Olive leaves, a by-product of the olive oil industry, are rich in bioactive compounds whose stability strongly depends on drying conditions. This study models drying kinetics and assesses temperature effects on phytochemical stability and antioxidant activity. Olive leaves were dried using hot air at four temperatures (40, 70, 95, and 120°C). Drying progress was monitored through continuous mass-loss measurements, and moisture ratios were calculated to characterize drying behavior. These data were fitted to 23 mathematical models, and moisture diffusivity and energy efficiency were determined. Ultrasound-assisted extraction was then performed to evaluate the effect of drying temperature on total phenolics, flavonoids, and antioxidant activity. The proposed kinetic model showed the best agreement with experimental data (R2= 0.999, χ2 = 1.60 × 10-4), demonstrating strong predictive performance. Effective diffusivity increased with temperature, accompanied by a substantial reduction in drying time. Lower temperatures (40°C) preserved the highest bioactive compound content, while 120 °C markedly accelerated drying (moderate compound loss). Intermediate temperatures (70-95°C) resulted in the lowest retention due to prolonged thermal exposure.

This study optimized the microwave drying of olive leaves by integrating mathematical modeling and proposing a novel drying model, along with a comprehensive analysis of energy efficiency and bioactive compound preservation. Experiments were conducted at microwave power levels ranging from 100 to 1000 W, assessing drying kinetics, energy efficiency, and retention of bioactive compounds. The optimal power of 700 W achieved a drying time of 21 minutes while preserving key bioactive compounds, with TPC, TFC, and antioxidant activity reaching 108.79 mg GAE/g DM, 12.12 mg RE/g DM, and 23.25 mg GAE/g DM, respectively. Several mathematical models from the literature were evaluated, and the Logarithmic, Modified Henderson–Pabis II, and Hii et al. models showed excellent agreement with the experimental data (R² > 0.99). The proposed new model also demonstrated strong predictive accuracy, with high R² values and low root mean square error and reduced chi-square (χ²). The lowest specific energy consumption was 0.236 × 10⁵ MJ/kg H₂O, accompanied by the highest energy efficiency. These results demonstrate that intermediate microwave power provides an optimal balance between energy efficiency, processing time, and bioactive compound preservation, highlighting both practical and economic advantages for olive leaf drying.