Effects of Seed Roasting Temperature on Sesame Oil Fatty Acid Composition, Lignan, Sterol and Tocopherol Contents, Oxidative Stability and Antioxidant Potential for Food Applications

Abstract

Roasting is a key step for preparing sesame oil that leads to important changes in its organoleptic properties and quality. In this study, white sesame seeds were roasted for 20 min in an electric oven at different temperatures (120, 150, 180, 210, 250 and 300 °C). The oils extracted from unroasted and roasted seeds were compared for their chemical composition: fatty acids (including trans isomers), phytosterols, lignans (sesamin and sesamolin), tocopherols and total phenolic compounds, as well as their oxidative stability and antiradical capacity. There were no obvious differences in the oil densities, refractive indexes or iodine values, but the saponification values were affected by temperature. Relevant primary and secondary lipid oxidation were observed at T > 250 °C, resulting in a higher p-anisidine value and K232 as well as K268 values. Roasting improved oil yield (from 33.5 to 62.6%), increased its induction period (from 5.5 to 10.5 h) and enhanced the total phenolic content (from 152 to 194 mg/100 g) and antiradical activity of the extracted oil. Depending on roasting temperature, a gradual decline was recorded in total amounts of phytosterols (up to 17.4%), γ-tocopherol (up to 10.6%), sesamolin (maximum of 27.5%) and sesamin (maximum of 12.5%). All the investigated oils presented a low quantity in triglyceride polymers, clearly below the maximum tolerated quantity according to the European regulation. The optimal roasting temperature for obtaining high nutritional grade oil within the permissible values was 210 °C. The unsaponifiable components (including lignans and sterols) extracted from roasted seeds have been shown to be natural additives to fresh meatball products to extend shelf life. The results of this study may help to boost the nutritional content of plant-based diets by allowing for the use of roasted sesame seed oil and its components.

Variability of Fatty Acid Composition and Lignan Content in Sesame Germplasm, and Effect of Roasting

“…As a consequence, the nutritional quality of derived sesame oil is affected. The present findings are in accordance with the previous studies conducted by Arab and coauthor . The roasting process has a strong effect on t -oleic acid.…”

A Comprehensive Review on Applicability and Bioactivity of Rogan-I-Kunjad (Sesamum indicum L-Oil): Unani Prospective

“…Utilizing this roasted sesame oil seed in plant-based diets may result in improved nutritional quality due to the great antioxidative efficacy of roasted seed oil. 8,16 Refined sesame seeds have more oxidative stability than unrefined sesame seeds oil due to more saturated fatty acids (SFA) and less Mono Unsaturated Fatty Acid (MUFA) and Polyunsaturate Fatty Acid (PUFA). The TOTOX value of refined sesame oil was significantly lower than unrefined.…”

Comparison of the effects of oven‐ and microwave‐roasting on the physicochemical properties and bioactive compounds of tomato seeds and oils

“…Similar results were reported for sesame seeds previously. [53,54] 3.1.2 Total phenolics, total flavonoids, and total carotenoids contents, and DPPH-radical scavenging activity of tomato seeds…”

“…Similar observations were reported for sesame, pomegranate, peony, and gurum oils extracted from roasted seeds. [11,17,28,53] Roasting as a pretreatment damages the chemical structure of cells and facilitates the release of biochemical substances. Thus, amounts of bioactive components such as phenolics, carotenoids, and tocopherols as well as the antioxidant capacity of the extracted oils, can be increased.…”