Stability of tocopherol homologs in soybean, corn, canola, and olive oils under different moisture contents at 25°C

Abstract

The stability of tocopherol homologs and oxidative stability were determined in edible oils including soybean, corn, canola, and olive oils under different relative humidities (RH), ranging from 0 to 93%, at 25°C for 8 months. The degree of oxidation was determined by conjugated dienoic acid (CDA) and p‐anisidine values (p‐AV), and any remaining tocopherols were also analyzed. The stability of tocopherols was significantly influenced by the presence of both moisture and other tocopherol homologs. Soybean and corn oils under low moisture conditions had significant remaining tocopherol levels, whereas canola and olive oils had different stabilities of tocopherols. The presence of δ‐tocopherol, which is found in soybean and corn oils, seems to play an important role in the stability of α‐ and γ‐tocopherols in vegetable oils stored at 25°C. The moisture content of the tested oils was different even when oils were stored at the same RH.Practical application: Many lipid‐rich foods contain tocopherol homologs to extend the shelf – life of the products. The stability of tocopherol homologs was significantly influenced by the presence of moisture, the types of oils, and the concentration of tocopherol homologs. Using the knowledge obtained in this study, shelf‐life of real foods containing oils can be enhanced by modifying the moisture content and concentration and types of tocol homologs.(i) Soybean and corn oils under low moisture conditions had significant remaining tocopherol levels, whereas canola and olive oils had different stabilities of tocopherols; (ii) the presence of δ‐tocopherol, which is found in soybean and corn oils, played an important role in the stability of α‐ and γ‐tocopherols in vegetable oils stored at 25°C; and (iii) the moisture content of the tested oils was different even when oils were stored at the same RH.