Synergistic effect of dual pretreatments and temperature gradients on convective drying and preservation of bioactive compounds in purple sweet potato

Abstract

This study investigated the effects of different pretreatments (ethanol, blanching, and cooking) followed by convective drying (60, 70, and 80 °C) on the drying kinetics, mass transfer parameters, and physical and bioactive properties of dehydrated purple sweet potato. Drying kinetics were significantly influenced by temperature and pretreatments, with the Midilli model providing the best fit for the experimental data (R² > 0.99). Effective diffusivity (Def) values ranged from 2.68 × 10⁻⁷ to 6.40 × 10⁻⁷ m²/min, with higher temperatures and pretreatments enhancing moisture diffusion. The combination of pretreatments and higher drying temperatures reduced the moisture content (2.67–9.88 %) and water activity (aw < 0.5) of the flours while increasing solubility (16.75–52.67 %). The combined cooking and ethanol pretreatment (CEP), and drying at 80 °C, were the most efficient strategies for preserving polyphenol and anthocyanin contents while enhancing their bioavailability. This demonstrates its potential for industrial applications requiring high-quality functional and bioactive products.