Antimicrobial Efficacy of Acidified Peroxyacetic Acid Treatments Against Surrogates for Enteric Pathogens on Prerigor Beef

Abstract

Two studies were conducted to evaluate the antimicrobial effects of pH-adjusted solutions of peroxyacetic acid (PAA) against nonpathogenic Escherichia coli surrogates for Shiga toxin–producing E. coli and Salmonella, inoculated on beef. In both studies, prerigor beef carcass surface tissue (10 × 10 cm pieces) was inoculated (6–7 log colony-forming units [CFU]/cm2) on the adipose side with a 5-strain mixture of E. coli biotype I. In the first study, samples were left untreated (control) or were immersed (10 s) in solutions of PAA (300 parts per million [ppm]) acidified with a sulfuric acid and sodium sulfate blend (SSS) (pH 1.2) or PAA (400 ppm) acidified with acetic acid (2%), citric acid (1%), lactic acid (3.5%), or SSS (pH 1.2 or pH 1.8). In the second study, samples were left untreated or were spray treated (10 s) using a spray cabinet, with water, PAA (350 ppm or 400 ppm), PAA (350 ppm or 400 ppm) acidified with SSS (pH 1.2), or PAA (400 ppm) acidified with acetic acid (2%). All immersion treatments effectively (P < 0.05) reduced inoculated E. coli populations (6.2 log CFU/cm2) by 2.3 to 2.8 log CFU/cm2. When the test solutions were applied by spraying, the water and all PAA-containing treatments lowered inoculated populations (6.4 log CFU/cm2) by 0.4 (P ≥ 0.05) and 1.7–1.9 (P < 0.05) log CFU/cm2, respectively. No (P ≥ 0.05) differences in decontamination efficacy were observed between the 5 PAA-containing spray treatments. Overall, the results showed that PAA and the pH-adjusted PAA treatments were effective in reducing levels of the surrogates for Shiga toxin–producing E. coli and Salmonella. Although no differences in antimicrobial efficacy were noted between the nonacidified and acidified PAA treatments immediately after treatment application, further studies are needed to evaluate how the acidified PAA treatments perform as part of a sequential multi-hurdle decontamination strategy to reduce pathogen contamination on beef carcasses.