Effect of Drying Methods on Drying Efficiency and Quality of Kiwifruit Slices

Kiwifruit is highly valued for its nutritional content and distinctive flavor but is prone to rapid deterioration, necessitating efficient drying techniques that preserve product quality. In this study, Xuxiang kiwifruit slices were subjected to vacuum freeze-drying (FD), microwave vacuum drying (MVD), and multiphase microwave drying (MMD), and their drying behavior, color, shrinkage, texture, microstructure (Micro-CT), volatile compounds, and nutritional attributes (vitamin C, total phenolics, and total sugars) were systematically compared. FD required the longest drying time (2880 min) but effectively preserved porous microstructure and overall flavor, whereas MVD markedly reduced drying time to 39 min but caused localized overheating, resulting in severe color degradation (ΔE=24.96±4.36), structural collapse, and flavor imbalance. In contrast, MMD achieved a comparable drying time (165 min) through staged regulation of microwave power and vacuum conditions, while exhibiting the lowest color difference (ΔE=8.43±0.56), well-maintained texture and microstructure, the highest volatile profile similarity to fresh kiwifruit (0.81), and superior retention of vitamin C, total phenolics, and total sugars. Overall, multiphase microwave drying demonstrated the best comprehensive performance in balancing drying efficiency and quality preservation, highlighting its potential for high-quality kiwifruit processing.