Temperature-controlled microwave-assisted and hybrid drying of acerola ( Malpighia emarginata ): Effects on kinetics and bioactive compound retention

Microwave (MW) drying offers rapid processing but poses challenges in controlling thermal exposure, which can degrade heat-sensitive bioactive compounds such as ascorbic acid (AA) and anthocyanins. Although conventional and hybrid MW configurations have been explored, real-time temperature-based power modulation remains underexplored as a strategy to balance drying efficiency and bioactive retention. This study evaluated a temperature-controlled MW drying mode (Tcon), in which magnetron power was dynamically regulated via infrared thermography surface feedback, and compared it against conventional MW, fluidized-bed (FB), and hybrid FB–MW configurations for drying acerola ( Malpighia emarginata ). Drying kinetics, drying rate, and thermal histories were assessed alongside the retention of total polyphenol content (TPC), antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl), anthocyanins, and AA. The Tcon mode achieved the shortest drying time among the treatments evaluated while maintaining moderate surface temperatures, and showed higher retention of TPC, antioxidant capacity, and AA compared to fixed-power MW and hybrid processes. Hybrid configurations accelerated drying relative to FB alone; however, longer residence times led to greater cumulative thermal exposure and reduced bioactive retention. These findings suggest that real-time infrared-based power modulation is a promising strategy for improving bioactive preservation during MW drying of thermally sensitive fruit products.