High-intensity ultrasound processing of kiwifruit juice: Effects on the ascorbic acid, total phenolics, flavonoids and antioxidant capacity

The objective of the study was to investigate the effect of high-intensity ultrasound processing (0, 4, 8, 12 and 16 min at 400 W, 25 kHz frequency) on the total phenolics, flavonoids, ascorbic acid, and antioxidant capacity of kiwifruit juice. The microstructural characteristics of treated kiwifruit samples were also measured. The results reveal that the total phenolics, flavonoids and antioxidant capacity of treated samples (16 min) significantly increased by 108.65%, 105.56%, and 65.67%, respectively compared to the control group. However, 16-min ultrasound treatment significantly decreased the total protein and ascorbic acid in kiwifruit juice. Microstructure measurement states the formation of microscopic channels or holes, cell walls rupture, torn and tissue distortion after ultrasound processing, which reveals the physical mechanism of ultrasound treatment in improving the extraction of bioactive molecules. These findings indicate that high-intensity ultrasound has an enormous potential to increase these bioactive molecules and antioxidants capacity of kiwifruit samples.