Vacuum-Microwave vs. Hot-Air Drying of Valencia Orange Slices: Evaluation of Process Optimization and Drying Kinetics with Bioactive Bioaccessibility, Intestinal Barrier Function, Advanced Glycation End-Products, and Sustainability

This study comparatively optimized and evaluated the quality, bioaccessibility, intestinal integrity, advanced glycation end-products (AGEs), and sustainability metrics of Valencia orange slices using vacuum-microwave drying (VMD) and hot-air drying (HAD). Response surface methodology based on a Box–Behnken design established optimum conditions for VMD at 4 kW microwave power, 80 °C, and 2.228 mm slice thickness, and for HAD at 80 °C, 1.806 m/s air velocity, and 2.0 mm thickness. VMD demonstrated superior quality preservation, retaining significantly higher levels of bioactive phenolics, organic acids, and individual carotenoids compared to HAD. Following INFOGEST 2.0 in vitro digestion, VMD achieved a higher total phenolic bioaccessibility (~56% vs. 42%) and basolateral transport efficiency (~7.8% vs. 5.2%) while better preserving CaCo-2 intestinal barrier function (higher TEER and lower FITC-dextran permeability). Compared to HAD, VMD significantly reduced thermal degradation, resulting in lower hydroxymethylfurfural (~10 vs. ~41 mg/kg) and fluorescent AGEs (~180 vs. ~340 AU/g) (p < 0.05). Kinetic evaluation revealed a sevenfold higher effective moisture diffusivity for VMD (1.07 × 10−9 m2/s) than HAD (1.49 × 10−10 m2/s). Multivariate analysis highlighted distinct separation between treatments based on drying kinetics, bioactive retention, and thermal markers. Thermodynamic and environmental analyses revealed an operational trade-off between the systems: while HAD exhibited a lower specific energy consumption (2.32 ± 0.08 kWh/kg H2O) and operational carbon emissions (1.01 kg CO2−eq/kg H2O), VMD achieved a ~78% reduction in drying duration and superior preservation of bioactive compounds, despite its higher specific energy consumption (4.12 ± 0.18 kWh/kg H2O) and carbon emissions (1.80 kg CO2−eq/kg H2O).