Impact of radio frequency inactivation on bacterial DNA and membrane integrity in meat-based food model systems with various microstructures

Radio Frequency (RF) bacterial inactivation has been successfully used in several food products. However, RF dielectric heating can be affected by several factors, including food composition. Changes in the food matrix can not only influence microbial inactivation but also potentially alter RF inactivation mechanisms. Despite this, limited studies have been conducted to understand RF heating in different food matrices and its inactivation mechanisms. In the present study, three meat-based model systems were used (Liquid, Emulsion and Aqueous gel) for RF inactivation of Listeria monocytogenes and Salmonella Typhimurium at 27.12 MHz. The presence of fat and gel in the matrix increased L. monocytogenes heat resistance only at mild temperatures (<60 °C) compared to liquid. On the contrary, S. Typhimurium inactivation rate was always slower in the presence of fat and gel in the matrix than in liquid during the whole RF treatment. dsDNA integrity did not show significant differences between treated and untreated samples, while cell membrane was damaged during RF heating for both microorganisms. Thus, RF microbial inactivation can be directly affected depending on the organisms and the medium complexity (e.g. fat, gel). Regarding RF inactivation mechanisms at 27.12 MHz, this study found no evidence of nonthermal effects. However, further research at the microscopic level is needed in order to better understand RF inactivation mechanisms.