Table 241

Considerations When Developing Standard Method(s) for Determining the Efficacy of Sanitizers in Killing Pathogenic Microorganisms, and Survival and Growth of Pathogens on Raw Fruits and Vegetables

Type of produce

Whole or cut

Washed, brushed, waxed, or oiled Botanical part (fruit, leaf, stem, flower, root, tuber) Pathogen of interest

Gram-negative or Gram-positive bacteria, parasite, or virus; mixture of strains or a single strain

Marker or no marker Conditions for preparing inoculum Number of cells in inoculum Procedure for inoculation

Composition of carrier Temperature of produce and inoculum Dip, spray, or spot inoculum

Temperature and relative humidity between time of inoculation, testing, and analysis Procedure for evaluating test condition

Define treatment, condition, or sanitizer

Method for measurement of concentration and activity

Temperature of produce and treatment condition or sanitizer

Dipping, spraying, fogging, or atmospheric

Agitated, rubbed, or static condition during exposure

Time of exposure of inoculated produce to sanitizer or condition

Ratio of sanitizer to produce sample

Blending, homogenizing, macerating, or washing

Time of treatment

Composition of neutralizer (for sanitizer studies) Detection and enumeration media Conditions for incubating plates and broth Confirmation procedures Reporting results

Number of replicates and samples/replicate CFU/g, CFU/cm2, CFU/piece, fraction negative Appropriate statistical analysis and interpretation methods can then be used in studies focused on determining survival and growth characteristics in challenge studies and efficacy of antimicrobial treatments in killing specific pathogenic and spoilage microorganisms that may be present on raw produce. The objective would be to develop, validate, and recommend, through an appropriate authoritative body, a basic experimental protocol or protocols that could be modified according to specific applications to various groups of fruits and vegetables.

Some of the factors that should be considered when developing a standard method(s) for determining the effectiveness of sanitizers in killing microorganisms or, in the case of challenge studies, to determine the survival and growth characteristics of microorganisms on raw fruits and vegetables are listed in Table 24.1. These include the type of produce to be examined, anticipated population of pathogenic or spoilage microorganism or group of microorganisms to be used in the inoculum or naturally present on produce, composition of the carrier for the inoculum, and conditions for storing produce between the time of inoculation and treatment or sampling. The time produce is exposed to chemical or physical treatment, the temperature of the produce and treatment solution, procedures for washing produce after treatment, and procedures for removing and enumerating viable cells of pathogenic and spoilage microorganisms after treatment should be standardized.

Modifications of a basic analytical method for groups of fruits and vegetables may be necessary to enable the most accurate detection or enumeration of microorganisms of interest and to determine accurately the efficacy of sanitization treatments. These modifications will be necessary for a yet to be determined number of groups of fruits and vegetables to be defined according to similarities and differences in surface morphology and hydrophobicity, internal tissue composition, and conditions of processing, e.g., washing, brushing, or waxing, to which they had been previously subjected. Observations on current methods and those under development, with options and suggestions concerning directions that might be taken to establish standard methods to detect accurately or enumerate pathogenic and spoilage microorganisms on raw fruits and vegetables, are presented here.

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