Impact of microwave pretreatment on drying kinetics, mass transfer and thermodynamic characteristics of Barhi dates during drying process

This study investigated the effects of microwave pretreatment on drying behavior, moisture transport, and thermodynamic properties of untreated Barhi dates (UBD) and microwave-pretreated Barhi dates (MBD) under different drying temperatures and air velocities. In addition, thin-layer drying models were evaluated to identify the most suitable predictive model. The results demonstrated that microwave pretreatment significantly enhanced drying efficiency, reducing drying time by up to 21% and accelerating internal moisture transfer, particularly during the initial drying stage. Among the evaluated models, the Logarithmic model provided the most accurate prediction of moisture ratio. Microwave pretreatment improved parameter consistency and slightly enhanced model accuracy, indicating more uniform moisture redistribution within the fruit. Both effective moisture diffusivity (Deff) and the convective mass transfer coefficient (hm) increased with temperature and air velocity, with MBD exhibiting up to approximately 367% higher Deff and 359% higher hm than UBD. Biot numbers increased with temperature (≈ 20–23% per 10 °C) but decreased with increasing air velocity, whereas Dincer numbers declined sharply (≈ 36–42% per 10 °C). Thermodynamic analysis confirmed that the drying process was endothermic and non-spontaneous. Compared with UBD, MBD exhibited slightly higher activation energy and enthalpy but lower Gibbs free energy, reflecting enhanced moisture mobility and improved energy efficiency. Overall, microwave pretreatment improved drying kinetics, moisture uniformity, and model predictability, providing a robust framework for optimizing thin-layer drying of Barhi dates at the industrial scale.