Thermal Stability of Rapeseed Oil Fortified with Unsaturated Fatty Acid Sterol Esters

Abstract The thermal stability of rapeseed oil fortified with 3 % sterol linolenate, sterol linoleate, and sterol oleate was investigated using the Rancimat accelerated oxidation method. The results indicated that the sterol ester content in fortified oil displayed positive correlations ( P < 0.05) with total phenols and tocopherols and significant negative correlations ( P < 0.05) with acid value (AV), peroxide value (POV), conjugated diene value, value, viscosity, and polyphenols and γ‐tocopherol levels. The sterol ester content in fortified oil was found to significantly decrease when the oil was heated at 110 °C. The rate of increase of the AV, POV, value, and viscosity, and the rate of decrease of polyunsaturated fatty acid, tocopherol, and polyphenol contents were accelerated with the increase of the degree of unsaturation of fatty acid sterol esters in rapeseed oil during heating. Therefore, the oxidative stability is further reduced by increasing the degree of unsaturation, as the instability of fortified oil is mainly due to the decomposition of unsaturated fatty acid sterol esters. The addition of lipid‐soluble polyphenols is an effective method to improve the stability of rapeseed oil fortified with unsaturated fatty acid sterol esters.