Improved drying performance and mass transfer in ginger slices using hot air-assisted radio frequency technique

Radio frequency (RF) heating technology has gained extensive attentions in agricultural product dehydration due to its volumetric thermal effect and rapid heating rate. But the drying efficiency and quality retention, especially for shape change, of ginger using RF technique are not clear as compared to conventional methods. This study comparatively evaluated performances (drying characteristics, physical characteristics and phytochemical profiles) between hot air drying (HAD) and hot air-assisted RF drying (HARFD) for processing ginger slice based on three target temperatures. Shrinkage ratio and roundness differences were systematically analyzed. Experimental results demonstrated that the optimal group of HARFD achieved a 19.23 % reduction in processing duration compared to the corresponding HAD, with notable improvements in mitigating structural deformation and volumetric shrinkage. The 60 °C HARFD protocol emerged as optimal, demonstrating significantly enhanced drying efficiency while preserving product quality relative to HAD60 since AA increased by 2.71 %, TPC and TFC differed by 0.22 % and 6.1 %, respectively. However, excessive RF heating at 70 °C caused notable quality degradation and microstructural damage. The findings indicate that combining hot air with RF drying at 60 °C may provide an effective industrial strategy for dehydrating ginger.