without the enzyme.As the aim of the enzyme inputis to reducethe content of
biologicallynon-degradable inorganicsubstances in the cleaningsolution to a
level that allowsit to be dischargedto the sewer without additionaltreatment,
Esperase, withits impactoptimum at pH 12.0,is eliminated fromthe rangeof
enzymes adequate for the heatexchangercleaning.
Figure 32.8shows the dependenceof the depositremovalfor Savinase at an
enzyme concentration of 0.025% and a temperature of 55 ÎC with an
unambiguous impactoptimumat pH 9.5, thusconfirming the informationin
the datasheetof the enzyme producer. Bothundershooting the optimum value
by 1.5 pH unitsand alsoexceedingit by the sameunitsresult in a clear
deterioration of the depositremoval. Nearly identicalresults wereobtainedfor
Properase, the impactoptimumof whichwas detectedat a slightly higherpH
10.0.Thusthe products Savinase and Properaseofferedby the producersNovo
NordiskandGenencorInternationalcan be considered as being moreor less
equal.
Reuse of usedenzymesolutionsand storageof enzymeconcentrates
For possible use in practice,it is of interestwhetherthe enzyme-containing
solution used can be storedhot afteruse and be reusedfor furthercleans.To this
end,a removaltrialwitha 0.025%Savinase solutionwasperformed in the
laboratory.Afterthe end of the trialthe solutionwas preservedfor 1 h at the
applicationtemperatureof 55 ÎC. Subsequently,a furthertest coupon,afteran
acid pretreatment, was pressurizedin the hot-storedenzyme solution:the reused
solution was practicallyinefficient. However, additionaldosingof freshenzyme
concentrateafter15 minutesled to a spontaneousdevelopmentof the deposit
removal. Analogous behaviour was registered for the 0.05%Properasesolution.
Fig. 32.8 Influenceof pH on depositremovalwith0.025%Savinase’.530 Handbookof hygiene controlin the foodindustry