Radio frequency heating of whole peanuts for microbial safety and quality preservation using interlayer displacement under stationary and moving conditions: Effects of salt coating and natural skin on heating behavior

This study aimed to improve the efficiency of a radio frequency (RF) heating system for pasteurizing whole peanuts while maintaining quality attributes using a stationary position or continuous movement. Heating efficiency was evaluated using commercially available roasted whole peanuts: salt-coated skin-on, unsalted skin-on, and unsalted peeled peanuts. To improve heating uniformity and ensure sufficient microbial inactivation of Salmonella enterica serovar Enteritidis PT30, a single interlayer-displacement strategy was applied in both stationary and continuous modes. Quality attributes including protein structure and fatty-acid profiles were assessed under the selected RF processing conditions. The RF system equipped with a conveyor belt was used to process peeled, unsalted peanuts inoculated with S. Enteritidis PT30 at approximately 7.9–8.5 log CFU/g. The three commercial peanut types exhibited differences in RF temperature distribution and heating uniformity, with salt-coated skin-on peanuts showing higher average temperature than unsalted peeled samples under the evaluated conditions. Continuous movement increased average temperature by approximately 10 °C but resulted in poorer heating uniformity, with a 3 °C higher standard deviation (SD). A single interlayer-displacement (overturning) step improved heating uniformity. This step increased Salmonella reductions from 3.41 to 4.77 log CFU/g under stationary processing and from 2.92 to 4.22 log CFU/g under continuous processing after 60 min of RF heating. The evaluated protein and lipid quality characteristics of unsalted peeled peanuts remained largely unchanged following RF processing. Overall, these findings demonstrated the potential of RF heating combined with interlayer displacement for microbial decontamination of unsalted peeled whole peanuts while maintaining the quality attributes evaluated in this study.