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A Multidisciplinary Approach to Develop a Safe and Effective Chlorine Dioxide Gas System for Controlling Pathogens in the Produce Industry


The main focus of this project is the engineering design and evaluation of a commercial scale chlorine dioxide (CD) treatment system that the food industry can use within the processing plant environment to improve produce safety and quality. <P> The specific, integrated outreach and research objectives are to: <OL> <LI> establish and engage a stakeholder advisory group to better identify key industry needs and operating parameters<LI> design and construct a produce treatment system<LI> evaluate the treatment system's effects on produce safety<LI> evaluate the treatment system's effects on produce quality<LI> develop extension-based, outreach program to transfer the technology to the industry </OL> In the first quarter, focus will be on forming and meeting with the stakeholder advisory group to identify specific industry needs. The main efforts during the remainder of the first year include the design and construction of the prototype chlorine dioxide treatment system(s). The evaluation of the prototype system(s) will begin as soon as construction is complete (ideally in the 4th quarter of year 1) and continue into the first half of year two. The second half of year two will focus on creation and delivery of an extension-based program for the produce industry and final project reporting. Outputs from the project include: experiments to determine the effectiveness of CD gas treatment on controlling pathogens on produce surfaces (tomatoes, cantaloupes strawberries, and green peppers will be used as the models) and the impact of CD treatment on product quality in a commercial setting; a prototype commercial-scale treatment system; and a workshop for the produce industry on the safe and effective use of CD gas. The system to be developed and tested during this project is expected to provide an effective method for obtaining a 5 log reduction of pathogens on produce surfaces without any detectable changes in sensory quality.

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NON-TECHNICAL SUMMARY: Today, produce safety is the number one concern of the Food and Drug Administration (FDA) and has always been a top priority for the fruit and vegetable industry from production through consumption. The overall goal of this project is to improve safety and shelf-life of fresh and minimally-processed fruit and vegetables through the effective application of a microbial reduction treatment system using chlorine dioxide (CD) gas. Since chlorine dioxide is commonly used to treat drinking water and is approved in aqueous form to treat poultry, meat, and fruits and vegetables, we anticipate that FDA approval of this technology should be straightforward. This project will provide a critically needed intervention strategy to control microorganisms that pose safety hazards in fresh produce. Past research at Purdue with CD gas has focused on determining treatment conditions required to inactivate pathogens in laboratory-based systems. The main focus of this project is the engineering design and evaluation of a commercial scale system that can be used within a food plant environment. Our approach is to better identify industrial needs through a stakeholder group, determine important operational procedures of a CD treatment system, and evaluate potential food safety and quality impacts of the treatment on produce. Initially, a stakeholder advisory group will assist with the operational criteria necessary for successful commercial implementation. Once the system is constructed, we will evaluate its effectiveness for inactivation of key produce pathogens (E. coli O157:H7, Salmonella, L. monocytogenes), using a non-pathogenic surrogate organism, on four different produce surfaces (tomatoes, strawberries, cantaloupes, peppers). To further ensure safety, chemical residues will be measured to ensure they are within acceptable limits. Additional produce quality measurements will be made to determine the effect on product shelf-life. Successful implementation of this technology will have a profoundly positive economic impact on producers and distributors in the specialty crops industry. Consumers should be positively impacted by improved safety of fresh and minimally-processed produce.


APPROACH: Produce will be spot inoculated with a surrogate organism (Hafnia alvei) which has been previously determined to have higher resistance to CD gas compared to targeted pathogens (salmonella, E. coli, and L. monocytogenes). The inoculated produce will be placed into their packaging containers after drying for two hours and treated in the prototype CD system at > 75 percent relative humidity and CD gas ranging from 0.3 to 5.0 mg/l. Different treatment times will be selected to achieve a 5 log reduction of the surrogate. The surviving bacterial populations after treatment will be determined using standard enumeration methods. Chemical residuals (CD, chloride, chlorite, and chlorate) will also be determined on triplicate samples by rinsing the produce with water and testing rinse samples using EPA approved methods (i.e. ion chromatography method 300.0). From pervious work, we expect the chemical residuals should be very low and at least as low as the maximum contaminant level (MCL) allowedfor drinking water, i.e. 0.8 mg/l for chlorine dioxide and 1.0 mg/l for chlorite. Finally, produce quality (color, microbiological counts for mesophilic bacteria, psychrotrophic bacteria, yeasts and molds) will be evaluated using standard methods for up to twice the anticipated product shelf-life. After completion of the project, a 1-day workshop will be assembled that focuses on the use and effectiveness of CD gas systems as an antimicrobial treatment for produce. This workshop will include the safe generation and use of chlorine dioxide gas, impacts on produce quality, treatments for pathogen inactivation on produce, and safe use in processing facilities. The success of the project will be evaluated based on the CD gas treatment system's effectiveness with acceptable residuals, FDA approval of the use of CD gas on produce, and increased interest or adoption of the technology by the industry.

Linton, Richard; Morgan, Mark
Purdue University
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