Multiphysics analysis for ultrasound settings that can disinfect food: Inactivation of E. coli in apples

Abstract

Ultrasonic technology has shown great promise in enhancing food safety and quality through disinfection. This study provides a rigorous multiphysics analysis to identify the ultrasonic pressure and frequency for efficient disinfection of apples, with a specific focus on eliminating E. coli. In this study the Finite Element Method (FEM) was used to solve the wave and heat equations describing the spectral and spatio-temporal behavior of the ultrasonic signals in the proposed disinfection setup, as well as a thermoacoustic analysis of the system. The food disinfection system included a chamber of 20 cm $\times$ 9 cm, two piezoelectric transducers, and a whole apple with an average radius of 7 cm. The spectral analysis was performed from 20 kHz to 100 kHz in order to identify the influential frequencies in the disinfection chamber and in the apple. This analysis revealed that there are spatial patterns of ultrasonic signal intensity in the system that depend on the selected operating frequency. This feature makes it possible to distinguish the greatest ultrasonic influence in the disinfection chamber and in the apple. Spatio-temporal analysis was performed to evaluate the thermal effects generated by the ultrasonic signals in the disinfection chamber and in the apple. Then, the ultrasonic irradiation pressure and time for inactivating E. coli in the apple were determined from the thermoacoustic behavior of the system. Finally, microbial analysis and parameter optimization were performed to determine the inactivation rate of E. coli in the disinfection system analyzed in this work.