Effects of quercetin or rutin on the oxidative stability of stripped or non‐stripped soybean oils containing α‐tocopherol

Abstract

This study investigated the effects of stripping treatment and the presence of α‐tocopherol on oxidative stability of stripped or non‐stripped soybean oils containing quercetin or rutin (0.4 mM) stored at 25°C for 45 days. The degree of oxidation of oils was determined by analyzing headspace oxygen content, conjugated dienoic acid, and p‐anisidine values. The contents of remaining α‐tocopherol and the moisture content in soybean oils were also determined. Added quercetin or rutin acted as an antioxidant in stripped soybean oils and as a prooxidant in non‐stripped soybean oils. The presence of 0.05 and 0.1 mM α‐tocopherol accelerated the rates of lipid oxidation in non‐stripped oils containing quercetin or rutin. Moisture content in non‐stripped oils with rutin was significantly higher than that in other samples, and increased with the concentration of α‐tocopherol (p < 0.05). In addition, quercetin and rutin helped increase the moisture content in stripped oils, but not in non‐stripped oils. Quercetin and rutin accelerated the decomposition of α‐tocopherol in both stripped and non‐stripped oils. The oxidative stability of oils containing tocopherols and phenolic compounds depended on the stripping process.Practical application: Phenolic compounds are natural antioxidants and are frequently found in edible oils. The presence of quercetin and rutin, which are aglycone and its glycoside phenolic compound, respectively, altered the oxidative stability of oils depending on the stripping process. The moisture content in oils could play an important role in the oxidative stability of bulk oils. For industrial applications, phenolic compounds should be added with care because they could lower the oxidative stability of non‐stripped oils.Added quercetin or rutin acted as an antioxidant in stripped soybean oils and as a prooxidant in non‐stripped soybean oils. Quercetin and rutin increased the moisture content in stripped oils, but not in non‐stripped oils. Quercetin and rutin accelerated the decomposition of α‐tocopherol in both stripped and non‐stripped oils. The oxidative stability of oils containing tocopherols and phenolic compounds depended on the stripping process.