Effect of Ultrasound Pretreatment on the Quality of Lotus Root Juice

To investigate the effects of ultrasonic treatment on lotus root juice quality, ultrasonic pretreatment was applied under varying conditions: frequencies (25, 33, 40, 59 kHz), power levels (40%, 60%, 80%, 100%), and treatment durations (0, 15, 30, 45, 60 min). Based on six nutritional quality indicators: soluble quinones, protein, vitamin C, color, soluble solids, and pH, along with four browning-related quality parameters: total phenolic content, browning degree, polyphenol oxidase (PPO) activity, and peroxidase (POD) activity, combined with principal component analysis and correlation analysis, to identify ultrasonic processing parameters that effectively enhance the comprehensive quality and sensory characteristics of lotus root juice. Finally, an electronic tongue analysis was conducted to evaluate the degree of flavor change in lotus root juice before and after ultrasonic treatment. Results indicated that moderate ultrasonic treatment improved lotus root juice quality. The optimal ultrasonic processing parameters identified were 30 min duration, 60% power, and 40 kHz frequency. Under these conditions, lotus root juice browning decreased by 28.13%, PPO and POD activities decreased by 66.67% and 62.07% respectively, while polyphenol and protein contents increased. Simultaneously, ultrasonic treatment reduced bitterness and enhanced acidity in the juice. These findings provide a foundation and theoretical basis for the development of lotus root products.