Modeling and Control of Food Processing Systems

NON-TECHNICAL SUMMARY: Modeling becomes an important approach to a diversity of problems encountered in the food industry. Models will allow for optimization of food processes, resulting in better process control. Thus, product development and processing may be improved, with increased process efficiency. As a result, food quality will be improved, with decreased health risks and increased consumer satisfaction. Escherichia coli O157:H7 is clearly a public health concern, since this microorganism has been associated with foodborne outbreaks from consumption of spinach, lettuce, and other leafy vegetables. Since current production and processing practices cannot ensure pathogen-free fresh and fresh-cut produce, effective food safety interventions are needed for implementation throughout the production, processing, and distribution of these foods. On August 22, 2008, the Food and Drug Administration (FDA) published a final rule that allows the use of ionizing radiation to make fresh iceberg lettuce and fresh spinach safer and last longer without spoiling. Many researchers have shown that irradiation kills pathogens or markedly reduces pathogen counts. We at Texas A&M University have established a sound research program in food safety engineering with emphasis on the application of electron beam irradiation. However, there is still work to do, since a bag of baby spinach leaves may not receive the dose in a uniform manner, leaving some parts of the food untreated. We are confident our intervention strategy will provide successful treatment of fresh and fresh-cut produce. The overall objective of this proposal is to develop an integrated protocol for improved pathogen inactivation at maximum retention of fresh and fresh-cut produce quality attributes. The central hypothesis for the proposed research is that ionizing radiation, if it is applied correctly and in combination with dose-reduction strategies, such as anti-microbial agents (cinnamaldehyde, eugenol, etc.) and/or modified atmospheric packages, is the best option. Additionally, a quantitative assessment of both the expected benefits and expected costs of the various irradiation technologies in a risk-analytic framework can provide support investments in these technologies. We plan to test the central hypothesis and accomplish the overall objective of this proposal by pursuing the following two specific objectives: (1) Determine the best dose-reduction strategies to combine with irradiation to treat fresh and fresh-cut fruits and vegetables (2) Establish the most cost effective technology evaluated in (1), using quantitative risk analysis approach

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APPROACH: Microorganisms. Stock cultures of pathogenic strains of E. coli O157:H7, Salmonella and Shigella sonnei will be grown by inoculation of 100ìl stock culture into 10ml sterile trypic soy broth (TSB). The resulting working culture will have a concentration of approximately 10e9 cfu/ml. Produce commodities. Fresh melons (Cucumis melo L.), spinach (Spinacea oleracea), and cilantro (Coriandrum sativum) will be purchased from local markets the day prior to the experiments. They will be washed and cut before use. Statistical analysis. The surviving population for each treatment will be compared with that of its respective untreated control using analysis of variance (ANOVA) using data pooled from the three plates for each of the three replications. Dosimetry: Monte Carlo simulation will be used to calculate dose distribution. The calculated dose distribution (from the radiochromic films) will be compared with the simulated data as for the leafy vegetables. Irradiation-tests. Electron-beam experiments will be performed using both a vertically mounted 10-MeV (19 kW) linear accelerator (LINAC) and a 5-MeV X-ray LINAC. Irradiation doses of 0.2, 0.5, 1, 2, and 3 kGy will be considered in this study. Radiosensitization using Antimicrobial Films. Effectiveness of natural compounds (cinnamaldehyde, eugenil, garlic extract, propolis extract, and lysozyme) incorporated into Mylar (polyester film)/-carrageenan) films against the target pathogens will be tested using a mixture of multiple strains microorganisms. Microencapsulation: The inclusion complex will be prepared and the minimum inhibitory concentration (MIC) of the active compounds against the test pathogens will be determined using the broth dilution method (Kim and others 1995). Modified Atmosphere Packaging under Irradiation. Produce will be prepared and inoculated with working cultures of each pathogen as described before. Two modified atmospheres will be tested besides air, pure oxygen (100% O2) and N2:O2 (1:1). A study of the synergistic effect of ionizing radiation, antimicrobial agent, and atmosphere will be conducted. The best packaging configuration will be determined by carrying out standard analyses of film properties. To fully understand and support investments in new technologies for food processing, such as irradiation, and dose-reduction technologies, requires a quantitative assessment of both the expected benefits and expected costs of these technologies in a risk-analytic framework. Such a framework necessitates a system-based approach that identifies and quantifies risks at each stage of the food supply chain, from harvest and production through consumer handling. Moreover, such a framework must include not only hazard data, but cost and food quality data as well. Within this framework, one can develop quantifiable measures of performance (e.g., means and quantiles of pathogen population distributions, operational costs (personnel and equipment), maintenance costs, food quality indices, etc.) that are modulated at each stage of the food supply chain.