only 0.4 and 3.7 log reductions on injured and uninjured green pepper surfaces, respectively, while water washing for 10 minutes showed 0.4 and 1.4 log reductions, respectively [33]. Costilow et al. [50] also found that up to 105mg/l aqueous ClO2 failed to reduce the population of microorganisms present on fresh cucumbers. Zhang and Farber [51] reported that ClO2 solution treatment (5mg/l, 10 minutes) at 22° C resulted in only a 0.8 log reduction of L. monocytogenes on both cut lettuce and cut cabbage. The mechanism of why aqueous ClO2 is not as effective as the gaseous form needs further study.

A continuous ClO2 gas treatment showed a higher efficacy compared to that of a batch treatment. Using a batch system (Figure 18.4), a 4.0mg/l ClO2 gas treatment for 30 minutes at 22° C and under 90% RH achieved an approximately 5 log reduction of E. coli O157:H7 and L. monocytogenes on strawberry surfaces [36]. With a continuous treatment system, more than a 6 log reduction of E. coli O157:H7 and L. monocytogenes on strawberries was achieved using a 3.0mg/l ClO2 gas treatment for 10 minutes [38].

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