Systematic Review and Meta-Analysis of the Efficacy of Interventions Applied during Primary Processing to Reduce Microbial Contamination on Pig Carcasses

Abstract

Interventions from lairage to the chilling stage of the pig slaughter process are important to reduce microbial contamination of carcasses. The aim of this systematic review and meta-analysis was to assess the effectiveness of abattoir interventions in reducing aerobic colony count (ACC), Enterobacteriaceae, generic Escherichia coli, and Yersinia spp. on pig carcasses. The database searches spanned a 30 year period from 1990 to 2021. Following a structured, predefined protocol, 22 articles, which were judged as having a low risk of bias, were used for detailed data extraction and meta-analysis. The meta-analysis included data on lairage interventions for live pigs, standard processing procedures for pig carcasses, prechilling interventions, multiple carcass interventions, and carcass chilling. Risk ratios (RRs) for prevalence studies and mean log differences (MDs) for concentration outcomes were calculated using random effects models. The meta-analysis found that scalding under commercial abattoir conditions effectively reduced the prevalence of Enterobacteriaceae (RR: 0.05, 95% CI: 0.02 to 0.12, I2 = 87%) and ACC (MD: −2.84, 95% CI: −3.50 to −2.18, I2 = 99%) on pig carcasses. Similarly, significant reductions of these two groups of bacteria on carcasses were also found after singeing (RR: 0.25, 95% CI: 0.14 to 0.44, I2 = 90% and MD: −1.95, 95% CI: −2.40 to −1.50, I2 = 96%, respectively). Rectum sealing effectively reduces the prevalence of Y. enterocolitica on pig carcasses (RR: 0.60, 95% CI: 0.41 to 0.89, I2 = 0%). Under commercial abattoir conditions, hot water washing significantly reduced ACC (MD: −1.32, 95% CI: −1.93 to −0.71, I2 = 93%) and generic E. coli counts (MD: −1.23, 95% CI: −1.89 to −0.57, I2 = 61%) on pig carcasses. Conventional dry chilling reduced Enterobacteriaceae prevalence on pig carcasses (RR: 0.32, 95% CI: 0.21 to 0.48, I2 = 81%). Multiple carcass interventions significantly reduced Enterobacteriaceae prevalence (RR: 0.11, 95% CI: 0.05 to 0.23, I2 = 94%) and ACC on carcasses (MD: −2.85, 95% CI: −3.33 to −2.37, I2 = 97%). The results clearly show that standard processing procedures of scalding and singeing and the hazard-based intervention of hot water washing are effective in reducing indicator bacteria on pig carcasses. The prevalence of Y. enterocolitica on pig carcasses was effectively reduced by the standard procedure of rectum sealing; nevertheless, this was the only intervention for Yersinia investigated under commercial conditions. High heterogeneity among studies and trials investigating interventions and overall lack of large, controlled trials conducted under commercial conditions suggest that more in-depth research is needed.

Salmonella spp., Escherichia coli and Enterobacteriaceae Control at a Pig Abattoir: Are We Missing Lairage Time Effect, Pig Skin, and Internal Carcass Surface Contamination?

“…These results, highlights the importance of the technological process of slaughter in reducing its contamination, already remarked by Zdolec et al [26].…”

Driving forces shaping the microbial ecology in meat packing plants

“…In commercial practice, carcasses are chilled either by spray chilling where carcasses are intermittently sprayed with water, or by dry chilling where they are exposed to a flow of refrigerated air ( Savell et al, 2005 ). Air chilling with appropriate parameters can be an effective antimicrobial intervention step, resulting in >2 log reductions of the carcass bacterial population, likely by the desiccating effect from the rapid evaporation of water from warm carcass surfaces in a refrigerated environment ( Greig et al, 2012 ; Liu et al, 2016 ; Zdolec et al, 2022 ). In contrast, no consistent antimicrobial effects have been reported for spray chilling, with increase, decrease and no change in bacterial numbers on carcass surfaces have been reported ( Yang, 2017 ).…”

“…This treatment is ineffective for reducing the number of bacteria on meat surface but may affect the survival and growth of subpopulations during extended storage under chilled and vacuum packaged conditions. In addition to antimicrobial interventions, bacteria on pork carcasses during dressing can also be significantly reduced by scalding and singeing but not by polishing or dehairing, all of which are unique to pork carcass dressing ( Zdolec et al, 2022 ).…”

Modernization Data Analysis and Visualization for Food Safety Research Outcomes

“…Intervention studies are an efficient methodology that can be applied in a processing plant to assess the effectiveness of microbial load reduction "before" and "after" treatments. These interventions can be implemented from the beginning of the process at the lairage area to the final part of the process [78]. Different antimicrobial interventions can be applied in the food industry, but it is necessary to analyze and define the expected results and evaluate which intervention will fit better.…”