Convective Drying of Apple Enhanced with Microwaves and Ultrasound—Process Kinetics, Energy Consumption, and Product Quality Approach

Abstract

This research explores the drying kinetics of apples, evaluating the impact of convective drying (CV), ultrasonically assisted convective drying (CVUS), and convective–microwave processes (CVMW1 and CVMW2) on energy consumption, drying time, temperature profiles, and product quality. Ultrasound-assisted convective drying (CVUS) exhibited a 10% reduction in drying time and a distinct “heating effect”. Convective–microwave processes (CVMW1 and CVMW2) significantly reduced drying times (47% and 66%, respectively, compared to CV), raising concerns about potential deteriorative processes due to elevated temperatures. Numerical analysis, using the Midilli–Kucuk model, highlighted its robust fit and emphasized the influence of microwave and ultrasound on the effective diffusion coefficient. Quality assessment indicated enhancements in polyphenolic compounds, particularly in convective–microwave processes. The convective–microwave process at higher power (CVMW2) emerged as a balanced option, displaying improved kinetics, energy efficiency, and product quality. The findings underscore the potential of judiciously applying microwave and ultrasound technologies for significant energy reduction and process enhancement, with a recommendation for further exploration of new parameters. This study emphasizes the importance of considering both drying kinetics and product quality in evaluating drying processes for fruits and vegetables, providing valuable insights for industrial applications.