ENERGY REQUIREMENT AND QUALITY ASPECTS OF CHINESE JUJUBE (ZIZYPHUS JUJUBA MILLER) IN HOT AIR DRYING FOLLOWED BY MICROWAVE DRYING

摘要

Chinese jujube samples were dried in hot air at 60C, and then switchedninto microwave drying of 45, 65 and 90 W at moisture contents of 50, 40 andn30%, respectively. Results indicated that the energy consumptions of combinedndrying at a transition point of 50% were all lower than that of microwavendrying by itself at three power levels, which might be ascribed to the reductionnof initial heat-up region in microwave drying of combined drying. As com-npared with hot air drying alone, the combined drying can save energy con-nsumption up to about 55%. Combined drying was higher in the rehydrationncapacity of the dried products than microwave drying alone or hot air dryingnalone, and is also beneficial to the preservation of vitamin C and less brown-ning. Hot air drying followed by microwave drying of 45 W at transitionnpoint of 50% was best in terms of higher product quality with less energynconsumption.