Study on the antioxidant activity of β-sitosterol and stigmasterol from Sacha Inchi oil and Prinsepia oil added to walnut oil

Abstract The qualitative and quantitative sterol compositions of Sacha Inchi oil and Prinsepia oil were analysed by high-performance liquid chromatography (HPLC). The sterol compounds were mixed with citric acid, VE and other natural antioxidants and added to walnut oil, oxidation resistence was determined by the peroxide value and acid value. Gas chromatography/mass spectrometry (GC/MS) analysis was used to measure the fatty acids. The results showed that the content of β-sitosterol and stigmasterol in Sacha Inchi oil was 156.46 mg/100 g and 68.74 mg/100 g, Prinsepia oil was 176.26 mg/100 g and 38.29 mg/100 g, respectively. After 12 days of accelerated oxidation, the antioxidant effect was TBHQ > compound antioxidants > BHA > sterols of Sacha Inchi oil > sterols of Prinsepia oil > 30% Prinsepia oil > citric acid > VE. After accelerated oxidation for 48 h, the total unsaturated fatty acids in blank walnut oil showed a decreasing trend, and the antioxidant group inhibited the decrease in total unsaturated fatty acids. In conclusion, the antioxidant treatment groups can delay the oxidative cycle of walnut oil and effectively prolong the shelf life of walnut oil, and the compound groups can significantly enhance the antioxidant effect of walnut oil. This study provides a technical reference for the storage stability of walnut oil.