Effect of Drying Methods on Chemical Composition, Color and Antioxidant Properties of Thai Red Curry Powder
Thai red curry pastes were transformed into powder by two different drying methods: microwave and hot-air drying. The microwave drying was carried out in a microwave oven with output powers of 180, 360 and 540 W and the hot-air drying was carried out at air temperatures of 60, 70 and 80°C. The quality attributes of Thai red curry powder were evaluated for proximate composition, color (Hunter L, a and b) and antioxidant properties (total phenolic content and antioxidant activities). The Folin-Ciocalteu method was used to determine total phenolic content, while 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidative power (FRAP) assays were used to elucidate antioxidant activities. The drying methods showed no significant effects on the chemical compositions of the red curry powder, whereas color and antioxidant properties were all affected by the two methods to different extents. Microwave drying resulted in darker and less yellow color than the hot-air drying. Almost all red curry powder in the microwave-dried samples had a greater phenolic content and antioxidant activity than hot-air dried samples.