cleanability. Theaim of the test, for example whether to assess in-place
cleanability of foodprocessing equipment (Anon,2003),or to evaluatenovel
surfacetreatmentsor cleaningregimes, will affectits design.
A recognitionof the environmentin whichthe surfaceis to be employed,
witha viewto its simulation,should be the startingpointfor development of
tests,but theremay also be regulations with whicha given productmustcomply.
Thelocationof a given process willalsoaffectthe typeof testingmethod
employed ± an aspect that will not be exploredin depthin this chapter, but is
addressed elsewhere in this volume.Thetypeof equipment (open, closed,
robust, delicate, flexible,rigid,mobile, static,clean room) will present different
cleanability and accessissuesif to be sampledin situ(or simulatedin vitro, for
example using rigs). Hygienic design should have been implicit in the
development of the process, and attention paid to appropriate hygiene
monitoring,cleaning-in-place (CIP), personneltrainingand other issues.This
chapterwill focusprimarily on the development of methodsthat are rigorous
and appropriatefor cleanability testing of surfaces primarily used in open
systems, but that are also feasibleas part of qualityassurance (QA)procedures,
or in developmental work whenconsideringnovel processes, materials or
cleaning/sanitation regimes.
The nature of the food,the microorganismand the substratumlikelyto be
usedin a given situation mayall affectthe findings of hygieneand cleanability
testing.Thischapteraddresses someof the issuesthat mightbe consideredin
attempts to improve testingmethodsand validateany claims as to hygienic
status. Threeaspects are considered,aloneand in combination,namely the
microorganism,the substratum and organicsoil.
34.2 Microorganisms
34.2.1 Modeof existence on substratum
In general, methodsusedfor monitoringhygiene,evaluatingnovelsurfaces or
cleaning regimens tendto soil using microorganisms perhaps combinedwith
someorganicmaterial suchas milkpowder,via singleevents, followed by
cleaning/sanitizationand an assessment of the number of cellsremaining, but
not usuallyof the amountof organicmaterial present. The simplest meansfor
this assessment is via removalof the remaining cells,and enumerationof viable
cellsby traditionalculture techniques(Wirtanenet al., 2000).Alternatively,the
material may be quantified in situ, for example using epifluorescence
microscopyto providedataon the areaof a microscopicfieldcovered,or on
totalcell numbers. Vital stainingof theseattached cells,or the applicationof
culture media ontotest surfaces to enable viable cellsto formcolonies, will
provideinformation on the proportionof viable cellspresent (Barneset al.,
1996).Thisscenario is appropriatefor hygienicsurfaces, where the expectation
in a foodfactorywouldbe that regularcleaning processes are carriedout, and
attached/retained cellsare relativelyfew (comparedwith the densepopulations
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