Amaranth (Amaranthus lividus L.) Drying Using Combined Microwave-Hot Air Dryer

Abstract

This research aimed to study the drying of Amaranthus by using combined microwave-hot air dryer. The microwave power at 5 levels, was 0 500 1,000 1,500 and 2,000 watts, in combination with hot air at 50 and 60°C, and drying until the water activity content was lower than 0.6. Then, the color values, chlorophyll value, and specific energy consumption were analyzed. The result showed that drying time decreased with increasing microwave power, i.e., at microwave power of 0, 500, 1000, 1,500, and 2,000 watts, drying took 8, 4, 3, 2.5, and 2 hours, respectively. The drying time of hot air at 50 and 60°C was not different. The final moisture content was in the range of 11.03 - 12.62 percent wet basis. The water activity content was in the range of 0.48 - 0.57. The brightness (L*) , greenness (a*) tended to decrease and yellowness (b*) tended to increase with increasing microwave power and temperature. Chlorophyll values of drying at microwave powers of 500 and 1000 watts were higher than drying at microwave power of 1,500 and 2,000 watts. In addition, the chlorophyll values of drying at 50°C were higher than drying at 60°C. In terms of quality and energy, it was found that drying at 1,000 watts of microwave power combined with hot air at 50°C was the suitable condition.