Validation of post-harvest antimicrobial interventions to control Shiga toxin-producing Escherichia coli (STEC) on market hog carcass surfaces

Abstract

Although swine are less associated with STEC foodborne disease outbreaks, the potential for swine to serve as a source of STEC infections in human beings cannot be disregarded. This study compared eight USDA-approved antimicrobial intervention technologies to quantify their ability to reduce STEC contamination on market hog carcasses. Hogs were harvested to provide skin-on carcass sides, and eight sides (per three replications) were inoculated with a 7-strain STEC cocktail (ca. 5 log CFU/cm² across all external and body cavity surfaces). Each side was randomly assigned to a final pre-chill wash treatment administered in a commercial Chad carcass cabinet using a low-volume spray [3% lactic acid (lLA; 130 °F), 400 ppm peracetic acid (lPAA), or acidified 400 ppm peracetic acid (laPAA)] or a high-volume wash [ambient water (hAW), 400 ppm PAA (hPAA), 400 or 600 ppm hypobromous acid (hDBDMH), or 71 °C water (hHW)] treatment according to a randomized complete block study design. Post-treatment (after a 10-min hanging drip) and post-chilling (18 h at 2 °C) STEC reductions were compared for external skin-on surfaces and internal body cavity lean surface tissue. Post-treatment color changes were determined for lean, adipose, and skin carcass surfaces before and after chilling. When applied to the external, skin-on surface, the hHW, hPAA, and hDBDMH₆₀₀ deluge washes were significantly (P ≤ 0.05) more effective than the other intervention technologies, achieving STEC reductions of 3.8, 3.4, and 3.2 log CFU/cm², respectively. In comparison, the hAW control reduced STEC by 1.7-log CFU/cm² on the external, skin-on surface. The carcass interventions were less effective at reducing STEC populations attached to interior body cavity (diaphragm region), with post-chill populations reduced by 0.9-2.2 log cycles, while the hAW control wash achieved a 0.6-log reduction. None of the treatments negatively impacted instrumental carcass color. While all market hog carcass interventions reduced STEC populations, larger reductions were observed when applied to the external, skin-on surface, with the largest reductions achieved by the hHW, hPAA, and hDBDMH₆₀₀ deluge washes. These data equip pork processors with the information necessary to support decision-making when selecting an intervention technology.

Keywords: Chemical washes; Color quality; Meat safety; Organic acids; Pork.