be compared.Cellswhichwereimmobilizedon features, evenif theywere
smallerthancells, required an increased force(in nanoNewtons) for removal
(Boydet al., 2002).Treatment withdetergent reducedthe forcerequired(results
not presented).
Although perhapsa cleaning forcedescribedin nanoNewtons is of little
relevance in termsof the more`macro'businessof cleaning and sanitizing
surfaces, these findingsdemonstrate that any topographical changein a surface
feature may affect its cleanability. Thus these changes may need some
considerationduring the developmentof novelmaterialsand finishes.
34.3.4 Other hygienic surfaces
Thereare manysurfaces deemedto be hygienicother than metals.Ceramic/glass
finishes are findinguse as choppingboards as wellas worktops and walland
floorcoverings.Wearof thesesurfaces tendsto occurvia chipping,generating a
pittedsurfaceratherthanone that is scratched(Verranet al., 2001a).Organic
polymers are more malleableand thereforeusedto fabricate curved surfaces.
Softerpolymers mayalso be more easilyscratched,whichwill make cleaning
moredifficult, thus affectinghygienicstatus.The use of flexible(more) porous
rubbers and similar materials as bungs,seals,maybe inevitable: thesewill
requireparticularattention in any cleaning regime. Surfacecoatingssuchas
polymers, resinsand powders, whichmaypresentenhanced cleanability and/or
Fig. 34.2 Pseudomonasaeruginosaculturesweresprayedontoabradedstainlesssteel
surfaces,and rinsedgentlyto removeunattachedor looselyretainedcells.Cellswere
stainedusingacridineorange,and viewedusingepifluorescencemicroscopy.Cellsare
retainedin grainboundariesand scratcheson abradedstainlesssteelsurfaces.(Image
fromDeborahRowe.)
Testing surfacecleanability in foodprocessing 563