Evaluation of the Composition and Oxidative Stability of Cold-pressed Sesame Oils in the Market of Zanjan Province, Iran (2019)

Supply centers of cold-pressed sesame oil have recently appeared in the market, while no data are available on the composition and oxidative stability of these oils. The present study aimed to investigate the properties of cold-pressed and refined sesame oil samples in the market of Zanjan province, Iran in 2019.

In total, 10 sesame oil samples were collected, including eight cold-pressed and two refined samples. Fatty acid and sterol compositions were determined by gas chromatography, and tocopherols were measured by high-performance liquid chromatography. In addition, oxidative stability, iodine, and peroxide values were determined.

Sesame oil was composed of 82-85% unsaturated fatty acids, with linoleic and oleic acids as the major fatty acids and β-sitosterol as the main sterol. Moreover, γ-tocopherol was the predominant tocopherol. Fatty acid composition significantly differed in various samples (P ˂ 0.05), and the total sterol and iodine values were within the standard ranges. Significant differences were observed between the cold-pressed and refined samples in terms of β- sitosterol, campesterol, ∆7-stigmastenol, γ-tocopherol, and oxidative stability (P ˂ 0.05). The mean oxidative stability of the pressed samples (8.61 hours) did not meet the standards of edible oils.

Due to low oxidative stability, the long-term preservation and use of the cold-pressed sesame oils extracted in shops are not recommended.