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Control of Food-Borne Pathogens in Pre-and Post-Harvest Environments


<ol> <li> Develop or improve methods for control or elimination of pathogens in pre-and post harvest environments including meat, poultry, seafood, fruits and vegetables and nutmeats. <li> Develop and validate mathematical modeling to gain understanding of pathogen behavior in macro- and micro-environments. <li> Investigate factors leading to the emergence, persistence and elimination of antimicrobial resistance in food processing and animal production environments. </OL> <P> Outputs: Validated decontamination methods that can be used by the fruit, vegetable, seafood, meat and poultry industry to enhance the safety of their finished product Outreach/extension education and training materials for regulatory personnel, producers, processors, consumers, extension agents Overall enhanced food safety for consumers Outcomes or Projected Impacts: Enhanced safety of fruit, vegetable, seafood, meat and poultry products Increased understanding of food safety measures by regulatory personnel, producers, processors, consumers, extension agents Overall enhanced food safety for consumers

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NON-TECHNICAL SUMMARY: Traditional microbiological methods are time-consuming and yield delayed results which are of limited value in the fast-paced food industry environment for assessing microbial growth. Expensive rapid enumeration techniques have been developed; but they need a large number of viable bacteria to yield a detectable response. Mathematical model have been developed to describe the growth of pathogens in food systems under various temperature profiles. Heat transfer model are developed to predict temperature histories for a wide variety of foodstuffs under numerous heating and cooling scenarios. From a food safety perspective, the effective combination of engineering heat transfer modeling and microbial growth modeling offers a powerful tool for the accurate prediction of microbial population dynamics under time-varying temperature scenarios. Our current focus is on assessing risk of Salmonella Enteritidis (SE) in shell eggs during cooling and storage by integrating heat transfer and microbial growth models. 4. Results from this study will improve the ability of egg and egg processing industry in evaluating the risk of Salmonella Enteritidis and minimize the risk, with eventual reduction in foodborne illness due to Salmonella Enteritidis from eggs and egg products.


APPROACH: Objective 2: Develop and validate mathematical modeling to gain understanding of pathogen behavior in macro- and micro-environments. Chilling studies: Temperature profiles of carcasses, meat products (primal and subprimal cuts) and pallets of egg cases at different locations and different depths will be measured under various chilling and heating conditions. Mathematical models will be developed to describe the chilling and heating rates using finite element analysis and computational fluid dynamics. These developed models will be validated in processing establishments using real-life scenarios. Microbial predictive models (e.g. Baranyi's model and modified Ratkowsky's equation) will be developed using growth kinetics derived from microbial growth experiments at different temperatures. These models will then be integrated with the mathematical models describing chilling of meat carcasses, egg cases and meat products to generate growth of food borne pathogens on the carcasses, eggs, or meat products. These models will be validated using industry chilling parameters. A model carcass chilling system (wind tunnel) has been fabricated at the University of Nebraska to simulate the chilling systems being used in the industry. This model system has controls for air velocity, temperature, and relative humidity. Humidity in the system is created by atomizing chilled water in the chamber. While majority of the industry uses intermittent water sprays to aid in chilling and prevent moisture loss, similar conditions can be created through atomizing chilled water for controlling humidity. Analysis of data collected during simulations will be used to verify mathematical chilling models for various meat products. Modeling for egg safety: Salmonella Enteritidis (SE) contamination of poultry eggs is one of the major human health concerns worldwide. The risk of SE from shell eggs can be significantly reduced through quick refrigeration after the eggs are laid and storage under safe temperature conditions. Predictive models for the growth of SE in egg yolk under varying ambient temperature conditions will be developed. The dynamic model will then be validated at several temperatures. A two-dimensional axisymmetric transient heat transfer model will be developed to predict temperature distribution in egg during cooling. The wind tunnel will be used to validate the heat transfer model by monitoring the central temperature of eggs during chilling with different air velocities. The heat transfer model will then be integrated with the microbial growth model and will be validated under several cooling scenarios.

Thippareddi, Harshavardhan; Subbiah, Jeyamkondan
University of Nebraska - Lincoln
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