Application as a Novel Disinfectant for Fruits and Vegetables

EO water has been extensively applied to fresh or fresh-cut vegetables and fruits because of its strong bactericidal effects [88,92]. Izumi [93] utilized EO water to reduce the total microbial counts of fresh-cut carrots, bell peppers, spinach, and potatoes and found microbial counts on all cuts reduced by 0.6 to 2.6log10 CFU/g. The bactericidal effect of EO water increased with available chlorine in the range of 15 to 50ppm for fresh-cut carrots, spinach, or cucumbers. Tissue pH, surface color, and general appearance of fresh-cut vegetables were not affected after treatment.

Park et al. [94] examined the efficacy of EO water and acidified chlorinated water (45 ppm residual chlorine) against E. coli O157:H7 and L. monocytogenes on lettuce. Each leaf was surface-inoculated and immersed in 1.51 of EO or acidified chlorinated water for up to 3 minutes at 22°C. Compared to water washes, a 3-minute EO water rinsing significantly decreased mean populations of E. coli O157:H7 and L. monocytogenes by 2.4 and 2.7log10 CFU per lettuce leaf, respectively (p < 0.05). There was no significant difference between the bactericidal activity of EO water and acidified chlorinated water (p > 0.05), and no obvious quality change was observed during two weeks of storage after washing.

Fresh tomatoes were surface-inoculated with E. coli O157:H7, S. Enteritidis, L. monocytogenes, and nonpathogenic E. coli and rinsed in neutral EO water for up to 60 seconds [95]. EO water rinsing reduced the surface population from 5 log10 to <1 log10 CFU/cm2 independent of the type of microorganism and treatment time. No cells were detected in the washing solution. There was no significant difference in organoleptic qualities compared to untreated tomatoes.

Ratna and Demirci [96] applied EO water to alfalfa seeds and sprouts inoculated with a five-strain cocktail of nalidixic acid-resistant E. coli O157:H7. Reductions were in the range 0.2 to 1.6 and 1.1 to 2.7log10 CFU/g for treated seeds and sprouts, respectively, corresponding to a percentage reduction of 38.2 to 97.1 and 91.1 to 99.8%, respectively. Germination of the treated seeds was reduced from 92 to 49% when soaking time and the electric current used to generate EO water were increased. No visible damage occurred to the sprouts.

Besides the inactivation of bacteria, EO water can also serve as an effective fungicide on fruits and the foliage and flowers of bedding plants. Al-Haq et al.

[97] immersed peach inoculated with Monilina fructicola in EO water up to 5 minutes to examine its effectiveness against postharvest brown rot. EO water did not control brown rot in wound-inoculated peaches, but did reduce the incidence and severity in nonwounded inoculated fruit. No chlorine-induced phytotoxicity was observed on treated products. In this case, EO water was an effective surface sanitizer that delayed disease development. Al-Haq et al.

[98] also evaluated the effects of EO water on suppressing fruit rot of pear caused by Botryosphaeria berengeriana. Pears with wounds necessary to cause "bot rot'' were inoculated with spore suspensions of B. berengeriana and immersed in EO for 10 minutes. No chlorine-induced phytotoxicity was observed on the treated fruits, and EO water suppressed the incidence and severity of disease, suggesting that EO water can be used as surface sanitizer to possibly reduce postharvest fungal rot development.

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