Optimization of Ohmic Heating Pasteurization for Passion Fruit Juice and Comparison with Conventional Thermal Treatment

Ohmic heating pasteurization (OHP) is a volumetric thermal processing technology that enables rapid and uniform heat generation within liquid foods. This study aimed to optimize the OHP conditions for passion fruit juice processing by maximizing thermal efficiency and preserving quality attributes. A Box–Behnken design combined with response surface methodology was applied to evaluate the effects of pasteurization temperature (75–95 °C), holding time (15–45 s), and voltage gradient (10–30 V/cm) on the system performance coefficient (SPC), total color difference (ΔE), and vitamin C retention. Multi-response optimization was conducted to simultaneously enhance SPC and vitamin C content while minimizing color change. The optimal OHP conditions were identified as a temperature of 82.5 °C, a holding time of 25 s, and a voltage gradient of 18.5 V/cm. Under these conditions, the processed juice exhibited a high SPC value (0.80 ± 0.05), moderate vitamin C retention (20.07 ± 3.18 mg/100 mL), and low total color difference (ΔE = 7.64 ± 1.08). Enzymatic assays further demonstrated substantial inactivation of quality-related enzymes, with residual activities of peroxidase and polyphenol oxidase reduced to 8.07 ± 1.74% and 12.6 ± 2.1%, respectively, compared with untreated juice. These results indicate that optimized ohmic heating pasteurization can achieve efficient thermal processing while maintaining the physicochemical and nutritional quality of high-acid fruit juices.