Effect of conventional and superheated steam roasting on the total phenolic content, total flavonoid content and DPPH radical scavenging activities of black cumin seeds
2018
Liang, L. C. | Zzaman, W. | Yang, T. A. | Easa, A. M.
The effect of superheated steam heating on the antioxidant properties of black cumin seed (Nigella sativa L.) compared to conventional hot air heating was investigated. A superheated steam oven was used in both methods using superheated steam mode and convection mode (hot air). It was operating at three different durations of 10, 20 and 30 min at 180 °C. The total phenolic content, total flavonoid content and radical scavenging activities were 15.04 mg GAE /g, 0.81 mg QE /g and 81.28% at 180°C for 30 min, respectively during superheated steaming. The total phenolic content (TPC), total flavonoid content (TFC) and DPPH radical-scavenging activities of black cumin seed increased significantly (p<0.05) when the time of heating was increased from 0 to 30 min for both treatments. The raw seed had the lowest antioxidant properties, which were TPC of 5.17 mg (GAE)/g, TFC of 0.29 mg (QE)/g and 61.27% radical scavenging activities. Positive correlations were found between the total phenolic content and DPPH scavenging activities of black cumin seed. The black cumin seed heated under superheated steam had significantly (p<0.05) higher TPC, TFC and DPPH radical scavenging activities compared with conventional hot air heating at almost all the heating times. Based on the results obtained, it can be concluded that superheated steam can be used as an alternative method for roasting black cumin seed that yet maintains higher antioxidant properties.
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