In order to elucidate oxidative deterioration of lipids in fish muscle during storage, the authors prepared homogenates of ordinary muscle of jack mackerel,
Trachurus japonicus, stored them at 5°C, extracted lipids by the method of Folch
et al., fractionated the whole lipids into non-polar and polar lipids, and determined their changes in fatty acid contents by GLC using
n-octadecane as an internal standard. As a result, polyunsaturated fatty acids constituting the whole lipids decreased with oxidation, C
22:6 acid decrease being most predominant; while saturated and monoenoic fatty acids showed comparatively little decrease, C
16:0 acid decrease being almost negligible. Changes in fatty acids constituting non-polar and polar lipids should be attributed not only to oxidative deterioration but also to enzymatic hydrolysis. Consequently the decrease rate of C
22:6 acid of the whole lipids may be used as a criterion for the oxidative deterioration of lipids in the muscle during storage. Furthermore, the authors propose that it is more convenient to measure the peak area ratio of C
22:6 to C
16:0 acids and to calculate the decrease rate of C
22:6 acid by using the following formula.
Decrease rate of C
22:6 acid (%)=(1-
tC
22:6/
tC
16:0/
0C
22:6/
0C
16:0)×100
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