minimal waterhardness (approx. 4 dH (40.00mg CaO/l)), thus having a required
minimal conductivityfor the operation of an inductive flowmeasurement.If
exhaust vapoursare usedfor the mixtureof enzymatic cleaningsolutions,the
volumes have to be measured withmechanicallyoperating systemsas the
conductivityfallsbelowthe minimumconductivity.
P3-Paradigm does not contain phosphates, nitrate or chlorine and the
surfactantsusedare completely degradable.Owing to the low concentrations
(approx. 1/10of the comparablechemicalquantityof conventionalcleaning
processes)the contributionof the containedchemicalsto the biological/chemical
oxygendemands(BOD/COD)contentof the wastewateris negligible.The
applicationsolutionsare not skin-irritating,non-toxic, and haveno corrosive
effect, whichaffects the lifespanof the valve seals,particularlyin the polymer
rotors in the impeller pumps of the milk inlet tubes in the bulktankers.
Furthermore, no negative effects havebeenobserved duringthe waste-water
treatment.
In Germany,the enzyme-basedprocessfor cleaningthe coldmilkzonehas
beenusedfor between 3 and 7 years.Afterthe requiredtechnicalre-equipment
of the plant,and afterthe trainingof the personnel(particularlydriversof the
bulktankers) by the supplier of the enzymatic cleaningagent, therehaveup to
nowbeenno disordersrelatedtoP3-Paradigm. As a securitymeasure for the
long-term use of the enzymatic cleaning process, Ecolab recommends a
conventionalbasiccleaningoncea year, bothfor the product transporting
devices, and for the tanks and componentsof the CIP plants.The cleaning effect
should alsobe regularly monitoredby microbiological controls and via ATP
measurement. If these requirements are fulfilled,the enzymatic process for
cleaningthe coldmilkzonein the dairyrepresents real progressallowingcost
economics in the purchase and disposal of chemicals, for moresecure handling
and,aboveall, enhancedenvironmentalaspects.
32.2.2 Enzyme-basedcleaning of the milkheatexchanger
Structureof the deposits
While heatingin the temperature range70±80 ÎC (for pasteurizationand short-
termheating of milk)fouling may develop on the surfaces of the heat exchanger
plates, whichcontainbetween 50 and 70%(mostly denatured)proteins,30±40%
minerals (of which3±10%is calcium),and 5±10%fat. In the verticaldirection,
the foulings are non-homogeneous.Immediatelyafterthe heating starts, accord-
ing to Belmar-Beinyand Fryer(1993), in onlya few seconds, a thin,4±10m
thick,denseand transparent film, mostlyfromcalciumphosphate withorganic
deposits, is formedon the metallic surfaceof the heatexchanger.It is onlyon
this filmthat the visible,measurablythickproteinousfoulingsdevelopat a
significantlylowervelocity.Owingto the calciumcontent of milk(in non-
heated milk,calciumlinkscasein submicellesto casein micelles in the formof
calcium phosphate bridges), stable water-insoluble casein whey protein
complexesdevelopduringheating by the depositionof denatured whey proteins
520 Handbookof hygiene controlin the foodindustry