Evaluation of microbial dynamics on low-sodium cooked bologna under different packaging conditions

Abstract

The purpose of this study was to assess the growth of spoilage and pathogenic bacteria on low sodium concentration sliced cooked bologna under refrigerated storage conditions. In study 1, the effect of three different sodium concentrations (1%, 2% and 3%) and two packaging conditions (aerobic and vacuum) on growth of a cocktail of inoculated spoilage bacteria such Lactobacillus curvatus, Leuconostoc mesenteroides, Brochothrix thermosphacta and Pseudomonas fluorescens were investigated by using culture-dependent and culture-independent techniques. In general, reducing the sodium concentration from 2% (the current industry standard) to 1% NaCl in the cooked bologna system did not have a significant effect on microbial growth. The utilization of Ion Torrent high-throughput sequencing in this study allowed the description of the total microbial community present on sliced cooked bologna. Taxonomic analysis revealed the microbial community belongs to the phyla Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. Finally, in this study, in situ meat redox measurement values were collected over time using platinum electrodes placed on top of, and in between bologna slices. While the redox values obtained were, in general, consistent with increasing bacterial cell numbers, issues of reproducibility and consistency were evident. The second study focused on the impact that the addition of a bacteriocin, Micocin X®, to the meat blend would have on growth of spoilage bacteria and in particular, Listeria monocytogenes, in vacuum-packaged cooked bologna formulated with 1% and 3% NaCl. In general, results demonstrated Micocin X® had a significant effect on the growth of Pseudomonas fluorescens and Listeria monocytogenes; however, no substantial effect was assessed in the control of lactic acid bacteria or Brochothrix thermosphacta.