Stability of Tocopherol Homologs in Bulk Oils at 60°C Oxidation and Chlorophyll Photosensitization by the Action of Moisture

The effects of deuterium oxide (D₂O) on the stability of tocopherol homologs were evaluated in corn oil stored at 60°C or in the process of chlorophyll photosensitization. The degree of oxidation, changes in moisture, and the levels of tocopherol homologs were analyzed. The moisture content in corn oil incubated with deuterium-free water (H₂O) was significantly (P < 0.05) higher than that in corn oil incubated with D₂O. The presence of D₂O accelerated the rate of lipid oxidation in corn oil, irrespective of whether it has been oxidized at 60°C or has been photosensitized by chlorophyll. After exposure to either of the oxidative stresses, the stability of β + γ-tocopherols present in corn oil was enhanced in the presence of D₂O compared to corn oil incubated in the presence of H₂O, or control corn oil without the addition of moisture. However, the stability of α-tocopherol in corn oil incubated with D₂O was significantly lower after oxidation at 60°C compared to the other conditions (P < 0.05), whereas it was significantly higher than under the other conditions after chlorophyll photosensitization (P < 0.05). The moisture and type of oxidative stress, therefore, play important roles in the stability of tocopherol homologs in bulk oils.