Purpose: The objective of this study was to investigate the effects RF pasteurization on microbial inactivation of E. coli with selected antimicrobials in beef homogenate.
Methods: Ground beef homogenate was inoculated (cell concentration of 6 log CFU/ml) with five strains of non-pathogenic Escherichia coli (ATCC BAA-1427, BAA-1428, BAA-1429, BAA-1430, and BAA-1431, all cattle isolate). These strains were used as surrogates for the E. coli O157:H7. The inoculated beef homogenate was packaged in a retortable plastic bag and subjected to RF heating (50 and 55°C). The RF heating temperature was monitored and recorded with a fiber optic probe. Microbial assays for coliform, mesophilic aerobic plate count (APC), and E. coli were performed to enumerate total coliform, E. coli. and APC counts were performed on 3M plates. The data was analyzed by two-way ANOVA (treatment × final temperature) using the JMP PRO 10 program.
Results: Results from this study revealed that RF pasteurization at 55°C of inoculated beef homogenates in the presence of 1.5% potassium bicarbonate with 0.5% citric acid resulted in a 6-log CFU/ml reduction of E. coli and mesophilic aerobic bacteria. Similar reduction in microbial population was observed with 2.5% lactic acid with 0.5% potassium bicarbonate combinations at 55°C temperature.
Significance: Decontamination of beef using antimicrobial intervention with RF heating may have potential for preserving the efficacy of applied antimicrobial as well as the quality attributes of beef products.