Comparison of ready-to-eat “organic” antimicrobials, sodium bisulfate, and sodium lactate, on Listeria monocytogenes and the indigenous microbiome of organic uncured beef frankfurters stored under refrigeration for three weeks

Abstract

Listeria monocytogenes has been implicated in several ready-to-eat (RTE) foodborne outbreaks, due in part to its ability to survive under refrigerated conditions. Thus, the objective of this study was to evaluate the effects of sodium bisulfate (SBS), sodium lactate (SL), and their combination as short-duration antimicrobial dips (10-s) on L. monocytogenes and the microbiome of inoculated organic frankfurters (8 Log10 CFU/g). Frankfurters were treated with tap water (TW), SBS0.39%, SBS0.78%, SL0.78%, SL1.56%, SBS+SL0.39%, SBS+SL0.78%. In addition, frankfurters were treated with frankfurter solution water (HDW)+SBS0.78%, HDW+SL1.56%, and HDW+SBS+SL0.78%. After treatment, frankfurters were vacuum packaged and stored at 4°C. Bacterial enumeration and 16S rDNA sequencing occurred on d 0, 7, 14, 21. Counts were Log10 transformed and calculated as growth potential from d 0 to d 7, 14, and 21. Data were analyzed in R using mixed-effects model and One-Way ANOVA (by day) with differences separated using Tukey’s HSD at P ≤ 0.05. The 16S rDNA was sequenced on an Illumina MiSeq and analyzed in Qiime2-2018.8 with significance at P ≤ 0.05 and Q ≤ 0.05 for main and pairwise effects. An interaction of treatment and time was observed among the microbiological plate data with all experimental treatments reducing the growth potential of Listeria across time (P < 0.0001). Efficacy of treatments was inconsistent across time; however, on d 21, SBS0.39% treated franks had the lowest growth potential compared to the control. Among diversity metrics, time had no effect on the microbiota (P > 0.05), but treatment did (P < 0.05). Thus, the treatments potentially promoted a stable microbiota across time. Using ANCOM, Listeria was the only significantly different taxa at the genus level (P < 0.05, W = 52). Therefore, the results suggest incorporating SBS over SL as an alternative antimicrobial for the control of L. monocytogenes in organic frankfurters without negatively impacting the microbiota. However, further research using multiple L. monocytogenes strains will need to be utilized in order to determine the scope of SBS use in the production of RTE meat.