Inactivation kinetics of pectin methyl esterase in the microwave-assisted pasteurization of orange juice

The enzyme pectin methyl esterase (PME) kinetic inactivation study in orange juice was performed by conventional heat treatment (thermal bath) and focused microwave heating (synthesis microwave reactor). Experiments have been performed in batch, with temperatures ranging between 50 °C and 95 °C for time between 0 and 60 s for both processes. Non-isothermal processes were considered and histories of time-temperature have been acquired. The kinetic model adjusted considered two fractions of PME (thermosensitive and thermoresistant), and the kinetic parameters to microwave processes at Tref = 90 °C were z1 = 13.7 °C, z2 = 20.3 °C, D1 = 0.231 s and D2 = 130.8 s with α = 0.95. Comparative analysis of processes was performed graphically by residual enzymatic activity versus lethality. The results demonstrated the microwave-assisted thermal process was more effective than conventional one under the same conditions, indicating the possibility for some additive non-thermal effects. Innovative conditions of inactivation were achieved: i.e. 90% at 60 °C after 10 s and 99% at 80 °C after 20 s.