Environmentalconditionsduringgrain-fillcanaffectthedurationofproteinaccumulationandstarchdeposition,andthusplayanimportantroleingrainyieldandflourqualityofwheat.Twobread-,onedurum-andonebiscuitwheatwereexposedtoextremelow(−5.5°Cfor3h)andhigh(32°C/15°Cday/nightforthreedays)temperaturesduringgrainfillingundercontrolledconditionsfortwoconsecutiveseasons.Flourproteincontentwasincreasedsignificantlyinonebreadwheat,Kariega,underheatstress.ColdstresssignificantlyreducedSDSsedimentationinbothbreadwheats.Kernelweightanddiameterweresignificantlydecreasedatbothstresstreatmentsforthetwobreadwheats.KernelcharacteristicsofthebiscuitwheatwereThermostable.Kernelhardnesswasreducedinthedurumwheatfortheheattreatment.DurumwheathadconsistentlylowSDSsedimentationvaluesandthebreadwheathighvalues.Acrossthetwoseasons,thestarchcontentinonebreadwheatwassignificantlyreducedbybothhighandlowtemperatures,asisreflectedinthereductionofweightanddiameterofthesekernels.Inthedurumwheat,onlyheatcausedasignificantreductioninstarchcontent,whichisagainreflectedinthereductionofkernelweightanddiameter.

Granuleboundstarchsynthase1(GBSS1)isakeyenzymeinamylosebiosynthesisandisencodedbytheA,BandDGBSS1wxlociinwheat.WheatlineswithmutationsatthethreeGBSS1locihavebeenidentified.WehavecharacterizedandcomparedthegrainstarchofCDCW6wheatline(nullBandDforGBSS1)withPI235238(nullAandBforGBSS1),waxy(nullA,BandDforGBSS1),andACReed(wildtypewheat)grainstarches.Thegrainstarchofwaxy,CDCW6,PI235238,andACReedlinescontained≈0,12,23,and25%amylose(w/w),respectively.Waxy,partiallywaxy,andwildwheatgrainstarchesshowedsignificantdifferencesinonsetandpeaktransitiontemperaturesasdeterminedbydifferentialscanningcalorimetricanalysis.Grainstarchesextractedfromwaxy,CDCW6,andPI235238alsohadhigherenthalpyofgelatinizationvaluesthandidwildwheatstarch.X-raydiffractionanalysisrevealedthehighestcrystallinityforstarchextractedfromwaxywheat,followedbyCDCW6.ThestarchproducedfromtheCDCW6linemayfindspecialfoodandindustrialapplicationsbecauseofitsrelativelylowamyloseconcentration.

Theamylosecontentsofstarchesfromvariousbotanicalorigins(potato,smoothpea,wrinkledpea,wheat,maize)andfrommaizemutants[waxy(wx),amyloseextender(ae),dull(du),sugary-2(su2),aewx,aedu,dusu2andwxdu]weredeterminedbysizeexclusionchromatography(SEC),iodine-bindingcapacity(IBC)measurements,differentialscanningcalorimetry(DSC)andcomplexationwithconcanavalinA.SEC(witha2.6x200cmcolumn)onHW75Sgelwasusedasthereferencemethodforanalyzingthemacromolecularcompositionofstarches.VariationsinthefinestructureofamylopectinaffecteditsreactivityinclassicalmethodssuchasIBCandwereprobablyresponsIBLeforerroneousvaluesindeterminationswhenthispolymerwastheonlystarchcomponentstudied.Whenstarcheswerecomposedoftwomacromolecules,allmethodsgavesimilarresults,butwithsomediscrepanciesinDSC.Theelutionvolumeforathirdclassofα-glucansdetectedinsomemaizemutantstarcheswasbetweenthatofamylopectinandamylose.OnlySECgaveaccurateresultsinthiscasesinceallothertestedmethodsshowedhigherapparentamylosecontents.

Astarchgranuleprotein,SGP-1,isastarchsynthaseboundtostarchgranulesinwheatendosperm.AwheatlackingSGP-1wasproducedbycrossingthreevariantseachdeficientinoneofthreeSGP-1classes,namelySGP-A1,-B1or-D1.Thisdeficientwheat(SGP–1nullwheat)showedsomealterationsinendospermstarch,meaningthatSGP-1isinvolvedinstarchsynthesis.Electrophoreticexperimentsrevealedthatthelevelsoftwostarchgranuleproteins,SGP-2and-3,decreasedconsiderablyintheSGP-1nullwheatthoughthatofthewaxyprotein(granule-boundstarchsyn-thaseI)didnot.TheA-typestarchgranulesweredeformed.Apparenthighamyloselevel(30.8–37.4%)wasindicatedbycolorimetricmeasurement,amperometrictitration,andtheconcanavalinAmethod.Thealteredstructureofamylopectinwasdetectedbybothhigh-performancesize-exclusionchromatographyandhigh-performanceanionexchangechromatography.Levelsofamylopectinchainswithdegreesofpolymerization(DP)6–10increased,whileDP11–25chainsdecreased.AlowstarchcrystallinitywasshownbybothX-raydiffractionanddifferentialscanningcalorimetry(DSC)analysesbecausemajorpeakswereabsent.AbnormalcrystallinitywasalsosuggestedbythelackofapolarizedcrossinSGP-1nullstarch.TheaboveresultssuggestthatSGP-1isresponsibleforamylopectinsynthesis.SincetheSGP-1nullwheatproducednovelstarchwhichhasnotbeendescribedbefore,itcanbeusedtoexpandvariationinwheatstarch.

LargeA-typeendospermstarchgranuleswereisolatedfromnear-isogenicwaxyandnon-waxylinesandlow-amylosemutantlinesofbreadwheatwithacommongeneticbackground.TheamylosecontentsofA-typestarchrangedfrom2.6%to23.6%.AmylopectinwasisolatedbyconcanavalinA(ConA)precipitationfromtheisolatedstarch.Theλ_max(range:532-538nm)andbluevaluesat680nm(range:0.026-0.037)oftheiodine-amylopectincomplexwerenotsignificantlydifferentamongtheisolatedamylopectins,indicatingthatamylopectinsfromnon-waxyandlow-amyloselinesdidnotcontainsuchlongchainsasamyloseorextra-longchainsofamylopectinaffectingiodinecomplexproperties.Chain-lengthdistributionprofilesmeasuredbybothhigh-performancesize-exclusionchromatography(HPSEC)andhigh-performanceanion-exchangechromatography(HPAEC)showedthattheamylopectinstructuresoftheselineswereindistinguishablefromeachother.Extra-longchainswerenotdetectedintheamylopectinsbyHPSECmeasurement.Theside-chainsmeasuredbyHPAECwereclassifiedintofourgroupsaccordingtotheirdegreeofpolymerization(DP),andtheproportionofeachgroupwereinthefollowingranges:DP6-12,26.5-27.5%;DP13-24,43.6-44.1%;DP25-36,13.6-14.2%,andDP37-60,11.0-11.7%.TheallelesontheWx-D1locus,i.e.,Wx-D1a,Wx-D1d,Wx-D1f,andWx-D1g,responsibleforgranule-boundstarchsynthase(GBSSI)biosynthesishadnoinfluenceonthepropertiesofiodine-amylopectincomplexandthechain-lengthdistributionprofilesofamylopectin.

Physicalpropertiesofstarchfromtwocultivarsofgamma-irradiatedgrainamaranthwithdifferentamylosecontentwereinvestigated.Pastingviscositiesdecreasedcontinuouslywiththeincreaseindosagesofirradiation.Furthermore,differentirradiationdosagesresultedinmodificationofthethermalpropertiesandcrystallinityofstarch.Dynamicoscillationonshearwasalsoemployed,temperatureandfrequencysweepsshowedthatchangesinstoragemodulusandlossmodulusweresignificant,withTibetYellowproducingmoreelasticgelsascomparedtoHy030atdifferentirradiationdosages.

Functionalpropertiesofsomeunderexploitedtuberandrootstarches(trueyam,gourdyam,taro,lotus,andsweetpotato)wereinvestigatedbeforeandafterhydroxypropylation,cross-linking,andhydroxypropylationandcross-linkingusingpotatostarchasthereference.LowswellingABIlity,poorviscositydevelopmentbuthighshearstability,gelhardness,andresistancetoenzymehydrolysiswasobservedinstarchesfromtrueyamandgourdyam.Theextentofretrogradationwasalsohighestinthesetwostarches.Mostofthefunctionalpropertiesoflotusstarchweresimilartothoseofpotatostarch.Hydroxypropylationtoamolarsubstitutionlevelof≈0.1increasedtheswellingfactorandsusceptibilitytoα-amylasehydrolysisbutdecreasedacidtoleranceofpasteviscosity,retrogradation,gelatinizationparameters,gelhardness,andshearstability.Cross-linkingdecreasedtheswellingfactorandamyloseleaching,andincreasedshearstabilityandresistancetoenzymeandacidtolerance.Cross-linkinghadverylittleinfluenceongelatinizationandretrogradationpropertiesbutalargereffectonpastingproperties.Increasedordecreasedpeakviscositiesandgelhardnessvalueswerenotedfordifferentcross-linkedstarches.Cross-linkingofhydroxypropylatedstarchesincreasedcommonlydesirablefunctionalpropertiesprovidingawiderrangeofpotentialapplications.

GranularpotatostarchesweremethylatedinaqueoussUSPensionwithdimethylsulfatetomolarsubstitution(MS)valuesupto0.29.Fractionscontainingmainlyamyloseoramylopectinwereobtainedafteraqueousleachingofthederivatisedstarchgranules.AmylopectininthesefractionswasprecipitatedwithConcanavalinAtoseparateitfromamylose.AmyloseremainedinsolutionandwasenzymaticallyconvertedintoD-glucoseforquantification,therebytakingintoaccountthedecreaseddigestibilityduetothepresenceofmethylsubstituents.ItwasfoundthattheMSofamylosewas1.6–1.9timeshigherthanthatofamylopectininmethylatedstarchgranules.Thedistributionsofmethylsubstituentsintrimersandtetramers,preparedfromamylose-oramylopectin-enrichedfractions,weredeterminedbyFABmassspectrometryandcomparedwiththeoutcomeofastatisticallyrandomdistribution.Itturnedoutthatsubstituentsinamylopectinweredistributedheterogeneously,whereassubstitutionofamylosewasalmostrandom.Theresultsarerationalisedonthebasisofanorganisedframeworkthatisbuiltupfromamylopectinsidechains.Thecrystallinelamellaearelessaccessibleforsubstitutionthanamorphousbranchingpointsandamylose.

Thedegradationofpeastarchgranulesbyacidhydrolysishasbeeninvestigatedusingarangeofchemicalandstructuralmethods,namelythroughmeasuringchangesinamylosecontentbyboththeiodinebindingandconcanavalinAprecipitationmethods,alongwithsmallangleX-rayscattering(SAXS),wideangleX-raydiffraction(XRD)andfieldemissionscanningelectronmicroscopy(FE-SEM).Therelativecrystallinity,intensityofthelamellarpeakandthelow-qscatteringincreasedduringtheinitialstagesofacidhydrolysis,indicatingearlydegradationoftheamorphousregions(growthringsandlamellae).Inthefirst2daysofhydrolysis,therewasarapiddeclineinamylosecontent,aconcomitantlossofprecipitabilityofamylopectinbyconcanavalinA,anddamagetothesurfaceandinternalgranularstructureswasevident.Theseobservationsareconsistentwithbothamyloseandamylopectinbeinglocatedonthesurfaceofthegranulesandattackedsimultaneouslyintheearlystagesofacidhydrolysis.Theresultsarealsoconsistentwithamylosebeingmoreconcentratedatthecoreofthegranules.Moreextensivehydrolysisresultedinthesimultaneousdisruptionofamorphousandcrystallineregions,whichwasindicatedbyadecreaseinlamellarpeakintensity,decreaseininterhelixpeakintensityandnofurtherincreaseincrystallinity.Theseresultsprovidenewinsightsintotheorganizationofstarchgranules.

Physicochemicalandfunctionalpropertiesofstarchesisolatedfromfifteengrainamaranthcultivars(Amaranthusspp.)producedinChinawereanalysedinthisstudy.Amaranthstarcheshadlowbutdiverseamylosecontents,rangingfrom4.7%to12.5%.Widevariationwasalsofoundinphysicochemicalproperties,suchasswellingpower,watersolubilityindex,pasting,thermalandtexturalproperties.Amylosecontentwassignificantlycorrelatedwithfunctionalproperties,includingpasting,thermalandtexturalpropertiesandappearedtobetheimportantdeterminantfortheseproperties.Correlationsamongpasting,thermalandtexturalparameterswerealsosignificant.Principalcomponentanalysisusing17variablesextractedfourprincipalcomponentsthatexplained88%ofthetotalvariance.Thefirstcomponentrepresentedamylosecontent,pastingandgeltexturalpropertiesandexplained59%ofthetotalvariance,whilethesecondcomponentrepresentedthethermalpropertiesandaccountedforanadditional14.5%ofthetotalvariance.