EFFICACY OF ORGANIC-ACIDS AGAINST ESCHERICHIA-COLI O157-H7 ATTACHED TO BEEF CARCASS TISSUE USING A PILOT-SCALE MODEL CARCASS WASHER

The efficacy of organic acids for controlling Escherichia coli O157:H7 attached to beef carcass tissue was determined using a pilot scale model carcass washer. Lean or adipose surface tissues from beef carcasses were inoculated with three strains of Escherichia coli O157:H7 or Pseudomonas fluorescens. After spraying either water, 1, 3, or 5% acetic, lactic, or citric acids at 24 degrees C, tissues were incubated for 24 h at 4 degrees C and bacterial populations enumerated. Statistical analyses of the data indicated that acid type was not a significant treatment factor (p greater than or equal to = 0.05); however, concentration, tissue type, and bacterial strain were significant (p less than or equal to = 0.0001) factors that influenced the reduction of bacterial populations on lean or adipose tissue. Of the concentrations tested on lean tissue, spray treatments with 5% were the most effective for reducing populations of E. coli O157:H7 or P. fluorescens. Differences in the resistances of the E. coli O157:H7 strains to acid washing also were observed. The magnitude of bacterial population reductions was consistently greater on adipose versus lean tissue for all bacterial strains. Surface pH data indicated that reductions of bacterial populations may have been due to the effects of acidic pH. This study demonstrates that, while organic acids did reduce populations of E. coli O157:H7 on red meat, treatments did not completely inactivate the pathogen.