脂質含量の異なる煮干しいわしの脂質酸化の相違について

抄録

Lipid oxidations in niboshi, boiled and dried anchovy Engraulis japonicus, with different lipid contents were studied.
In the case of fatty anchovy, percentage of highly unsaturated fatty acid (HUFA, C20:5 and C22:6) in the triglyceride fraction (TG) decreased rapidly during drying up to 5h at 25°C and then slowly up to 20h. Contrary to this, percentage of HUFA is the polar lipid fraction (PL) decreased slowly during drying up to 5h and then rapidly up to 20h. Thereafter, the per-centages of HUFA in the TG and PL were held at a similar level. A microscopic observation of the lipid distribution in fatty anchovy meat showed that the depot fat migrated to the inner portion of the muscular tissue in an early stage of drying. From these findings, it was suggested that the TG distributed in the surface portion of the fish was oxidized in an early stage of drying and that the oxidized TG penetrated into the inner portion of the muscular tissue to come in contact with the PL and participated in its oxidation.
In the case of lean anchovy, percentage of HUFA in the TG decreased rapidly during drying up to 5h and then slowly. On the other hand, percentage of HUFA in the PL decreas-ed slightly throughout the drying period. Microscopic observation on the lipid distribution in lean anchovy meat showed that the migration of the depot fat to the inner portion of the muscular tissue did not occur during drying. This seems to be one of the reasons that the PL in niboshi produced from lean anchovy is stable for oxidation.