Effects of seed roasting on the yield, physicochemical properties, and oxidative stabilities of Niger seed oil

Abstract

In this study, the effect of seed roasting using an automated roasting machine at 120, 140, and 160 ℃ for 15 min on the yield, physicochemical properties and oxidative stabilities of Niger seed oil was investigated. The yield increased from 42.13% to a maximum value of 55.11% after roasting. The refractive index ranged between (1.503–1.550) and iodine value (127.25–129.93 g I/100 g oil), saponification value (171.67–194.67 mg KOH/g), and specific gravity (0.93–1.33 g mol-) for oil samples from unroasted and roasted Niger seed, respectively. The oil from the roasted Niger seed was found to be pale brown, while the oil from the unroasted seed was pale yellow with the lowest (8) and highest (43) b* values. The peroxide value, acid value, and free fatty acid value for the oil from unroasted and roasted Niger seed were also found to be between 0.91 and 1.32 mEq oxygen/kg of oil, 2.39–2.43 mg KOH/gm, and 1.20–1.22%, respectively. The induction period increased from 0.17 h (unroasted) to 8.08 h (seed roasted at 160 ℃). This study discovered that automated roasting of Niger seed can be considered as a major unit operation during oil processing to improve the yield, physicochemical properties, and oxidative stabilities of Niger seed oil, and these valuable experimental data can benefit both small and large-scale oil processing firms.