LAUSR

The aim of this work was to study the effect of power ultrasound (PUS) application on physicochemical, antioxidant, and microbiological properties of a juice blend from oranges and celery stalks. Juice samples were sonicated in an ultrasonic bath (20 kHz, 5.57 ± 0.87 kW/m3, 20 ± 5 °C) at different sonication times (0, 15, 30, 45, 60, 75, and 90 min). Samples were stored in the dark for 24 h at 4 °C and subsequently analyzed. Significant (p < 0.05) positive effects of PUS treatment on bioactive, antioxidant, and microbiological properties of the treated juice blend were observed even after the shortest sonication time (t = 15 min), with best results being obtained for 45 min PUS treatment (13% increase in total phenols to 280.35 ± 4.51 mg GAE/100 mL; twofold increase in total flavonoids to 3.16 ± 0.11 mg EQ/100 mL; 17% increase in antioxidant activity to 24.46 ± 0.02 mg TE/100 mL). Importantly, ascorbic acid content (37.78 ± 7.24 mg AA/100 mL) and some important physicochemical properties of the juice (total soluble solids, pH, titratable acidity) were unaffected by PUS. However, PUS-induced changes in color attributes were strongly correlated (|r| > 0.60; p < 0.001) with an increase in bioactive compound content and antioxidant activity. Also, the 53% increase in cloud value (1.70 ± 0.03) points to an increased stability of the PUS-treated juice blend. Therefore, ultrasonic treatment could represent a viable non-thermal technology for microbial inactivation in fresh orange and celery juice blend while increasing its stability and preserving its bioactive properties and quality attributes.