surfaces witha highATPcountand low microbial count(e.g.UHTmilk),thus a
small increasein product residuecan increasethe ATPcountbut not microbial
numbers. Similarly, depending on the foodproduct, e.g. raw foods, and their
level of microbial contamination,it is possible to havea low ATPincrease with
higher increases in microbial numbers. Factors that mayinfluence the choiceof
howcleaningis monitored are presented in Table36.2.
Theaims of this chapterare to review microbiological and non-micro-
biologicalmethodsfor monitoringcleaningefficacyand suggest waysto manage
an integratedprogrammeof monitoring, in an attemptto ensure adequate and
cost-effectivecleaning.
36.2 Microbiologicalsurfacesampling
Microbiologicalsurfacesamplingcannotbe describedas new,withreports of its
use goingback to the 1920sand 1930s(Saelhof and Heinekamp,1920;Krogg
and Dougherty, 1936),although precisemethodological detailsare lacking.
However, mostof this earlyworkwasbasedon swabbingwithdirectagar
contact methodsonlydevelopedlater.
Advancesin microscopyhaveresulted in the developmentof methods based
on epifluorescent,confocalscanning laserand episcopicdifferentialinterference
contrast microscopy.Theselatermethods, whileproviding useful laboratory
information,are impractical for routineuse in foodbusinesses.Themain
methodsin use within the foodindustryincludethe use of swabsand sponges to
recover organismsfromthe surfacefollowedby theircultivation on/innutrient
media (effectivelyindirect). Methodswherethe nutrient medium is in direct
contact withthe surfacetested involveimpressionplatesor dipslides.The choice
of methodwill dependon the precise information requiredand the prevailing
circumstances(see Table36.3).Additionaloptionsare whether to test for: an
aerobic colonycount± a generalmeasureof surfacecontamination; indicator
organisms,someof whichcan providea measure of hygiene standards;or
specific pathogens. Oftenthe latter maybe like lookingfor a `needlein a
haystack',althoughis of particular benefitif:
∑ a specificpathogenhas beenfoundin a foodsample;
∑ investigating cases of foodpoisoning;
∑ part of a specificpathogencontrolprogramme, e.g. controllingListeriain
foodpremises.
36.2.1 Swabbing/sponges
Swabbingin one formor anotherremainsthe oldestand probably the most
widely usedmethodfor surfacemonitoring(Moore and Griffith,2002a). It
should be notedthat althoughthe termmonitoringis used, it doesnot conformto
the definitionusedwithin HACCP. For the latter,resultsmustbe obtained in
timefor corrective action to be takenand swabbing, like impressionplates,
596 Handbookof hygiene controlin the foodindustry