Modeling and experimental validation of the time-temperature profile, pectin methylesterase inactivation, and ascorbic acid degradation during the continuous flow microwave-assisted pasteurization of orange juice

This work evaluated the effect of microwave-assisted pasteurization on pectin methylesterase (PME) and ascorbic acid (AA) in orange juice (OJ) and proposed a model to predict the time-temperature profile of the process and consequent effect on inactivation and quality. Fresh OJ was pasteurized in a pilot-scale unit at four processing temperatures (70, 80, 90 and 100) °C, five holding times, using two heating systems (conventional and microwave). The experimental overall heat transfer coefficient was determined from the heat loads and correlated with Reynolds and Prandtl numbers. The best-adjusted correlation was used to predict the time-temperature profile considering a unidimensional mathematical model for flow and heat transfer. Predicted and experimental temperatures showed differences below 0.9 °C for all conditions. The model was able to predict PME inactivation and AA retention, indicating that microwave pasteurization of OJ can be as efficient as conventional heating on PME inactivation with less impact on AA.