MICROBIAL CHANGES ON FRESHLY SLAUGHTERED PORK CARCASSES DUE TO "HOT" LACTIC ACID DECONTAMINATION

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

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.

Evaluation of the safety and efficacy of the organic acids lactic and acetic acids to reduce microbiological surface contamination on pork carcasses and pork cuts

Studies evaluating the safety and efficacy of lactic and acetic acids to reduce microbiological surface contamination on pork carcasses pre-chill and pork meat cuts post-chill were assessed. Lactic acid treatments consisted of 2-5% solutions at temperatures of up to 80°C applied to carcasses by spraying or up to 55°C applied on cuts by spraying or dipping. Acetic acid treatments consisted of 2-4% solutions at temperatures of up to 40°C applied on carcasses by spraying or on cuts by spraying or dipping. The maximum treatment duration was 30 s. The Panel concluded that: [1] the treatments are of no safety concern, provided that the substances comply with the European Union specifications for food additives; [2] spraying of pork carcasses pre-chill with lactic acid was efficacious compared to untreated control, but based on the available data, the Panel could not conclude whether lactic acid was more efficacious than water treatment when spraying of pork carcasses pre-chill or pork meat cuts post-chill. The Panel concluded that dipping of pork meat cuts post-chill in lactic acid was more efficacious than water treatment. However, it could not conclude on the efficacy of acetic acid treatment of pork carcasses pre-chill and/or pork meat cuts post-chill; [3] the potential selection and emergence of bacteria with reduced susceptibility to biocides and/or resistance to therapeutic antimicrobials linked to the use of the substances is unlikely as long as Good Hygienic Practices are implemented; and [4] the release of both organic acids is not of concern for the environment, assuming that wastewaters released by the slaughterhouses are treated, if necessary, to counter the potentially low pH caused by lactic or acetic acid, in compliance with local rules.

Evaluation of Electrolytically-Generated Hypochlorous Acid ('Electrolyzed Water') for Sanitation of Meat and Meat-Contact Surfaces

'Electrolyzed water' generators are readily available in the food industry as a renewable source of hypochlorous acid that eliminates the need for workers to handle hazardous hypochlorite concentrates. We applied electrolyzed water (EW) directly to multi-strain cocktails of Listeria monocytogenes, E. coli O157:H7, and Salmonella sp. at 250 ppm free available chlorine (FAC) and achieved greater than 6-log reductions in 2 min. Lower EW values were examined as antimicrobial interventions for fresh meat (beef carcasses), processed meats (frankfurters), and food contact surfaces (slicing blades). Little or no reduction relative to controls was observed when generic E. coli-inoculated beef carcasses or L. monocytogenes-inoculated frankfurters were showered with EW. Spray application of EW (25 and 250-ppm FAC) onto L. monocytogenes-inoculated slicing blades showed that greater reductions were obtained with 'clean' (3.6 and 5.7-log reduction) vs. 'dirty' (0.6 and 3.3-log reduction) slicing blades, respectively. Trials with L. monocytogenes-inoculated protein-EW solutions demonstrated that protein content as low as 0.1% is capable of eliminating FAC, reducing antimicrobial activity against L. monocytogenes. EW appears better positioned as a surface sanitizer with minimal organic material that can otherwise act as an effective reducing agent to the oxidizing solution rendering it ineffective.