Effect of microwave radiation on the antioxidant activity of black cumin seed.

BACKGROUND: Black cumin seed contains considerable amounts of bioactive phenolics that have physiological activity and antioxidant potency, which may be boosted by microwave radiation. The core objective of the study was to evaluate the influence of microwave radiation on the antioxidant activity of cumin seed as a function of pretreatment time and extract concentration. METHODS: In this study, total flavonoid content (TFC) and antioxidant activity of methanol (CME), 70% methanol in water (CMW), ethanol (CEE) and 70% ethanol in water (CEW) extracts of microwaved radiated cumin seed were measured. The antioxidant activity was determined using a Folin-Ciocalteu assay, phosphomolybdenum assay, DPPH radical scavenging activity, H2O2 scavenging activity, hydroxyl radical scavenging activity and reducing power. To predict antioxidant potency, FTIR spectra of extracts were also recorded. RESULTS: Microwave pretreatment significantly reduced the TFC with the pretreatment time. Antioxidant activity increased with increasing pretreatment time and extract concentration in all extracts. Aqueous methanolic extract from radiated seeds appeared to display the highest effectiveness. The results from FT-IR of ex- tracts indicating the existence of multiple functional groups were comparable to those obtained from multiple antioxidative assays. The antioxidant effectiveness of the samples was ranked: CMW > CEW > CME > CEE. CONCLUSIONS: Both treatment duration and extract concentration were found to be critical factors in determin- ing the overall quality of the product. The present study revealed important information for using black cumin seed in developing food products with high antioxidant potency.

Volatile compounds of black cumin seeds (Nigella sativa L.) from microwave-heating and conventional roasting.

The volatile compounds in raw, conventionally roasted and microwave roasted black cumin (Nigella sativa L.) seeds at 0.45 kW for 2, 4, and 8 min, were analyzed by headspace-SPME gas chromatography-mass spectrometry. Among the 38 volatile compounds identified, the major compounds were thymoquinone and p-cymene in all samples. The levels of these compounds decreased with roasting. However, concentrations of pyrazines and furans increased significantly as a result of roasting and these compounds may affect the flavor of roasted black cumin seeds. Methyl pyrazine and 2,5-dimethylpyrazine were major pyrazines, formed at high concentration in seeds roasted for 8 min and in conventional roasting.