The effect of ozone and open air factor on environmental microbial isolates of significance in the food industry
Author
Nicholas, Rebecca Charlotte
Date
2014Type
Thesis
Publisher
Cardiff Metropolitan University
Metadata
Show full item recordAbstract
Ozone and open air factor (OAF) have been reported in the research literature as
being effective anti-microbial agents. The action of ozone on microbes is relatively
well understood, but the action of OAF is not well characterised. Both ozone and
OAF have relatively short half-lives and do not leave behind toxic residues. The
advantages of using a gas instead of aerosols, or droplets produced by fogging to
decontaminate surfaces, is that a gas will come into contact with the horizontal,
vertical and inverted planes of the surfaces (by diffusion), whereas aerosols or
droplets will be affected by gravity.
The effect of gaseous ozone, OAF and ozonated water with or without d-limonene
emulsified in alcohol on surface attached and biofilm environmental L.
monocytogenes amd P. aeruginosa were investigated. The interaction of each
treatment with microorganisms was elucidated by determining microbial survival on
different food contact surfaces, detecting cell injury by examining treated
environmental L. monocytogenes cells using scanning electron and atomic force
microscopy. All treatments were significantly more effective in eliminating the gram
negative than the gram positive bacteria. This may be due to differences in cell wall
structure and the cell’s ability to produce extracellular polymeric substances.
Scanning electron microscopy revealed that gaseous ozone caused the cells to bleb
out their cellular contents, whereas for OAF treated cells, holes were apparent in the
cell wall. The ozonated water treatments were more effective in stripping the biofilm
away from the surface substrata. The atomic force microscope showed that OAF,
ozonated water and terpene, and the terpene in water treatments caused visible cell
surface property changes, compared to gaseous ozone and ozonated water
treatment alone.
Description
PhD Thesis
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