however, significantlyincrease the cost (10±25%) and the volumeof the rubber
component (34%)(Anon1993).Greeneet al.(1994)testedthe resistance of
gaskets made from a number of materials commonly found in the food
processing environment, to ozoneand chlorine.The results werethat the use of
ozonedid not affectmostof the gaskets morethanchlorine,withthe exception
of polytetrafluoroethylene (PTFE). Latex, mostsilicones,viton,polycarbonate
and rigidpolyvinyl chloride are resistantto the effectsof ozone(Dusseauet al.
2004).A thoroughaudit must,therefore, be conducted priorto usingozoneto
replacethesematerials withalternatives that will not be degradedby ozone.
31.4.2 Health and safetyconsiderations
As ozoneis a highlyreactive substance, it reactswithany organic substance,
including the human body.The health effectsare mainlyat the sitesof initial
contact, normallythe respiratory tract, lungsand eyes,and thereis a degreeof
variationamongindividuals in sensitivityto ozone.The principaleffectsare
irritation and damage to the smallairwaysof the lung,and exposureto high
levels(1 ppmand above)may lead to more serioushealtheffectsincluding lung
damage(Anon1998a).If this exposure exceeds24 hours, thenthe damagemay
be irreversible(Dusseauet al.2004).
The OccupationalExposure Standard(OES) in the UK for ozoneis 0.2 ppm
averagedovera 15 minute referenceperiod(Anon 1998a). The US has a
threshold limitvalue±long-term exposurelimit(TLV-LTEL)of 0.1 ppmfor a
normal8 hour day (40 hoursper week) and a TVL-LTELof 0.3 ppmfor 15
minutes (Xu 1999).
31.5 Practical applicationsof ozone
31.5.1 Case studies of the use of ozonein the foodindustry
Gaseousozone
The use of ozonefor processplantdecontaminationwas implementedinto a
smallcheese-making factory thathad problems withcontaminationof the
processing environment. Theheterotrophic aerobic platecountand levelsof
Enterobacteriaceae on both food contact and environmental surfaces were
reducedby treating the whole plantwith2 ppmozoneovernight for a periodof
two months. Whenozoneuse was discontinued, the heterotrophic platecounts
and levelsof Enterobacteriaceae increased. It is importantto note,however, that
thesereductionswereobservedaftercleaninghad takenplace.Ozonationmust
be usedas a terminaldisinfectionstep and is not a replacementfor cleaning or
goodhygienepractices.
Ozonated water
It is wellreportedthat cells withina biofilmare moreresistantto antimicrobial
compounds suchas commerciallyavailable cleaning solutions(Lewis2001).In
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