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Standardization of Methods for Determining the Efficacy of Raw Fruit and Vegetable Sanitizers.

Beuchat, Larry
University of Georgia
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End date
  1. Develop a standard method(s) for inoculating the surface of six types of raw fruits and vegetables with three pathogenic bacteria.
  2. Determine the effects of time between inoculation and retrieval on viability and recoverability of pathogens.
  3. Develop a standard method(s) for evaluating the effectiveness of sanitizers to remove or kill pathogenic bacteria on the surface of raw fruits and vegetables.
  4. Validate these methods in collaborating laboratories (Center for Food Safety, University of Georgia and Department of Food Science and Technology, University of California, Davis).
More information
The effects of three inoculation procedures (dipping, spraying, spotting) and two inoculum drying procedures on the efficacy of chlorinated water to remove or inactivate three bacterial pathogens on six raw fruits and vegetables will be determined. The performance of methods under practical conditions will be evaluated. Research will focus on providing information necessary to establish a standard inoculation method(s) for performing sanitizer efficacy tests. During the first 14 months of the project, work at the University of Georgia will focus on vegetables and work at the University of California will focus on fruits. During the last 10 months of the study, the focus in each laboratory, in terms of produce type, will be reversed for the purpose of validation of the method(s). It is anticipated that different combinations of inoculation procedure and attachment time may be more suitable for various types of produce and test pathogen.

Outbreaks of illness associated with raw fruits and vegetables in the U.S. have occurred with increased frequency in recent years. Contamination of raw fruits and vegetables can occur at any of several points from the field through the time of consumption. Given sufficient time at an appropriate temperature, some pathogens can grow on produce to populations exceeding one million per gram. Researchers have investigated conditions affecting survival and growth of pathogens on raw produce as well as the effectiveness of sanitizers for decontamination. However, it is difficult to assess the effectiveness of sanitizers in killing or removing pathogens because substantial variations exist in testing methods. The aim of this project is to develop and validate a standard method to test the efficacy of sanitizers for raw fruits and vegetables. Three pathogenic bacteria (enterohemorrhagic E. coN 0157:H7, Salmonella, and Listeria monocytogenes) will be studied. Tomatoes, parsley, lettuce, apples, cantaloupes, and strawberries will serve as models for raw produce. Various procedures for contaminating produce with pathogens and treating with sanitizers will be investigated. The method that is developed and validated can be used by the raw produce industry, researchers, and regulatory agencies to demonstrate the effectiveness of produce sanitizers. The legal process for authorizing the use of safe, highly efficacious treatments to reduce the risk of human illnesses associated with consuming potentially contaminated raw fruits and vegetables can then more expeditiously proceed.

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Bacterial Pathogens