Drying of wolfberry fruit juice using low-intensity pulsed ultrasound

Abstract

Abstract In this study, the low-intensity pulsed ultrasound-assisted vacuum drying (LPUVD) was applied to improve the efficiency in drying wolfberry fruit juice with acceptable quality. The low-intensity ultrasound used was 0.7\xa0W/cm2, and the effects of pulsed ultrasound ratio and drying temperature on the drying kinetics and quality parameters (color, total flavonoid, total polyphenol content, DPPH radical scavenging activity and powder properties) were investigated and compared with continuous ultrasound-assisted vacuum drying (CUVD). It was shown that LPUVD offers an advantage over CUVD in quality retention, and LPUVD at 10\xa0s: 10\xa0s pulsed ultrasound ratio took only 30\xa0min more than CUVD. Significant influence of pulsed ultrasound ratio on quality parameters was not observed (p\xa0≥\xa00.05). The minimal quality loss was found in the sample dried at 50\xa0°C whereas the maximum was found in the sample dried at 40\xa0°C. Also, the drying methods and conditions showed no significant effects on the powder properties. Overall, the optimal drying conditions of LPUVD was found to be drying temperature of 50\xa0°C and pulsed ultrasound ratio of 10\xa0s: 10\xa0s. The findings in current work demonstrate that LPUVD is a promising drying technique for wolfberry fruit juice.