Effects of storage conditions on the lipid oxidation and tocopherol content of full fat soyflour

초록

Full fat soyflour is a very good material to make tofu and soybean oil due to high content of tocopherols, essential fatty acids, and isoflavonoids. However, it has some problems of off-flavor, mainly from lipid oxidation, to decrease the consumer acceptability of the final products. It is important to evaluate the lipid oxidation in soyflour during storage to obtain good quality soy products. This research was thus performed to study the effects of storage conditions on the lipid oxidation, tocopherol content of full fat soyflour. Lipid oxidation and tocopherol contents in full fat soyflour during storage were evaluated by determining p-anisidine (PAV) and conjugated dienoic acid (CDA) values by AOCS method, and by high performance liquid chromatography, respectively. Full fat soyflour (200g) was put into a serum bottle and bottles were tightly sealed with teflon coated septa and aluminum caps. They were stored at 20℃ under dark, and at 60℃ under dark or light for 24 days. Lipid in samples was extracted by the Folch method with chloroform and methanol (2:1, v/v). PAV and CDA of samples before storage were 1.39 and 0.12%, respectively. Those of samples stored at 60℃ under light and dark increased with storage time. Higher value was observed in soyflour stored at 60℃ under light than in samples stored at 60℃ under dark. On the other hand, samples stored at -20℃ under dark showed little change in PAV and CDA. This clearly indicates that light and heat accelerated the lipid oxidation of full fat soyflour. There was no significant difference in tocopherol contents of samples during storage at -20℃ under dark. However, contents of tocopherol in full fat soyflour decreased with storage time when stored at 60℃, and light did not affect the tocopherol contents in samples during storage at 60℃. Higher oxidative stability of full fat soyflour stored at -20℃ under dark partly resulted from higher residual amount of tocopherol during storage.