Source: PURDUE UNIVERSITY submitted to
A MULTIDISCIPLINARY APPROACH TO DEVELOP A SAFE AND EFFECTIVE CHLORINE DIOXIDE GAS SYSTEM FOR CONTROLLING PATHOGENS IN THE PRODUCE INDUSTRY
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0216049
Grant No.
2008-51180-19580
Project No.
IND011650G1
Proposal No.
2009-01236
Multistate No.
(N/A)
Program Code
SCRI
Project Start Date
Sep 1, 2008
Project End Date
Aug 31, 2012
Grant Year
2009
Project Director
Morgan, M. T.
Recipient Organization
PURDUE UNIVERSITY
(N/A)
WEST LAFAYETTE,IN 47907
Performing Department
FOOD SCIENCE
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.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
40%
Developmental
60%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
5011420202010%
5011420302010%
5011460202010%
5011460302010%
5011461202010%
5011461302010%
7121122202010%
7121420202010%
7121460202010%
7121461202010%
Goals / Objectives
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. The specific, integrated outreach and research objectives are to: 1. establish and engage a stakeholder advisory group to better identify key industry needs and operating parameters, 2. design and construct a produce treatment system, 3. evaluate the treatment system's effects on produce safety, 4. evaluate the treatment system's effects on produce quality, and 5. develop extension-based, outreach program to transfer the technology to the industry. 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.
Project Methods
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.

Progress 09/01/08 to 08/31/12

Outputs
OUTPUTS: Over the project period, significant progress has been made towards the commercial application of chlorine dioxide (CD) gas for direct treatment of fresh produce. Initial experiments were performed in the laboratory to evaluate the effectiveness of CD gas when treating produce for up to 10 min. Interaction with an advisory group from industry identified that 10 minute treatment times were too long for applications to on-line processing of fresh produce, so further experiments were performed to shorten the treatment time and evaluate effectiveness against surface pathogens, extended shelf-life, and chemical residues using radio-labeled CD gas. Most of these significant results have already been published in the scientific literature while others are still pending. Based on these results, a novel CD gas treatment system was designed and constructed for treatment of produce(tomatoes was the first application with our collaborator, a large Midwest tomato packer/distributor). The CD treatment system consists of an all-stainless steel, gas-tight tunnel with a conveyor belt and drive system, controls for conveyor speed and gas containment, and a CD gas generation system for control of concentration and operation safety. The key engineering advancement in the system design is the mechanism for containing gas inside the treatment tunnel with zero fugitive emissions while still allowing produce to enter and exit on the conveyor system. The design was also made fail-safe to minimize the chances of operator exposure to CD gas in the event of a power failure. The entire treatment system is self-contained in a sea container which can be easily transported to locations for testing and demonstration. PARTICIPANTS: This project was performed in collaboration with Michael Burke and Dan Plaatje, Enerfab, Inc., Cincinnati, OH; and Bill Piper, Grant Co. Foods, Dry Ridge, KY. Enerfab provided the major support for design and construction of the CD gas treatment system and CD gas generator. Grant Co. Foods provided the end-user perspective and the opportunity to perform testing in their facility. TARGET AUDIENCES: Produce industry safety specialists are the target audience. More interest and open discussions have been achieved through commodity groups and local meetings with selected company representatives. Both Enerfab and Purdue have created websites including applications of chlorine dioxide and its characteristics, lists of recent publications on produce applications, and EPA approved used of chlorine dioxide. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The results from experiments to treat produce with CD gas for short times (< 3 min) have successfully demonstrated that up to 5 log reductions in Salmonella, E. coli, and Listeria can be obtained. Results also showed that no significant quality changes were visually observed in the products. Shelf-life evaluations showed that treated samples had significantly delayed mold growth and spoilage which is indicative of economic benefits to industry in addition to the safety aspects. The only aspect of CD gas treatment for fresh produce that is still missing is regulatory approval from EPA (and FDA for processed products) for use. Data was generated on several produce items (melons, tomatoes, strawberries, etc.) and one application was submitted by our collaborator to EPA for review, which is an 18 month process. Data showed that residues on most produce items were below the regulatory levels for drinking water. Based on these data, more EPA approval applications are planned by our collaborators. Once this regulatory hurdle is overcome, further demonstration and dissemination of the use of CD gas for control of pathogens on fresh produce will be performed. Plans have been made to display the CD gas treatment system at future industry trade shows to demonstrate the technology. After the recent outbreak of salmonella due to melons, a presentation to major melon producers in southern Indiana was held to describe the technology and receive their feedback on operating parameters, system design and potential for adoption. However, the main focus quickly became regulatory approval. Another follow up meeting is scheduled for December, 2012 and similar meetings with fresh produce distributors and producers are planned in the future. The results of this project will continue to move the application of CD gas for improvement of fresh produce safety forward towards commercialization. Only economic evaluations for each adoption scenario and regulatory approval are needed to effectively promote this technology.

Publications

  • Trinetta V, Morgan M, Linton R. 2012. Use of chlorine dioxide gas for the postharvest control of Alternaria alternata and Stephylium vesicarium on Roma tomatoes. (In preparation).
  • Trinetta V, Linton R, Morgan M. 2012. High-concentration-short time chlorine dioxide gas application for the specialty crops industry: the case of Roma tomatoes (Lycopersicon esculentum), cantaloupes (Cucumis melo ssp. melo var. cantaloupensis) and strawberries (Fragaria x ananassa). Food Microbiology. (pending).
  • Trinetta V, Vaid R, Xu Q, Linton R, Morgan M. 2012. Inactivation of Listeria monocytogenes on Ready-to-Eat food processing equipment by chlorine dioxide gas. Food Control 26, 357-362.


Progress 09/01/10 to 08/31/11

Outputs
OUTPUTS: Experiments were performed during this reporting period to assess residues on selected produce surfaces and to assess extension of shelf-life after chlorine dioxide (ClO2) gas treatment. Residues of ClO2, chlorite, chlorate, and chloride on seven different produce surfaces (tomatoes, oranges, apples, strawberries, lettuce, alfalfa sprouts and cantaloupe) after treatment with ClO2 gas were evaluated. A rinse procedure was used and water samples were analyzed by DPD and Ion Chromatography Method (300.0). This procedure, although not acceptable to EPA for approval, is sufficient as a screening test to determine which products are likely to have significant residues of concern. The results obtained in this research showed that detectable residual levels may be left after ClO2 treatments, especially in produce like lettuce and sprouts. On the contrary, tomatoes, oranges, apples, strawberries and cantaloupe were all found to have very low residuals when compared to the EPA acceptable levels for drinking water. Produce quality and shelf-life attributes after ClO2 treatment and during storage were evaluated on tomatoes, cantaloupe and strawberries. The same treatment (10 mg/l for 3 min) selected for the evaluation of ClO2 antimicrobial effectiveness against human pathogen was also used for produce shelf-life study. The samples were treated, packaged into plastic clamshells, wrapped in PVC films and stored at 25 deg C. At appropriate intervals, samples were analyzed for mesophilic and psychotrophic bacteria, yeast and molds, change in color and overall appearance. Treatments significantly (P<0.05) reduced initial microflora population: at the end of the shelf-life study treated microbial load was 2 log CFU/(sq cm) lower as compared to the untreated produce. ClO2 gas did not significantly (P>0.05) affect the skin color of treated produce during the storage; on the contrary, the green color of strawberries leaves was visibly and significantly compromised. After 21 days for tomatoes, 14 days for strawberries, and 7 days for cantaloupe, untreated controls had considerable visible mold growth, while produce treated with high-concentration-short-time ClO2 did not present any mold growth. In preparation for the final stage of this project, a treatment system consisting of a spiral conveyor was designed. Discussions with a local conveyor manufacturer are underway to get a system built to specifications for testing in a tomato packing facility. PARTICIPANTS: Mark Morgan worked closely with collaborators at Enerfab, Inc (Cincinnati, OH) in designing the chlorine dioxide gas delivery system and treatment chamber. Products directly from our collaborator, Grant county Foods (Dry Ridge, KY) were tested in a pilot scale treatment conveyor at Purdue. The postdoc, Valentina Trinetta, recently left Purdue for a job with a major chemical sanitation company. TARGET AUDIENCES: Food safety engineers and microbiologists. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Residue data measured from tomatoes using radio-labeled chlorine dioxide gas was submitted to the EPA as part of an application by our industry collaborator. If the data is accepted by EPA and determined to be of no health concern, approval to use ClO2 gas on tomatoes as a raw agricultural commodity may be forthcoming. Based on the residue data for other produce, it can be assumed that these low levels will not likely pose harm if consumed. However, since EPA does not officially have a tolerance established for residues on these products, either a petition for establishment of a tolerance or an exemption from tolerance will need to be made with EPA prior to commercially using chlorine dioxide gas on fresh produce. In addition, EPA will require data on any organo-chlorine byproducts that may have formed during the treatment (not measured in this study). If the assumption is valid that no byproducts remain inside or on the products after rinsing, residue levels suggest that chlorine dioxide gas has great potential as a sanitizer technology for fruits and vegetables products, without any significant risks of chemical residual for consumers' health. No experiments have shown that chlorine dioxide gas penetrates into the products, but further experiments are necessary to quantify any chemical reactions that may be occurring in the food products. Optimization of conditions for short-time-high-concentration treatment of produce will allow for the implementation of a commercial-scale system directly on a processing line within a tomato packing facility.

Publications

  • Trinetta V, Vaidya N, Linton R, Morgan M. Evaluation of Chlorine Dioxide Gas Residues on Selected Food Produce. Journal of Food Science, 2011. 76,1, T11-T15
  • Trinetta V, Vaidya N, Linton R, Morgan M. A comparative study for the effectiveness of chlorine dioxide gas, ozone gas and e-beam irradiation treatments for inactivation of pathogens inoculated on tomato, cantaloupe and lettuce seeds. International Journal of Food Microbiology, 2011, 146: 203-206
  • Trinetta V, Morgan M, Linton R. Chlorine dioxide for food decontamination. Submitted March 2011. In: Food decontamination: novel methods and applications. A. Demirci (ed). Woodhead Publishing, UK.
  • Trinetta V, M. Morgan, R. Linton, The Use of Chlorine Dioxide Gas to Control Alternaria alternata and Stemphylium vesicarium on Roma Tomatoes. Presented at IAFP Annual Meeting, Milwaukee, WI. August 2011.
  • Trinetta V, Linton R, Morgan M. Prevention of berries spoilage by chlorine dioxide gas treatments. Presented at IUFOST International Meeting, Cape Town (South Africa), August 2010. Trinetta V, Morgan M, Linton R. Inactivation of Salmonella on Roma tomatoes by high-concentration-short-time chlorine dioxide gas treatment. Presented at IAFP Annual Meeting, Anaheim, CA (USA), August 2010.


Progress 09/01/09 to 08/31/10

Outputs
OUTPUTS: During this project period, chlorine dioxide gas treatments for reductions in Salmonella, E. coli, and Listeria have been completed on cantaloupes, strawberries, and tomatoes using high concentrations and short times. These treatments less than 3 minutes could reduce the population of a Salmonella cocktail by 5 log/cm2, E. coli and Listeria 3 log/cm2 on produce surfaces. In preparation for testing a treatment system at a packing facility, data was also collected on a non-pathogen surrogate (Hafnia Alvei). This surrogate will be used to evaluate the effectiveness of a new treatment system in a packing plant. Results on tomatoes showed that the surrogate underwent similar log reductions to E. coli when treated at ~ 10 mg/l ClO2 for 3 minutes. Since our initial advisory panel discussion on the project advised that an extension of shelf-life for each product (in addition to pathogen reduction) would likely be necessary for the industry to adopt the technology, experiments were also run on two common spoilage molds found on tomatoes. Methods were developed to culture and test the effectiveness of ClO2 gas on these two molds, Alternaria and Stephylium. Effectiveness on both the spores and mycelium was evaluated on inoculated petri plates. Treatment with ClO2 at 10 mg/l for 1 minute resulted in a 2.5 log/cm2 reduction in each mold. Similar treatments on inoculated tomatoes, which were injured in order to get the mold to grow on the surface, resulted in significant extension of shelf-life for Stephylium inoculated tomatoes but no extension of shelf-life for tomatoes inoculated with Alternaria. A meeting with EPA officials was held to discuss the residue data collected by washing tomato surfaces and analyzing the rinse water for chlorite, chlorate, and chloride. EPA was not convinced that there was no residue still remaining in or bound to the surface of the tomatoes. Therefore, they suggested a radio-labeled chlorine test procedure to evaluate residues in the product itself. A presentation was made on our progress at the United Fresh Produce Conference in 2009. Attendance and interest was high. Producers and processors also inquired about the ability to control plant pathogens using this technology. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: The target audiences for this project is the produce industry and government regulators. Presentations to an industry conference and several companies have explained the technology and its benefits and limitations. It is clear that this technology is not appropriate for leafy greens, but has tremendous potential for other fruits, vegetables, and grains. PROJECT MODIFICATIONS: Two major changes have been made to the project which have added to the scope of the work. After submitting residue data to the EPA, it was determined that a significant effort (time and cost) was necessary to obtain sufficient residue data using the radio-labeled, 36Cl, procedure. We have contacted an ARS laboratory in Fargo, ND to assist in collecting data on tomato residue. This will significantly save on the costs. However, the lack of EPA approval based on potential residues has delayed our ability to test a system in a commercial facility (without disposing of the product). Residue data using this method on the other produce is likely beyond the scope of this projects budget. The second major change has been the addition of experiments to control the plant pathogens on tomatoes in an attempt to better understand the treatment parameters necessary to obtain extended shelf-life.

Impacts
All of the results from our experiments to date show potential for ClO2 gas treatments to effectively reduce human pathogens on the surfaces of selected produce with minimal residues and an extended shelf-life. Extension of produce shelf-life, in addition to improved safety through human pathogen control, would be a tremendous benefit to the industry. Every product that is discarded due to spoilage rather than consumed represents a huge amount of energy wasted during production, harvesting, transportation and storage. One week of extended shelf-life is considered a large benefit to the industry for many fresh products.

Publications

  • Trinetta, V. M.T. Morgan, R.H. Linton. 2010. Use of high concentration short time chlorine dioxide gas treatments for the inactivation of Salmonella enterica spp. inoculated onto Roma Tomatoes. Food Microbiology 27(8):1009-1015.


Progress 09/01/08 to 08/31/09

Outputs
OUTPUTS: The start of this project involved a meeting of a stakeholder advisory group to better identify the industry needs and operating parameters for a chlorine dioxide (CD) gas treatment system for product. One of the main results of the meeting indicated that EPA approval of CD gas for treatment of produce was a key milestone that would need to be achieved in order to test a system in a commercial facility. To this end, a consultant has been hired by our industry collaborators to pursue this approval process. Another main result of the meeting was that demonstrating an extension of shelf-life, in addition to the target pathogen reduction, was important for companies to consider adopting this technology. CD gas treatment experiments have been conducted on tomatoes as the first targeted application. To this end, Roma tomatoes have been treated with various gas concentrations (0 - 10 mg/l) for a range of times (0 - 10 min) at 75 percent RH and room temperature to determine the effectiveness on pathogens and extended shelf-life. After treatment with CD gas, tomatoes were rinsed with distilled water to detect residuals of chlorine dioxide, chlorite, and chlorate on the surfaces. A new chamber has been designed for boxed product in order to examine the effectiveness of CD gas treatment within boxes of tomatoes. Once challenge has been the effective exposure of all produce surfaces to the gas to achieve microogramism lethality. Both vacuum assistance and agitation of boxed produce is being studied to overcome this challenge. The alternative is to treat produce in a conveyor-type system prior to packing in a box. This treatment option requires the high gas concentrations for short times in order to be acceptable to our industry partners. PARTICIPANTS: A seven member panel of stakeholders included representatives from USDA ARS, FDA, the Fresh Produce industry and CD gas technology and equipment industry. The PI's Dr. Morgan, Dr. Linton, and Mr. Burke have been involved in the testing of tomatoes and design of the new treatment system. A post-doc Dr. Valentina Trinetta has been the main person running experiments with the help of several undergraduate students. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Currently a new treatment chamber is under construction by our industry partner. Results from the treatment of tomatoes with high concentrations of CD gas (8-10 mg/l) for less than 180 s, has shown promise in reducing inoculated levels of salmonella (up to 5 log reduction), mesophilic bacteria ~ 3 log* and yeast and molds ~ 2 log* (*these were levels naturally present on the tomatoes). No significant differences in tomato color between treated and non-treated samples were detected using a hunter colorimeter over 28 days of storage. However, the first occurrence of spoilage for the treated samples was visible approximately 7+ days later than for the controls. This result, although preliminary, indicates that the CD gas treatment at the tested levels could extend shelf-life of tomatoes by more than 7 days at room temperature and humidity. Results from the measurements of residual chlorine dioxide immediately after treatment was only significantly higher than the control samples for the CD gas treatment of 10 mg/l for 180 s. After 24 h, the residuals for all the treated samples were not significantly different than for the untreated samples. This result indicates that the CD gas treatment leaves no significant chemical residue on the tomatoes after 24 hrs.

Publications

  • No publications reported this period