Handbook of Hygiene Control in the Food Industry

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includebeingmoresuitedto flat surfaces and on verycontaminatedsurfaces
providing onlyan approximate or semi-quantitativeestimate. This can make
statistical analysis of resultsmore problematic. However, if onlyan indication of
cleaning adequacy,i.e. pass or fail is required, ratherthan the precise numberof
organisms,this may not be a problem.It is easyto countthe individual colonies,
obtained frommarginallyunclean/cleansurfaces, basedon cleansurfacecounts
currently consideredattainable(see Section36.5.2). If a moreprecisenumber of
colonies, froma heavilycontaminatedsurface, is required thenagarcontact
methodsmaybe inappropriate.


36.3 Non-microbiologicalsurfacesampling

Historically,priorto swabbing, visual assessmentwas the onlymeansto assess
the effectivenessof cleaning and is still the mostwidelyusedmethodin food
serviceand the home. Visualassessmentstill also has an importantrole to play
in foodmanufacturing as part of an integrated assessmentprotocol(see Section
36.4.1). In isolation it is not a goodmethodfor assessing anythingotherthan
grosssurfacesoil.It can be combined withmagnification, withor without UV/
blacklightassistance, as well as touch, dust or powder to detectgreaseresidues.
Mostauditors willtakea torch(flashlight)withthemto inspect the visual
cleanlinessof dark/hidden,out of the wayplaces in foodpremises.
Various types of microscopyenable individualmicroorganismsand biofilms
to be observedbut these are not practical for routineuse. Morerecentlya device
for visually assessing surface cleanliness, based on detecting fluorescing
chemicals, e.g. chlorophyll residues in faecesor meat,has become available.
Thiscan be of use in surface assessmentin somefoodprocessingareas.The
adventof swabbingin the early1900soffered the onlymajoralternative for
routineuse untilthe late 1980s.Sincethenalternative, rapidchemical detection
methods, startingwithATP,havebeendeveloped(Griffithet al., 1997).These
methodsdetectfood/organic debrisratherthan microorganisms. As cultivationis
not required, onlya rapidchemical reaction,the test resultsare available in
seconds or minutes,rather thanhoursor days.Thesenewer tests probably
represent a truerassessment of cleanliness (absenceof soil),thandoesa micro-
bial count.Soil can protectmicroorganisms, and therefore knowledgethat the
surfaceis free of soil provides reassuranceconcerningthe potentialfor microbial
growth. Thusthe philosophy of theiruse is different, offering proactive cleanli-
ness managementwithresultsavailable in timefor corrective actionto be taken
(includingrecleaning) priorto surface use. Microbialenumerationis reactive
and proves, by whichtimethe productmayhaveleft the factory, that a surface
was or was not contaminatedaftercleaning.Some traditionalmicrobiologists
still feel happierwith assessing surfacemicrobial contamination,althoughtheir
approach is furtherchallenged by increasedconcern overfoodallergies. If
cleaning is inadequatelyperformed,foodallergensfromone foodmayremain
on a surfaceand cross-contaminate otherfoods.Rapidchemicaltestsare not a


Improvingsurfacesamplingand detection of contamination 603
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