Effect of Negative Air Ions on Escherichia coli ATCC 25922 Inoculated onto Mung Bean Seed and Apple Fruit†

Abstract

The effect of negative air ions on the reduction of Escherichia coli ATCC 25922 inoculated onto mung bean sprout seed and whole or fresh-cut apple fruit was studied. Mung bean seeds, whole Gala apples, and Gala apple slices were inoculated with E. coli ATCC 25922 before being exposed to negative air ions for up to 18 h at room temperature (∼23°C). Results revealed a less than 0.5-log reduction of E. coli on mung bean seed even after 18 h of exposure. The reduction of E. coli on the surface of whole apples increased with increasing exposure time from 0.5 to 3 h, but the maximum reduction was less than 1 log CFU/g. Increasing exposure time from 3 to 18 h did not lead to increased treatment efficacy. No reduction of E. coli was observed on apple slices after 3 h of treatment. When the negative air ion system was applied with acetic acid vapor, no additive or synergistic effect of negative ions on the reduction of E. coli was found. These results suggest that negative air ions have a very limited effect on the population of E. coli on mung bean seed and apples.