食品發(fā)酵工藝英文版課件：第三章 培養(yǎng)基滅菌與空氣凈化

Chapter3Sterilization

Unit1MediumSterilizationUnit2AirSterilizationBasictermsSterilizationDisinfectionAntisepsisBacteriostasis

AsepsisSterilizationDestructionofallformsofmicrobiallife,includingbacterialspores.

MorethoroughthandisinfectionDisinfectionTokillmostofmicrobialformsexceptsomeresistantorganismsorbacteriumspores.e.g.useofalcoholbeforedruginjection.

Aboutsterilizationanddisinfection,whichiswrong?A.Sterilizationisthekillingofallmicroorganismsinamaterialoronthesurfaceofanobject.

B.Disinfectionmeansreducingthenumberofviablemicroorganismspresentinasample.C.Typicallythelastthingstodiewhenoneattemptssterilizationisthehighlyheat-(andchemical-,etc.)resistantendospores.D.Alldisinfectantsarecapableofsterilizing.Antisepsis

Processofinhibitingorpreventinggrowthofmicrobes,mostlyinvitroandnotbactericidalorsporicidal.e.g.useofchemicalagentsonskinetc.Bacteriostasis

Processofinhibitingthegrowthofmicroorganisms,invivo(mostly)orinvitro.

e.g.bacteriostaticantibioticsDifferentKindsofBacteria“Death”1.Bacteriostatic2.Bacteriocidal3.BacteriolyticLogCell#TimeTotalcellcountViablecellcountAsepsis

Nolivingmicroorganismsexists.e.g.OR(OperatingRoom)SterilizationconvenientlycategorizedasfollowsI.Physicalmethods①Heat:DryheatMoistheat②RadiationsUltravioletradiationsIonizingradiations③FiltrationII.Chemicalmethods1.

Chemicalagents

Alcohols

,Chlorine,FormalinSuitableforskinandinstruments2.Radiation3.DryHeatUltravioletandIonizingRadiation

Suitable

forsterileroomandinoculationhoodDirectflaming:e.g.inoculatingloopHot-airsterilization:160℃,2hinhotairoven4.MoistHeat121℃，30mininautoclaveSuitableformediumandinstruments5.FiltrationRemovalofbacteriabyfiltermediumUsedforheatsensitivematerialsandfiltratedairFlamingHotairoven

-170°Cfor1hour-140°Cfor3hours.DryHeat1.Pasteurization(below100°C)

Destroyspathogenswithoutalteringtheflavorofthefood.Lowtemperature(holdingmethod):63℃,30minHightemperature(flashmethod)

:72℃,20secMoistHeat2.Boiling(at100°C)-killingmostvegetativeformsofbacteria-10minorlongertime3.Autoclaving(above100°C)-killingbothvegetativeorganismsandendospores-121-132oCfor15minorlongerMoistHeatvsDryHeat

MoistheatDryheatPenetratingpotency higher lowerTemp.forproteinclotting lower higher

Extraheatreleased yes no fromcondensationSterilizingpotency:Moistheat﹥﹥DryheatWhyismoistheatmoreefficientthandryheat?Conductivity.Moistureconductstheheatbetterthanadrysystem.dryheatormoistheat?

islesspenetratingandrequireslongerexposure.Anautoclaveisahighpressuredeviceusedtoallowtheapplicationof

abovethenormal-atmosphereboilingpointofwater.Pasteurizationistheapplicationof

ofless-thanboilingtemperaturestofoodstopreventthegrowthoffood-spoilingorganismsaswellasvariousheat-labilepathogens.Cannedfoodcouldbestoredforalongtime,because

A.Bacteriacan’tgointocan.

B.Bacteriacan’tbreathincan.

C.Therearenobacteriaincan.

D.Bacteriacan’tsurvivalincan.SterilizationprocessesBatchsterilizationContinuoussterilization

Batchsterilizationusessteamordirectfiringtoelevatethetemperature,andthencoolingwaterstopstheprocessandbringsthematerialbacktowardroomtemperature.BatchsterilizationBatchsterilizationwastesenergyandcanovercookthemediumContinuoussterilizationisusedtoalmosteliminatetheseundesiredtimesbecausetherecanbemorerapidheattransfertoflowingmediuminpipes.ContinuoussterilizationAlsocalledhightemperatureshorttime(HTST)Generallycarriedoutat140°C,wherebysterilizationtimesof2-3minaresufficientfermentorstreamstreamCoolingwaterSterilemediummixingtankpumpsterilizingcolumnMaintainingtankcoolingpipeWhataretheequipmentsofcontinuoussterilization?QuestionContinuoussterilizationprocessesInjectionsterilizers

Steamisfeddirectlyintorawmedium,sothattemp.risestodesiredlevelalmostimmediately.AdvantagesShortersterilizationtimemeanslessthermaldegradationofmedium.DisadvantagesInsufficientforsterilizingmediacontainingsolidmatter,onaccountofinferiorrateofheat-transferinsolids.(batchprocessisrecommendedforsterilizingsuchmedia.)BatchandContinuousSterilizationInaword:Hightemperaturesforshorttimesareusedinpreparingnutrientmediaforindustrialfermentationsandinpasteurizingmilk,becausethiscauseslessdamagetobiochemicalsthanmoreprolongedtimesatlowertemperatures.Filtration

Sterilizesolutionsthatmaybedamagedordenaturedbyhightemperaturesorchemicalagents.Theporesizeforfilteringbacteria,yeasts,andfungiisintherangeof0.22-0.45μm

(filtrationmembranesaremostpopularforthispurpose).Filtration:Fluids&AirUnit2AirSterilizationVerylargevolumesofsterileairisrequiredinmanyaerobicfermentationprocess.MethodsforairsterilizationRadiationHightemperature

ElectrostaticbacteriaremovalFiltration

Airsterilizationisgenerallycarriedoutbyfiltrationtoremoveallparticlesandm/o(bacteria,spores,yeast,mould)fromatmosphericflow.Forreasonofcost,absolutesterilityisneitherpossiblenorcustomaryinpractice.Forgerm-filtrationofliquids(hydrophobicmembranefilters),theporewidthis0.2μm.Forair-filtration,theporewidthoffiltersisover0.45

m.Removalofm/ofromairbythefibrousfiltermayoccurbyone,orcombinationofthefollowingmechanisms:InertialimpactionInterceptionDiffusionElectrostaticattraction–SizeexclusionRemovalmechanisms–DiffusionalInterception–ElectrostaticAttraction–InertialimpactionDepthFiltersFibrousmaterial(cellulose,syntheticfibers,glassfibers)Granularmaterial(activatedcharcoal)AiroutletSupportgridStainlesssteelcasingFibrousfilterpackingSupportgridAirinletSimpleairfilterContaminantsinCompressedAirAtmosphericdust,smoke,fumes,watervapour,bacteriaandviruses!Oilcarriedoverfromthecompressor.Solidcontaminantsgeneratedwithinthesystem.TheproposeofairpretreatmentMakingairmoreclean-upperaircollectingpipe-coarsefilterOilandwaterdischargeTheprocessofairfiltrationexample1.Coarsefilter5.Cycloneseparator2.Aircompressor(120

150℃)7.Wiremeshdemister3.Recovertank8.Heater(3035℃)4.6.Cooler(20

25℃)9.FilterCycloneseparatorwiremeshdemisterorwiremeshmisteliminatorsAllaircompressorscreatecondensate.Duringtheactofcompression,theairtemperatureisraisedwhichincreasestheair’smoistureholdingcapacityandpreventscondensation.However,whenthecompressedaircoolsintheaftercooler,air-receiver,piping,etc,thedewpointisreachedandcondensationoccurs.180M3FermenterPlantAirCompressorAirFiltersinFermentationPlantMethodsused