The stability of toasted and untoasted sesame oil and the feasibility of developing sesame seed-derived antioxidants for applications to other food systems
Previous studies have been performed to quantify and identify sesame lignans, tocopherols, and fatty acids as well as to identify the radical scavenging activity of sesame oil and its stability against oxidation to gain an understanding of the antioxidant activities if sesame oil. Sesame lignans and tocopherols were identified with HPLC-PDA and HPLC-ECD, respectively, and fatty acids as well as aldehyde, ketone, and furan content were identified with GC/MS. These experiments were conducted at Kalsec Inc. located in Kalamazoo, Michigan. Sesaco Corporation provided S-30 lot#028 sesame seeds. The oil from the sesame seeds was extracted either by solvents or by an expeller press. Hexane solvent yielded the most oil out of all the extraction methods. In the present study, major and minor sesame lignans and tocopherols were identified in several laboratory prepared sesame oils. Sesamin and gamma-tocopherol were the most abundant sesame lignan and tocopherol, respectively, in most of the sesame oils. It was confirmed that oleic acid and linoleic acid were the most abundant fatty acids in the sesame oils. The radical scavenging activity of sesame oil had a range of 293.7 ±28.8 ppm - 407.1 ±5.0 ppm in carnosic acid equivalents and was dependent on the extraction method and roasting conditions. The stability of sesame oil was identified by a weight gain experiment that showed a less than 1.7% increase in weight over 66 days. This data was supported by an accelerated oxidative stability index experiment that showed a larger induction time relative to the vegetable oils. Sunflower oil, canola oil, and soybean oil were used as comparison oils. Initially, these oils did not have a radical scavenging activity similar to that of Spectrum Natural toasted sesame oil and were then dosed with Herbalox® type “O” rosemary extract to have similar activity, 310 ppm – 340 ppm. With similar radical scavenging activity, these dosed vegetable oils were compared for weight gain, and aldehyde, ketone, and furan content to sesame oil and all were found to have similar stabilities to sesame oil after 50 days.