Lactic acid has little effect on E.coli

Buffered lactic acid has little effect on the proliferation of E.coli in beef tissue, Belgian scientists report this week. Scientists from the Department of Food Technology and Nutrition, at University of Gent in Belgium studied a varied level of acid resistance among the 14 tested strains of Escherichia coli O157:H7. Eight strains were categorised as acid resistant, four strains as acid sensitive, and two strains demonstrated acid-inducible acid resistance. The survival of an acid-resistant (II/45/4) and acid-sensitive (IX/8/16) E. coli O157:H7 strain on chilled beef tissue treated with 1 and 2 per cent buffered lactic acid, sterile water, or no treatment (control) was followed. A gradual reduction of E. coli O157:H7 was noticed during the 10 days of storage at 4°C for each of the treatments. Decontamination with 1 per cent and 2 per cent buffered lactic acid did not appreciably affect the pathogen, the scientists report and differences in the pH-independent acid resistance of the strains had no effect on the efficacy of decontamination. The effect of modified atmosphere packaging (MAP) on survival of E. coli O157:H7 in red meat was also studied. MAP (40% CO2/60% N2) or vacuum did not significantly influence survival of E. coli O157:H7 on inoculated sliced beef (retail cuts) meat compared to packing in air. The relative small outgrowth of lactic acid bacteria during storage under vacuum for 28 days did not affect survival of E. coli O157:H7. The scientists conclude that neither lactic acid decontamination nor vacuum or MAP packaging could enhance reduction of E. coli O157:H7 on beef, which underlines the need for preventive measures to control the public health risk of E. coli O157:H7. Full findings are published in the November 2001 issue of Journal of Food Protection.​