Effects of drying treatments on the antioxidant properties of leaves and teas of Alpinia species

Fresh leaves of five Alpinia species were screened for antioxidant properties (AOP) with comparison to three commercial ginger species. AOP assessed included total phenolic content (TPC), ascorbic acid equivalent antioxidant capacity (AEAC) and ferric reducing power (FRP). Effects of thermal and non-thermal drying treatments were analysed. The screened leaves can be categorized into high, moderate and weak categories. Thermal drying of leaves resulted in significant loss of TPC and AEAC values. Air-dried leaves of A. zerumbet showed drastic losses in AOP while freeze- dried leaves had significant gains. The freeze-dried tea of A. zerumbet was superior to the commercial tea for all AOP studied.