Effects of Supplemental Antioxidative Substances on Micronutrient Retention and Antioxidative Capacity in Rapeseed Oil During Low-Temperature Ethanol Steam Deodorization

This study investigated the effects of four antioxidative substances, α-tocopherol (α-TP), phytosterols (PS), squalene (SQ), and propyl gallate (PG), on micronutrient retention and antioxidative capacity of rapeseed oil during ethanol steam deodorization (ESD, 140-220 °C). Results demonstrated that supplementation with these antioxidants increased the retention rates (percentage relative to initial content) of tocopherols, phenols, carotenoids, phytosterols, and squalene by up to 2.92%, 46.25%, 25.82%, 1.03%, and 60.15%, respectively. These improvements are attributed to the protective effects of the supplemental antioxidative substances against thermal and oxidative degradation. Moreover, α-TP and PG increased the antioxidative capacity of the oil after ESD at 180 °C for 60 min by 10.37% and 5.35%, respectively, which can be attributed to their increased concentrations and synergistic interactions with endogenous antioxidants. A model oil system of caprylic triglyceride supplemented with binary mixtures of antioxidative substances revealed synergistic behavior in blends of α-TP with PG or CE (β-carotene), and of CE with PG or PS, through complementary interactions, whereas antagonism occurred in blends of PS with PG, and of SQ at a high concentration (40.10 mg/100 g) with α-TP, PG or CE, due to unfavorable molecular interactions.