Effect of Dry Heat Treatment of Six Spices on Antioxidant Activity of their Water Extracts

This study investigated the effect of dry heat on the antioxidant capacity of water extracts of six spices, namely black pepper (Piper nigrum Linn.), cumin (Cuminum cyminum Linn.), clove (Syzygium aromaticum Linn.), cinnamon (Cinnamomum verum, syn. C. zeylanicum Blume), sumac (Rhus coriaria L.) and golpar (H. persicum Desf. Ex.), which were either roasted or heated in a microwave oven, powdered and extracted with water. Untreated spices served as controls. The antioxidant capacities of water extracts of spices were measured by reducing power, DPPH assay and total antioxidant capacity. Varying results were obtained depending upon the assay used and the spice. Clove had the highest radical scavenging activity (85.5% at 0.2 mg level) among all six spices and it was higher than the control in heat-treated samples. Heat-treated samples of cinnamon showed significantly lower activity with reducing power (0.609-1.910) but not with other assays whereas black pepper and cumin exhibited higher activities with reducing power (ranging from 0.276-1.026). Roasted golpar sample also had a higher antioxidant potential in all assays, but sumac was significantly different only in the DPPH assay. Microwave treatment did not affect the antioxidant activity of sumac. Results indicate that heat treatment of spices influenced the antioxidant activity of their water extracts. _____________________________________________________________________________________________________________