Listeria Monocytogenes inactivation kinetics under microwave and conventional thermal processing in a kiwifruit puree

Abstract

The inactivation of Listeria monocytogenes in a kiwifruit puree by conventional and microwave heating was studied. Survival curves at three microwave power levels (600 1000 W) and three temperatures (50 60 °C) were obtained. Data were properly fitted by a first-order kinetic model. Processing times under both technologies were corrected to isothermal treatment for the kinetic study. Microwave heating was shown to effectively inactivate L. monocytogenes. In the range of microwave and conventional processing conditions assayed, the 5-log10 reductions of L. monocytogenes recommended by the FDA for pasteurized products were achieved. The level of microwave power applied had a considerable influence on the Listeria monocytogenes inactivation rate. The higher the power level, the faster the inactivation. The inactivation of Listeria monocytogenes under microwave heating at 900 W (D60°C=17.35 s) and 1000 W (D60°C=17.04 s) happened faster than in a conventional thermal process (D60°C=37.45 s). Consequently, microwave heating showed greater effectiveness for Listeria monocytogenes inactivation than conventional heating.