Drying Kinetics, Bioactive Compounds, and Physicochemical Properties of Olive Pomace Dried in the Tray Dryer

Olive pomace, an underutilized agro-industrial by-product, has considerable potential as a functional ingredient; therefore, optimizing drying conditions is essential to preserve its quality attributes. In this study, fresh olive pomace was dried at 60°C, 70°C, and 80°C to evaluate moisture removal behavior, bioactive retention, and structural changes. Drying was fastest at 80°C, reaching below 4% moisture within 165 min, with 47.08% of the moisture removed in the first hour. The Page model best described the drying kinetics, and effective moisture diffusion coefficients (D_eff) increased with temperature (1.05-1.81 × 10^- ⁸ m²/s), yielding an activation energy (E_a) of 26.60 kJ/mol. Although higher temperatures caused significant reductions in phenolic content, flavonoids, and antioxidant activity, the dried samples exhibited statistically comparable levels of bioactive compounds. FTIR, microscopy, and color analyses revealed temperature-dependent structural and physicochemical changes. These findings highlight optimized drying as a practical strategy to stabilize olive pomace while preserving its potential as a functional food ingredient.