Studies on the Variation of Lipid in Discoloration of Salted and Drid Fish

Two fillets which had similar properties to each other as shown in Table 1 were prepared from several samples of Mackerel for the present study. One fillet of the sample was protected from rusting by treating with Butyl-hydroxyanisol (B. H. A.) as antioxidant and with NaCl before drying and the other, control, salted without antioxydant, then dried. When standing for 6-23 days after drying, each fillet was separated to three layers: inner surface, skin layer and interior layer between them, of which to examine lipids. From the results represented in Tables 3-8, the following facts have been revealed. 1) When salted dried fish is disolored, the lipids transfer from the skin layer to the inner surface (Fig. 1, Tables 7, 8). 2) Lipids of the inner surface of dried fish which has been discolored is remarkably deteriorated, whereas lipids of the interior layer or the skin layer do not suffer so much variation (Tables 3-6). 3) It seems that during the discoloration of dried fish various conjugated double bonds are formed in fatty acids of the surface lipids due to the transition of their proper double bonds (Figs. 2, 3).