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 α-, γ-, and δ-tocopherols instead of fatty acid compositions. Binary mixtures consisting of L-AP and α-, γ-, or δ-tocopherols exhibited desirable synergistic antioxidant effects in comparison with individual species. The optimal synergistic effects were found at ratios of L-AP to α-, γ-, δ-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.

Practical applications: Vegetable oils packaged in 4–5 L bottles are one of the most important forms for home cooking. Although deoxygenation techniques are applied to increase their shelf life during storage, they will experience a more violent oxidation reaction after opening. The oils are typically oxidized to rancidity before ending up in consumption. L-AP was therefore involved into the vegetable oils to prevent them from oxidation during uses. The results of study can help companies to select the optimal L-AP addition amount according to different endogenous tocopherol types and contents in the target oil in order to extend the use life of the vegetable oil.