Ozone
Ozone, a molecule comprised of three oxy-
gen atoms, is naturally occurring in the earth’s
upper atmosphere. It acts as a powerful and
nonselective oxidant and disinfectant, (which
indicates that it will attack any organic
material that it contacts) and may control
microbial and chemical hazards. Common
by-products of ozonation are molecular oxy-
gen, acids, aldehydes, and ketones. This sani-
tizer does not cause a harmful residue or
contaminated flavor.
This sanitizer is a more powerful disinfec-
tant than chlorine. It has been used safely and
effectively in water treatment and is approved
in the United States as Generally Regarded
as Safe (GRAS) for treatment of bottled
water and has been applied in the food indus-
try in Europe during the past. It has a broad
spectrum of germicidal activity. Generally,
ozone is a more effective bactericide and viru-
cide than chlorine and chlorine dioxide.
Ozone is being evaluated as a chlorine substi-
tute. Because it oxidizes rapidly, it poses less
environmental impact than some compounds.
Ozone is expensive, unstable, corrosive,
temperature sensitive, very reactive, and
should be generated as needed at the site of
application. It is produced commercially
through the incorporation of an ozone gen-
erator that uses electricity to generate the gas
and ozone. The ozone is used as a gas or is
contacted with water for application. A high
voltage, alternating electric discharge is
passed through a gas stream (dry air or oxy-
gen). To control the electrical discharge and
maintain a corona, a dielectric space or dis-
charge gap is formed using a dielectric mate-
rial such as ceramic or glass. A grounded
electrode that is usually produced from
stainless steel acts as a boundary to the dis-
charge space. The most common shape for
ozone generators is a cylinder, which is the
most space-efficient, economic form (Stier,
2002). Care must be taken to ventilate the
equipment properly as released ozone can be
irritating to workers. Ozone is very unstable
at a high as well as at a low pH.
Ozone is most effective at a pH range of
6.0 to 8.5. As water temperature increases,
the solubility of ozone decreases. It dissi-
pates almost immediately at 40°C. Ozone is a
broad-spectrum germicide which is effective
against food pathogens, yeasts, and molds,
and viruses and protozoa. It has been used
to sanitize winery equipment and to disinfect
water, including pools, spas, and cooling
towers and for algae control in water and
wastewater treatment plants. It is not toler-
ant of organic soil. The probable mode of
action of ozone is through the attack on the
cell membrane, rupturing and killing the cell.
Another application is to release gaseous
ozone in cold storage rooms to control
molds and eliminate ethylene, which can
accelerate ripening in fruits and vegetables.
Ozone is more stable in the gas phase and in
an aqueous phase.
The use of ozone presents safety issues. It
is a powerful irritant to the respiratory tract
and a cellular poison that interferes with the
ability of lungs to fight infectious agents.
Ozone, as chlorine dioxide, has been found
to produce brominated organic compounds
that are alleged potential carcinogens. Fur-
thermore, there is a high capital cost associ-
ated with the use of ozone including the need
for generators at point of use as well as the
energy costs to operate them. Also, ozone is
corrosive to soft metals and mild steel as well
as rubber and some plastics.Glutaraldehyde
This sanitizer has been used to control the
growth of common gram-negative and
gram-positive bacteria, as well as species of
yeasts and filamentous fungi found in con-
veyor lubricants used in the food industry.