Effects of radio frequency heating inactivation on foodborne pathogens in model foods varying in structural matrix complexity

Radio Frequency (RF) heating is a promising alternative for conventional heating to inactivate pathogens during food processing, but a knowledge gap exists concerning RF effects on bacteria in relation to different food microstructural aspects. This study focusses on RF inactivation of Listeria monocytogenes and Salmonella Typhimurium in differently-structured food matrices, tackling (i) indirect effects of RF compared to conventional heating in different matrices, and (ii) food matrix rheology influence on inactivation. RF and conventional thermal inactivation experiments were conducted in a low-viscosity and high-viscosity liquid, and an aqueous gel. Indirect RF effects (inactivation rate k higher for RF than for conventional heating) at higher temperatures occurred in the aqueous gel for L. monocytogenes, and in the liquids for S. Typhimurium. The effect of increasing liquid matrix viscosity on RF inactivation was similar to conventional heating for both microorganisms; increasing viscosity resulting in smaller k. The effect of the presence of a gelled matrix on RF inactivation was similar to conventional heating for S. Typhimurium, i.e., k higher for high-viscosity liquid than for aqueous gel. For L.monocytogenes, the decrease in k in the aqueous gel was lower than for conventional heating, indicating possible RF-specific inactivation in gelled systems.