《食品生物化學(xué)》課件-6-3酶與食品加工

EnzymesandfoodprocessingFoodBiochemistry食品生物化學(xué)目錄catalogue12ImportantenzymesinfoodEffectsofenzymesonfoodqualityAndapplyImportantenzymesinfood01Enzymesandfoodprocessing6.3HydrolaseImportantenzymesinfoodamylaseproteasepectinaselipaseOxidoreductasespolyphenoloxidaseLipoxygenaseglucoseoxidasecatalasePeroxidaseflavourenzymeFoodbiochemistryEnzymesandfoodprocessing6.3alpha-amylaseEndonuclease,whichrandomlyhydrolyzesalpha-1,4-glucosidebonds,cannothydrolyzealpha-1,6-glucosidebonds.Hydrolyzedamyloseendproductsmaltoseandglucose.Theendproductsofhydrolyzedamylopectinareglucose,maltoseandaseriesoflimitingdextrinsorisomaltosecontainingα-1,6-glucosidebonds.FoodbiochemistryEnzymesandfoodprocessing6.3beta-amylaseExonucleasecanonlyhydrolyzetheβ-1,4-glucosidebond.Startingfromthenon-reducingendofstarchmolecules,themaltoseunitsarecutoffsuccessively,andthecutβ-maltoseisconvertedintoβ-maltose.Theendproductsoftheactionareβ-maltoseandincompletelimitdextrin.FoodbiochemistryEnzymesandfoodprocessing6.3GlucoseamylaseExonucleasehydrolyzesalpha-1,4,alpha-1,6,andalpha-1,3glycosidicbonds,butthelattertwoarehydrolyzedmoreslowly.Whenactingonthestarchfulcrum,oneglucoseunitiscutoffsuccessivelyfromthenon-reducingend.Whenactingonamyloseoramylopectin,theendproductisglucose.FoodbiochemistryEnzymesandfoodprocessing6.3DebranchingenzymeDebranchedenzymesaredistributedinmanyplants,animalsandmicroorganisms.Theyareaclassofenzymesthathydrolyzeα-1,6-glucosidebondsinstarchandglycogenmolecules,includingPullulanaseandisoamylase.FoodbiochemistryEnzymesandfoodprocessing6.3AnimalproteaseAnimalproteasesarefoundinthedigestivetractsofhumansandmammals.Suchaspepsin,trypsin,chymotrypsin,elastaseandcarboxypeptidase.Animalproteasesaremainlyusedinmedicine.FoodbiochemistryEnzymesandfoodprocessing6.3PlantproteaseThemainpapain,figsinandbromelainhavebeenwidelyusedinfoodindustry.Allbelongtomercaptoproteaseandendopeptidase,andhavebroadspecificitytosubstrate.FoodbiochemistryEnzymesandfoodprocessing6.3MicrobialproteaseManymicroorganismscontainavarietyofproteases,whichareimportantsourcesfortheproductionofproteasepreparations.ThemainstrainsproducingmicrobialproteaseareBacillussubtilis,AspergillusNigerandAspergillusoryzae.FoodbiochemistryEnzymesandfoodprocessing6.3pectinesteraseItcancatalyzethereactionofpectindemethylationtoformpolygalacturonicacidchainandmethanol.Intheprocessingoffruitsandvegetables,ifpectinesteraseisactivated,itwillcausealargenumberofpectintodemethylester,affectthetextureoffruitsandvegetables,andproducemethanol,whichistoxictohumanbody.FoodbiochemistryEnzymesandfoodprocessing6.3polygalacturonaseTheenzymesthatdegradepectinicacidcanbedividedintotwotypesaccordingtothedifferentwaysofactingonthesubstrate:Oneistherandomhydrolysisoftheglycosidebondofpectinicacid,whichispolygalacturonicendonuclide;Theotheristobreaktheglycosidebondonebyonefromtheendofthepectinicacidchain,whichispolygalacturonicacidexonuclease.FoodbiochemistryEnzymesandfoodprocessing6.3PectinlyaseAgeneraltermforendogenouspolygalacturonicacidlyase,exogenouspolygalacturonicacidlyase,andendogenouspolymethylgalacturonicacidlyase.ThehydrogenattheC4~C5positionofthegalacturonicacidresidueofpectinorpectincanbetrans-eliminatedtobreaktheglucosidebondandgenerategalacturonicacidcontainingunsaturatedbond.FoodbiochemistryEnzymesandfoodprocessing6.3lipaseThecatalytichydrolysisoffattyacidtoglycerolandfattyacidisspecifictothepositionoftheesterbondofthehydrolyzedglyceryltriester.First,the1and3esterbondsarehydrolyzedtogenerateglycerylmonoester,andthenthesecondesterbondistransferredtothefirstorthirdpositionafternon-enzymaticisomerization,andthencompletelyhydrolyzedtoglycerolandfattyacidbylipase.FoodbiochemistryEnzymesandfoodprocessing6.3PolyphenoloxidaseFoundinavarietyofplantsandmicroorganisms.TheoptimalpHisgenerallypH4~7.CationicdetergentandCa2+canactivatepolyphenoloxidase.FoodbiochemistryEnzymesandfoodprocessing6.3LipoxygenaseHighlyspecifictothesubstrate,theactingsubstratefatmustcontainacis-1,4-pentadieneunit(-CH=CH-CH2-CH=CH-)onitsfattyacidresidues.FoodbiochemistryEnzymesandfoodprocessing6.3GlucoseoxidaseAerobicdehydrogenasecatalyzestheoxidationofglucoseunderaerobicconditions.Glucose+O2→gluconicacid+H2O2Thereactioncanbeusedtoremoveglucoseoroxygen.FoodbiochemistryEnzymesandfoodprocessing6.3catalaseCatalaseisderivedfrommicroorganismsandbreaksdownhydrogenperoxide.Hydrogenperoxidehasstrongoxidation,whichcanleadtounstablequalityoffoodandreducefoodsafety.FoodbiochemistryEnzymesandfoodprocessing6.3peroxidasePeroxidaseusuallycontainsahemeasacogroupthatcatalyzesthefollowingreactions:ROOH+AH2→H2O+ROH+AFoodbiochemistryEnzymesandfoodprocessing6.3FlavorenzymeThespecificenzymesthatplayakeycatalyticroleintheconversionofflavorprecursorstoflavorarecalledflavorenzymes.Thecommonflavorenzymesareallinase,lipoxygenaseandsoon.FoodbiochemistryEffectsandapplicationsofenzymesonfoodquality02Enzymesandfoodprocessing6.3Thebadflavoroffattyfoodsmainlycomesfromthehydrolysisproductsoflipase,andthehydrolyticranciditycanpromoteoxidativerancidity.Afterthelipaseactioninfoodprocessing,someshortchainfreefattyacids(butyricacid,caproicacid,etc.)arereleased,andwhentheirconcentrationisbelowacertainlevel,goodflavorandaromawillbeproduced.TheeffectoflipaseonfoodqualityFoodbiochemistryEnzymesandfoodprocessing6.3Lipoxygenasecanimprovethequalityofsomefoodsundersomeconditions.Inaddition,duetothestronglowtemperaturetoleranceoflipoxygenase,itisbesttostoregreenbeans,soybeans,broadbeans,etc.atlowtemperaturescanalsobehottreatment,sothatlipoxygenasepassivation,otherwiseitiseasytocausequalitydeterioration.EffectoflipoxygenaseonfoodqualityFoodbiochemistryEnzymesandfoodprocessing6.3Hydrogenperoxidecanleadtounstablefoodqualityandreducefoodsafety,sothelowerthecontentinfood,thebetter.Peroxidasealsohaseffectsonnutritionandflavor,suchascatalyzingtheoxidationofvitaminCanddisruptingitsphysiologicalfunction;Catalyticperoxidecrackingofunsaturatedfattyacidsproducesundesirableodor.EffectofcatalaseonfoodqualityFoodbiochemistryEnzymesandfoodprocessing6.3Someoftheflavorcompoundsinfruitsandvegetablesareproducedbytheconversionofflavorenzymesdirectlyorindirectlytoflavorprecursors.Aftertheplanttissueisdamaged,theflavorprecursorscanbetransformedintoodorousvolatilecompounds.EffectofflavorenzymesonfoodqualityFoodbiochemistryEnzymesandfoodprocessing6.3Amylasepreparationistheearliesttoachieveindustrialproductionandthelargestproductionofenzymepreparations,accountingforabout50%ofthetotalproductionofenzymepreparations,iswidelyusedinfood,fermentationandotherindustries.ApplicationofamylaseinfoodprocessingFoodbiochemistryEnzymesandfoodprocessing6.3Plantproteasesareoftenusedintenderizingmeatandclarifyingbeer,andarealsousedinmedicineasdigestiveAIDS.Theuseofmicrobialproteaseinfoodindustryismoreandmoreextensive,andtheapplicationofmicrobialproteaseinmeattenderizingcanachievebetterresults.ApplicationofproteaseinfoodprocessingFoodbiochemistryEnzymesandfoodprocessing6.3Intheextractionandclarificationoffruitjuice,thequalityoftheproductproducedbypectinasetreatmentisbetter.Intheprocessin