Quality Changes of Red Pitaya ( Hylocereus undatus ) Slices Dried in Hot Air, Microwave-Hot Air and Microwave-Vacuum Dryers

摘要

Quality changes of red pitaya (Hylocereus undatus) slices dried in hot air, microwave-hot air and microwave-vacuum dryers were investigated. The quality parameters were colour, water activity, shrinkage, rehydration ratio, ascorbic acid content and visual market quality. Microwave-vacuum produced pitaya with the best quality compared to hot air and microwave-hot air. Pitaya dried in microwave-vacuum had the highest rehydration ratio while the other methods presented similar rehydration ratios. Ascorbic acid in dried pitaya was also better retained when drying by microwave-vacuum. Apart from that, the drying time of pitaya dried in microwave-vacuum could be reduced by 83% compared to hot air.