The Effect of Dipping in Organic Acids for Short or Extended Times on Reduction of Escherichia coli Surrogates on Pieced Beef Clods

Introduction: Small business meat processors need simple methods to reduce Escherichia coli and shiga toxin-producing E.coli (STEC) in ground beef. Organic acid dips may provide controls for STEC.

Purpose: The objective was to evaluate the effect of short or extended dip time and antimicrobial on the reduction of E. coli (study 1) and to evaluate the effect of short or extended dip time on lean or fat surfaces on the reduction of E. coli (study 2).

Methods: A five-strain cocktail of Rifampicin resistant E. coli (E.coli^RIF) was inoculated on beef shoulder clod pieces and allowed to attach for 20 minutes. Lean inner surfaces (study 1 and 2) and medial fat surfaces (study 2) were dipped in 4.5% lactic acid (LA, study 1 and 2), or 380 ppm peroxyacetic acid (PAA, study 1) for 15 s or 3 min at 22.2°C. Sample cores (25.3 cm²) were taken before and after dipping and a 25 g sample after grinding (study 1). Samples were stomached in buffered peptone water containing Rifampicin and dilutions plated on ACP petrifilms (3M; study 1 and 2).

Results: E.coli^RIF counts pretreatment were not different among treatments. Posttreatment, E.coli^RIF counts for PAA and LA dipped for three minutes were lower (P<0.05) than the inoculated control. Reduction of E.coli^RIF counts using PAA at 3 min (0.721 log CFU/cm²) were also different than inoculated control (0.015 log CFU/cm²; P<0.05). After grinding E.coli^RIF counts for LA 15 s, PAA 15 s, and PAA 3 min were all different than inoculated control. No differences in E.coli^RIF counts for lean or fat surfaces (study 2). However, reductions at three min were greater than reductions at 15 s.

Significance: Reduction levels were greater at longer time periods of dipping. However, if dipped for greater time intervals, product quality could be negatively affected.