Effect of the chemical refining process on composition and oxidative stability of evening primrose oil

The effect of there fining process on the physicochemical properties, fatty acid composition, bioactive components, and antioxidant properties of evening primrose oil (EPO) was investigated. The results showed that the peroxide value, acid value, and p-anisidine value changed significantly throughout the refining process (p < .05). Twelve fatty acids were identified in oil samples, while their percentage contents were not significantly different during the refining process. Contents of tocopherol and total phenols were removed by 23.5% and 79.4%, respectively, after refining. The refining process resulted in losses of campesterol and beta-sitosterol of approximately 16.0% and 13.8%, respectively. Moreover, squalene was detected in evening primrose oil for the first time, and its content decreased by 20.2% during the refining process. Furthermore, during the whole refining process, the DPPH free radical-scavenging ability of EPO decreased by 10.6%, and the FRAP reducing capacity dropped by 56%, meanwhile, its antioxidant stability was affected. Practical applications The purpose of this research was to study the changes in the physicochemical properties, bioactive components, and antioxidant capacity of evening primrose oil at various stages of refining. Exploring the influence of the refining process on the quality of evening primrose oil provides a theoretical basis for improving the quality of evening primrose oil in industrial production.