Field-guided dielectric drying of foods: dynamic material properties, heating uniformity and scale-up boundaries

Background Dielectric drying is increasingly investigated as a means of intensifying food dehydration through the in-situ conversion of electromagnetic energy into heat. Microwave (MW), radio-frequency (RF), vacuum microwave drying (VMD), microwave-assisted freeze-drying (MWFD), and hot-air-assisted RF (HARF) systems have been reported to shorten drying time and preserve selected quality attributes under controlled product and process conditions. However, industrial translation remains constrained by non-uniform field distribution, the untracked evolution of dielectric properties during drying, limited spatial validation, and inconsistent energy-accounting boundaries. Scope and approach This critical review reframes dielectric drying as a field-guided dehydration strategy, not merely as a set of rapid-heating applications. Here, 91 representative matrix records selected through a transparent, purposive scoping search are organized into an evidence matrix covering dielectric-property measurement, field uniformity, coupled transport, quality and safety endpoints, modeling, sensing, and energy or carbon reporting. The synthesis indicates that dielectric drying becomes transferable only when material state, field distribution, transport behavior, local outcomes, and scale-up boundaries are reported as part of a continuous evidence chain. Key findings and conclusions This evidence-chain perspective explains why faster drying alone is insufficient for scale-up decisions. The review identifies moisture-, temperature- and frequency-dependent dielectric behavior, MW/RF field non-uniformity, moving-load or spouted/fluidized mitigation, stage-dependent heat and mass transfer, local quality and safety-relevant validation, and whole-system energy boundaries as the main determinants of transferability. Future studies should prioritize standardized uniformity metrics, accepted-product validation, validated model-sensor-actuator links and pilot-scale reporting that separates drying-rate claims from industrial feasibility and carbon-reduction claims.