narrow limits are fixed to the temperature parameterby the temperature resist-
ance,or by the temperature optimum of the availableenzymes(cf. below).
Exceedingthe upperresistance threshold, whichis differentfromenzymeto
enzyme, results in its spontaneousdeactivation,so that the temperatureas an
independent variableis availableonlyto a verylimited extent.
Sakiyamaet al.(1998)reportedthe firstassayson enzymatic cleaning of
protein-soiled surfaces madeof stainlesssteel.They soiledcolumns, whichwere
packed withstainless steel particles, with -lactoglobulin or gelatin, and used
differentproteases to removethe soilsthus created. Grasshoff (1999)performed
practicaltrialson enzymaticcleaningof stainlesssteel surfaces on which
predominantly proteinaceous foulings had developedas a consequenceof the
heatapplicationduringmilkheating.
32.3 Laboratory trialsof enzyme-basedcleaning
32.3.1 Testsoilsand experimentalprocedure
The basisfor conclusivetrialsfor detectingthe efficiencyof cleaningchemicals
or cleaning processesis the availability of soiledsurfaces,whichhaveto fulfil
the followingrequirements:
∑ the soil has to correspond to that occurringin practice;
∑ the soil has to be reproducible; and
Fig. 32.1 LaboratoryCIP plantwithflowchanneland videoequipment.522 Handbookof hygiene controlin the foodindustry