Effects of Screw-Press Temperatures on Oil Yield and Phytoconstituents of Roasted and Unroasted Black and White Sesame Cultivars

In the context of exploring new methods and techniques for the sustainable production of high-quality oil, the present study aimed to evaluate the influence of temperatures during screw-press extraction and roasting (200 °C for 15 min) on the oil yield, phytochemicals, and antioxidant contents of white and black seeds of Sesamum indicum L. In this study, the oil of roasted and unroasted white and black sesame seeds was extracted using the screw-pressing technique at various temperature increments between 40 and 200 °C. The total phenolic contents (TPC), antioxidant capacity (FRAP (Ferric Reducing Antioxidant Capacity) and CUPRAC (Cupric Reducing Antioxidant Capacity)), lignans (sesamin, sesamolin, and sesamol contents), and fatty acids were quantitatively determined by spectrophotometry, high-performance liquid chromatography, and gas chromatography–mass spectrometry. The results revealed that the values of TPC, antioxidant capacity and sesamol in black seeds or its derived oil were significantly greater than those present in equal quantities of white seeds or its derived oil; however, oil yield, sesamin, and sesamolin were higher in white sesame. When temperatures increased up to 150 °C during seed pressing, this resulted in increased oil yields of unroasted seeds; however at 200 °C, the oil yield dropped slightly. The roasted seeds resulted in slightly less oil yield than unroasted seeds, which could be attributed to seed moisture. Moreover, sesamin, sesamolin, sesamol, and fatty acid compositions of unroasted and roasted seeds did not show considerable changes with increased temperatures during seed pressing. In fact, these phytoconstituents were found to possess robust screw-press thermal stability, while TPC and antioxidant capacity showed considerably negative effect with increasing screw-press temperature. The results highlight that moderate pressing temperatures optimize oil yield while maintaining the integrity of key bioactive constituents, emphasizing the potential of sustainable mechanical extraction for high-quality sesame oil production.