Understanding the Role of Individual Tocopherol Homologues on the Shelf Life of Refined Soybean Oil

Refined vegetable oils depend on tocopherols as their primary natural antioxidants, yet their behavior differs from that observed in model-stripped systems. This study evaluated how tocopherol homologue degradation relates to the lipid oxidation lag phase in refined soybean oil (RSO) and stripped soybean oil (SSO). Tocopherol depletion, lipid hydroperoxides, and headspace hexanal were monitored during accelerated oxidation at 55 °C. In RSO, α-tocopherol depletion coincided with the end of the hexanal lag phase (12 days), despite 56% and 74% of (γ+β)- and δ-tocopherol remaining, respectively, suggesting limited antioxidant contributions from these homologues. In contrast, in SSO, all tocopherol homologues, whether added individually or in combinations, were depleted by more than 90% by the end of the lag phase, indicating that each homologue actively participated in inhibiting lipid oxidation. These differences are likely related to association colloids in refined oils that restrict homologue activity, highlighting opportunities to improve shelf life by enhancing tocopherol effectiveness.