Comparison of the effect of 2450 MHz and 915 MHz microwave heating on the inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium in large-scale peanut butter processing.

Background: This study investigated the effectiveness of 2450 MHz and 915 MHz microwave treatments for inactivating foodborne pathogens during large-scale peanut butter processing (400 g batches). Peanut butter samples inoculated with Escherichia coli O157:H7 and Salmonella Typhimurium were exposed to either 2450 MHz or 915 MHz microwave heating. After treatment, the acid and peroxide values and color changes were assessed to determine the impact of the process.

Results: As treatment time increased, pathogen populations showed a corresponding decrease. The 915 MHz microwave treatment for 90 s achieved a reduction of 3.73 to 4.95 log CFU g^-1. The 2450 MHz treatment for 160 s resulted in a smaller reduction, ranging from 1.59 to 3.24 log CFU g^-1. The 915 MHz microwave treatment did not impact the acid, peroxide, or color values of the peanut butter. In contrast, the 2450 MHz treatment led to higher acid and peroxide values and caused noticeable changes in the color of the peanut butter.

Conclusion: The findings indicate that 915 MHz microwave processing could be an effective method for the food industry to use in peanut butter pasteurization as it achieves pathogen reduction without compromising product quality. © 2025 Society of Chemical Industry.