Enhanced freeze-drying efficiency in restructured peach: Multiscale insights into heat and mass transfer mechanisms from experiments and computational simulations

Abstract

While restructuring agricultural products enhances heat and mass transfer during freeze-drying, the underlying mechanisms remain poorly understood. This study employed a multiscale approach, combining freezing dynamics, sublimation drying kinetics, X-ray tomography, gas permeability assessments, thermodynamic parameters analysis, and mathematical modeling to systematically investigate the differences in transfer properties between natural and restructured peaches across the freezing and sublimation drying processes. Key results demonstrated that restructuring decreased the freezing time by 21.30 min–26.70 min and the sublimation time by 24 h–32 h, achieving an overall time reduction of 25.27 %–33.73 % compared to natural peaches. Microstructural analysis showed that restructuring significantly modified pore architecture, resulting in increased average pore size, overall porosity, open porosity, pore connectivity, specific surface area, and gas permeability, while simultaneously reducing closed porosity and relative apparent density. Thermodynamic characterization further revealed that restructuring not only reduced the heat capacity but also enhanced the thermal conductivity of peaches across the freezing and sublimation drying stages. The developed model successfully predicted experimental parameters and provided visualizations of the temporal evolution of the solidification and sublimation fronts, along with vapor velocity, temperature, and pressure distributions. Particularly noteworthy was the observation that restructured peaches exhibited lower pressure at the interface and accelerated movement of the sublimation front during the sublimation stage. These findings collectively demonstrate that restructuring significantly improved the heat and mass transfer characteristics of peaches during freezing and sublimation, enabling a more energy-efficient and environmentally friendly freeze-drying process with promising industrial applications.