Comparison of Electrostatic Spray, Spray, or Dip Using Lactic Acid, Peroxyacetic Acid, or Beefxide on the Reduction of Rifampicin-resistant E. coli

Introduction: Very small meat processing operations often purchase beef sub-primals for grinding that have not been tested for Shiga toxin-producing E. coli (STEC).  The use of antimicrobial interventions applied to sub-primals may offer small processors a method to minimize the risk of STEC in ground beef.

Purpose: The purpose was to evaluate the effectiveness of three antimicrobial solutions using three application methods for use in small meat processing facilities. Also, to evaluate the effectiveness of antimicrobial treatments on the mostly fat covered outer surface versus the mostly lean inner surface of the sub-primal.

Methods: The outer fat or inner lean surfaces of beef shoulder clod roasts were inoculated with a five strain cocktail (~5.6 log CFU/cm²) of Rifampicin resistant E. coli (E. coli^Rif).  Three replications of 4.5% lactic acid, 380 ppm peroxyacetic acid, or 2.5% Beefxid were applied at 19-23°C to the sub-primal surface using spray (5 s, 20 psi), dip (15 s), or electrostatic spray (10 s). E. coli^Rif were enumerated on ACP and E. coli/coliform Petrifilm.

Results: All antimicrobial treatments reduced (P<0.0001) E. coli^Rif counts when compared to the inoculated control (0.39-1.13 log CFU/cm² reduction). However, dip and spray applications were more effective at reducing E. coli^Rif as compared to electrostatic spray (P=0.0008).  The reduction of E. coli^Rif counts were greater on the outer fat versus the inner lean surface of the roast (P=0.0054).  Microbial samples of ground beef produced from the clod roasts showed that E. coli^Rif counts for only spray and dip treatments were different from the control. Ground beef E. coli^Rif counts were higher from roasts treated on the lean surface versus the fat surface when measured by E. coli/coliform Petrifilm (P=0.0001) and ACP Petrifilm (P<0.0001).

Significance: Small meat processors can select an antimicrobial treatment to reduce the STEC on the surface of beef sub-primals and in ground beef.