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Megazyme/Amyloglucosidase (Aspergillus niger) /E-AMGDF-10ML/10ML
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4000-520-616
HighpurityAmyloglucosidase(Aspergillusniger)foruseinresearch,biochemicalenzymeassaysandinvitrodiagnosticanalysis.
EC3.2.1.3
CAZyFamily:GH15
CAS:9032-08-0
glucan1,4-alpha-glucosidase;4-alpha-D-glucanglucohydrolase
FromA.niger.Highpurity. Electrophoreticallyhomogeneous.
StABIlisedliquidin50%(v/v)glycerol.
Forusein MegazymeTotalStarchandDietaryFiber methods.
E-AMGDF-A-100MLspecificallytobeusedwithANKOMTDFDietaryFiberAnalyzer.
Specificactivity:
~36 U/mg(40oC,pH4.5onsolublestarch);
~200U/mL(40oC,pH4.5,p-nitrophenylβ-maltoside);
~3,260U/mL(40oC,pH4.5,solublestarch).
Stability:>4yearsat4oC.
DatabookletsforeachpacksizearelocatedintheDocumentationtab.
ViewMegazyme’slatestGuideforDietaryFiberAnalysis.
Hydrolysisofα-D-glucansandα-D-gluco-oligosaccharidesbycladosporiumresinaeglucoamylases.
McCleary,B.V.&Anderson,M.A.(1980).CarbohydrateResearch,86(1),77-96.
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CulturefiltratesofCladosporiumresinaeATCC20495containamixtureofenzymesabletoconvertstarchandpullulanefficientlyintoD-glucose.Cultureconditionsforoptimalproductionofthepullulan-degrADIngactivityhavebeenestablished.Theamylolyticenzymepreparationwasfractionatedbyion-exchangeandmolecular-sievechromatography,andshowntocontainα-D-glucosidase,α-amylase,andtwoglucoamylases.Theglucoamylaseshavebeenpurifiedtohomogeneityandtheirsubstratespecificitiesinvestigated.Oneoftheglucoamylases(termedP)readilyhydrolysesthe(1→6)-α-Dlinkagesinpullulan,amylopectin,isomaltose,panose,and63-α-D-glucosylmaltotriose.Eachoftheglucoamylasescleavesthe(1→6)-α-Dlinkageinpanosemuchmorereadilythanthatinisomaltose.
Measurementofdietaryfibrecomponents:theimportanceofenzymepurity,activityandspecificity.
McCleary,B.V.(2001),“AdvancedDietaryFibreTechnology”,(B.V.McClearyandL.Prosky,Eds.),BlackwellScience,Oxford,U.K.,pp.89-105.
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Interestindietaryfibreisundergoingadramaticrevival,thanksinparttotheintroductionofnewcarbohydratesasdietaryfibrecomponents.Muchemphasisisbeingplacedondetermininghowmuchfibreispresentinafood.Linkingaparticularamountoffibretoaspecifichealthbenefitisnowanimportantareaofresearch.Theterm"dietaryfibre"firstappearedin1953,andreferredtohemicelluloses,cellulosesandlignin(Theandere/tf/.1995).Trowell(1974)recommendedthistermasareplacementforthenolongeracceptableterm"crudefibre".Burkitt(1995)haslikenedtheinterestindietaryfibretothegrowthofariverfromitsfirsttrickletoamightytorrentHeobservesthatdietaryfibre"wasfirstviewedasmerelythelessdigestIBLeconstituentoffoodwhichexertsalaxativeactionbyirritatingthegut",thusacquiringthedesignation"roughage"-atermlaterreplacedby"crudefibre"andultimatelyby"dietaryfibre".Variousdefinitionsofdietaryfibrehaveappearedovertheyears,partlyduetothevariousconceptsusedinderivingtheterm(i.e.originofmaterial,resistancetodigestion,fermentationinthecolon,etc.),andpartlytothedifficultiesassociatedwithitsmeasurementandlabelling(Mongeauetal.1999).Theprincipalcomponentsofdietaryfibre,astraditionallyunderstood,arenon-starchpolysaccharides(whichinplantfibreareprincipallyhemicellulosesandcelluloses),andthenon-carbohydratephenoliccomponents,cutin,suberinandwaxes,withwhichtheyareassociatedinnature.In1976,thedefinitionofdietaryfibrewasmodifiedtoincludegumsandsomepecticsubstances,basedontheresistancetodigestionofthesecomponentsintheupperintestinaltract.Forthepurposesoflabelling,Englystetal.(1987)proposedthatdietaryfibrebedefinedas"non-starchpolysaccharides(NSP)inthedietthatarenotdigestedbytheendogenoussecretionsofthehumandigestivetract".MethodswereconcurrentlydevelopedtospecificallymeasureNSP(Englystetal.1994).
Dietaryfiberandavailablecarbohydrates.
McCleary,B.V.&Rossiter,P.C.(2007).“DietaryFiber:AnInternationalPerspectiveforHarmonizationofHealthBenefitsandEnergyValues”,(DennisT.GordonandToshinaoGoda,Eds.),AACCInternational,Inc.,pp.31-59.
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Debatecontinuesonthedefinitionofdietaryfiber(DF),methodsformeasurementofDF,andmethodsformeasurementofthecarbohydratesthatarereadilyhydrolyzedandabsorbedinthehumansmallintestine.HenNEBergandStahmanndevelopedthe"Wende"proximatesystemforanalysisoffoodsin1860,andasetofvaluesobtainedusingthismethodwerepublishedbyAtwaterandBryantin1900.ThismethodisstillinuseintheUSAforthemeasurementoftotalcarbohydrate.Inthisprocedure,totalcarbohydrateismeasuredbydifferenceafterdeductingthemoisture,protein,fatandashfromthetotalweight.Carbohydratecalculatedinthiswaycontainsnotonlysugarandstarch,butalsothe"unavailablecarbohydrate"ofDF.However,thereareanumberofproblemswiththisapproach,asthe"bydifference"figureincludesanumberofnon-carbohydratecomponentssuchaslignin,organicacids,tannins,waxesandsomeMaillardproducts.Inadditiontothiserror,itcombinesalloftheanalyticalerrorsfromtheotheranalyses(FAO1997).AneedforinformationonthecarbohydratecompositionoffoodsfordiabeticspromptedMcCanceandLawrence(1929)toattempttomeasurecarbohydratecompositiontogainresultsthatwouldbeofBIOLOGicalsignificance.Theydividedthecarbohydratesinfoodsintotwobroadgroups,"available"and"unavailable".Theavailablecarbohydrates,thatis,sugarplusstarch,weredefinedasthosethataredigestedandabsorbedbymanandareglucogenic.Theunavailablecarbohydratesweredefinedasthosethatarenotdigestedbytheendogenoussecretionsofthehumandigestivetract.Inthemid1920s,McCanceobtainedagrantof£30peryearfromtheMedicalResearchCounciltoanalyserawandcookedfruitsandvegetablesfortotal"availablecarbohydrate";valuesneededforcalculatingdiabeticdiets.
MeasurementofamyloglucosidaseusingP-nitrophenylβ-maltosideassubstrate.
McCleary,B.V.,Bouhet,F.&Driguez,H.(1991).BiotechnologyTechniques,5(4),255-258.
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Anenzyme-linkedassayforthemeasurementofamyloglucosidaseincommercialenzymemixturesandcrudeculturefiltratesisdescribed.Amethodforthesynthesisofthesubstrateemployed,p-nitrophenylβ-D-maltoside,isalsodescribed.Thesubstrateisusedinthepresenceofsaturatinglevelsofβ-glucosidase.WitharangeofAspergillussp.culturefiltrates,anexcellentcorrelationwasfoundforvaluesobtainedwiththisassayandaconventionalassayemployingmaltoseassubstratewithmeasurementofreleasedglucose.
Measuringdietaryfibre.
McCleary,B.V.(1999).TheWorldofIngredients,50-53.
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Interestindietaryfibreisundergoingadramaticrevivalthanksinparttotheintroductionofnewcarbohydratesasdietaryfibrecomponents.Muchemphasisisbeingplacedondetermininghowmuchfibreispresentinafood.Linkingaparticularamountoffibretoaspecifichealthbenefitisnowanimportantareaofresearch.TotalDietaryFibre.Theterm“dietaryfibre”firstappearedin1953andreferredtohemicelluloses,cellulosesandlignin(1).In1974,Trowell(2)recommendedthistermasareplacementforthenolongeracceptableterm“crudefibre”Burkitt(3)haslikenedtheinterestindietaryfibretothegrowthofariverfromitsfirsttrickletoamightytorrent.Heobservesthatdietaryfibre“wasviewedasmerelythelessdigestibleconstituentoffoodwhichexertsalaxativeactionbyirritatingthegut“thusacquiringthedesignation“roughage”atermwhichwaslaterreplacedby“crudefibre”andultimatelyby“dietaryfibre”Variousdefinitionsofdietaryfibrehaveappearedovertheyears,partlyduethevariousconceptsusedinderivingtheterm(i.e.originofmaterial,resistancetodigestion,fermentationinthecolonetc.),andpartlytothedifficultiesassociatedwithitsmeasurementandlabelling(4).Theprinciplecomponentsofdietaryfibre,astraditionallyunderstood,arenon-starchpolysaccharides,whichinplantfibreareprincipallyhemicellulosesandcelluloses,andthenon-carbohydratephenoliccomponents,cutin,suberinandwaxeswithwhichtheyareassociatedinNature.
Enzymepurityandactivityinfibredeterminations.
McCleary,B.V.(1999).CerealFoodsWorld,44(8),590-596.
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Dietaryfiberismainlycomposedofplantcellwallpolysaccharidessuchascellulose,hemicellulose,andpecticsubstances,butitalsoincludesligninandotherminorcomponents(1).Basically,itcoversthepolysaccharidesthatarenothydrolyzedbytheendogenoussecretionsofthehumandigestivetract(2,3).Thisdefinitionhasservedasthetargetforthosedevelopinganalyticalproceduresforthemeasurementofdietaryfiberforqualitycontrolandregulatoryconsiderations(4).Mostproceduresforthemeasurementoftotaldietaryfiber(TDF),orspecificpolysaccharidecomponents,eitherinvolvesomeenzymetreatmentstepsoraremainlyenzyme-based.InthedevelopmentofTDFproceduressuchastheProskymethod(AOACInternational985.29,AACC32—05)(5),theUppsalamethod(AACC32-25)(6),andtheEnglystmethod(7),theaimwastoremovestarchandproteinthroughenzymetreatment,andtomeasuretheresidueasdietaryfiber(afterallowingforresidual,undigestedproteinandash).Dietaryfiberwasmeasuredeithergravimetricallyorbychemicalorinstrumentalprocedures.Manyoftheenzymetreatmentstepsineachofthemethods,particularlytheprosky(5)andtheUppsala(6)methodsareverysimilar.Asanewrangeofcarbohydratesisbeingintroducedaspotentialdietaryfibercomponents,theoriginalassayprocedureswillneedtobereexamined,andinsomecasesslightlymodified,toensureaccurateandquantitativemeasurementofthesecomponentsandofTDF.These“new”dietaryfibercomponentsincluderesistantnondigestibleoligosaccharides;nativeandchemicallymodifiedpolysaccharidesofplantandalgalorigin(galactomannan,chemicallymodifiedcelluloses,andagarsandcarrageenans);andresistantstarch.Tomeasurethesecomponentsaccurately,thepurity,activity,andspecificityoftheenzymesemployedwillbecomemuchmoreimportant.Aparticularexampleofthisisthemesurementoffructan.Thiscarbohydrateconsistsofafractionwithahighdegreeofpolymerization(DP)thatisprecipitatedinthestandardProskymethod(5,8)andalowDPfractionconsequentlyisnotmeasured(9).Resistantstarchposesaparticularproblem.Thiscomponentisonlypartiallyresistanttodegradationbyα-amylase,sothelevelofenzymeusedandtheincubationconditions(timeandtemperature)arecritical.
Importanceofenzymepurityandactivityinthemeasurementoftotaldietaryfibreanddietaryfibrecomponents.
McCleary,B.V.(2000).JournalofAOACInternational,83(4),997-1005.
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Astudywasmadeoftheeffectoftheactivityandpurityofenzymesintheassayoftotaldietaryfiber(AOACMethod985.29)andspecificdietaryfibercomponents:resistantstarch,fructan,andβ-glucan.Inthemeasurementoftotaldietaryfibercontentofresistantstarchsamples,theconcentrationofα-amylaseiscritical;however,variationsinthelevelofamyloglucosidasehavelittleeffect.Contaminationofamyloglucosidasepreparationswithcellulasecanresultinsignificantunderestimationofdietaryfibervaluesforsamplescontainingβ-glucan.Pureβ-glucanandcellulasepurifiedfromAspergillusnigeramyloglucosidasepreparationswereusedtodetermineacceptablecriticallevelsofcontamination.Sucrose,whichinterfereswiththemeasurementofinulinandfructooligosaccharidesinplantmaterialsandfoodproducts,mustberemovedbyhydrolysisofthesucrosetoglucoseandfructosewithaspecificenzyme(sucrase)followedbyborohydridereductionofthefreesugars.Unlikeinvertase,sucrasehasnoactiononlowdegreeofpolymerization(DP)fructooligosaccharides,suchaskestoseorkestotetraose.Fructanishydrolyzedtofructoseandglucosebythecombinedactionofhighlypurifiedexo-andendo-inulinases,andthesesugarsaremeasuredbythep-hydroxybenzoicacidhydrazidereducingsugarmethod.Specificmeasurementofβ-glucanincerealflourandfoodextractsrequirestheuseofhighlypurifiedendo-1,3:1,4β-glucanaseandA.nigerβ-glucosidase.β-glucosidasefromalmondsdoesnotcompletelyhydrolyzemixedlinkageβ-glucooligosaccharidesfrombarleyoroatβ-glucan.Contaminationoftheseenzymeswithstarch,maltosaccharide,orsucrose-hydrolyzingenzymesresultsinproductionoffreeglucosefromasourceotherthanβ-glucan,andthusanoverestimationofβ-glucancontent.Theglucoseoxidaseandperoxidaseusedintheglucosedeterminationreagentmustbeessentiallydevoidofcatalaseandα-andβ-glucosidase.
Twoissuesindietaryfibermeasurement.
McCleary,B.V.(2001).CerealFoodsWorld,46,164-165.
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Enzymeactivityandpurityofthesetopics,theeasiesttodealwithistheimportanceofenzymepurityandactivity.Asascientistactivelyinvolvedinpolysaccharideresearchoverthepast25years,Ihavecometoappreciatetheimportanceofenzymepurityandspecificityinpolysaccharidemodificationandmeasurement(7).Thesefactorstranslatedirectlytodietaryfiber(DF)methodology,becausethemajorcomponentsofDFarecarbohydratepolymersandoligomers.ThecommitteereportpublishedintheMarchissueofCerealFOODSWORLDrefersonlytothemethodologyformeasuringenzymepurityandactivity(8)thatleduptheAOACmethod985.29(2).Inthisworkenzymepuritywasgaugedbythelackofhydrolysis(i.e.,completerecovery)ofaparticularDFcomponent(e.g.β-glucan,larchgalactanorcitruspectin).Enzymeactivitywasmeasuredbytheabilitytocompletelyhydrolyzerepresentativestarchandprotein(namelywheatstarchandcasein).Theserequirementsandrestrictionsonenzymepurityandactivitywereadequateatthetimethemethodwasinitiallydevelopedandservedasausefulworkingguide.However,itwasrecognizedthattherewasaneedformorestringentqualitydefinitionsandassayproceduresforenzymesusedinDFmeasurements.
Dietaryfibreanalysis.
McCleary,B.V.(2003).ProceedingsoftheNutritionSociety,62,3-9.
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The"goldstandard"methodforthemeasurementoftotaldietaryfibreisthatoftheAssociationofOfficialAnalyticalChemists(2000;method985.29).Thisprocedurehasbeenmodifiedtoallowmeasurementofsolubleandinsolubledietaryfibre,andbuffersemployedhavebeenimproved.However,therecognitionofthefactthatnon-digestibleoligosaccharidesandresistantstarchalsobehavephysiologicallyasdietaryfibrehasnecessitatedare-examinationofthedefinitionofdietaryfibre,andinturn,are-evaluationofthedietaryfibremethodsoftheAssociationofOfficialAnalyticalChemists.Withthisrealisation,theAmericanAssociationofCerealChemistsappointedascientificreviewcommitteeandchargeditwiththetaskofreviewingand,ifnecessary,updatingthedefinitionofdietaryfibre.Itorganisedvariousworkshopsandacceptedcommentsfrominterestedpartiesworldwidethroughaninteractivewebsite.Morerecently,the(US)FoodandNutritionBoardoftheInstituteofHealth,NationalAcademyofSciences,undertheoversightoftheStandingCommitteeontheScientificEvaluationofDietaryReferenceIntakes,assembledapaneltodevelopaproposeddefinition(s)ofdietaryfibre.Variouselementsofthesedefinitionswereinagreement,butnotall.Whatwasclearfrombothreviewsisthatthereisanimmediateneedtore-evaluatethemethodsthatareusedfordietaryfibremeasurementandtomakeappropriatechangeswhererequired,andtofindnewmethodstofillgaps.Inthispresentation,the"stateoftheart"inmeasurementoftotaldietaryfibreanddietaryfibrecomponentswillbedescribedanddiscussed,togetherwithsuggestionsforfutureresearch.
Measurementofnoveldietaryfibres.
McCleary,B.V.&Rossiter,P.(2004).JournalofAOACInternational,87(3),707-717.
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Withtherecognitionthatresistantstarch(RS)andnondigestibleoligosaccharides(NDO)actphysiologicallyasdietaryfiber(DF),aneedhasdevelopedforspecificandreliableassayproceduresforthesecomponents.TheabilityofAOACDFmethodstoaccuratelymeasureRSisdependentonthenatureoftheRSbeinganalyzed.Ingeneral,NDOarenotmeasuredatallbyAOACDFMethods985.29or991.43,theoneexceptionbeingthehighmolecularweightfractionoffructo-oligosaccharides.ValuesobtainedforRS,ingeneral,arenotingoodagreementwithvaluesobtainedbyinvitroproceduresthatmorecloselyimitatetheinvivosituationinthehumandigestivetract.Consequently,specificmethodsfortheaccuratemeasurementofRSandNDOhavebeendevelopedandvalidatedthroughinterlaboratorystudies.Inthispaper,modificationstoAOACfructanMethod999.03toallowaccuratemeasurementofenzymicallyproducedfructo-oligosaccharidesaredescribed.SuggestedmodificationstoAOACDFmethodstoensurecompleteremovaloffructanandRS,andtosimplifypHadjustmentbeforeamyloglucosidaseaddition,arealsodescribed.
Anintegratedprocedureforthemeasurementoftotaldietaryfibre(includingresistantstarch),non-digestibleoligosaccharidesandavailablecarbohydrates.
McCleary,B.V.(2007).AnalyticalandBioanalyticalChemistry,389(1),291-308.
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Amethodisdescribedforthemeasurementofdietaryfibre,includingresistantstarch(RS),non-digestibleoligosaccharides(NDO)andavailablecarbohydrates.Basically,thesampleisincubatedwithpancreaticα-amylaseandamyloglucosidaseunderconditionsverysimilartothosedescribedinAOACOfficialMethod2002.02(RS).Reactionisterminatedandhighmolecularweightresistantpolysaccharidesareprecipitatedfromsolutionwithalcoholandrecoveredbyfiltration.RecoveryofRS(formostRSsources)isinlinewithpublisheddatafromileostomystudies.Theaqueousethanolextractisconcentrated,desaltedandanalysedforNDObyhigh-performanceliquidchromatographybyamethodsimilartothatdescribedbyOkuma(AOACMethod2001.03),exceptthatforlogisticalreasons,D-sorbitolisusedastheinternalstandardinplaceofglycerol.Availablecarbohydrates,definedasD-glucose,D-fructose,sucrose,theD-glucosecomponentoflactose,maltodextrinsandnon-resistantstarch,aremeasuredasD-glucoseplusD-fructoseinthesampleafterhydrolysisofoligosaccharideswithamixtureofsucrase/maltaseplusβ-galactosidase.
Developmentandevaluationofanintegratedmethodforthemeasurementoftotaldietaryfibre.
McCleary,B.V.,Mills,C.&Draga,A.(2009).QualityAssuranceandSafetyofCrops&Foods,1(4),213–224.
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Anintegratedtotaldietaryfibre(TDF)method,consistentwiththerecentlyacceptedCODEXdefinitionofdietaryfibre,hasbeendeveloped.TheCODEXCommitteeonNutritionandFoodsforSpecialDietaryUses(CCNFSDU)hasbeendeliberatingforthepast8yearsonadefinitionfordietaryfibrethatcorrectlyreflectsthecurrentconsensusthinkingonwhatshouldbeincludedinthisdefinition.Asthisdefinitionwasevolving,itbecameevidenttousthatneitherofthecurrentlyavailablemethodsforTDF(AOACOfficialMethods985.29and991.43),noracombinationoftheseandothermethods,couldmeettheserequirements.Consequently,wedevelopedanintegratedTDFprocedure,basedontheprincipalsofAOACOfficialMethods2002.02,991.43and2001.03,thatiscompliantwiththenewCODEXdefinition.Thisprocedurequantitateshigh-andlow-molecularweightdietaryfibresasdefined,givinganaccurateestimateofresistantstarchandnon-digestibleoligosaccharidesalsoreferredtoaslow-molecularweightsolubledietaryfibre.Inthispaper,themethodisdiscussed,modificationstothemethodtoimprovesimplicityandreproducibilityaredescribed,andtheresultsofthefirstroundsofinterlaboratoryevaluationarereported.
Determinationoftotaldietaryfiber(CODEXdefinition)byenzymatic-gravimetricmethodandliquidchromatography:collaborativestudy.
McCleary,B.V.,DeVries,J.W.,Rader,J.I.,Cohen,G.,Prosky,L.,Mugford,D.C.,Champ,M.&Okuma,K.(2010).JournalofAOACInternational,93(1),221-233.
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Amethodforthedeterminationoftotaldietaryfiber(TDF),asdefinedbytheCODEXAlimentarius,wasvalidatedinfoods.BasedupontheprinciplesofAOACOfficialMethodsSM985.29,991.43,2001.03,and2002.02,themethodquantitateshigh-andlow-molecular-weightdietaryfiber(HMWDFandLMWDF,respectively).In2007,McClearydescribedamethodofextendedenzymaticdigestionat37°CtosimulatehumanintestinaldigestionfollowedbygravimetricisolationandquantitationofHMWDFandtheuseofLCtoquantitatelow-molecular-weightsolubledietaryfiber(LMWSDF).Themethodthusquantitatesthecompleterangeofdietaryfibercomponentsfromresistantstarch(byutilizingthedigestionconditionsofAOACMethod2002.02)todigestionresistantoligosaccharides(byincorporatingthedeionizationandLCproceduresofAOACMethod2001.03).ThemethodwasevaluatedthroughanAOACcollaborativestudy.Eighteenlaboratoriesparticipatedwith16laboratoriesreturningvalidassaydatafor16testportions(eightblindduplicates)consistingofsampleswitharangeoftraditionaldietaryfiber,resistantstarch,andnondigestibleoligosaccharides.Thedietaryfibercontentoftheeighttestpairsrangedfrom11.57to47.83.DigestionofsamplesundertheconditionsofAOACMethod2002.02followedbytheisolationandgravimetricproceduresofAOACMethods985.29and991.43resultsinquantitationofHMWDF.ThefiltratefromthequantitationofHMWDFisconcentrated,deionized,concentratedagain,andanalyzedbyLCtodeterminetheLMWSDF,i.e.,allnondigestibleoligosaccharidesofdegreeofpolymerization3.TDFiscalculatedasthesumofHMWDFandLMWSDF.Repeatabilitystandarddeviations(Sr)rangedfrom0.41to1.43,andreproducibilitystandarddeviations(SR)rangedfrom1.18to5.44.Theseresultsarecomparabletootherofficialdietaryfibermethods,andthemethodisrecommendedforadoptionasOfficialFirstAction.
Determinationofinsoluble,soluble,andtotaldietaryfiber(codexdefinition)byenzymatic-gravimetricmethodandliquidchromatography:CollaborativeStudy.
McCleary,B.V.,DeVries,J.W.,Rader,J.I.,Cohen,G.,Prosky,P.,Mugford,D.C.,Champ,M.&Okuma,K.(2012).JournalofAOACInternational,95(3),824-844.
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Amethodforthedeterminationofinsoluble(IDF),soluble(SDF),andtotaldietaryfiber(TDF),asdefinedbytheCODEXAlimentarius,wasvalidatedinfoods.BasedupontheprinciplesofAOACOfficialMethodsSM985.29,991.43,2001.03,and2002.02,themethodquantitateswater-insolubleandwater-solubledietaryfiber.ThismethodextendsthecapabilitiesofthepreviouslyadoptedAOACOfficialMethod2009.01,TotalDietaryFiberinFoods,Enzymatic-Gravimetric-LiquidChromatographicMethod,applicabletoplantmaterial,foods,andfoodingredientsconsistentwithCODEXDefinition2009,includingnaturallyoccurring,isolated,modified,andsyntheticpolymersmeetingthatdefinition.ThemethodwasevaluatedthroughanAOAC/AACCcollaborativestudy.Twenty-twolaboratoriesparticipated,with19laboratoriesreturningvalidassaydatafor16testportions(eightblindduplicates)consistingofsampleswitharangeoftraditionaldietaryfiber,resistantstarch,andnondigestibleoligosaccharides.Thedietaryfibercontentoftheeighttestpairsrangedfrom10.45to29.90%.DigestionofsamplesundertheconditionsofAOAC2002.02followedbytheisolation,fractionation,andgravimetricproceduresofAOAC985.29(anditsextensions991.42and993.19)and991.43resultsinquantitationofIDFandsolubledietaryfiberthatprecipitates(SDFP).Thefiltratefromthequantitationofwater-alcohol-insolubledietaryfiberisconcentrated,deionized,concentratedagain,andanalyzedbyLCtodeterminetheSDFthatremainssoluble(SDFS),i.e.,alldietaryfiberpolymersofdegreeofpolymerization=3andhigher,consistingprimarily,butnotexclusively,ofoligosaccharides.SDFiscalculatedasthesumofSDFPandSDFS.TDFiscalculatedasthesumofIDFandSDF.Thewithin-laboratoryvariability,repeatabilitySD(Sr),forIDFrangedfrom0.13to0.71,andthebetween-laboratoryvariability,reproducibilitySD(sR),forIDFrangedfrom0.42to2.24.Thewithin-laboratoryvariabilitysrforSDFrangedfrom0.28to1.03,andthebetween-laboratoryvariabilitysRforSDFrangedfrom0.85to1.66.Thewithin-laboratoryvariabilitysrforTDFrangedfrom0.47to1.41,andthebetween-laboratoryvariabilitysRforTDFrangedfrom0.95to3.14.Thisiscomparabletootherofficialandapproveddietaryfibermethods,andthemethodisrecommendedforadoptionasOfficialFirstAction.
MeasurementoftotaldietaryfiberusingAOACmethod2009.01(AACCInternationalapprovedmethod32-45.01):Evaluationandupdates.
McCleary,B.V.,Sloane,N.,Draga,A.&Lazewska,I.(2013).CerealChemistry,90(4),396-414.
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TheCodexCommitteeonMethodsofAnalysisandSamplingrecentlyrecommended14methodsformeasurementofdietaryfiber,eightofthesebeingtypeImethods.OfthesetypeImethods,AACCInternationalApprovedMethod32-45.01(AOACmethod2009.01)istheonlyprocedurethatmeasuresallofthedietaryfibercomponentsasdefinedbyCodexAlimentarius.OthermethodssuchastheProskymethod(AACCIApprovedMethod32-05.01)givesimilaranalyticaldataforthehigh-molecular-weightdietaryfibercontentsoffoodandvegetableproductslowinresistantstarch.Inthecurrentwork,AACCIApprovedMethod32-45.01hasbeenmodifiedtoallowaccuratemeasurementofsampleshighinparticularfructooligosaccharides:forexample,fructotriose,which,intheHPLCsystemused,chromatographsatthesamepointasdisaccharides,meaningthatitiscurrentlynotincludedinthemeasurement.Incubationoftheresistantoligosaccharidesfractionwithsucrase/β-galactosidaseremovesdisaccharidesthatinterferewiththequantitationofthisfraction.Thedietaryfibervalueforresistantstarchtype4(RS4),variessignificantlywithdifferentanalyticalmethods,withmuchlowervaluesbeingobtainedwithAACCIApprovedMethod32-45.01thanwith32-05.01.ThisdifferenceresultsfromthegreatersusceptibilityofRS4tohydrolysisbypancreaticα-amylasethanbybacterialα-amylase,andalsoagreatersusceptibilitytohydrolysisatlowertemperatures.OnhydrolysisofsampleshighinstarchintheassayformatofAACCIApprovedMethod32-45.01(AOACmethod2009.01),resistantmaltodextrinsareproduced.Themajorcomponentisaheptasaccharidethatishighlyresistanttohydrolysisbymostofthestarch-degradingenzymesstudied.However,itishydrolyzedbythemaltase/amyloglucosidase/isomaltaseenzymecomplexpresentinthebrushborderliningofthesmallintestine.Asaconsequence,AOACmethods2009.01and2011.25(AACCIApprovedMethods32-45.01and32-50.01,respectively)mustbeupdatedtoincludeanadditionalincubationwithamyloglucosidasetoremovetheseoligosaccharides.
ModificationtoAOACOfficialMethods2009.01and2011.25toallowforminoroverestimationoflowmolecularweightsolubledietaryfiberinsamplescontainingstarch.
McCleary,B.V.(2014).JournalofAOACInternational,97(3),896-901.
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AOACOfficialMethods2009.01and2011.25havebeenmodifiedtoallowremovalofresistantmaltodextrinsproducedonhydrolysisofvariousstarchesbythecombinationofpancreaticα-amylaseandamyloglucosidase(AMG)usedintheseassayprocedures.Themajorresistantmaltodextrin,63,65-di-α-D-glucosylmaltopentaose,ishighlyresistanttohydrolysisbymicrobialα-glucosidases,isoamylase,pullulanase,pancreatic,bacterialandfungalα-amylaseandAMG.However,thisoligosaccharideishydrolyzedbythemucosalα-glucosidasecomplexofthepigsmallintestine(whichissimilartothehumansmallintestine),andthusmustberemovedintheanalyticalprocedure.HydrolysisoftheseoligosaccharideshasbeenbyincubationwithahighconcentrationofapurifiedAMGat60°C.ThisincubationresultsinnohydrolysisorlossofotherresistantoligosaccharidessuchasFOS,GOS,XOS,resistantmaltodextrins(e.g.,Fibersol2)orpolydextrose.TheeffectofthisadditionalincubationwithAMGonthemeasuredleveloflowmolecularweightsolubledietaryfiber(SDFS)andoftotaldietaryfiberinabroadrangeofsamplesisreported.Resultsfromthisstudydemonstratethattheproposedmodificationcanbeusedwithconfidenceinthemeasurementofdietaryfiber.
Physical,microscopicandchemicalcharacterisationofindustrialryeandwheatbransfromtheNordiccountries.
Kamal-Eldin,A.,Lærke,H.N.,Knudsen,K.E.B.,Lampi,A.M.,Piironen,V.,Adlercreutz,H.,Katina,K.,Poutanen,K.&Aman,P.(2009).Food&nutritionresearch,53.
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Background:Epidemiologicalstudiesshowinverserelationshipbetweenintakeofwholegraincerealsandseveralchronicdiseases.Componentsandmechanismsbehindpossibleprotectiveeffectsofwholegraincerealsarepoorlyunderstood.Objective:Tocharacterisecommercialryebranpreparations,comparedtowheatbran,regardingstructureandcontentofnutrientsaswellasanumberofpresumablybioactivecompounds.Design:SixdifferentryebransfromSweden,DenmarkandFinlandwereanalysedandcomparedwithtwowheatbransregardingcolour,particlesizedistribution,microscopicstructuresandchemicalcompositionincludingproximalcomponents,vitamins,mineralsandbioactivecompounds.Results:Ryebransweregenerallygreenerincolourandsmallerinparticlesizethanwheatbrans.Theryebransvariedconsiderablyintheirstarchcontent(13.2–;28.3%),whichreflectedvariableinclusionofthestarchyendosperm.Althoughryeandwheatbranscontainedcomparablelevelsoftotaldietaryfibre,theydifferedintherelativeproportionsoffibrecomponents(i.e.arabinoxylan,β-glucan,cellulose,fructanandKlasonlignin).Generally,ryebranscontainedlesscelluloseandmoreβ-glucanandfructanthanwheatbrans.Withinsmallvariations,theryeandwheatbranswerecomparableregardingthecontentsoftocopherols/tocotrienols,totalfolate,sterols/stanols,phenolicacidsandlignans.Ryebranhadlessglycinebetaineandmorealkylresorcinolsthanwheatbrans.Conclusions:Theobservedvariationinthechemicalcompositionofindustriallyproducedryebranscallsfortheneedofstandardisationofthiscommodity,especiallywhenusedasafunctionalingredientinfoods.
Relationshipofgrainfructancontenttodegreeofpolymerisationindifferentbarleys.
Nemeth,C.,Andersson,A.A.M.,Andersson,R.,Mangelsen,E.,Sun,C.&Åman,P.(2014).FoodandNutritionSciences,5,581-589.
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Fructansareimportantinthesurvivalofplantsandalsovaluableforhumansaspotentiallyhealthpromotingfoodingredients.Inthisstudyfructancontentandcompositionweredeterminedingrainsof20barleybreedinglinesandcultivarswithawidevariationinchemicalcomposition,morphologyandcountryoforigin,grownatonesiteinChile.Therewassignificantgenotypicvariationingrainfructancontentrangingfrom0.9%to4.2%ofgraindryweight.Fructandegreeofpolymerisation(DP)wasanalysedusinghigh-performanceanion-exchangechromatographywithpulsedamperometricdetection(HPAEC-PAD).Changesinthedistributionofdifferentchainlengthsandthepatternofstructuresoffructanweredetectedwithincreasingamountoffructaninthedifferentbarleys.Apositivecorrelationwasfoundbetweenfructancontentandtherelativeamountoflongchainfructan(DP>9)(r=0.54,p=0.021).Ourresultsprovideabasisforselectingpromisingbarleylinesandcultivarsforfurtherresearchonfructaninbarleybreedingwiththeaimtoproducehealthyfoodproducts.
Howdoesthepreparationofryeporridgeaffectmolecularweightdistributionofextractabledietaryfibers?
Rakha,A.,Åman,P.&Andersson,R.(2011).Internationaljournalofmolecularsciences,12(5),3381-3393.
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Extractabledietaryfiber(DF)playsanimportantroleinnutrition.ThisstudyonporridgemakingwithwholegrainryeinvestigatedtheeffectofresttimeofflourslurriesatroomtemperaturebeforecookingandamountofflourandsaltintherecipeonthecontentofDFcomponentsandmolecularweightdistributionofextractablefructan,mixedlinkage(1→3)(1→4)-β-D-glucan(β-glucan)andarabinoxylan(AX)intheporridge.ThecontentoftotalDFwasincreased(fromabout20%to23%ofdrymatter)duringporridgemakingduetoformationofinsolubleresistantstarch.Asmallbutsignificantincreaseintheextractabilityofβ-glucan(P=0.016)andAX(P=0.002)duetoresttimewasalsonoted.ThemolecularweightofextractablefructanandAXremainedstableduringporridgemaking.However,incubationoftheryeflourslurriesatincreasedtemperatureresultedinasignificantdecreaseinextractableAXmolecularweight.Themolecularweightofextractableβ-glucandecreasedgreatlyduringaresttimebeforecooking,mostlikelybytheactionofendogenousenzymes.Theamountofsaltandflourusedintherecipehadsmallbutsignificanteffectsonthemolecularweightofβ-glucan.TheseresultsshowthatwholegrainryeporridgemadewithoutaresttimebeforecookingcontainsextractableDFcomponentsmaintaininghighmolecularweights.Highmolecularweightismostlikelyofnutritionalimportance.
Baselinesrepresentingbloodglucoseclearanceimproveinvitropredictionoftheglycaemicimpactofcustomarilyconsumedfoodquantities.
Monro,J.A.,Mishra,S.&Venn,B.(2010).BritishJournalofNutrition,103(2),295-305.
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Glycaemicresponsestofoodsreflectthebalancebetweenglucoseloadinginto,anditsclearancefrom,theblood.Currentinvitromethodsforglycaemicanalysisdonottakeintoaccountthekeyroleofglucosedisposal.Thepresentstudyaimedtodevelopafoodintake-sensitivemethodformeasuringtheglycaemicimpactoffoodquantitiesusuallyconsumed,asthedifferencebetweenreleaseofglucoseequivalents(GGE)fromfoodduringinvitrodigestionandacorrespondingestimateofclearanceofthemfromtheblood.Fivefoods–whitebread,fruitbread,mueslibar,mashedpotatoandchickpeas–wereconsumedonthreeoccasionsbytwentyvolunteerstoprovidebloodglucoseresponse(BGR)curves.GGEreleaseduringinvitrodigestionofthefoodswasalsoplotted.GlucosedisposalratesestimatedfromdownwardslopesoftheBGRcurvesallowedGGEdose-dependentcumulativeglucosedisposaltobecalculated.BysubtractingcumulativeglucosedisposalfromcumulativeinvitroGGErelease,accuracyinpredictingtheinvitroglycaemiceffectfrominvitroGGEvalueswasgreatlyimproved.GGEinvivo=0·99GGEinvitro+0·75(R20·88).FurThermore,thedifferencebetweenthecurvesofcumulativeGGEreleaseanddisposalcloselymimickedinvivoincrementalBGRcurves.Weconcludethatvalidmeasurementoftheglycaemicimpactoffoodsmaybeobtainedinvitro,andexpressedasgramsofglucoseequivalentsperfoodquantity,bytakingaccountnotonlyofGGEreleasefromfoodduringinvitrodigestion,butalsoofbloodglucoseclearanceinresponsetothefoodquantity.
Effectofprocessingonslowlydigestiblestarchandresistantstarchinpotato.
Mishra,S.,Monro,J.&Hedderley,D.(2008).Starch‐Stärke,60(9),500-507.
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Theeffectofanumberoflaboratory-scalepretreatmentsontheproportionsofrapidlydigested(RDS),slowlydigested(SDS)andresistantstarch(RS)inrawandcookedpotatohasbeenexaminedusinganinvitrodigestionprocedure.PotatoesofthevarietyFrisiawerepreparedinthreestates:raw,cooked,andcookedfollowedbyacoldtreatment(4°C,twodays).Eachpreparationwasthensubjectedintriplicatetofreeze-drying,coarselymincing,pasting,freezing,dry-millingafterfreeze-drying,in22differentcombinations,beforedigesting.Inrawpotato,verylittleRDSandSDS(<5% total="" starch="" (ts))="" were="" present,="" and="" the="" mechanical="" treatments="" of="" the="" potato="" did="" not="" affect="" the="" amounts="" of="" rds="" and="" sds.="" cooking="" resulted="" in="" an="" almost="" complete="" conversion="" to="" rds="" (="">95%TS)infreshly-cookedpotato,butafterpost-cookingcoldtreatmentmuchoftheRDStransformedtoSDS,whichreachedamaximumofabout45%TS.SDSformationwasindependentofthedegreeoftissuedisruptionaftercooking,andwasgenerallyassociatedwithformationofRS,however,freezingaftercookingallowedSDSformationwithoutprolongedcoldtreatmentandwithverylittleassociatedRS(SDS35%andRS4%ofTS).Freeze-dryingcausedanincreaseinRSinmosttreatmentsofthecookedpotatoes.Theobservedeffectsprovidedguidanceforsamplehandlinginpotatoresearch,butalsosuggestedseveralapproachestotheenrichmentofSDSand/orRS,withaconcurrentreductioninRDS,thatcouldbeusedtoimprovethenutritionalprofileofpotatoproductsbydecreasingRDS(loweredglycaemicimpact),andincreasingSDS(moresustainedenergyavailability)andRS(prebioticbenefits).
InvestigationofdigestibilityinvitroandphysicochemicalpropertiesofA-andB-typestarchfromsoftandhardwheatflour.
Liu,Q.,Gu,Z.,Donner,E.,Tetlow,I.&Emes,M.(2007).CerealChemistry,84(1),15-21.
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Inthisstudy,thefunctionalpropertiesofA-andB-typewheatstarchgranulesfromtwocommercialwheatflourswereinvestigatedfordigestibilityinvitro,chemicalcomposition(e.g.,amylose,protein,andashcontent),gelatinization,retrogradation,andpastingproperties.ThebranchchainlengthandchainlengthdistributionoftheseA-andB-typewheatstarchgranuleswerealsodeterminedusinghigh-performanceanionexchangechromatography(HPAEC).Wheatstarcheswithdifferentgranularsizesnotonlyhaddifferentdegreesofenzymatichydrolysisandthermalandpastingproperties,butalsodifferentmolecularcharacteristics.Differentamylosecontent,proteincontent,andbranchchainlengthofamylopectininA-andB-typewheatstarchgranulescouldalsobethemajorfactorsbesidesgranularsizefordifferentdigestibilityandotherfunctionalpropertiesofstarch.ThedataindicatethatdifferentwheatcultivarswithdifferentproportionofA-andB-typegranularstarchcouldresultindifferentdigestibilityinwheatproducts.
Determinationofresistantshort-chaincarbohydrates(non-digestibleoligosaccharides)usinggas–liquidchromatography.
Quigley,M.E.,Hudson,G.J.&Englyst,H.N.(1999).FoodChemistry,65(3),381-390.
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Wehaveproposedthetermshort-chaincarbohydrates(SCC)forthosespecies,otherthanthefreesugars,thataresolublein80%ethanolunderwell-definedconditions.WedescribeatechniqueforthemeasurementofresistantSCC(RSCC),whicharenotsusceptibletopancreaticamylaseorthebrushborderenzymesandthereforesometimestermednon-digestibleoligosaccharides.Intheprocedure,alpha-glucans(starchandmaltodextrins)arehydrolysedenzymaticallytoglucoseandthenon-starchpolysaccharides(NSP)areprecipitatedinethanol.Fructansarehydrolysedenzymaticallyandthemonosaccharideconstituentsarereducedtoacid-stablealditolderivativesbeforetheremainingRSCCarehydrolysedwithsulphuricacid.Alltheconstituentsugarsaremeasuredasalditolacetatederivativesbygas–liquidchromatography.TheprotocolallowsboththemeasurementoftotalRSCCandaseparate,specificmeasurementoffructans.
Thephysicochemicalpropertiesandinvitrodigestibilityofselectedcereals,tubersandlegumesgrowninChina.
Liu,Q.,Donner,E.,Yin,Y.,Huang,R.L.&Fan,M.Z.(2006).FoodChemistry,99(3),470-477.
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Digestibility,gelatinization,retrogradationandpastingpropertiesofstarchinvariouscereal,tuberandlegumefloursweredetermined.Rapidlyandslowlydigestiblestarchandresistantstarchwerepresentin11selectedflours.Ingeneral,cerealstarchesweremoredigestiblethanlegumestarchesandtuberstarchescontainedahighamountofresistantstarch.Thermalandrheologicalpropertiesoffloursweredifferentdependingonthecropsource.
Developmentandphysicochemicalcharacterizationofnewresistantcitratestarchfromdifferentcornstarches.
Xie,X.S.&Liu,Q.(2004).Starch‐Stärke,56(8),364-370.
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Resistantstarchhasdrawnbroadinterestforbothpotentialhealthbenefitsandfunctionalproperties.Inthisstudy,atechnologywasdevelopedtoincreaseresistantstarchcontentofcornstarchusingesterificationwithcitricacidatelevatedtemperature.Waxycorn,normalcornandhigh-amylosecornstarcheswereusedasmodelstarches.Citricacid(40%ofstarchdryweight)wasreactedwithcornstarchatdifferenttemperatures(120–150°C)fordifferentreactiontimes(3–9h).Theeffectofreactionconditionsonresistantstarchcontentinthecitratecornstarchwasinvestigated.Whenconductingthereactionat140°Cfor7h,thehighestresistantstarchcontentwasfoundinwaxycorncitratestarch(87.5%)withthehighestdegreeofsubstitution(DS,0.16)ofallstarches.High-amylosecornstarchhad86.4%resistantstarchcontentand0.14DS,andnormalcornstarchhad78.8%resistantstarchand0.12DS.Thephysicochemicalpropertiesofthesecitratestarcheswerecharacterizedusingvariousanalyticaltechniques.Inthepresenceofexcesswateruponheating,citratestarchmadefromwaxycornstarchhadnopeakintheDSCthermogram,andsmallpeakswerefoundfornormalcornstarch(0.4J/g)andHylonVIIstarch(3.0J/g)inthethermograms.Thisindicatesthatcitratesubstitutionchangesgranuleproperties.Therearenoretrogradationpeaksinthethermogramswhenstarchwasreheatedafter2weeksstorageat5°C.AllthecitratestarchesshowednopeaksinRVApastingcurves,indicatingcitratesubstitutionchangesthepastingpropertiesofcornstarchaswell.Moreover,citratestarchfromwaxycornismorethermallystablethantheothercitratestarches.
Determinationof“NetCarbohydrates”usinghigh-performanceanionexchangechromatography.
Lilla,Z.,Sullivan,D.,Ellefson,W.,Welton,K.&Crowley,R.(2005).JournalofAOACInternational,88(3),714-719.
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Forlabelingpurposes,thecarbohydratecontentoffoodshastraditionallybeendeterminedbydifference.Thisvalueincludessugars,starches,fiber,dextrins,sugaralcohols,polydextrose,andvariousotherorganiccompounds.Insomecases,thecurrentmethodmaylacksufficientspecificity,precision,andaccuracy.Thesearesubsequentlyquantitatedbyhighperformanceanionexchangechromatographywithpulsedamperometricdetectionandexpressedastotalnonfibersaccharidesorpercent“netcarbohydrates.”Inthisresearch,anewmethodwasdevelopedtoaddressthisneed.Themethodconsistsofenzymedigestionstoconvertstarches,dextrins,sugars,andpolysaccharidestotheirrespectivemonosaccharidecomponents.Thesearesubsequentlyquantifiedbyhigh-performanceanionexchangechromatographywithpulsedamperometricdetectorandexpressedastotalnonfibersaccharidesorpercent“netcarbohydrates.”Hydrolyzedendproductsofvariousnovelfibersandsimilarcarbohydrateshavebeenevaluatedtoensurethattheydonotregisterasfalsepositivesinthenewtestmethod.Thedatageneratedusingthe“netcarbohydrate”methodwere,inmanycases,significantlydifferentthanthevaluesproducedusingthetraditionalmethodology.Therecoveriesobtainedinafortifieddrinkmatrixrangedfrom94.9to105%.Thecoefficientofvariationwas3.3%.
CerealByproductshavePrebioticPotentialinMiceFedaHigh-fatDiet.
Berger,K.,Falck,P.,Linninge,C.,Nilsson,U.,Axling,U.,Grey,C.,Stålbrand,H.,Karlsson,E.N.,Nyman,M.,Holm,C.&Adlercreutz,P.(2014).JournalofAgriculturalandFoodChemistry,62(32),8169-8178.
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Barleyhusks,ryebran,andafiberresiduefromoatmilkproductionwereprocessedbyheatpretreatment,variousseparationsteps,andtreatmentwithanendoxylanaseinordertoimprovetheprebioticpotentialofthesecerealbyproducts.Metabolicfunctionswereintendedtoimprovealongwithimprovedmicrobialactivity.Theproductsobtainedwereincludedinahigh-fatmousedietsothatalldietscontained5%dietaryfiber.Inaddition,high-fatandlow-fatcontrolsaswellaspartiallyhydrolyzedguargumwereincludedinthestudy.Thesolublefiberproductobtainedfromryebrancausedasignificantincreaseinthebifidobacteria(logcopiesof16SrRNAgenes;median(25–75percentile):6.38(6.04–6.66)and7.47(7.30–7.74),respectively;p<0.001)=""in=""parallel=""with=""a=""tendency=""of=""increased=""production=""of=""propionic=""acid=""and=""indications=""of=""improved=""metabolic=""function=""compared=""with=""high-fat=""fed=""control=""mice.=""the=""oat-derived=""product=""caused=""an=""increase=""in=""the=""pool=""of=""cecal=""propionic=""(from=""0.62=""±=""0.12=""to=""0.94=""±=""0.08)=""and=""butyric=""acid=""(from=""0.38=""±=""0.04=""to=""0.60=""±=""0.04)=""compared=""with=""the=""high-fat=""control,=""and=""it=""caused=""a=""significant=""increase=""in=""lactobacilli=""(log=""copies=""of=""16s=""rrna=""genes;=""median=""(25–75=""percentile):=""6.83=""(6.65–7.53)=""and=""8.04=""(7.86–8.33),=""respectively;="">p<0.01)=""in=""the=""cecal=""mucosa.=""however,=""no=""changes=""in=""measured=""metabolic=""parameters=""were=""observed=""by=""either=""oat=""or=""barley=""products.="">
Extractionofβ-glucanfromoatsforsolubledietaryfiberqualityanalysis.
Doehlert,D.C.,Simsek,S.&McMullen,M.S.(2012).CerealChemistry,89(5),230-236.
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Extractionprotocolsforβ-glucanfromoatflourweretestedtodetermineoptimalconditionsforβ-glucanqualitytesting,whichincludedextractabilityandmolecularweight.Wefoundmassyieldsofβ-glucanwereconstantatalltemperatures,pHvalues,andflour-to-waterratios,aslongassufficienttimeandenoughrepeatextractionswereperformedandnohydrolyticenzymeswerepresent.Extractscontainedabout30–60%β-glucan,withlowerproportionsassociatedwithhigherextractiontemperaturesinwhichmorestarchandproteinwereextracted.Allcommercialstarchhydrolyticenzymestested,eventhosethatareconsideredhomogenous,degradedβ-glucanapparentmolecularweightasevaluatedbysize-exclusionchromatography.Higherconcentrationβ-glucansolutionscouldbepreparedbycontrollingtheflour-to-waterratioinextractions.Eightgramsofflourper50mLofwatergeneratedthehighestnativeβ-glucanconcentrations.Routineextractionscontained2gofenzyme-inactivatedflourin50mLofwaterwith5mMsodiumazide(asanantimicrobial),whichwerestirredovernight,centrifuged,andthesupernatantboiledfor10min.Thepolymerextractedhadamolecularweightofabout2millionandwasstableatroomtemperatureforatleastamonth.
Effectofdietarystarchsourceongrowthperformances,digestibilityandqualitytraitsof
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产品名称： 小鼠αN已酰氨基葡糖苷酶(αNAG)ELISA Kit（elisa试剂盒） 国内优质ELISA厂家 产品简介： 小鼠αN已酰氨基葡糖苷酶(αNAG)ELISA Kit（elisa试剂盒） 国内优质ELISA厂家 ELISA试剂盒 国产现货 SIXIN生产的优质ELISA试剂盒直供全国。http://www.aatbio.com.cn/elisa/ 小鼠αN已酰氨基葡糖苷酶(αNAG)ELISA Kit（elisa试剂盒） 国 查看更多
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产品名称： 小鼠凝血酶抗凝血酶复合物试剂盒 国内优质ELISA厂家 产品简介： 小鼠凝血酶抗凝血酶复合物试剂盒 国内优质ELISA厂家 ELISA试剂盒 国产现货 SIXIN生产的优质ELISA试剂盒直供全国。http://www.aatbio.com.cn/elisa/ 小鼠凝血酶抗凝血酶复合物试剂盒 国内优质ELISA厂家 进口试剂采购网，上海通善生物科技有限公司（BioLeaf）旗下生命科学研究B2C一站式采购平台。 进口试剂采购 查看更多
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产品名称： 小鼠甲基化酶(Methylase)ELISA Kit（elisa试剂盒） 国内优质ELISA厂家 产品简介： 小鼠甲基化酶(Methylase)ELISA Kit（elisa试剂盒） 国内优质ELISA厂家 ELISA试剂盒 国产现货 SIXIN生产的优质ELISA试剂盒直供全国。http://www.aatbio.com.cn/elisa/ 小鼠甲基化酶(Methylase)ELISA Kit（elisa试剂盒） 国内优质 查看更多
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“酶可以从食物中获得吗?”?123
蘑菇神u132018-04-10
可以的。
食物酶：
天然存在於所有的生食物中。他们是消化酶的外部来源。食物酶在烹饪和处理过程中很容易被破坏。
一些富含酶的食物:
青木瓜内含丰富的木瓜酵素、木瓜蛋白酶、凝乳蛋白酶、胡萝卜素。
绿豆富含维生素B族、葡萄糖、蛋白质、淀粉酶、氧化酶。
生的蔬菜水果坚果种子富含各种酶，如菠菜、海藻等。
胡萝卜富含维生素C分解酶，萝卜、香瓜、菜花富含过氧化物酶，南瓜含维生素C分解酶，蕨菜含有维生素B1分解酶，菠萝和猕猴桃富含蛋白酶，无花果富含淀粉酶和蛋白酶，纳豆菌中富含淀粉酶、纤维酶。
人体内存在大量酶，结构复杂，种类繁多，到目前为止，已发现3000种以上（即多样性）．如米饭在口腔内咀嚼时，咀嚼时间越长，甜味越明显，是由于米饭中的淀粉在口腔分泌出的唾液淀粉酶的作用下，水解成麦芽糖的缘故．因此，吃饭时多咀嚼可以让食物与唾液充分混合，有利于消化．此外人体内还有胃蛋白酶，胰蛋白酶等多种水解酶．人体从食物中摄取的蛋白质，必须在胃蛋白酶等作用下，水解成氨基酸，然后再在其它酶的作用下，选择人体所需的20多种氨基酸，按照一定的顺序重新结合成人体所需的各种蛋白质，这其中发生了许多复杂的化学反应．可以这样说，没有酶就没有生物的新陈代谢，也就没有自然界中形形色色、丰富多彩的生物界．
食物酶：
天然存在於所有的生食物中。他们是消化酶的外部来源。食物酶在烹饪和处理过程中很容易被破坏。
一些富含酶的食物:
青木瓜内含丰富的木瓜酵素、木瓜蛋白酶、凝乳蛋白酶、胡萝卜素。
绿豆富含维生素B族、葡萄糖、蛋白质、淀粉酶、氧化酶。
生的蔬菜水果坚果种子富含各种酶，如菠菜、海藻等。
胡萝卜富含维生素C分解酶，萝卜、香瓜、菜花富含过氧化物酶，南瓜含维生素C分解酶，蕨菜含有维生素B1分解酶，菠萝和猕猴桃富含蛋白酶，无花果富含淀粉酶和蛋白酶，纳豆菌中富含淀粉酶、纤维酶。
人体内存在大量酶，结构复杂，种类繁多，到目前为止，已发现3000种以上（即多样性）．如米饭在口腔内咀嚼时，咀嚼时间越长，甜味越明显，是由于米饭中的淀粉在口腔分泌出的唾液淀粉酶的作用下，水解成麦芽糖的缘故．因此，吃饭时多咀嚼可以让食物与唾液充分混合，有利于消化．此外人体内还有胃蛋白酶，胰蛋白酶等多种水解酶．人体从食物中摄取的蛋白质，必须在胃蛋白酶等作用下，水解成氨基酸，然后再在其它酶的作用下，选择人体所需的20多种氨基酸，按照一定的顺序重新结合成人体所需的各种蛋白质，这其中发生了许多复杂的化学反应．可以这样说，没有酶就没有生物的新陈代谢，也就没有自然界中形形色色、丰富多彩的生物界．
酶的别构调节与化学修饰调节有何异同_123
我爱罗hr洍鮻2018-03-31
（1）相同点：都属于细胞水平的调节，属酶活性的快速调节方式。
（2）不同点：①影响因素：变构调节是由细胞内变构效应剂浓度的改变而影响酶的活性；化学修饰调节是激素等信息分子通过酶的作用而引起共价修饰。②酶分子改变：变构效应剂通过非共价键与酶的调节亚基或调节部位可逆结合，引起酶分子构像改变，常表现为变构酶亚基的聚合或解聚；化学修饰调节是酶蛋白的某些基团在其他酶的催化下发生共价修饰而改变酶活性。③特点及生理意义：变构调节的动力学特征为S型曲线，在反馈调节中可防止产物堆积和能源的浪费；化学修饰调节耗能少，作用快，有放大效应，是经济有效的调节方式。
（2）不同点：①影响因素：变构调节是由细胞内变构效应剂浓度的改变而影响酶的活性；化学修饰调节是激素等信息分子通过酶的作用而引起共价修饰。②酶分子改变：变构效应剂通过非共价键与酶的调节亚基或调节部位可逆结合，引起酶分子构像改变，常表现为变构酶亚基的聚合或解聚；化学修饰调节是酶蛋白的某些基团在其他酶的催化下发生共价修饰而改变酶活性。③特点及生理意义：变构调节的动力学特征为S型曲线，在反馈调节中可防止产物堆积和能源的浪费；化学修饰调节耗能少，作用快，有放大效应，是经济有效的调节方式。
【2017年整理】肌钙蛋白I定量与心肌酶谱联合检测123
husayn2021-08-02
相关疾病：肺癌Wednesday,June07,2017A58-y-oldwomanpresentstotheemergency......
山东日照市2019届高三生物上学期期中试卷(含答案)莲山课件123
婉豆20142021-08-13
具体情况具体分析，先要看这些酶之间是否有相互作用，比如蛋白酶可以降解其他酶。还要看是否反应条件被改变，比如一种酶催化后产生的反应改变体系的ph，温度什么的，影响其他的催化效率
灭活酶 是个什么东东?? 123
2018-01-25
灭活酶到底是什么呀？定义是什么啊？其作用机制勒？谢谢哟~
蛋白质与酶的功能123
dxy_xw6ase2q2021-08-10
蛋白质和酶分子的基本结构单位相同吗？
在应激条件下OGlcNAc修饰促进SIRT1的脱乙酰化酶活性和细胞保护...123
wangyy19902021-07-20
2017年11月14日，糖生物实验室在NatureCommunications发表了题为“O-GlcNAcylationofSIRT1enhancesitsdeacetylaseactivityandpromotescytoprotectionunderstress”（《在应激条件下O-GlcNAc修饰促进SIRT1的脱乙酰化酶活性和细胞保护作用》）的最新研究成果（论文链接：https://www.nature.com/articles/s41467-017-01654-6），发现了长寿基因SIRT1活性调控的新机制。
衰老是生命进程中一个不可逆的过程，延年益寿则是人类的一个普遍期望，也是衰老研究的终极目标。SIRT1是一种高度保守的NAD+依赖性的脱乙酰化酶，通过对底物蛋白的脱乙酰化抵抗各种压力应激和修复基因突变，发挥细胞保护作用；SIRT1参与了许多重要的生理和病理过程,如代谢调节、基因组稳定性、代谢应激、衰老等；在多种模式生物中，SIRT1均被证实能延长寿命，并能够通过抑制各种老年性疾病的发生发展发挥延长“健康寿命”的作用。因此，SIRT1是目前最受关注的长寿基因，SIRT1激活剂已成为医药领域研究与开发的前沿和热点。然而，机体对抗衰老时SIRT1激活的分子机制并不十分清楚。
O-GlcNAc糖基化修饰是一种细胞内普遍存在、动态可逆的蛋白质翻译后修饰现象。O-GlcNAc可以通过影响蛋白稳定性、细胞定位和酶活性等调节蛋白质功能并在生理和病理过中发挥重要作用。该研究成果首次发现了SIRT1蛋白具有O-GlcNAc修饰，且修饰位点是549位的丝氨酸。SIRT1的O-GlcNAc修饰增加其与底物蛋白的亲和力并提高SIRT1的脱乙酰化酶活性。进一步研究表明，在应激（氧化应激、代谢应激和基因毒等）条件下，细胞内SIRT1的O-GlcNAc修饰显著增加，并促进其对p53、FOXO3等靶蛋白的脱乙酰化从而发挥细胞保护作用。众所周知，卡路里限制能降低衰老相关疾病的发生和延年益寿。本研究成果表明，卡路里限制能可能通过O-GlcNAc修饰激活SIRT1而起到细胞保护作用，从而揭示了节食延年益寿的一个新的分子机制。综上所述，该研究发现了SIRT1活性调控的新机制，首次证明了O-GlcNAc修饰是SIRT1抵抗应激的分子开关，表明O-GlcNAc修饰可能成为抗衰老和老年性疾病的新靶点，为抗老年性疾病药物和长寿药物的研究开辟了新途径，具有重要的理论意义和明确的应用前景。
该研究成果由糖生物学实验室独立完成，博士研究生韩翠芳、单慧和顾玉超副教授是该论文的共同第一作者，顾玉超副教授和于文功教授是共同通讯作者。该研究由NSFC-山东省海洋科学研究中心联合基金项目(No.U1606403)、青岛海洋科学与技术国家实验室鳌山科技创新计划项目（No.2015ASKJ02）、国家自然科学基金面上项目(No.81272264)等资助。
于文功教授和顾玉超副教授长期从事糖生物学研究，发现了蛋白质的O-GlcNAc糖基化修饰促进肿瘤发生和转移并阐明了其分子机制（CancerRes.2010Aug1;70(15):6344-51；BiochimBiophysActa.2011Apr;1812(4):514-9.）。经过多年的积累，该团队已经建立了系统的O-GlcNAc糖基化修饰研究技术体系，目前正在进行O-GlcNAc修饰对肿瘤和糖尿病等重大疾病发生过程中关键蛋白的调控作用和机制研究，以期阐明相关疾病发生的机制并发现新的治疗靶点。
人体缺酶=慢性自杀?危害这么多,别再忽视它了!123
2018-04-16
会导致吃下去的食物消化了也无法吸收或者吸收的很慢，进而导致人体出现健康问题。没是一种高效催化剂，食物在进行基本消化后还要在酶的帮助下才能被分解成基本单位物质（如葡萄糖，氨基酸，脂肪酸等），而且要在酶的帮助下吸收。
RNA聚合酶可以解旋吗为什么转录过程的酶只有RNA聚合酶一种 DNA...123
_碎心__2021-08-09
聚合酶是主要的酶还有很多其他的，，高中里是不要求记的
Nature：挑战常规！ 半胱天冬酶12并不作为炎性体的负调节物《现代...123
ANRC-6662018-01-04
炎性体（inflammasome）是细胞内的一类多蛋白复合物，在炎性反应中发挥着至关重要的作用。炎性体包括半胱天冬酶-1（caspase1）、PYCARD和NALP，有时也包括半胱天冬酶-5（caspase5，也被称作半胱天冬酶-11或ICH-3）。它是在骨髓细胞（myeloidcell）中产生的，也是先天性免疫系统的一个组分。炎性体的确切组成依赖于启动炎性体组装的激活物，如双链RNA和石棉会引发不同的炎性体组成。炎性体促进炎性细胞因子IL-1β和IL-18成熟。
在一项新的研究中，来自比利时法兰德斯生物技术中心/根特大学（VIB/UGent）的LieselotteVandeWalle博士、DanielJiménezFernández以及教授MoLamkanfi研究团队对半胱天冬酶-12（caspase12）的功能产生新的认识。基于此，他们打破了这个领域对半胱天冬酶-12的固执观念：半胱天冬酶-12是炎性体的负调节物。这些新的认识为研究人员挣脱现有的研究路线和鉴定它的真正生理学功能铺平道路。相关研究结果发表在2016年6月2日那期Nature期刊上，论文标题为“Doescaspase-12suppressinflammasomeactivation?”。
研究人员也指出这将需要进行大量的“重新研究（re-researching）”。之前所谓的半胱天冬酶-12在细胞死亡、应激反应、疟疾和败血症等中的作用---引用了9000多次---必需复核，这是因为这些作用经常是基于不正确的小鼠模型得出的。
VIB/UGent教授MoLamkanfi说，“我们发现在很多情形下，对半胱天冬酶-12的研究是基于对半胱天冬酶-11（caspase11）和半胱天冬酶-12都进行基因敲除的小鼠模型开展的。因此从研究结果中推断半胱天冬酶-12的作用是不可能的。我们如今引入新的选择性半胱天冬酶-12基因敲除小鼠，这应当能够让我们追踪半胱天冬酶-12的确切功能。”
利用这些新的小鼠，Lamkanfi团队证实在体外模拟的BMDM（bonemarrow-derivedmacrophage,骨髓衍生性巨噬细胞）和体内接种的小鼠中，半胱天冬酶-12缺乏都不能增加半胱天冬酶-1激活。剔除半胱天冬酶-12也不会增强炎性体途径释放出成熟的IL-1β和IL-18。他们的发现表明不论半胱天冬酶-11的表达状态如何，半胱天冬酶-12都不会作为半胱天冬酶-1激活的生理学上负显性调节物，因而也不会作为炎性体的生理学上负显性调节物。
【求助/交流】为什么酶切总是切不开? 微生物 综合其他...123
悠悠游游cho2021-07-24
我的质粒抽提自DH5a大肠杆菌，用EcoRI37℃酶切2h，之前还用这个酶切条件酶切了其他质粒都会出现拖带，酶量适中没有加过量，电泳上样量在200ng左右，我以为是酶不好了，用了两个牌子的酶，都会这样，我是真不明白，为什么会有这样的拖带，哪位大神可以指教一下，感激不尽！
为什么人体内的消化酶不会将自身的组织器官消化掉?123
2018-03-29
因为酶在消化的时候是先识别的，通过蛋白质的空间结构，先识别结合之后再水解蛋白质，自身的蛋白质是不会消化的
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