Design and Validation of a Hybrid Non-Thermal Treatment System for Juice Preservation Combining Pulsed Electric Field and High-Intensity Ultrasound

Non-thermal food processing technologies including pulsed electric field and high-intensity ultrasound individually offer advantages over thermal pasteurisation in preserving the nutritional and sensory quality of juices, but their combined application in a continuous flow system may achieve synergistic effects at lower individual treatment intensities. This study designs, fabricates, and validates a hybrid continuous flow treatment system combining pulsed electric field and high-intensity ultrasound for the preservation of tropical fruit juices, with specific application to hibiscus-zobo juice and pineapple juice from Kano and Oyo States respectively. The theoretical contribution is a coupled electrochemical-acoustic cavitation model that predicts the cell membrane disruption efficiency of combined pulsed electric field and ultrasound treatment as a function of treatment parameters, drawing on electrokinetic theory and acoustic cavitation physics. The system was designed to operate at pulsed electric field intensities of 10 to 30 kV/cm and ultrasound at 20 to 60 kHz frequency, with residence times of 30 to 120 seconds. Treatment efficacy was evaluated by measuring inactivation of Escherichia coli, Salmonella enteritidis, and Aspergillus niger to a minimum of 5-log reduction. Retention of anthocyanins, ascorbic acid, total phenolics, and antioxidant activity was compared against thermal pasteurisation controls. The combined treatment at 20 kV/cm and 40 kHz achieved the target inactivation while retaining 95 percent of anthocyanins and 89 percent of ascorbic acid, compared to 71 percent and 64 percent retention for equivalent microbial inactivation by thermal pasteurisation. The study contributes an original hybrid system design, theoretical model, and validation dataset. Keywords: pulsed electric field, ultrasound, non-thermal processing, juice preservation, hybrid treatment