Use of Ozone to Enhance the Safety of Produce

NON-TECHNICAL SUMMARY: Fresh produce is often contaminated with serious pathogens. The purpose is to minimize the risk of foodborne diseased resulting from the consumption of fresh produce.

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APPROACH: Fresh produce, including lettuce, cabbage, broccoli and peppers, are to be tested in this study. These products are prepared and washed using procedures that simulate commercial processing. Standard chlorine wash is compared to ozone treatments. Ozone treatments that are superior to chlorine, in eliminating natural microbial contaminants and preserving product quality, are chosen for further investigation and optimization. Challenge studies will be carried out to optimize ozone usage and maximize the efficacy of the treatment against known spoilage and pathogenic microorganism. Products are inoculated with selected spoilage (e.g., Pseudomonas fluorescens) and pathogenic (e.g., Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella spp.) bacteria and treated with ozone. Inactivation Kinetics are investigated and optimum dosages (concentration and time) are concluded. Data are subjected to analysis of variance and mean comparisons using SAS statistical programs. At the conclusion of the project, recommended ozone treatments are made available to the produce industry. The project will be carried out in the food microbiology laboratories of the Department of Food Science and Technology. In case of pathogenic challenge studies, Biosafety Level II laboratories will be used.

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PROGRESS: 2001/07 TO 2006/09<BR>
Minimally-processed fresh-cut produce (FCP) is implicated in foodborne disease outbreaks. Chlorine is currently used by the FCP industry to reduce microbial contamination; however, the use of this sanitizer raises safety and environmental concerns. Ozone could be an alternative to chlorine due to its high sanitization power and environment-friendly attributes. The objective of this study was to design and evaluate a pilot-scale washer that uses ozone to sanitize fresh-cut lettuce. A pilot-scale continuous washing system, allowing adjustments to optimize the mechanics of the process, was designed. The capability of ozone to sanitize fresh-cut lettuce was tested using a two-step washing procedure. Whole lettuce heads (150 lbs) were cut manually into pieces (2x3 cm) and pre-washed with water containing 0.1% tetra-sodium pyrophosphate (TSPP) at 5 lbs-lettuce/min feeding rate and 13.2 gal/min water flow rate. Samples were drained and divided into equal amounts for subsequent washings using either tap water or ozonated tap water (10 ppm maximum delivered concentration) with sample collections at 5, 10, 15 and 20 min. Processed lettuce was tested for mesophilic aerobic and psychrotropic microbial counts. Results indicated that pre-washing lettuce with TSPP, followed by washing with ozonated tap water effectively decreased an initial population (~105 CFU/g lettuce) of mesophilic aerobic and psychrotrophic microorganisms by >1 log for all treatment times. On the other hand, the initial population of natural microflora in cut-lettuce treated with the TSPP and subsequently washed with tap water alone remained unchanged.
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IMPACT: 2001/07 TO 2006/09<BR>
These experimental trials satisfactorily simulate an industrial sanitizing procedure and demonstrate the effectiveness of ozone and its potential as an alternative to chlorine.