Modelling Mass Transfer and Biophysical Changes in Kale During Cryo-Osmotic Dehydration Enhanced by Dielectric Heating

This study presents a comprehensive modelling framework for analyzing mass transfer and biophysical changes in kale leaves (Brassica oleracea var. acephala) during cryo-osmotic dehydration enhanced by dielectric (radio frequency, RF) heating. A custom-designed system employing precooled sucrose solutions (50–60%, 1–5 °C) enabled controlled dehydration over 3–9 h, while RF heating (27.12 MHz, 1.5 kW) promoted internal moisture migration under low-temperature conditions. Moisture loss, solute uptake, and temperature distribution were simulated using Fick’s second law of diffusion and a semi-empirical RF heating model. The effective moisture diffusivity (Dₑff) ranged from 1.8 × 10⁻⁹ to 3.6 × 10⁻⁹ m²/s, increasing significantly with sucrose concentration and temperature (p < 0.05), indicating adjustable dehydration rates that can be tailored to product sensitivity. The dielectric loss factor and RF penetration depth, modelled as functions of moisture content, identified optimal energy absorption in samples 1.5–2.5 cm thick, informing equipment design for uniform internal heating. Experimental validation showed strong agreement between model predictions and observed values for weight loss, chlorophyll retention, and firmness (R² >0.92), demonstrating the reliability of the models for quality control. By integrating cryo-osmotic dehydration with RF-assisted heating, an underutilized combination in leafy vegetable processing, this study advances mechanistic understanding of coupled heat and mass transfer during non-thermal food preservation. The modelling framework offers a scalable basis for process optimization and supports the development of energy-efficient, nutrient-retentive technologies for minimally processed vegetable products.

Clinical Trial Number Not applicable.