Drying Performance and Optimization of Ginger Slices Using Microwave Vacuum Drying

Microwave vacuum drying (MVD) is a promising technique for enhancing drying efficiency and product quality in ginger processing. In this study, the effects of microwave power, vacuum degree, and slice thickness on the MVD behavior of ginger slices were systematically investigated. The drying performance of MVD was also compared with hot-air drying (HAD) and microwave drying (MD). The results showed that increasing microwave power and vacuum degree, together with reducing slice thickness, significantly accelerated moisture removal, with microwave power being the dominant factor. Under comparable conditions, MVD required only one-sixth of the drying time of HAD and approximately 25% less time than MD. Multi-objective optimization-identified optimal MVD conditions of 200 W microwave power, 0.08 MPa vacuum degree, and 2 mm slice thickness, resulting in a drying time of about 40 min, which was experimentally validated. The optimized process exhibited improved color retention and favorable rehydration performance compared with extreme drying conditions. Among the evaluated thin-layer drying models, the Page model provided the best description of the MVD drying kinetics. Microstructural observations revealed that drying intensity strongly influenced tissue morphology, with slow drying causing uniform shrinkage and fast drying inducing pore formation and structural rupture, explaining the observed trade-offs between drying rate and product quality. Overall, this study demonstrates that MVD is an efficient and controllable drying method for ginger slices, offering practical guidance for process optimization and industrial application.