Influence of heating rate during microwave pasteurization of ground beef products: Experimental and numerical study

Abstract

AbstractA finite element model coupling electromagnetism with standing‐wave propagation, heat transfer and microbial inactivation equations has been developed to study microwave food pasteurization with three heating rates (7, 10, and 13°C/min). Inactivation of a target microorganism was studied from a single temperature measurement at a given location. Electric fields, temperature distribution and inactivation kinetics were predicted as a function of time and space coordinates. Good agreement was found between experimental and predicted thermal and inactivation curves. The inactivation kinetics parameters (D and z‐value) identified under water bath heating remained valid during the microwave process. Thus, the E. coli inactivation is mainly due to the thermal effect under lethal conditions. The differences between logarithmic reductions between both heating processes was attributed to the non‐uniform temperature distribution.Practical ApplicationsFrom the industrial point of view, temperature heterogeneity is known to be the main barrier impeding the development of microwave food pasteurization technology. The use of a multiphysics model that takes into account the real geometry of the microwave cavity made it possible to optimize the process and achieve a more uniform temperature distribution within the product. Therefore, the simulation of the electric field distribution can provide relevant information on the amplitude and shape of the electromagnetic field. The degrees of freedom of the model led to the optimization of parameters, such as cavity size, microwave frequency shifting, product mass, the position of the sample in the cavity, and the optimization of the shape of the product containers and supports. The combination of microwaves (with or without modulated power input) with other energy sources (i.e., hot air injection, immersion of the product in water) also seemed promising for pasteurization applications.