Effect of thermal treatments (roasting, microwaving, steaming) on anti-nutritional factors and physical and antioxidant properties of black gram (Vigna cylindrica L. Skeels)

The aim of this research was to investigate the effect of thermal treatments, including roasting, microwaving, and steaming, on anti-nutritional factors and physical and antioxidant properties of black gram (Vigna cylindrica L. Skeels). Regarding its physical properties, thermal treatment increased the water-holding capacity (WHC) and decreased the oil-holding capacity (OHC) of the black gram samples. No significant difference was observed between the roasted sample and the control. Regarding the chemical properties, anthocyanins accounted for the vast majority of total phenolic content (TPC). The steamed sample had the lowest TPC and anthocyanin values, which were 272.46 mg/100 g dry basis and 121.20 mg/100 g dry basis, respectively. Among the three types of thermal treatments, roasting resulted in the highest TPC content, which was 424.35 mg/100 g dry basis. Particularly, the steaming treatment led to the lowest anthocyanin content and antioxidant capacity (AC) in the flour sample; furthermore, there were no significant differences in the TPC and AC values between the microwaved and roasted samples. The phytate content was significantly reduced in all heat-treated samples and there were no significant differences among these cooked samples. The tannin content of the steamed sample was recorded to be the lowest, which was 164.19 mg/100 g dry basis. In summary, roasting, microwaving, and steaming significantly influenced the nutritive values of black gram (Vigna cylindrica L. Skeels).