| Effects of commercial scale pulsed electric field (PEF) processing on the qualities of tomato juice and orange juice were studied and compared with those of thermal processing. The inactivation of tomato juice lipoxygenase (LOX) by PEF was studied using kinetic models.;Tomato juice was prepared by hot break at 88°C for 2 min or cold break at 68°C for 2 min and then thermally processed at 92°C for 90 s or PEF processed at 40 kV/cm for 57 μs. Freshly squeezed orange juice was thermally processed at 90°C for 90 s or processed by PEF at 40 kV/cm for 97 μs.;Tomato juice was treated by a laboratory scale PEF system with the combinations of electric field strength (0, 10, 15, 20, 30, 35 kV/cm), PEF treatment time (20, 30, 50, 60, 70 μs), and PEF treatment temperature (10, 20, 30, 40, 50°C) to study inactivation kinetics of tomato juice LOX by PEF.;Both thermally and PEF processed tomato juices maintained microbial shelf life at 4°C for 112 d. PEF processed tomato juice retained more flavor compounds than thermally processed or unprocessed control juice (p < 0.05). The lipoxygenase activities of thermally and PEF processed tomato juices were 0 and 47%, respectively. PEF processed tomato juice retained more ascorbic acid than thermally processed juice at 4°C for 42 d (p < 0.05). PEF processed tomato juice had significantly lower nonenzymatic browning than thermally processed or control juice (p < 0.05). Sensory evaluations indicated that PEF processed tomato juice had more preferred flavor and higher overall acceptability than thermally processed juice (p < 0.01).;Thermally and PEF processed orange juices maintained microbial shelf life at 4°C for 196 d. PEF processed orange juice retained more ascorbic acid, flavor, and color than thermally processed juice (p < 0.05). Sensory evaluation of texture, flavor, and overall acceptability were ranked highest for control orange juice, followed by PEF processed juice and then by thermally processed juice (p < 0.01).;Laboratory scale PEF treatment at 30 kV/cm for 60 μs at 50°C inactivated 88.1% of LOX. The first-order kinetic models, the Hulsheger's model, and the Fermi's model adequately described the LOX inactivation by PEF. Applied electric field strength was the primary variable for the inactivation of LOX by PEF. |
