Surface inoculation of fruits and vegetables with pathogens or spoilage microorganisms can be done by dipping or spraying with a suspension of cells or by applying a known volume of suspension containing a known population (spot inoculation). Some of the advantages and disadvantages of these methods are listed in Table 24.5. The inoculation method should ideally simulate various contamination events and postcontamination conditions prior to washing and sanitization. If contamination of produce is suspected to occur by an immersion process, dipping the produce in the test cell suspension may be an appropriate method for inoculation. A problem associated with inoculation by dipping or spraying is that the number of cells actually applied or adhering to the produce is not known. The population remaining on the surface and in subsurface tissues after dip or spray inoculation is not consistent among
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