Effect of roasting on physicochemistry properties and bioactivity of sesame oil extracted by solvent and cold pressing methods

Abstract

This study aimed to evaluate the effect of roasting on physicochemical properties, fatty acid compositions and bioactivity of Sesame oil. In the present study, Sesame oil was extracted at different conditions by two different methods including solvent and cold-pressing methods. The solvent extraction was done by Soxhlet apparatus for 6 hours, using hexane as solvent. The cold- pressing was conducted at pressure of 24MPa and room temperature, using expeller press device. Sesame seeds were roasted at different conditions at 180 °C, 200 °C and 220 °C for 10, 20 and 30 min to find out the optimum conditions. The two methods were compared by the extraction yield and several indicators such as density, total phenolic content, total flavonoid content, free fatty acid (FFA), peroxide value (PV) and antioxidant capacity. The roasting temperature affected significantly the physico- chemical characteristics. Moreover, according to the results, the roasted oils had better quality than the unroasted oil and the optimum roasting temperature to obtain the best quality oil was at 200 °C or 220 °C. The quality of black Sesame and white Sesame was not significant different (p >0.05). The TPC, TFC, antioxidant capacity and FFAs were significant different between 2 methods but density and PVs were insignificant different. The results showed that the total phenolic content (TPC) in solvent method was 10.63 ± 0.3mg GAE/g and in cold- pressing was 13.9 ± 0.88 mg GAE/g. The free-radical scavenging capacity, determined by the 1, 1-diphenyl-2picrylhydrazyl (DPPH) free-radical scavenging assay, of oil from solvent extraction (8.8 ± 0.88%) were significantly lower than that of cold- pressing (12.4 ± 0.99%). The free fatty acid values (FFA) and peroxide values (PV) of oil from solvent method were higher than cold- pressed oils. Keywords: antioxidant, cold-pressing, flavonoid, Sesame oil, phenolic, solvent extraction.