Quality and Safety for Thermally Processed Foods

NON-TECHNICAL SUMMARY: The quality of thermally processed foods integrate with the process efficiency and determine the process design and operation. The efficiency of a processing schedule depends on an improved yield at a reduced cost. The results of this project should help commercial processors optimize the design and operation of their thermal processes in terms of profitability and safety. The information is important for risk assessment and the development of HACCP plans for thermally processed foods.
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APPROACH: The primary focus of this research effort is the correlation of food quality and safety. The proposed approach is to carefully investigate thermal pathogen destruction as related to time-varying process conditions during processing. Various commercial products will be studied. Salmonella and Listeria will be used. Studies will be conducted in lab- and pilot-scale processing.

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PROGRESS: 2000/10 TO 2006/09<BR>
Listeria monocytogenes is considered to be one of the most hazardous microbes that can cause a serious infection in human bodies. CDC estimated that 2,500 serious illnesses and 500 deaths with listeriosis occur in the US annually. The economic impact of illness due to foodborne pathogens has been estimated as high as ten billion dollars annually. A USDA survey showed that 1-10 per cent of retail ready-to-eat food products were contaminated with L. monocytogenes. Food producers need more effective methods for eliminating pathogen contamination of ready-to-eat foods while maintaining quality characteristics important to consumers. The objectives of this project are: (1) conduct experiments to determine the effect of hot water and steam treatment of packaged read-to-eat poultry products with various sizes and shapes on the inactivation of Listeria; and (2) develop a predictive model of heat and mass transfer with pathogen kinetics to predict pathogen inactivation as a function of time, moisture, and temperature. In this project, fully cooked chicken products including chicken breast, wings and drumsticks were surface inoculated with non-pathogenic, heat-resistant Listeria innocua at an initial level of approximately 10 to seventh power CFU/g. Individual inoculated chicken products were vacuum packaged followed by thermal treatment in a water bath at 60, 70, 80, and 90 degrees C for different treatment times (20 s to 30 min). The cell number of L. innocua in chicken products after hot water treatment was determined using cultural plate count method with modified Oxford (MOX) agar overlaid with tryptic soy agar (TSA). A 24 h enrichment procedure at 37 degrees C was followed to check the survival of L. innocua. Our results showed that when heated at 60, 70, 80, and 90 degrees C, the Listeria reduction in log CFU/g was 5.0 after 12 min, 3.4 after 4 min, 2.6 after 2.3 min and 2.8 after 2 min, respectively. Enrichment data indicated that the 7 log (CFU/g) reduction of L. innocua in chicken breast products occurred at 30, 10, 7 and 5 min for hot water treatment at 60, 70, 80, and 90 degrees C, respectively. A primary model was developed based on the Weibull function to predict the survival of L. innocua at each heating temperature. The root mean square errors (RMSE) of the model and plot of predicted versus observed data showed a good fit and prediction of the model. The results indicated that post-package hot water treatment could be an effective intervention strategy to control Listeria in RTE poultry products. The results from this study would be useful for poultry processors to evaluate post-cooking treatment of RTE poultry products and provide consumers with safer foods. We completed a computational simulation software, "ThermalSimu", to provide a convenient way for researchers and food processors to use the predictive model for its applications to the research and industrial practice of ensuring food safe and quality. The software "ThermalSimu" is completed and ready for use.
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IMPACT: 2000/10 TO 2006/09<BR>
Contaminated food is estimated to cause 76 million illnesses, 325,000 serious illnesses resulting in hospitalization, and 5,000 deaths in the United States each year (CDC, 1999). The USDA Economic Research Service estimates a total of $6.9 billion per year for medical costs, productivity losses, and costs of premature deaths for diseases caused by five foodborne pathogens (USDA/ERS, 2002).. The projected cost in relating to L. monocytogenes alone was estimated at $233 million per year in the United States. The low infectious dose required for pathogens dictates that successful prevention must focus on reducing, controlling, or eliminating the bacterial pathogens with a HACCP (hazard analysis and critical control point) plan. The results from this research will be applicable to many different thermal food processes and a variety of food products for which pathogen contamination is a significant issue. The results from this research will help to reduce food-borne illness outbreaks and product recalls among ready-to-eat foods, which have cost hundreds of millions of dollars in the industry and forced many small and large U.S. companies out of business.