Control of Pathogenic Bacteria in Raw Pork using Organic Acid Salts in Combination with Freezing and Thawing

Abstract

The effect of sodium lactate, sodium acetate and potassium sorbate on growth inhibition of seven bacterial species: Escherichia coli, Listeria monocytogenes, Pseudomonas fluorescens, Salmonella Rissen, Salmonella Typhimurium, Staphylococcus aureus and Yersinia enterocolitica was investigated by determining the minimum inhibitory concentration (MIC) values at pH 4.5-7.0. Sodium lactate and potassium sorbate provided overall greater inhibition to all tested bacterial strains in comparison with sodium acetate. At a low pH level (4.5-5.5), sodium lactate was more effective in inhibiting most tested bacteria than at a high pH level (6.0-7.0). The most sensitive bacteria to sodium lactate at pH 4.5 were L. monocytogenes and E. coli. Potassium sorbate had good inhibitory activity against E. coli and P. fluorescens at pH 4.5-5.0. The pH value had less effect on the antibacterial action of sodium acetate particularly at pH 5.0-6.5. Y. enterocolitica was the most sensitive strain to sodium acetate at pH 4.5-7.0. The effect of these organic acid salts in combination with freezing (-23±2°C for 72 h) and slow thawing on the survival of Salmonella Rissen and S. aureus in pork was investigated. Survival cells of Salmonella Rissen and S. aureus decreased as the freezing time increased. Of all the tested organic acid salts, potassium sorbate showed the greatest inhibitory effect on Salmonella Rissen, while sodium lactate inhibited S. aureus well. These organic acid salts provided a synergistic effect with freezing and thawing on lowering survival of both bacterial species.