Easy Digital Control of Refractance Window and Microwave Heating Drying for Sustainable Valorization of Orange Residuals

This study explores the stabilization of orange pomace with digitally controlled drying system that combines Refractance Window™ (RW) and Microwave (MW) technology, to obtain a sustainable pomace powder, a by-product of orange processing. The setup includes a microwave cavity, a water-filled glass container, Mylar film, and orange pomace spread over the film. Controlling MW-assisted heat transfer is challenging due to high heating rates and limitations in using thermal probes, which may interfere with the electromagnetic field. The dehydration process was optimized by controlling the drying time through a system that followed the time-evaluation of the temperature of the RW water and the orange pomace. Under optimal conditions, the RW-MW system reduced the water activity (Aw) of orange pomace below 0.3 within 40 minutes, ensuring microbial stability and suitability for long-term storage while preserving product quality. Compared to conventional drying methods like freeze-drying or hot-air drying, the RW-MW system offers faster drying with energy consumption (~4.8 kWh/kg). This approach offers a sustainable solution for agro-industrial waste valorization, supporting circular economy principles and reducing environmental impact.