TAG VP Research Study Provides New Thinking on Salmonella Interventions
According to the National Chicken Council’s 2018 data, chicken is the number one protein consumed in the U.S., and the U.S. has the largest broiler chicken industry in the world. However, Salmonella control in chicken meat products continues to be a challenge for both industry and policymakers.
The food industry has made significant progress by leveraging technology and preventive approaches, but the risk of contamination with pathogens during conversion of live poultry into products for human consumption is still present. In fact, CDC attributes nearly 14% of the U.S. nontyphoidal Salmonella annual cases to chicken products. Chicken processors have often adopted new interventions on the basis of limited technical assessments, market factors, or anecdotal evidence from industry peers lacking a robust scientific assessment to base their decisions. Additionally, there is still a high degree of variability among the poultry industry in terms of the antimicrobials used and the selection of processing stages to apply the intervention.
To help poultry processors prioritize food safety interventions to maximize Salmonella reduction and public health protection, TAG Vice President of Public Health Rolando Gonzalez, et al, conducted a study on Prioritization of Chicken Meat Processing Interventions on the Basis of Reducing the Salmonella Residual Relative Risk, which was published in the IAFP Journal of Food Protection (Vol. 82, No. 9, 2019, Pages 1575–1582). The aim of the study was to evaluate the Salmonella chicken meat processing interventions in the U.S. broiler industry and develop a risk-based prioritization framework to rank the interventions that achieve the greatest Salmonella relative risk reduction. Given the limited data available on Salmonella levels for preharvest interventions, the study was focused on the analysis of processing level control measures.
The study. A basic simulation model (built on the FAO/WHO Poultry Risk Management Tool, v. 1.0), and, additional production scenarios were created, then the researchers selected for comparison 18 interventions showing the highest efficacy on reducing Salmonella prevalence or concentration or both within each stage (one to three interventions per stage). Additional production scenarios were built on the basis of data from published literature and expert elicitation to compare the Salmonella relative risk level between the basic model (no interventions), the baseline model (current U.S. practices), and scenarios combining interventions at specific stages of the chicken meat production chain, considering both prevalence and concentration of this pathogen.
When assessed as single interventions, all 18 showed a reduction of Salmonella prevalence or concentration or both, with relative risk estimates varying from 0.01 (most effective, 98.8% reduction) to 0.98 (least effective, 2.0% reduction). Showing the greatest reduction in the relative risk of Salmonella (75% or greater) were irradiation after packaging, use of acidified sodium chlorite (ASC) during evisceration, cetylpyridinium chloride (CPC) in the inside-outside bird washer (IOBW), trisodium phosphate during prechill or peroxyacetic acid (PAA) during chilling, peroxyacetic acetic or lactic acid during postchill, and acetic acid applied at portioning.
Irradiation was shown to be the most effective intervention at doses of 0.9 to 3.6 kGy, achieving 2- to 5-log reduction. However, low consumer acceptability and significant cost considerations have limited its application and wider adoption as an overall meat (including poultry) food safety intervention.
ASC was the second most effective single intervention, but its use has declined over the past decade due to global market restrictions, higher cost, and the need to combine it with generally recognized as safe acids (e.g., citric) to maintain a low (~2 to 3) pH.
The third most effective single intervention was the use of PAA as a postchill intervention. Poultry processors have successfully reduced Salmonella prevalence with the use of postchill antimicrobial applications, a fact that is confirmed with the results obtained in this simulation. However, a better understanding of the impact of PAA at the postchill stage and the pathogen dynamics during portioning is needed. Preliminary data show an abrupt increase of Salmonella prevalence during portioning. One of the potential reasons for the pathogen prevalence difference between postchill and portioning stages may be the use of large amounts (~400 ppm) of PAA at postchill that could produce a sanitizer carryover interfering with the laboratory analysis used to detect Salmonella in chicken meat.
When combinations of antimicrobial treatments are sequentially applied during processing (the “hurdle approach”), they have been shown to enhance the microbial reductions obtained by single interventions alone, improving both the safety and quality of poultry carcasses. As validated by the simulation results of production scenarios assessed in this study, studies have shown:
Adding chlorine to the chiller as a single intervention produces only a 27% Salmonella relative risk reduction, but adding chlorine to the IOBW and PAA to the OLR steps, increases the risk mitigating efficacy to 98%.
Using combinations of chlorine and acetic acid or trisodium phosphate has been shown to result in a 2.0-log CFU/mL reduction in Salmonella Typhimurium on the surface of poultry carcasses and parts, as compared with lower reductions (e.g., 0.9 log CFU/mL) when the interventions were applied individually.
Combinations of chlorine and either chlorine dioxide or trisodium phosphate reduced the Salmonella prevalence up to 91% in poultry carcasses and parts.
In addition to determining the efficacy of intervention steps, the study identified the current U.S. practices for use of antimicrobials in broiler chicken processing through plant visits and interviews with poultry industry experts.
The combination of chlorine at the bird wash station and PAA at the OLR and chill stages were identified as the most current U.S. industry practices, with all three steps contributing to an overall decrease in Salmonella concentration ranging from 0.4 to 2.0 log CFU/g.
The two most effective production scenarios (98% risk reduction) were this current U.S. practice and the baseline scenario of substituting chlorine for PAA at the IOBW, which many chicken processors have adopted.
Alternate baseline scenarios (use of chlorine at the IOBW, ASC at OLR, and PAA at the chill stage; substituting PAA for chlorine at the chill stage) were not as effective (88 to 94.3% overall risk reduction) as the current set of interventions applied by the industry. However, they were all still more effective than any individual intervention, except irradiation (98.8% risk reduction).
A follow-up study will be published by the authors examining cost implications of these interventions and effectiveness in reducing the number of cases of salmonellosis.
Thus, in brief:
Chlorine at the wash station and PAA at the OLR and chill stages were the most common
Irradiation was the most effective single intervention (98.8% reduction)
Adding PAA to chill stages achieved 99% Salmonella reduction
Adding more interventions did not achieve further Salmonella reduction (2%)
This research study was able to characterize the behavior of Salmonella in the chicken meat production chain and can help poultry processors identify optimal processing scenarios that will maximize risk reduction. The framework developed as part of this work can be applied to assess the level of risk associated with other food-pathogen combinations and the mitigating impact of scenarios of control measures at similar stages of processing and beyond. Read the full study at the Journal of Food Protection.
About The Acheson Group (TAG) Led by Former FDA Associate Commissioner for Foods Dr. David Acheson, TAG is a food safety consulting group that provides guidance and expertise worldwide for companies throughout the food supply chain. With in-depth industry knowledge combined with real-world experience, TAG's team of food safety experts help companies more effectively mitigate risk, improve operational efficiencies, and ensure regulatory and standards compliance. www.AchesonGroup.com