The long-term goal of this proposed research effort is to improve food safety and quality of fresh and minimally processed fruits and vegetables by developing a ClO2 gas decontamination technology for the produce industry under approved regulatory status. <P>
The specific objectives are to: <OL> <LI> Determine the kinetics and efficacy of ClO2 gas on the inactivation of pathogenic bacteria (L. monocytogenes, Salmonella spp., and E. coli O157:H7) using a laboratory treatment system on selected fruits and vegetables, including sprouts, cantaloupes, oranges, strawberries, lettuce, and tomatoes. Additionally, non-pathogenic surrogates will be selected for use as a processing evaluation tool in a miniaturized tunnel ClO2 decontamination system <LI> Design, develop, and evaluate a miniaturized continuous tunnel ClO2 gas treatment system for reducing microbial pathogens on produce. <LI>Determine the effects of ClO2 gas treatment on produce quality and chemical safety of selected whole fruits and vegetables using the continuous tunnel ClO2 treatment system<LI> Develop a series of outreach, extension, and industrial programs to assist in transferring the technology to the produce industry and other interested parties.
NON-TECHNICAL SUMMARY: Numerous outbreaks of foodborne pathogenic infections have been associated with fresh and minimally processed produce, such as green onions (Hepatitis A), lettuce (E. coli O157:H7, Listeria monocytogenes), sprouts (E. coli O157:H7), cantaloupes (Salmonella spp.), and tomatoes (L. monocytogenes). Improving produce safety has been challenging for regulatory agencies and the produce industry due to low effectiveness (<2 log reduction) of current decontamination treatments, such as washing with chlorinated water and other aqueous sanitizers. Research is needed to determine bacterial inactivation kinetics, efficacy data on other high-risk produce models, quality effects, and ClO2-related by-products in/on treated produce. The long-term goal of this proposed research effort is to improve food safety and quality of fresh and minimally processed fruits and vegetables by developing a ClO2 gas decontamination technology for the produce industry under approved regulatory status. In this study, we propose to further study efficacy of chlorine dioxide gas by: a) designing, developing, and evaluating a miniaturized continuous tunnel ClO2 gas treatment system for reducing microbial pathogens on produce, b) determining the effects of ClO2 gas treatment on produce quality and chemical safety of selected whole fruits and vegetables using the continuous tunnel ClO2 treatment system, and, c) developing a series of outreach, extension, and industrial educational programs to assist in transferring the technology to the produce industry and other interested parties. <P>
APPROACH: Whole sprouts, cantaloupes, oranges, strawberries, lettuce, sprouts and tomatoes will be selected as model systems. Targeted pathogenic microorganisms will be spot or dip inoculated with levels of 106-7 cells/cm2 or g fresh weight on the surface of whole samples and then treated with different concentrations (0.1 to 6 mg/l) of ClO2 gas to achieve a goal of 3-5 log reduction using a laboratory continuous flow treatment chamber that we will design and develop. Efficacy of ClO2 gas on inactivation of these target microorganisms will be determined based on microbial log reduction data after treatments and reported as D-values and Z-values. The target microorganisms will include Escherichia coli 0157:H7, Listeria monocytogenes, and Salmonella spp. ClO2 gas will be generated using a laboratory and a pilot scale generators or the automated Mindox-M ClO2 gas generator/monitor unit using 0.5-4% chlorine gas in nitrogen. Attachment of target pathogens to the surfaces of selected commodities will be investigated using scanning electronic microscopy (SEM) and viability of target pathogens after ClO2 gas treatment will be visually studied using confocal laser scanning microscopy (CLSM). Non-pathogenic surrogates (with equal or more resistance compared to pathogens) will be identified to evaluate ClO2 gas treatment on a miniaturized industrial scale system. Optimized ClO2 gas treatment combinations (gas concentration and treatment time) will be selected and validated for a target of 3-5 log kill (non-pathogenic surrogates) using the tunnel system. Texture changes after ClO2 gas treatment and over storage time will be determined using an Instron testing machine. Color will be measured using a LabScan XE Hunter Colorimeter. Oxidation of pigments by low concentration of ClO2 may have little change of color. Vitamin C will be determined by the 2,6-dichlorophenol indophenol titration method. Vitamin A will be determined by a spectrophotometric method. Each product immediately after ClO2 gas treatment and/or over storage time will be washed with MQ water and the content of oxychloro compounds in the washing liquid will be analyzed using the amperometric method and ion chromatography.