In this study, Cynara scolymus L. leaves aqueous extract powder was produced using a novel spray drying approach by incorporation of ongoing ultrasonic atomization and vacuumed drying chamber. A Response Surface Methodology (RSM)-based central composite face-centered design was employed for optimization of the operating conditions of ultrasonic vacuum spray dryer. The independent variables of the prepared mode include inlet temperature, the vacuum pressure in drying chamber and concentration of extract solution. Drying experiments were carried out with an inlet temperature range of 55–75 °C, a vacuum pressure range of 20–40kPa and extract solution concentration of 2–3%. The responses were Moisture Content (MC), Solubility Index (SI), the bulk density of extract powder, Total Phenolic Content (TPC) and DPPH scavenging capacity. Optimum operating conditions were found to be an inlet temperature of 70.58℃, a vacuum pressure of 20kPa, and an extract solution concentration of 3%. In this optimum condition, Moisture Content (MC), Solubility Index (SI), bulk density of extract powder, Total Phenolic Content (TPC) and DPPH scavenging activity were found to be 6.73%, 58.5%, 0.5838 g/cm3, 13.53 mg of GAE/g of spray dying extract powder and 18.43%, respectively. The morphology of microstructures analyzed with Scanning Electron Microscopy (SEM) also showed spherical and smooth particles in optimum condition.
