A new strategy to improve heating uniformity of low moisture foods in radio frequency treatment for pathogen control

Multistate Salmonella outbreaks in low moisture foods have created food safety concerns in recent years. Radio frequency (RF) heating could be applied to eliminate pathogens and reduce the damage to food quality. However, non-uniform heating in RF treatment is still a major problem for developing a food pasteurization process. In this study, commercial peanut butter in a cylindrical jar was used as a model of low moisture food for studying the RF heating uniformity. Polyetherimide (PEI) was placed around peanut butter samples to provide better heating uniformity. A computer simulation model was established with COMSOL Multiphysics®, and experiments with a RF machine (27.12 MHz, 6 kW) were performed to validate the effectiveness of the PEI assisting method. Top surface and vertical cross-sectional temperature distributions of peanut butter in a cylindrical container were obtained with an infrared camera, and temperatures at 18 locations inside the container were measured with T type thermocouples. The results showed that PEI assistance reduced the difference between maximum and minimum temperature of top surface from 13 to 7 °C and cross-sectional surface temperatures from 28 to 18 °C. The same strategy was used on wheat flour and heating uniformity was also improved. The computer model was then used with a group of 9 jars of peanut butter to RF processing, and PEI assistance was also found to be effective in improving heating uniformity. Thus, PEI assisted RF heating has potential as a pasteurization intervention for low moisture foods after optimization of this process by the food industry.