couldoccurare the preheating sections of heatexchangersfor pasteurisation
of products.In the pre-heatingsectionveryfavourablegrowthconditionsare
found.Although the productis pasteurisedafterwards preventionof growth
would allow for milder heat treatment or reduces the level/chance of
survivors.
Whensurfacescontaina highlevelof microorganismsdirectlyfromthe
startof the process, the growth curvewillbe muchsteeper. Thiscan be
causedby insufficient cleaning, leavingproductresidues behind that will
protect microorganisms against subsequent disinfection. Next to being a
sourceof microorganisms,the residues present a problemin otherareassuch
as heattransfer,sourceof allergens,etc. Cleaningcould be facilitatedby the
use of non-stickmaterial.Non-stick material is not usuallysuitable as a
materialof constructionand thereforeneedsto be applied on the surface of a
constructionmaterialas a coating.In general the materialof construction
needsto be resistantto the productand CIP fluids,otherwiseany damage to
the coatingwouldinevitablylead to localcorrosionthat continues behindthe
coating.Often this will leadto stainless steelas the materialof construction.
Froma hygienicpointof viewit is importantthat the coatingwill not blister
off the materialof construction,even whenthe colour of the coatingmatches
the colourof the product.As this is very difficult to avoid it could be
considered to develop a coatingwhoseintegritycouldbe monitoredon-line
continuously.
17.6 Plantdesign
Buildingon this simplicitythe idealplantshouldbe continuousand consist only
of piping.Rawmaterials could be supplied in containers,whichare directly
coupledto the pipingsystemand are returned without cleaningto the supplier. A
widerangeof equipmentis alreadyavailableas pipes.Mostunit operationsand
sensors can be donein piping,static mixers, hosepumps, tubein tubeheat
exchangers,membrane pressureand temperature sensors,etc. However, it is
clearthat thesedevices havetheirlimitationsand oftenneedto be replaced with
in-linedevices that differin geometry. As longas the devices havea similar
cleaning characteristicas a pieceof pipe, the principle doesnot change.
To avoidall problemsrelatedto pipingsuchas cleaning,productloss during
cleaningand change-over,and residencetimedistribution,the conceptof the
pipe-lessplantcouldbe applied.Here,smallvesselsmoveto the factory,from
a dosingstationto a processingstation,to the fillingmachine.Sucha system
requiresno pipingat all and givesa veryaccuratecontroloverthe residence
time.Thereis still a needto cleanthe vesselsbeforepreparinga newbatch.
Thiscouldbe overcomeby applyingan internaldisposablelining,whichcould
be removedeasily,for examplea thin,plasticfoil, shapedto matchthe vessel.
Current developments in automation make this option more and more
attractive.
Improving the hygienicdesignof pipes 277