Effect of heat treatment on the antioxidant capacity of aqueous and ethanol extracts of aframomum angustifolium seed

Abstract

Spices are rich in phytochemicals which are responsible for their observed antioxidant property. This potential can be affected by heat treatment when spices are used as food additives. This research studied the effect of heat treatment on the antioxidant capacity of aqueous and ethanol extracts of Aframomum angustifolium seeds. The antioxidant capacity was measured in vitro by evaluating the metal chelating activity (MCA), ferric reducing ability (FRA), hydroxyl radical (•OH) scavenging activity, nitric oxide (NO) scavenging activity and total antioxidant capacity (TAC) before and after heat treatment. The percentage metal chelating activity of the extracts before heating were comparable (p > 0.05) to that of ascorbic acid while the percentage metal chelating activity of the ethanol extract decreased significantly (p < 0.05) from 65.99% to 47.62% after heat treatment for 30 min. The percentage hydroxyl radical scavenging activity of the aqueous extract was unaffected (p > 0.05) by heat treatment whereas the activity in ethanol extract decreased. The ferric reducing ability of the extracts decreased significantly after heat treatment while the NO scavenging activity increased with heat treatment. The total antioxidant capacity (TAC) of the extracts measured as ascorbic acid equivalents reduced but were not significantly affected by heat treatment. The results of this study suggest that the antioxidant potential of aqueous and ethanol extracts of A. angustifolium seeds is not totally lost by heat treatment.