Quality indexes, mayor and minor constituents and oxidative stability of sesame and soybean virgin oils

The chemical compositions of cold pressed virgin oils from two sources of sesame and soybean seeds were evaluated. Official analytical methods were employed for the determination of two quality indexes: peroxide value (PV) and free acidity. Fatty acid profiles and several minor components were also quantified. The oxidative stabilities were measured by the Rancimat test. Results showed that the P V and acidities were below the maximum allowed levels established by the Codex Alimentarius for good quality edible virgin oils. The fatty acid profiles revealed that the linoleic acids were the most abundant in the oils obtained from the sesame seeds. This oil also showed the highest gamma tocopherol concentrations (6500 mg.kg(-1)), while the soybean contained 625 mg.kg. The beta-sitosterol was the most important phytosterol in both types of virgin oils represent ivy up to the 50%. Volatile compounds belonging to the groups of aldehydes, alcohols, hydrocarbons and terpenes were present in all oils, while the esters of hexanoic and octanoic were only observed in the sesame oils. The concentrations of total phenols ranged between 24.20 and 27.64 mg.kg(-1) for sesame oils and between 325.6 and 393.8 mg.kg for the soybean virgin oils, this last was less stable under the accelerated oxidation compared with the oils obtained from the sesame seeds.