Sep. 1, 2008 - Aug. 31, 2009Award Number
Center for Produce SafetyAmount Awarded
Alejandro Castillo, Ph.D.
Texas A&M University
Cisneros-Zevallos, L., Mattina, M., Dickson, J.Summary
While the application of Good Agricultural Practices (GAP) seems to be effective at preventing the introduction of bacterial pathogens in produce in most cases, other factors not yet understood may favor contamination in some instances. Therefore, contaminated fruits and vegetables may reach consumers before the time it takes to understand the factors that promote the presence, spreading or magnification of pathogens in crops along the processing chain. This makes it necessary for consumers to rely on a treatment that ensures the safety of fruits as well as meeting the government's nutritional goals which include an increase in the consumption of fresh fruits and vegetables. Even though electron beam (e-beam) irradiation can reduce or eliminate the pathogens, the quality of the product may be affected. To develop meaningful e-beam treatments it is imperative to determine the D-value of Salmonella, Escherichia coli O157:H7 and hepatitis A virus (HAV), which are the 3 foodborne pathogens that most frequently are found to cause outbreaks of foodborne diseases linked to produce. It is also paramount to determine the maximum dose that each commodity can withstand without physical damage. The effect of postharvest irradiation of produce on the alteration, if any, of produce-borne agrochemicals is also important in evaluating the consequences of e-beam irradiation of produce. Therefore, the objectives of this project are: to determine D-values for Salmonella and E. coli O157:H7 on lettuce, spinach, fresh-cut cantaloupes, fresh-cut tomatoes, and of HAV on green onions and fresh strawberries; to determine the maximum dose of e-beam energy that can be irradiated onto each of these commodities without changes in firmness, color, respiration rate, and overall microbiological counts; and to determine the effect of post-harvest e-beam irradiation on the molecular stability of produce-borne agrochemicals. For determining D-values, produce will be spiked with the selected pathogens and then subjected to e-beam irradiation at increasing doses. Plate counts will be conducted on samples of irradiated produce. HAV enumeration will be conducted using the Virus Plaque Assay. Non-inoculated batches of the same commodities will be irradiated at increasing doses up to 5 kGy and subjected to instrumental analysis including firmness, color and respiration rate tests, and microbiological analysis including aerobic plate counts, lactic acid bacteria and yeasts and molds counts. The final objective will be achieved by testing produce from crops that have field-incurred agrochemicals to determine the pre- and postirradiation chemical signatures of these compounds using mass spectrometry interfaced to both gas and liquid chromatography. This study should permit collecting useful data for further development of strategies for reducing pathogens in fresh and fresh-cut produce after GAP and Good Manufacturing Practices are applied.