脂質酸化指標

The methods most commonly used for determining oxidative deterioration of lipids in fish products are the peroxide value (POV), the carbonyl value, and the 2-thiobarbituric acid value (TBAV). However, these tests are not always effective because they are based on the quantitative analyses of unstable oxidative products, which are also liable to react with components of fish products. In order to elucidate oxidative deterioration of lipids in fish meal and lyophilized fish muscle during storage, the authors advocate that it is more effective to measure the peak area ratio of C_22:6 to C_16:0 acids on gas chromatogram and to calculate decrease rate of C_22:6 acid as follows: Decrease rate of C_22:6 acid (%) = (1 － _tC_22:6/tC_16:0/_oC_22:6/oC_16:0) × 100 Decrease rate of C_22:6 acid, POV and TBAV were measured for extracted lipids, fish meal and lyophilized fish muscle of jack mackerel (Trachurus japanicus) during the progress of oxidative deterioration of lipids. The results obtained are summarized as follows: 1. The changes in decrease rate of C_22:6 acid was more closely related with oxidative deterioration of lipids than those of POV and TBAV, because both POV and TBAV were liable to vary considerably with the composition of the samples and the conditions of oxidation (Figs. 1, 2). 2. In case of samples such as fish meal that lipids hydrolysis could be disregarded due to the inactivation of enzymes by the heating process, the decrease rate of C_22:6 acid of polar lipids was more available as an index for oxidative deterioration of lipids than those of non-polar and whole lipids (Fig. 7). 3. Oxidative products of lipids had no significant influence on GLC while determining the decrease rate of C_22:6 acid (Fig. 6).