Enhancing infrared drying of red dragon fruit by novel and innovative thermoultrasound and microwave-mediated freeze-thaw pretreatments

This study investigated the effectiveness of novel and innovative pretreatments (NIP) using thermoultrasound and microwave-mediated freeze-thaw (TSFT, MWFT) for improving the mid-infrared drying of dragon fruit, as compared with recent pretreatment methods using cold plasma (CP), ultrasound (US), edible coating (EC), microwave and infrared blanching (MWB, IRB). Except for EC, all selected pretreatment methods induced ultrastructural changes, resulting in accelerated moisture removal and reduced drying time. In addition, all the pretreatments also induced modifications in colour, structure, and texture, with NIP demonstrating superior outcomes for colour, rehydration, shrinkage, and hardness properties. Blanching pretreatments (MWB and IRB) improved phytochemical and antioxidant properties, including total phenolics, betacyanin, betaxanthin, CUPRAC, hydroxyl radical scavenging, and ABTS, except for ascorbic acid, which was better preserved by TSFT. The study underscores the time-saving and quality enhancement advantage of NIP, over other recent methods for improving mid-infrared drying.