L-ascorbyl palmitate and endogenous micronutrients in vegetable oils provide synergistic antioxidant activities: Micronutrient species and concentration

In the present study, antioxidant impacts of L-ascorbyl palmitate (L-AP) on 14 kinds of typical vegetable oils were studied, whose ratios of C18:1 to C18:2 ranged from 0.15 to 9.57. Regression analyses between vegetable oils and their micronutrient-free counterparts revealed that the antioxidant capacity of L-AP was closely related to concentrations of alpha-, gamma-, and delta-tocopherols instead of fatty acid compositions. Binary mixtures consisting of L-AP and alpha-, gamma-, or delta-tocopherols exhibited desirable synergistic antioxidant effects in comparison with individual species. The optimal synergistic effects were found at ratios of L-AP to alpha-, gamma-, delta-tocopherols, being 1:2-1:4. Further EPR spin trapping test figured out that the combined antioxidants reduced the total amount of spin adducts significantly during lipid oxidation, which were contributed by regenerating tocopherols from L-AP. The results will highlight the application of L-AP in protecting packed cooking oils after opening and during cooking.