air, water, peopleand pests.Processing, packagingmaterial and equipment, and
transport vehicles may also act as vectors.Contact between foodmaterial and an
inertsurfaceleaves residual fooddebris thatfavours the growthof micro-
organisms.Overtime,thesecan multiplyto significant numbers and become
endemic in a processingplant.Chemical contamination mayalsoresult from
contact withsurfaces, if theyare not adequatelyrinsed after cleaning and
disinfection procedures. Lubricants, often unavoidable in equipment with
moving parts,mayalso contributeto chemical contamination (Steenaardet al.,
2002).Non-contact surfaces,suchas floors, walls,ceilings,overhead beams and
equipmentsupports, are potentialreservoirsof microbial contaminationand can
also be a sourceof physicaland chemicalcontaminants (e.g.fromflaking plaster
and its associated chemicals). Theyneedto be designedso that theyare durable
and can be cleanedeffectively.
Animals are importantreservoirsof microorganisms,and slaughteranimals
introduce largenumbers of microorganismsinto the processingplant. Among
themare many so-calledzoonotic pathogensthat are present on the skin and in
the gastrointestinaland respiratory tracts. Pathogenscarried on handsare also a
majorsourceof contamination(Taylorand Holah,2000).
Air can be a significantmediumfor the transfer(vector) of contaminantsto
foodproducts (Brown, 1996 ). Unlessthe air is filtered,microorganismswill be
present, and air mayalso carry `light'foreignbodies, suchas dust, straw-type
debris and insects.Chemical taints can enter the productionareathrough
airborne transmission.Wateris usedin the foodindustry as an ingredient, a
processingaid and for cleaning.Its use as an ingredientor processingaid can
giverise to bothmicrobial and chemical contamination,so it is importantto use
waterof a highmicrobiologicaland chemical quality(i.e.potable quality).
Water usedin hand-washing facilitiesposesa potentialproblem, as doesthat
fromcondensationof steamor watervapour, leakingpipesand drains, and
rainwater.Stagnant wateris particularlyhazardous,sincemicrobiallevels can
increase rapidly under favourableconditions. Thewater used in cleaning
programmesalso needsto be of adequate quality (Holah,1997;Dawson, 1998,
2000).Personnelcan transfer entericand respiratorypathogensto food,e.g. via
aerosol droplets fromcoughing nearthe processing line (Guzewich and Ross,
1999).Peoplecan equallybe vectorsof physicalcontaminants,suchas hair or
fingernailfragments, earrings,plastersand smallpersonalbelongings.
Pests, such as birds, insects and rodents, are potentially a major
contamination problem, and particular careneedsto be takento prevent their
entryinto foodproduction areas. Buildingsmustbe designedto keepthemout.
Floors, ceilingsand wallsshould not allowinsectsand otherinvertebratesthe
chance to live and breed.
1.3.1 Microbial contaminants
Pathogenicmicroorganismsare the majorsafetyconcern for the foodindustry.
The vastmajority of outbreaks of food-relatedillnessare due to microbial
14 Handbookof hygiene controlin the foodindustry