《食品發(fā)酵工藝》英文課件PPT,食品發(fā)酵工藝,食品,發(fā)酵,工藝,英文,課件,PPT Chapter3SterilizationUnit1MediumSterilizationUnit2AirSterilizationBasictermsSterilizationDisinfectionAntisepsisBacteriostasisAsepsisSterilizationDestructionofallformsofmicrobiallife,includingbacterialspores.MorethoroughthandisinfectionDisinfectionTokillmostofmicrobialformsexceptsomeresistantorganismsorbacteriumspores.e.g.useofalcoholbeforedruginjection.Aboutsterilizationanddisinfection,whichiswrong?A.A.Sterilizationisthekillingofallmicroorganismsinamaterialoronthesurfaceofanobject.B.B.Disinfectionmeansreducingthenumberofviablemicroorganismspresentinasample.C.C.Typicallythelastthingstodiewhenoneattemptssterilizationisthehighlyheat-(andchemical-,etc.)resistantendospores.D.D.Alldisinfectantsarecapableofsterilizing.AntisepsisProcessofinhibitingorpreventinggrowthofmicrobes,mostlyin vitroandnotbactericidalorsporicidal.e.g.useofchemicalagentsonskinetc.Bacteriostasis Processofinhibitingthegrowthofmicroorganisms,in vivo(mostly)orin vitro.e.g.bacteriostaticantibioticsDifferent Kinds of Bacteria“Death”1.Bacteriostatic2.Bacteriocidal3.BacteriolyticLog Cell#TimeTotal cell countViable cell countAsepsis Nolivingmicroorganismsexists.e.g.OR(OperatingRoom)SterilizationconvenientlycategorizedasfollowsI.PhysicalmethodsHeat:Dry heat Moist heatRadiationsUltraviolet radiationsIonizing radiationsFiltrationII.Chemicalmethods1.Chemical agents Alcohols,Chlorine,FormalinSuitableforskinandinstruments2.Radiation3.Dry HeatUltravioletandIonizingRadiationSuitableforsterileroomandinoculationhoodDirect flaming:e.g.inoculatingloopHot-air sterilization:160,2hinhotairoven4.Moist Heat121121，30min 30min inautoclaveSuitableformediumandinstruments5.FiltrationRemovalofbacteriabyfiltermediumUsedforheatsensitivematerialsandfiltratedairFlamingHotairoven -170 C for 1 hour -140 C for 3 hours.DryHeat1.Pasteurization(below100C)Destroyspathogenswithoutalteringtheflavorofthefood.Lowtemperature(holdingmethod):63,30minHightemperature(flashmethod):72,20secMoistHeat2.Boiling(at100C)-killingmostvegetativeformsofbacteria-10minorlongertime3.Autoclaving(above100C)-killingbothvegetativeorganismsandendospores-121-132oCfor15minorlongerMoistHeatvsDryHeatMoistheatDryheatPenetratingpotency higherlowerTemp.forproteinclottinglowerhigherExtraheatreleasedyesnofromcondensationSterilizingpotency:Moistheat DryheatWhyismoistheatmoreefficientthandryheat?Conductivity.Moistureconductstheheatbetterthanadrysystem.dryheatormoistheat?A.is less penetrating and requires longer exposure.B.An autoclave is a high pressure device used to allow the application of above the normal-atmosphere boiling point of water.C.Pasteurization is the application of of less-than boiling temperatures to foods to prevent the growth of food-spoiling organisms as well as various heat-labile pathogens.Cannedfoodcouldbestoredforalongtime,because A.Bacteriacantgointocan.B.Bacteriacantbreathincan.C.Therearenobacteriaincan.D.Bacteriacantsurvivalincan.SterilizationprocessesBatchsterilizationContinuoussterilization Batch sterilization uses steam or direct firing to elevate the temperature,and then cooling water stops the process and brings the material back toward room temperature.BatchsterilizationBatchsterilizationwastesenergyandcanovercookthemediumContinuoussterilization is used to almost eliminate these undesired times because there can be more rapid heat transfer to flowing medium in pipes.ContinuoussterilizationAlso called high temperature short time(HTST)Generally carried out at 140C,whereby sterilization times of 2-3 min are sufficientfermentorstreamstreamCoolingwaterSterilemediummixingtankpumpsterilizingcolumnMaintainingtankcoolingpipeWhataretheequipmentsofcontinuoussterilization?QuestionContinuoussterilizationprocessesInjectionsterilizersSteamisfeddirectlyintorawmedium,sothattemp.risestodesiredlevelalmostimmediately.AdvantagesShorter sterilization time means less thermal degradation of medium.DisadvantagesInsufficient for sterilizing media containing solid matter,on account of inferior rate of heat-transfer in solids.(batch process is recommended for sterilizing such media.)BatchandContinuousSterilizationInaword:Hightemperaturesforshorttimesareusedinpreparingnutrientmediaforindustrialfermentationsandinpasteurizingmilk,becausethiscauseslessdamagetobiochemicalsthanmoreprolongedtimesatlowertemperatures.Filtration Sterilizesolutionsthatmaybedamagedordenaturedbyhightemperaturesorchemicalagents.The pore size for filtering bacteria,yeasts,and fungi is in the range of 0.22-0.45 m(filtration membranes are most popular for this purpose).Filtration:Fluids&AirUnit2AirSterilizationVerylargevolumesofsterileairisrequiredinmanyaerobicfermentationprocess.MethodsforairsterilizationRadiationHightemperatureElectrostaticbacteriaremovalFiltration Airsterilizationisgenerallycarriedoutbyfiltrationtoremoveallparticlesandm/o(bacteria,spores,yeast,mould)fromatmosphericflow.Forreasonofcost,absolutesterilityisneitherpossiblenorcustomaryinpractice.n For germ-filtration of liquids(hydrophobic membrane filters),the pore width is 0.2 m.n For air-filtration,the pore width of filters is over 0.45 m.Removalofm/ofromairbythefibrousfiltermayoccurbyone,orcombinationofthefollowingmechanisms:Inertial impactionInterceptionDiffusionElectrostatic attractionSize exclusionRemoval mechanisms DiffusionalInterception ElectrostaticAttraction Inertial impactionDepthFiltersFibrous material(cellulose,synthetic fibers,glass fibers)Granular material(activated charcoal)Air outletSupport gridStainless steel casingFibrous filter packingSupport gridAir inletSimple air filterContaminantsinCompressedAirAtmospheric dust,smoke,fumes,water vapour,bacteria and viruses!Oil carried over from the compressor.Solid contaminants generated within the system.TheproposeofairpretreatmentMakingairmoreclean-upperaircollectingpipe-coarsefilterOilandwaterdischargeThe process of air filtrationexample1.Coarse filter 5.Cyclone separator 2.Air compressor(120 150)7.Wire mesh demister 3.Recover tank 8.Heater(30 35)4.6.Cooler(20 25)9.FilterCycloneseparatorwire mesh demister or wire mesh mist eliminatorsAllaircompressorscreatecondensate.Duringtheactofcompression,theairtemperatureisraisedwhichincreasestheairsmoistureholdingcapacityandpreventscondensation.However,whenthecompressedaircoolsintheaftercooler,air-receiver,piping,etc,thedewpointisreachedandcondensationoccurs.180M180M3 3 Fermenter PlantFermenter PlantAirCompressorAir Filters in Fermentation PlantMethods used in food preservationMethods used in food preservationFreezingOsmoticpressure(additionofsaltorsugar)OxygendeficitAcidDry(desiccation)AntisepticagentFoodPreservation Killorganisms:canning,pasteurization,cooking,irradiation Inhibitgrowth:refrigeration,freeze,dehydration,lower pH,high salt or sugar,chemicals01036.56072100BoilingPoint PasteurisingTemperature Freezer Fridge BodyTemperature Temperature zonesSAFETY SAFETY DANGERDANGERReviewQuestions1.Tell the difference between sterilization and disinfection,batch sterilization and continuous sterilization(describe the advantages and disadvantages respectively).2.State the procedures of continuous sterilization and the process of air filtration.Tell the functions of each equipment.HappyNationalDay