CONTINUOUS-FLOW MICROWAVE INACTIVATION KINETICS OF PECTIN METHYL ESTERASE IN ORANGE JUICE

Abstract

The use of microwave energy as an alternative to conventional continuous-flow pasteurization of orange juice was explored. One advantage of microwave heating is obvious: it can prevent surface fouling of heat exchanger, due to prevailing higher surface temperature. Microwave heating may also have the potential for intensified enzyme inactivation which is explored in this study. To elucidate conditions suitable for continuous pasteurization of orange juice, a microwave heating system was designed using a domestic microwave oven (700W) under a full power operation. The residence time of the juice in the heating coil in the microwave oven was dependent on the juice flow rate and dimensions of the heating tube. Based on time-temperature profile and predetermined enzyme inactivation kinetics, the effectiveness of microwave heating (come-up) was evaluated. The PME decimal reduction time for microwave heating were ∼38, 12, 4.0 and 1.3 s at 55, 60, 65 and 70C, respectively, as compared with ∼150 and 37s at 60 and 70C under conventional heating, respectively. Microwave heating is, therefore, substantially more effective in inactivating PME in orange juice than conventional method.