Purpose: To evaluate the reduction efficacy of 5% lactic acid on the “Big 6” non-O157 STECs on chilled beef sub-primals.
Methods: Two briskets were randomly assigned to each of 3 treatments consisting of a positive control, sterile water, or 5% lactic acid and submerged into an inoculum consisting of the “Big 6” non-O157 STEC serotypes (O26, O11, O103, O121, O45, O145) for 1 minute before removal and placement onto a rack to facilitate pathogen attachment for 30 minutes. Positive controls were sampled and remaining briskets were sprayed with either sterile, room temperature water or 5% lactic acid. A 50 cm2 area was swabbed, stomached at 230 rpm for 1 minute and serially diluted and plated onto MacConkey agar-tryptic soy agar overlay to facilitate injured cell recovery. Manual plate counts were conducted to assess efficacy and data analyzed using SigmaStat®.
Results: Microbial counts were converted to CFU/cm2 and the positive control was determined to be 2.5 log CFU/cm2. Treatment averages for water and lactic acid were 1.91 and 1.96 log CFU/cm2, respectively. Statistical analysis was conducted using the two-way analysis of variance function of SigmaStat® 3.5. Pairwise multiple comparisons indicated statistical differences between Positive Control and Water (P < 0.008) and Positive Control and Lactic Acid (P < 0.009), but no differences were detected between Water and Lactic Acid (P > 0.05). No differences were detected between repetitions (P > 0.05).
Significance: These data detected no differences in reduction efficacy between water and lactic acid treatments but both were significantly different from the control. Water and 5% lactic acid may be an efficacious intervention against non-O157 STECs on beef subprimals. A longer contact time may increase the efficacy of the 5% lactic acid.