Autoxidation of cod liver oil with tocopherol and ascorbyl palmitate

Summary

Cod liver oil (CLO) with no added antioxidants (REF), 200 mg/kg ascorbyl palmitate (AP), and/or 800 mg/kg tocopherol concentrate (TOH) were stored in sealed bottles with a small headspace of air at 25 degrees C in the dark. A binary mix of TOH + AP affected the sensory perception of CLO by leading to a more grass/cucumber-like and less herring oil-like impression, whereas TOH alone had no effect. This was caused by the different influence of the antioxiclants with regard to formation of volatile oxidation products. TOH + AP promoted formation of, e.g., hexanal, 2-hexenal, and 2,6-nonadienal and inhibited formation of, e.g., 2,4-heptadienal. TOH affected the proportions of trans,cis-and trans, trans-2,4-heptadienal that were formed and inhibited formation of, e.g., 1-penten-3-ol, whereas formation of acetic acid and some other volatiles was inhibited by both antioxiclants. The total amount of volatiles increased during the experiment, and with REF were significantly higher (P < 0.05) than with TOH. The PV increased during the first 2 wk of storage. PV levels were in the order of TOH > REF > TOH + AP. The observed effects could partly be explained by hydrogen donation from TOH to peroxyl radicals, but the mode of action for AP was unclear.