Innovative protection system for lipid oxidation using insoluble antioxidant material

Abstract: Omega-3 fatty acids gained attention as a functional ingredient. However, they are very easily oxidized and produce harmful products so that it is difficult to store for long periods. Therefore, it is important to prevent its oxidation, but the addition of lipid-soluble antioxidants such as vitamin E (VEH) is not an effective mean. The reason is that the VEH in oil can convert to radicals during antioxidation and conversely promote the lipid oxidation. On the other hand, in our previously study, polyamines with secondary amine groups were found to act synergistically with VEH to inhibit lipid oxidation without oxidation promoting. In this study, we focused on polyethyleneimine (PEI), a high viscosity polymer with many secondary amine groups that is insoluble in oil and aim to establish new protection system by coating to storage container and investigated the suppression effect by PEI as insoluble antioxidants on lipid oxidation in a model system and a practical system.

The model oil was methyl linoleate, and the practical oil was commercial perilla oil with rich (61%) in omega-3 fatty acids. The oxidation experiments were performed in Rancimat under accelerated conditions at 120˚C. PEI with high viscosity was added by coating to the bottom of the reaction tube with equal area at each experiment.

In the oxidation behavior of model oil, the inhibition period (IP) in case of the only VEH or PEI addition was slightly prolong compared with that without the addition (0.2 h). In contrast, in case of co-addition of VEH (7 mmol) and PEI (3 mg), the IP prolonged until about 5 h, and expanded with the PEI amount increased, indicating that PEI proceed the synergistic suppression reaction with VEH. In practical oil, the IP with co-existence of PEI (10mg) and VEH (naturally contained in the oil; 5mmol) extended significantly to 28 h compared with the existence of VEH alone (0.3 h). Thus, this PEI system is innovative technology that dramatically extends the suppression period by regenerating naturally contained VEH and allowing it to function repeatedly without any additions even in actual omega-3 fatty acid-containing oils.