Cardiff Metropolitan University
8172 - Rebecca Nicholas 3.pdf (15.97 MB)
Download file

The Effect of Ozone and Open Air Factor on Environmental Microbial Isolates of Significance in the Food Industry

Download (15.97 MB)
posted on 2022-10-17, 16:16 authored by Rebecca Charlotte Nicholas

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.    



  • School of Sport and Health Sciences

Qualification level

  • Doctoral

Qualification name

  • PhD

Publication year


Usage metrics

    Cardiff Met Theses Collection