Thermal Processing Impacts on Drying Kinetics, LC–ESI–MS Based Chemical Profiling, and Antioxidant Capacity of Garlic (Allium sativum L.) Leaves

The leaves of garlic (Allium sativum L.), known for their mild flavor and rich bioactive compounds, were subjected to oven drying within the temperature range of 40–70 °C. This study explored the impact of these drying conditions on the modeling of drying kinetics, the phenolic profile, and radical-scavenging activity. Page’s model provided the most accurate representation of the experimental drying kinetics. Effective moisture diffusivity ranged from 2.11 to 7.18 × 10⁻¹² m²/s, and the activation energy was determined as 34.66 kJ/mol using the modified Arrhenius equation. Utilizing liquid chromatography–electrospray ionization–tandem mass spectrometry, 11 flavonoids and 5 phenolic acids were identified, with flavonoids being the dominant class among them. Quercetin 3-O-rhamnoside was identified as the major compound (9.42 mg/g extract) in dried garlic leaves at 40 °C. Drying at this temperature also significantly increased the phenolic content to ~ 12.5 mg/g extract, compared to ~ 1.28 mg/g extract in the fresh material. However, increasing the drying temperature to 70 °C led to a reduction in phenolic content to 7.33 mg/g extract. Notably, leaves dried at 40 °C showed the highest DPPH⋅ radical-scavenging activity.