IMPROVED PATHOGEN CONTROL FOR POULTRY PROCESSING: EXPERIMENTALLY-VALIDATED MATHEMATICAL MODELS FOR SCALDING, CHILLING, AND POST-CHILLING

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: ACTIVE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1029748
• Grant No.: 2023-67017-39208
• Cumulative Award Amt.: $498,178.00
• Proposal No.: 2022-08999
• Project Start Date: Jun 1, 2023
• Project End Date: May 31, 2026
• Grant Year: 2023
• Program Code: [A1332]- Food Safety and Defense

Recipient Organization
CLEVELAND STATE UNIVERSITY
2121 EUCLID AVE
CLEVELAND,OH 44115

Performing Department
(N/A)

Non Technical Summary
Problematic levels of Campylobacter and Salmonella continue to be detected on processed poultry products. While current control measures have improved poultry safety, they have not significantly impacted human illness rates nor been able to respond in real-time to pathogen contamination issues. Therefore, there is an urgent need for new research to explain the fundamental way bacteria shed from, attach to, and survive on chicken during critical processing steps. Not meeting this need represents a serious problem, because without clear scientific foundations informing pathogen control, the increased demand for poultry products translates into increased potential for foodborne disease outbreaks.Addressing these concerns, our main objective is to build tools from experiments and mathematical models to predict pathogen transfer and survival dynamics during the scalding, chilling and post-chill stages. This research is significant, since it will provide the poultry industry with science-based strategies to reduce Salmonella and Campylobacter contamination levels during processing. The resulting new insight into pathogen cross-contamination will also furnish key information for public health experts seeking to characterize risk along the poultry supply chain. Finally, due to growing populations, limited resources, and the continued public health burden from Salmonellosis and Campylobacteriosis, our results will work towards providing all Americans access to safer poultry products and help ensure the USDA's continued global role at the cutting edge of food safety.

Animal Health Component

15%

Research Effort Categories

Basic

70%

Applied

15%

Developmental

15%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
712	3260	2080	50%
712	3260	1100	30%
712	3260	2000	10%
712	3299	2020	10%

Knowledge Area
712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins;

Subject Of Investigation
3299 - Poultry, general/other; 3260 - Poultry meat;

Field Of Science
2020 - Engineering; 2080 - Mathematics and computer sciences; 1100 - Bacteriology; 2000 - Chemistry;

Keywords

chilling

cross-contamination

mathematical modeling

post-chilling

poultry

scalding

Goals / Objectives
Without fundamental understanding of the mechanisms dictating bacterial cross-contamination and survival, critical poultry processing steps will continue acting as persistent reservoirs of foodborne pathogens.Accordingly, there is an urgent need to develop novel strategies whichappropriate Salmonella/Campylobacter dynamics during the scalding, chilling and post-chill stages.Not meeting this need represents a serious problem because without clear scientific foundations informing pathogen control, the increased demand for poultry products translates into increased potential for foodborne disease outbreaks.Therefore, ourlong-term goalsare (i) develop optimal real-time sanitization strategies for Salmonella/Campylobacter, adjustable to processing specifications, (ii) develop data-modeling informed surveillance to improve processor compliance.Towards these goals,this proposal'smain objectiveis to constructexperimentally-validated modelsfor predicting pathogen dynamics during the scalding, chilling and post-chill stages in terms of processing specifications. The main objective will be realized via the following three aims:1. Quantify the fundamental mechanisms regulating pathogen transfer and inactivation during immersion scalding.Wehypothesize, based on preliminary lab-scale experimentsand our previous modeling work, that mathematical models for pathogen (Salmonella,Campylobacter) inactivation and transfer could be developed as functions of scald water temperature and sanitizer chemistry, which have strong predictive capacity at the commercial-scale.2. Elucidate the key mechanisms determining pathogen cross-contamination and survival during immersion and air chilling.Considering our previous modeling results, wehypothesizethat (i) mathematical forms for pathogen (e.g.,Salmonella) transfer and inactivation could be quantified from simulated processing experiments and chemical reactions/dynamical systems theory, which have predictive merit at the industrial scale; and (ii) fluid dynamics modeling guided by experiments linking air flow/ temperature/ relative humidity to bacteria shed, transport and attachment dynamics can be used to accurately map potential pathogen spread during air chilling.3. Identify the major determinants of pathogen spread and survival during the post-chill portioning/comminuted process.Based on pertinent literature and in collaboration with Mr. Glenn Mott (Advisory team), wehypothesizethat mathematically describing pathogen (Salmonella,Campylobacter) cross-contamination and survival during the cutting/ grinding processes, contact between parts prior to tray pack, as well as during the post-chill dips, will lead to models that can provide a benchmark against which the relative risk of different post-chill treatment strategies can be compared.

Project Methods
A unique feature of our project, illustrated in our methodolgy, is highlighted bythe following guiding principle:Iterative mathematical modeling development via experiments progressing from lab to pilot to commerical scale. In order to quantify fundamental mechanisms that govern pathogen shed from, attachment to, and survival on poultry carcasses during processing, as well as pathogen inactivation dynamics in shared water environments (eg. scald/chillwater), controlled experiments at the lab scale are needed. These in combination with theory from biology, chemistry and mathematics will provide keyinformation for building mathematical forms describing the aforementioned mechanisms. In order to test and potentially adjust how these models and their predictions scale with experimental scope (i.e. pilot/industrial scale), we will test and inform the developed models with data from pilot scale experiments and industrial scale data (from the literature andour advisory team).Research Objective #1: Quantify the fundamental mechanisms regulating pathogen transfer and inactivation during immersion scalding.The mechanisms of pathogen survival in scald water have not been sufficiently quantified in terms of scald water characteristic. The goal of the research proposed under Objective #1 is to determine the underlying dynamics of Salmonella and Campylobacter inactivation and carcass-to-carcass transfer via scald water. The hypothesis for this aim is that mathematical models for pathogen inactivation and transfer can be developed as functions of scald water temperature and chemistry, with strong predictive capacity at the commercial scale. We will evaluate this claim by building (i) mathematical forms for the bacterial dynamics informed by lab and pilot-scale experiments and pertinent mathematical, chemical, and biological metrics, and (ii) models to predict pathogen inactivation and cross-contamination in the context of a simulated pilot-scale scalding process as well as against commercial-scale scalding data. The rationale behind our approach is that consistent control of pathogens during scalding is not possible without fundamental understanding of such pathogen dynamics. When the proposed research for Objective #1 is completed, we expect the overall outcome to be validated models for Salmonella/ Campylobacter cross-contamination during scalding. This result is expected to have a significant impact on food safety, leading to improved decision-making for pathogen control during scalding.Research Objective #2: Elucidate the key mechanisms underlying pathogen cross-contamination and inactivation during immersion and air chilling.Recently there have been two North American industry trends regarding poultry chilling: (i) the switch from chlorine to PAA for water sanitization during immersion chilling (IC) and (ii) the increased use of air chilling (AC) in regions with limited water resources. Given the potential for water and air to mediate pathogen cross-contamination during the respective chilling processes and the limitation of studies examining the causative mechanisms for such pathogen dynamics, our goal here is to quantify Salmonella/ Campylobacter dynamics with respect to PAA kinetics during IC and Salmonella dynamics with respect to air temperature/flow configurations for AC. Our hypothesis for IC, based on our previous modeling results, is that mathematical forms for pathogen transfer and inactivation could be quantified from simulated processing experiments, which have predictive merit at the industrial scale. Similarly, our hypothesis for AC is that fluid dynamic models guided by experiments quantifying the effect of air temperature/air flow and relative humidity on shed, transport and attachment dynamics can be used to accurately map potential pathogen spread during tunnel AC.For IC, we will test our hypothesis by building mathematical forms for the aforementioned pathogen dynamics from lab and pilot-scale experiments and pertinent mathematical, chemical and biological metrics, constructing models to predict pathogen inactivation and cross-contamination during a simulated pilot chilling process as well as against industrial scale data. For AC, we will test our hypothesis by applying our experimentally-informed model predictions to contamination patterns observed in commercial studies in the literature. The rationale behind our approach is that effective control of pathogens during chilling cannot be achieved without basic understanding of such dynamics. The overall outcome from Objective #2 will be validated models for pathogen cross-contamination during chilling, which will have a significant impact on the safety of poultry products by advancing decision making for pathogen control.Research Objective #3: Identify the major determinants of pathogen spread and survival during the post-chill portioning (parts)/comminuted process.A recent study confirmed a problematic industry trend: a significant increase in Salmonella prevalence on poultry parts as compared to post-chill numbers, with cutting/ deboning processes possibly responsible for cross-contamination. While a moderate increase in prevalence moving from carcasses to parts seems logical due to various machinery involved, no detailed causal models have been developed to date quantifying pathogen cross-contamination during this process. Thus, our goal is to quantify the mechanisms of Salmonella/ Campylobacter transfer and inactivation along typical industry steps from post-chill to parts/ comminuted products. We hypothesize that detailed stochastic descriptions of pathogen transfer and survival during the cutting/ grinding processes, as well as the contact between chicken parts prior to tray pack as well as during post-chill dip treatments, will lead to models providing a benchmark against which the relative risk of different post-chill treatment strategies can be compared. In particular, using input from Mr. Glenn Mott (Gerber's Poultry), we will simulate the parts process typically used in industry by using a pilot setup in our lab to generate data from which to build and train an individual based model (IBM). Our premise will also be tested by training the developed IBMwith prevalence data in the literature, and then running in silico studies to test the efficacy of various sanitizers on poultry parts. The rationale behind our approach is that a dynamic understanding of post-chill pathogen transfer/survival rates will provide insights difficult to obtain from experiments alone. When the proposed research for this objective is successfully accomplished, we expect the overall outcome to be an experimentally informed modeling tool capable of performing contamination scenario analysis. This result is expected to significantly contribute towards poultry product safety by providing quantified guidelines for commercial level studies to improve cross-contamination control during the post-chill process.Regardingevaluation, our advisory team (poultry industry, advisory firms, public health officials from North America) willguide and advise us on industry practices, USDA established norms, and current trends in food safety practices for modernpoultry processing in North America.Also, our advisory team will ensure that our results are translatable/practical for the poultry industry, amenable for use in QMRA modeling, and formulated to improve food safety decision making. Our project success will be measured by the robustness and predictive success of our developed models for each of the scalding, chilling and post-chilll stages, indicated by publication in top, peer-reviewed journals.On the industry side, the acheivement of our long term goalswill be measured by how our results directly and indirectly influenceboth processing practice in the poultry industryand compliance measures in the policy making realm.

Progress 06/01/24 to 05/31/25

Outputs
Target Audience: Researchers in the field of poultry food safety in both industry and regulatory organizations. Poultry processors - both high and low volume facilities. Risk analysts constructing more realistic QMRAs for food safety connected to poultry consumption. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Our doctoral student Vyshnavi Ciluveru has received training todesign and develop new experiments for scalding and chilling Salmonella cross-contamination dynamics both at the lab and pilot-scale. In terms of data analysis, she also took a statistics class last Spring (Design of experiments, STA 536), together with mentoring from the PI's, has assisted here with the aforementioned experiments. Furthermore, as our group works at the interface of experimental data and modeling, Vyshnavi has learned important principles of model development in conjunction with specific data collection to ensure the utility of model applicability and prediction. Vyshnavi has also been trained in publicly presenting scientific results, both in manuscript writing (1 submitted paper) as well as at conference venues.She presenteda talk at the annual Poultry Science Association (PSA)conference in Raleigh, NC in July 2025 as well as aposter at the annual IAFP meeting (Cleveland, OH), in July of 2025. In addition, at Cleveland State, we obtained internal funding (Undergraduate Summer Research Award) for both the summer of 2024 and summer of 2025. For summer of 2024, we trained an undergraduate student to build mathematical models to determine which of the indicators (turbidity, TDS, and COD), were most effective in quantifying PAA dynamics for both lab scale and industrial scale data. This past summer, we (the PIs and the doctoral student)trained an undergraduate student in both experiments and modeling work to elucidate pH-dependent thermal inactivation models for pathogen control during poultry scalding. Note that both these undergraduate students are also participating in manuscript writing.It is worth noting that these mentoring activities follow a tiered approach, providing opportunities for student leadership in scientific work in the context of a supportive environment of professional scientists. How have the results been disseminated to communities of interest?For peer-reviewed manuscripts we have the following: Publications (posted on PubAg): Munther, D.*, Ryan, S.D., Kothapalli, C.R. and Zekaj, N., 2025. Spatial characterizations of bacterial dynamics for food safety: Modeling for shared water processing environments.Applied Mathematical Modelling,139, p.115818. Munther, D*., Ryan, S.D., Kothapalli, C.R. and Zekaj, N., 2025. Spatial cross-contamination profiles: Effect of water reuse on dynamics of Campylobacter and E. coli during poultry processing.Food and Bioproducts Processing. Submitted: Ciluveru, V., Simon J., Ryan, S.D., Kothapalli, C.R., Farber, J., and Munther, D.*, PAA efficacy and decay kinetics in poultry processing under chiller conditions, International Journal of Food Microbiology. In preparation: Ciluveru, V., Ryan, S.D., Kothapalli, C.R., and Munther, D., Free chlorine decay kinetics and efficacy in pathogen reduction during poultry processing Ciluveru, V., Ryan, S.D., Kothapalli, C.R., and Munther, D., Cross-contamination dynamics of Salmonella in scalding and chilling processes. For conference presentations, we have the following: Invited Talk: Evaluation free chlorine decay kinetics, efficacy in pathogen reduction, and interactions with organic matter during poultry processing, V. Ciluveru (graduate student), PSA annual meeting, Raleigh, NC, July 2025 Invited Talk: Peracetic acid inactivation of Salmonella during immersion poultry chilling: mathematical modeling of fundamental dynamics, D. Munther (PI), IAFP annual meeting, Cleveland, OH, July 2025 Poster: Efficacy and decay kinetics of Peracetic acid (PAA) as disinfectant in poultry processing, V. Ciluveru (graduate student), IAFP annual meeting, Cleveland, OH, July 2025 Invited Talk: Spatial characterizations of bacterial dynamics for food safety:Effect of water reuse on dynamics ofCampylobacterandE. coliduring poultry chilling, Society of Industrial Applied Mathematics - Dynamical systems, May 2025, Denver, Colorado To make our results more relevant to the industry, we have discussed our PAA efficacy and model resultsduring chilling with representatives from Enviro Tech. We have also had discussions with a local processor in Ohio about implementing sanitizer intervention steps between rehang and chilling and are exploring the potenital for testing specific strategies. What do you plan to do during the next reporting period to accomplish the goals? We plan to accomplish the goals outlined in AIM 3. Finish up Aim 1 -Model development and validation of inactivation and cross-contamination during scalding. Finish up Aim 2 - Validation of model results,Parameter analysis, Model simulations useful for processors Submit the manuscripts that are in preparation (Aims1 and 2)as well as submitresults under Aim3 for publication. Continue discussion/collaborationwith the local Ohio processor as well as with Dr. Elizabeth McMillan regarding Campylobacter studies.

Impacts
What was accomplished under these goals? During reporting period 2 we have made substantial progress in meeting our goals under Aims 1 and 2, that is, quantifying the fundamental mechanisms regulating pathogen inactivation and transfer during immersion scalding and chilling. Poultry chilling: Following up from year 1, we validated the result, using our developed models and data from a commercial plant in Ontario, that total dissolved solids (TDS) measurements can accurately predict peracetic acid levels at the commercial scale. In particular, we showed that TDS readings perform better than chemical oxygen demand (COD) measurements. This finding is critical for processors as TDS can be measured in real-time versus COD which is measured on the order of hours. In terms of mechanisms dictating Salmonella levels on poultry and in the water during the chiller process, we report on our developed experimentally-informed-mechanistic-modeling. Experimentally, the shedding and survival of a five-strain cocktail of poultry-plant derived Salmonella enterica serovars, at high/low loads, with exposure to peracetic acid (PAA; 0 - 200 mg×L-1) for up to 60 min in 10-L chiller tanks, in the presence/absence of whole chicken carcass or parts, were measured. Process water parameters versus time were simultaneously monitored. A mathematical model for PAA decay and pathogen shedding/inactivation was developed. This model accurately predicted PAA level changes in the pre/main chiller of a high-speed poultry processing plant in North America. Without PAA, Salmonella shedding from chicken thighs is influenced by rinse time and number of rinses. Without organic load, we found that residual PAA (1 mg×L-1) may suffice to inactivate Salmonella given sufficient exposure time, although PAA at levels > 5 mg×L-1 is essential for rapid bacterial inactivation. In the presence of an organic load, the initial PAA concentration (> 40 mg×L-1) and exposure time (> 2 min) were critical for bacterial inactivation, with model results connecting process conditions to dominate modes of bacterial inactivation on chicken. The insights from such experimental-modeling studies provides key tools for processors to improve pathogen control during chilling. Specifically, our conclusions are: The utility of an experimentally-informed-mechanistic-modeling approach to describe the mechanisms of bacterial shedding and inactivation during the poultry chilling process. Salmonella transfer rate from chicken surfaces to chiller water is a decreasing function of time, with approximately 50% of the total shedding occurring within the first 15-30 s. This is important as it indicates that the cross-contamination risks associated with Salmonella levels in chiller water is a function of process time and potentially a function of process time and space, depending on the type of chiller setup (batch vs counterflow). Related to this, we just published a modeling paper in Food and Bioproducts Processing and this paper was presented at the Society for Industrial and Applied Mathematics (SIAM) -Dynamical Systems meeting in Denver, May 2025. Without the presence of an organic load, we demonstrated that Salmonella in water is effectively eliminated by a PAA concentration >5 mg×L-1 with an exposure time >3 min. Our model results showed that the inactivation rate k_wis independent of bacteria load and is a function of PT = [PAA concentration]x[exposure time]. The inactivation rate of Salmonella on the surface of chicken thighs, k_sduring simulated chilling, was verified to be about 70-90% of the killing rate in water with no organic load. In the post-dissociation of PAA, acetic acid promotes the release of more soluble breakdown products, whereas H2O2aggressively oxidizes particulate organic matter. Using the developed model to compare the time scales of Salmonella shedding and PAA inactivation both in the water and on chicken surfaces, we found that for lower PTvalues, shedding dominates the removal of Salmonella from chicken, but for PTvalues above 17 (min×mg×L-1), PAA inactivation plays a dominate role. This result illustrates the synergy of our approach while re-emphasizing the critical role of tracking changes in PAA levels in connection with specific control, i.e., log reduction of Salmonella levels. We also conducted lab scale experiments tracking water chemistry dynamics associated to free chlorine (FC) level changes during simulated chiller setups as a comparison point for PAA level changes as well as FC inactivation of Salmonella during simulated chilling. While the US has mostly moved away from using FC, many plants globally still utilize chlorine and these results (especially when compared with PAA) will be important for them. The above findings were presented at IAFP in Cleveland, OH, July 2025 (poster & invited talk) and at PSA in Raleigh, NC, July 2025 (invited talk). Currently, we are finishing up pilot-scale experiments and modeling work quantifying water-mediated cross-contamination (without PAA and with continuous dosing of PAA, simulating industry practice) of Salmonella. Regarding upcoming peer-reviewed journal articles we currently have 1 submitted and 2 in preparation, see "dissemination of results" section for more details. Scalding: We have completed most of the experiments outlined under AIM 1. These include: quantify the inactivation of Salmonella as a function of scald water temperature, pH and organic load at the lab scale quantify the inactivation/cross-contamination of Salmonella during larger scale (pilot scale setup in the lab) simulation of the scald process Currently, we are working on summarizing the data and model construction, testing and validation. For shed, transfer and PAA inactivation of Campylobacter during chilling and scalding, we have designed experiments in collaboration with Dr. Elizabeth McMillan (U.S. National Poultry Research Center, USDA-Agricultural Research Service) and these will be underway this fall. Regarding Aim 3, we are currently designing experiments to quantify cross-contamination and survival during the cutting/ grinding processes, contact between parts prior to tray pack, as well as during the post-chill dips.

Publications

• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: Munther D, Ryan SD, Kothapalli CR, Zekaj N. Spatial characterizations of bacterial dynamics for food safety: Modeling for shared water processing environments. Applied Mathematical Modelling. 2025 Mar 1;139:115818.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: Munther D, Ryan SD, Kothapalli CR, Zekaj N. Spatial cross-contamination profiles: Effect of water reuse on dynamics of Campylobacter and E. coli during poultry processing. Food and Bioproducts Processing. 2025 Aug 5.
• Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: IAFP annual conference talk, July 2025, Cleveland, Ohio: Peracetic acid inactivation of Salmonella during immersion poultry chilling: mathematical modeling of fundamental dynamics, D. Munther
• Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Society of Industrial Applied Mathematics  Dynamical systems, May 2025, Denver, Colorado: Spatial characterizations of bacterial dynamics for food safety: Effect of water reuse on dynamics of Campylobacter and E. coli during poultry chilling, D. Munther
• Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Evaluation free chlorine decay kinetics, efficacy in pathogen reduction, and interactions with organic matter during poultry processing, V. Ciluveru (graduate student), PSA annual meeting, Raleigh, NC, July 2025
• Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Poster: Efficacy and decay kinetics of Peracetic acid (PAA) as disinfectant in poultry processing, V. Ciluveru (graduate student), IAFP annual meeting, Cleveland, OH, July 2025

Progress 06/01/23 to 05/31/24

Outputs
Target Audience:Researchers in the field of poultry food safety in both industry and regulatory organizations. In addition, poultry processors in the U.S. and Canada. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A doctoral student from chemical engineering, Vyshnavi Ciluveru, has been trained to perform water chemistry experiments, recording factorslike turbidity, total dissolved solids (TDS), and chemical oxygen demand (COD) to determine which of them are the best indicators for depletion of PAA levels during simulated poultry chilling as well as in a commercial processor setting. She has also been trained to perform experiments for quantifying Salmonella and Campylobacter levels on carcass surfaces and in water during simulated chilling setups. We have also guided an undergraduate student (supported by an Undergraduate Research Student Award from Cleveland State University) to build mathematical models to determine which of the indicators (turbidity, TDS, and COD), were most effective in quantifying PAA dynamics for both lab scale and industrial scale data. How have the results been disseminated to communities of interest?We have one research paper under review in the journal Applied Mathematical Modelling, entitled "Spatial characterizations of bacterial dynamics for food safety: Modeling for shared water processing environments" and are preparing two more manuscripts for submission. Thespatial modeling journal article results were presented by the project director Dr. Daniel Munther at IAFP 2024 during a poster session: "Spatial modeling of the poultry chilling process: impact of water recirculation and counterflow on E. coli and Campylobacter dynamics". We have discussed our chiller water chemistry results with processors in Ohio and in Ontario, Canada. Our results have provided the Ohio plant with independent compliance confirmation of their targeted water chemistry parameters. We have also discussed our Salmonella inactivation experiments and results with microbiologist collaborators from the USDA. These discussions have led to experimental procedure refinements and have promoted further collaborative efforts in understanding how to control this pathogen during poultry chilling. Finally, the chiller water chemistry results and modeling predictions of PAA levels as well as the Salmonella killing rates via PAA during simulated chilling were presented by Dr. Daniel Munther at the combined AMR and Food Safety Project Directors meeting precedingIAFP 2024 in Long Beach, Ca. What do you plan to do during the next reporting period to accomplish the goals?We plan to finish the goals laid out under the immersion chilling section of AIM #2 of our proposal. Specifically, we plan to: Analyze data from the Salmonella inactivation experiments via PAA and inform model killing forms. These experiments and model development will be repeated for Campylobacter in collaboration with a microbiologist from the USDA. Conduct pilot scale cross-contamination chilling experiment in our lab to inform pathogen transfer mathematical forms for our model. Conduct industrial scale validation for our chiller models. Conduct sensitivity analysis for the developed models listed above. Conduct in-silico experiments via our validated models for scenario analyses - categorizing high risk scenarios during chilling. Furthermore,we plan to complete the majority of the tasks indicated under AIM #3: Identify the major determinants of pathogen spread and survival during the post-chill portioning (parts)/comminuted process as well as begin experiments under AIM #1: Quanitfy the fundamental mechanisms regulating pathogen transfer and inactivation during immersion scalding.

Impacts
What was accomplished under these goals? During this reporting period we focused on the immersion chilling section of AIM 2 (as listed above). Quantifiable prediction ofperacetic acid (PAA) levelchanges in terms of poultry chilling process parameters is essential for optimizing pathogen control and compliance strategies. We conducted experiments in our lab, and at a processing plant in Ohio, tracking water chemistry dynamics during simulated and industrial poultry chilling and acquired data from a poultry processing plant in Ontario, Canada. [Note that we also conducted lab scale experiments tracking water chemistry dynamics associated to free chlorine (FC) level changes during simulated chiller setups as a comparsion point for PAA level changes. Thesedata will be important for quantifying the relative decay rates of PAA versus FC in terms of organic load parameters]. Using chemistry and mathematics principles, we constructed novel models for PAA level dynamics during poultry chilling at both the lab and industrial scale. Importantly, we found that changes in total dissolved solids (TDS) measurementshavepredictive merit for peracetic acid (PAA) sanitizerdecay rates (in chiller water) during industrial poultry chilling operations. This result is significant because TDS can be measured quickly (in seconds)as opposed to chemical oxygen demand (COD), for instance, which takes hours to determine and did not predict PAA decay rates as accurately. This finding was presented at IAFP 2024 (poster) and has been discussed with processors in the US and in Ontario Canada as well as with researchers both at the USDA (Georgia) and OMAFRA. This result will aid processors with compliance and decision making towards optimizing sanitization during immersion chilling. Given chiller tank configurations, and water recirculation and reuse specifications used in many facilities, sanitizer concentrations may not be the same at various locations in the tank. To address this, we developed a novel mathematical model that captures spatial variations in sanitizer levels in chiller water under dynamic conditions. This model will be useful in conjunction with our PAA level model (above) as a tool to provide processors with vital information connecting chiller water recirculation and counterflow specifications (i.e. chiller setup design) to decision making for pathogen control during immersion chilling. A key aspect of tracking pathogen changes on chicken carcasses (and in the water) during immersion chilling is quantifying pathogen kill rates in terms of PAA levels, contact time, and other processing variables (like TDS levels in the water, etc.). Towards this goal, we conducted lab scale experiments to determine the shed rate of Salmonella from poultry carcass surfaces, the kill rate of Salmonella in chiller water via PAA, and the kill rate of Salmonella on carcass surfaces via PAA, during simulated chilling conditions. Initial analyzation of this data indicates a reduced kill rate of Salmonella on carcass surfaces versus in chiller water. We are in the process of using this data to inform our model building and parameterization to help characterize the transfer and inactivation of Salmonella during the chilling process.

Publications

• Type: Journal Articles Status: Under Review Year Published: 2024 Citation: Spatial characterizations of bacterial dynamics for food safety: Modeling for shared water processing environments
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Spatial modeling of the poultry chilling process: impact of water recirculation and counterflow on E. coli and Campylobacter dynamics