromides insoluble in ether and petroleum-ether were prepared, and they were subsequently analysed. Eventually, the following conclu-sion was given. The oxidation mainly occurs in highly unsaturated fatty acid of the oil, and most of other acids still remain unchanged. The storing experiment during 100 days showed that the free acid of oil amounted to 15%, and that about 20% of the fatty acid were oxidised. Hence the neutral oil which remains unchanged should be only 65% of the original oil.