Validation of Lactic Acid Dip and Spray in Reducing Escherichia coli O157:H7, Salmonella, and Non-O157 Shiga-toxigenic Escherichia coli (STEC) on Beef Trim and Ground Beef

Introduction: Organic acids are frequently applied to beef carcass tissues as an antimicrobial intervention to reduce E. coli O157:H7, non-O157 STEC, Salmonellaand other pathogenic populations that may be present. 

Purpose: The objective of this research was to compare the effectiveness of two different application methods (dip vs. spray) of 4.4% lactic acid on reducing E. coli O157:H7, non-O157:H7 STEC and Salmonella on inoculated beef trim and ground beef. 

Methods: Beef trim inoculated with E. coli O157:H7, non –O157 STEC or Salmonella (10⁵ to 10⁶CFU/g) at separate times was subjected to four different treatments: 4.4% lactic acid dip (LD), 4.4% lactic acid spray (LS), water dip (WD), water spray (WS), plus an inoculated, untreated control (CTL). Intervention effectiveness on pathogen reduction was measured at the following processing points: 1 h and 20 h after treatment (trim), and 1 h, 24 h, 72 h and 7 days after grinding (ground beef). 

Results: The LD treatment reduced all pathogens significantly (P < 0.05) on both beef trim and ground beef. The LD reduced E. coli O157:H7 by 0.91 to 1.41 log cycles on beef trim and ground beef, STEC by 0.48 to 0.82 log cycles, and Salmonella by 0.51 to 0.81 log cycles. No other treatment, including the LS treatment, significantly reduced (P> 0.05) any pathogen from the CTL. 

Significance: These data indicate that a lactic acid dip treatment was more effective at reducing E. coli O157:H7, Salmonella and non-O157 STEC when compared to a conventional lactic acid spray treatment. Further research is needed to determine if factors such as temperature, acid type, acid concentration and length of exposure impact the effectiveness of a dip treatment on these pathogens.