Changes in Quality Attributes of Strawberry Purees Processed by Power Ultrasound or Thermal Treatments

The effect of thermal and ultrasound treatments on the physicochemical properties (pH, total soluble solids, titratable acidity, electrical conductivity, viscosity and color attributes), bioactive compounds (ascorbic acid, total pheolics and total anthocyanins) and antioxidant activity of strawberry puree was investigated. No significant difference in pH, total soluble solids and titratable acidity was observed among the treated and control samples whether thermal or ultrasound treatments were used. Ultrasound treatments significantly increased the electrical conductivity, while significantly reducing the viscosity of strawberry puree samples. Ultrasound treatments were found to better maintain or increase the bioactive compounds and the color attributes compared to the thermally treated samples. Ultrasound treatments significantly increased the radical scavenging activity compared to that of the control sample except when the ultrasound treatment was carried out at 0.42 W/mL for 20 and 30 min. These results indicate that ultrasound treatments can greatly improve the quality of strawberry puree.