Comparative study of seed roasting effects on Sesamum radiatum Schumach. & Thonn and Sesamum indicum L. oils quality

Abstract

Several species of sesame have been extensively studied but little is known about Sesamum radiatum (SR). In this work, seeds roasting impact on two Sesamum spp, SR and S. indicum (SI) oils quality was studied. Physicochemical parameters (PP), fatty acids profile (FAL) and antioxidant activities were evaluated using spectrophotometry methods and gas chromatography coupled to mass spectrometry (GC-MS). Unroasted seeds (US) of SR oil extraction showed a yield of 40.26 ± 0.86% while roasted seeds (RS) at different temperatures (145-200°C) demonstrated a yield of 40.11 ± 1.36%. Evaluation of PP of oils according to the French Standardization Association (AFNOR) standards showed the following results: refractive index: 1.47435-1.47665 for SR and 1.46660-1.47065 for SI; acid number: 2.01-3.35 for RS against 10.04±0.53 mg KOH/g for US; saponification number: 186.82-191.53 for SR and 189.74-190.42 mg KOH/g for SI. Iodine value: 100.31-127.74 for SR against 117.96-128.04 g I₂/100 g for SI; peroxide value: 1.19-4.00 for SR against 1.66-2.58 meq/Kg active O₂ for SI. FAL was slightly modified during roasting showing that SR oil is an oleic-linoleic oil. More, SR oil demonstrated twice antioxidant activity than SI. These results demonstrated that roasting has positive effects on SR oil nutritional quality. SR oil could be recommended in food after toxicity studies.