Changes in baking quality of winter wheat with different ...

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Vol. 29, 2011, No. 4: 420–429 Czech J. Food Sci.

Changes in baking quality of winter wheat with different intensity of Fusarium spp. Contamination detected

by means of new rheological system mixolab

Ludmila PaPouškoVá1, Ivana CaPouChoVá 2, Marta koSteLaNSká 3, alena škeříkoVá 2, evženie ProkINoVá 2, Jana haJšLoVá 3, Jaroslav SaLaVa1

and oldřich FaMěra2

1Division of Plant Genetics, Breeding and Product Quality, Crop research Institute, Prague, Czech republic; 2Faculty of agrobiology, Food and Natural resources, Czech university of Life

Sciences Prague, Prague, Czech republic; 3Department of Food Chemistry and analysis, Faculty of Food and Biochemical technology, Institute of Chemical technology Prague,

Prague, Czech republic

Abstract

PapouškováL.,CapouchováI.,KostelanskáM.,ŠkeříkováA.,ProkinováE.,HajšlováJ.,SalavaJ.,FaměraO.(2011):Changes in baking quality of winter wheat with different intensity of Fusarium spp. contamination detected by means of new rheological system mixolab.CzechJ.FoodSci.,29:420–429.

TheaimofourworkwastoassessthepossibilityofdetectingthechangesinthebakingqualityofwinterwheatwithdifferentlevelsofFusariumspp.contaminationusinganewrheologicalsystemMixolab,andtodeterminethecor-relationsbetweentheMixolabcharacteristicsandotherqualityparametersofwheatflourandgrain.Thestandardtechnologicalcharacteristics(crudeprotein,Zelenysedimentationindex,wetgluten, fallingnumber), loafvolume,shapefeaturesofbread(heightanddiameter),Mixolabparameters,andmycotoxindeoxynivalenol (DON)contentweredetermined in3winterwheatcultivars (Akteur–qualitygroupE–elite;Eurofit–qualitygroupA;Meritto–qualitygroupB)withdifferentlevelsofFusariumspp.contamination(8variants)intwoyears.IncreasingintensityofFusarium spp.contaminationevidentlyworsenedtherheologicalqualityand itsnegativeeffectsonproteinandmainlyonthestarchpartofthegrainwasobviousinMixolabcurves.HighcorrelationswerefoundbetweenMixolabcharacteristicsandstandardtechnologicalparameters,aswellasbetweenMixolabparametersandthemainbakingcriterion–loafvolume.

Keywords:winterwheat;Fusariumspp.;breadmakingquality;Mixolab

SupportedbytheMinistryofEducation,YouthandSportsoftheCzechRepublic,ProjectsNo.MŠMT2B08049,andbytheMinistryofAgricultureoftheCzechRepublic,ProjectNo.MZE0002700604.

Mixolabisarelativelynewsystem,acceptedastheICCstandardmethodNo.173(ICC2006),whichmakespossibletoevaluatephysicaldoughpropertiessuchasdoughstabilityorweakening,andstarchcharacteristicsinonemeasurement

(Kahramanet al.2008).Itisenabledbyexces-sivemixingandcontrolledheatingofthekneaderto90°Candsubsequentcoolingto50°C.Mixolabrecordsinrealtimethetorque(innm)producedbythedoughbetweentwoblades.AtypicalMixolab

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Czech J. Food Sci. Vol. 29, 2011, No. 4: 420–429

curveisseparatedintofivestages,characterisedbyfivepoints(C1–C5)andotherparametersresult-ingfromthedifferencesbetweentheindividualpoints(Figure1).

CharacteristicsevaluatedfromthemeasuredMixolabcurveare:

isadecreaseinthetemperatureandanincreaseinconsistencyasaresultofthegelformation,anditisalsorelatedtothestarchretrogradation(Rosellet al.2007).Thisstagedependsmainlyonthelevelofamylosepresent,whichstartstheprocessofretrogradation.Forexample,forwaxywheatthatcontainsonlyalowlevelofamylose,noincreaseofthecurveisdetected(Grayboschet al.2003).

Mixolabparametersshow,basedontheresultspublisheduptonow,highcompatibilitywithstand-ardrheologicalanalysis(forexamplefarinograph,extensograph,oramylograph).Consequently,itispossibletoanticipateapotentialpredictionofbreadmakingqualityofcommonwheatfromtheseparameters(Cato&Mills2008).ButtherearehardlyanystudiesontheefficiencyofthisMixolabsystemtopredictrheologicalparametersofwheatwithchangedcharacteristicscausedbyfungispe-cies,whichhavebecomeaseriousprobleminthewheatcultivationduringrecentyears.Thisfungicontamination,incerealsmainlyFusariumspp.contamination,causesnotonlygrainyieldlossbut,becauseoftheirsecondarymetabolitesmycotoxins,hasalsoanegativehealthimpact(Garciaet al.2009).Themostimportantisthetrichothecenemycotoxindeoxynivalenol(DON),consideredasacontaminationmarkersubjectedtotheEuropeanCommissionRegulation(EC2006).DONmaxi-mumlevelwassetat1250μg/kgforunprocessedcerealsand750μg/kgforcerealflours.

Besidesthesefacts,severalauthorsalsomen-tionednegativeeffectsofFuariuminfectiononbreadmakingqualityofwheatandthereductionofloafvolumes(Seitzet al.1986;Nightingaleet al.1999;Gärtneret al.2008).Ontheotherhand,therearesomecontradictorystudieswhere

C1 usedtodeterminewaterabsorption

C2 representstheweakeningoftheproteinbasedonthemechanicalworkandtheincreasingtemperature

C3 representstherateofstarchgelatinisation

C4 representsthestabilityofthehot-formedgel

C5 representsstarchretrogradationduringthecoolingperiod

C1–C2 indicatestheproteinnetworkstrengthunderincreasingheating

C3–C4 showsdiastaticactivityandrelateswithfallingnumber

C5–C5 correlateswiththeanti-stalingeffects,rep-resentstheshelflifeoftheendproducts

Dough stability indicates the stability of the doughbeforeweakening

Time (s)curve of sample temperature curve

1 0 302 0.063 303 0.083 304 0.108 305 0.133 306 0.158 307 0.183 308 0.208 309 0.233 30

10 0.258 3011 0.286 3012 0.316 3013 0.343 3014 0.368 3015 0.395 3016 0.419 3017 0.441 3018 0.464 3019 0.488 3020 0.508 3021 0.523 3022 0.535 3023 0.543 3024 0.549 3025 0.555 3026 0.563 3027 0.571 3028 0.578 3029 0.584 3030 0.591 3031 0.594 3032 0.599 3033 0.607 3034 0.62 30

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1 251 501 751 1001 1251 1501 1751 2001 2251 2501

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0102030405060708090100

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curve of sample

temperature curve

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C3C4

C5

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Figure 1. Standard Mixolabcurve

Thetwofirststagesofthecurvecorrespondtotherheologicalcharacteristicsofstability,elas-ticity,andwaterabsorption,relatedtoproteins. Theconsistencyofdough,whichdecreaseswithexcessivemixing,isanindicationofproteinweak-ening.Thefasterandgreateristhedecreaseofthedoughconsistency,theloweristheproteinqual-ity.Theotherstagesrelatemainlytostarchandamylolyticactivity.Theincreaseintheconsistencycurveismainlyduetostarchgelatinisation.Atthefourthstage,consistencydecreasesasaresultofamylolyticactivityfadingamylolyticactivityandburstingofstarchgranules.Atthefifthstage,there

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astrongFusariumcontaminationdidnotsig-nificantlyinfluencethebreadmakingproperties(Anteset al.2001;Prangeetal.2005).

Theaimofthisworkis(i)toconfirmthecor-relationsbetweentheMixolabcharacteristicsandotherqualityparametersofwheatflourandgrain;(ii)todetectthechangesinthebakingqualityofwinterwheatduetodifferentlevelsofFusariumspp.contaminationusingthenewrheologicalsystemMixolab.

mATEriAL And mETHOds

Plant material.Asetof24winterwheatsam-plesfromtheexactfieldplottrial,conductedintheyearsof2008and2009ontheexperimentalstationoftheDepartmentofCropProductionoftheCzechUniversityofLifeSciencesPragueinUhříněves(295mabovesealevel,averageannualtemperature8.4°C,averagesumofprecipitation575mm),wasusedfortheevaluationofthebreadmakingqualityandDONcontentingrain.Thesetincluded3winterwheatcultivars(Akteur–qual-itygroupE;Eurofit–qualitygroupA;Meritto–qualitygroupB)and8variantscomingfromthefieldplottrial.

Artificial inoculation and evaluation ofFusari-um spp.infestation.DifferentconditionswereusedofartificialinoculationofwheatwithFusariumspp.andsimultaneouslyseveralwaysoffungicidetreatment,withtheaimtoobtainascaleofsampleswithdifferentlevelsofFusariumspp.contamina-tion.ThelistofvariantsisgiveninTable1.

TheisolatesofF. culmorumandF. graminearumusedfortheartificialinoculationwereobtainedfromthemycologicalcollectionoftheCropRe-searchInstituteinPragueandcultivatedonsterilewheatgrains.Thepreparationofinoculumsfortheapplication:wheatgrainswiththeculturesofF. cul-morumandF.graminearumwereputintoavesselwithwaterandshakenfor15mininalaboratoryshakertoreleasethesporesintowater.Theobtainedsuspensionwasfilteredthroughthegauze.ThenartificialinoculationwasmadewiththesuspensionofF.culmorumandF.graminearumsporesintheratioof1:1,107ofspores/ml(Bürkerchamberwasusedfortheverificationofinoculumsdensity),2lofsuspensionperexperimentalplot(12m2).Thesuspensionwasdosedaccordingtothelistofvari-antswithahandsprayeratthebeginningandattheendofthewheatflowering.Thefungicide(effectivesubstancesprothioconazoleandtebuconazole)wasappliedtwodaysbeforetheinoculation.

Grainsamplesweretakenfortheevaluationafterthewheatharvest.PCRassaywasusedforFusariumspp.detection.TotalDNAwasextractedfromthegrainsamplesusingtheDNeasyPlantMiniKit(Qiagen,Hilden,Germany).Thesequencesoftheprimers,PCRreactionmixture,andtheconditionsusedfordetectingF.culmorumandF. graminearum inthisstudywereidenticaltothosedescribedbySchillinget al.(1996).ThistypeofPCRassayenablestodistinguishonlytheintensityofFusariumspp.attackwithoutquan-titativeformulation,thereforetheDONcontentwasconsideredasanindicatoroftheintensityofFusariumspp.contamination.

Deoxynivalenol content.UPLC-TOFMSsystemconsistingofUltra-PerformanceLiquidChro-matography(Acquity,Waters,USA)coupledtoatime-of-flightmassspectrometer(LCTPremier,Waters,USA)wasusedforthedeterminationofdeoxynivalenol(DON)inwheatgrain.Allofwheatsamplesweremilledandhomogenisedpriortotheextractionprocedure.Therepresentativesample(12.5g)wasextractedwith50mlofacetonitrile:watermixture(84:16,v/v)for60minutes.Anal-iquotofthecrudeextract(4ml)wasevaporatedtodrynessandtheresiduewasthandissolvedin1mlofmethanol:water(1:1,v/v)mixture.Fortheseparationofanalytes,AcquityUPLCHSST3column(100×2.1mmi.d.,1.7µmparticlesize,Waters,USA)wasused.Theworkingparametersoftheanalyticalmethodwereestablishedasfollows:flowrate0.3µl/min,columntemperature40°C,

Table1.Listofthefieldplotvariants

Variantsignification Treatment

I preventivefungicidaltreatment

II checkvariantwithoutanytreatment

III artificialinoculationattheendofflowering+fungicide

IV artificialinoculationattheendofflowering

V artificialinoculationatthebeginningofflowering+fungicide

VI artificialinoculationatthebeginningandattheendofflowering+fungicide

VII artificialinoculationatthebeginningofwheatflowering

VIII artificialinoculationatthebeginningandattheendofflowering

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injectionvolume5µl,auto-samplertemperature10°C,themobilephaseconsistedof5mMammo-niumformiateinwater(A)andmethanol(B).Thefastlineargradientprogramfortheseparationofthetargetcompoundswasused.Theorthogonaltime-of-flightmassspectrometerwasoperatedinthenegativeelectro-spray ionisation(ESI-)mode.Capillaryvoltagewassetat3500V,conevoltage40V,sourcetemperature120°C,desolva-tiontemperature350°C.Nitrogenwasusedasasolventaswellasconegas; itsflowrateswere750l/hand10l/h,respectively.Targetanalyteswereidentifiedaccordingtotheirretentiontimesandaccuratemasses.SoftwareMassLynx4.1withtheapplicationofQuanLynxmanagerwasusedforthedataacquisitionandprocessing.

Sample preparation for technological quality evaluation.Thewheatgrainsampleswerepuri-fiedusingsieves(2.2×22mm)andconditionedto15.5%moisturebeforemillingonaBühlermillautomatMLU202.Millingproceededintwosec-tionsdividedintothreepartswithdifferentcondi-tionsofgrindingandsieving.Allmillingfractions(3fractionsofbreakflourand3fractionsofreduc-tionflour)werecollected(totalflouryield65%approximately)andusedfortheevaluationoftherheologicalpropertiesandforthebakingtrial.

Bread making quality analyses.Withintheframeofthebreadmakingquality,crudeproteincontent(CP)accordingtoKjeldahlmethod(ENISO20483;ICC-StandardNo.105/2),wetglutencontent(WG)ingraindrymatterusingtheap-paratusGlutomaticPerten(ISO5531), fallingnumber(FN)–ISO3093,Zelenysedimentationindex(ZS)–ISO5529,andashcontent(AC)–ISO2171weredetermined.

Breadwasmadeaccordingtotheinternalpro-tocolfromflour(300g),yeast(12g), fat(3g),sugar(4.5g),salt(5.1g).Thedoughwaskneadedusingafarinographwiththewateradditionac-cordingtothedeterminedretentioncapacityoftheflour.Thedoughheavedinthermostatfor45minin30°Candthenitwasdividedtofourball-shapedpartsandleftinathermostatfor50minutes.Afterwards,thepieceswereputintheovenat240°Cfor14minutes.Aftercooling(90min),bakingcharacteristicsweremeasured,i.e.theheight(H)anddiameter(D)ofbreads,andtheratiosH/Dwerecalculated.Theloafvolumes(LV)weredeterminedbyrapeseeddisplacement.

Mixolab determination.Rheologicalcharacter-isticsweredeterminedusingtheapparatusMixolab

(Chopin,TripetteetRenaud,Paris,France)accord-ingtotheMixolabprotocolChopin+forwhiteflour(Mixolabappl.Handbook,2008).PointC1wasnotincludedinthefinalevaluationbecausethissidepointissufficientlyrepresentedbythedifferencebetweenpointsC1andC2(C1C2).

Statistical analysis.Theresultswerestatisti-callyevaluatedbytheone-wayanalysisofvariance(ANOVA)withsubsequentTukeyHSDtest.Theirrelationswereassessedbythecorrelationanalysiswiththestatisticalsignificanceexpressiononthelevelα=0.05;0.01.ThecalculationwasdoneinthesoftwareSTATISTICA8.0CZ(StatSoft).

rEsULTs And disCUssiOn

intensity of Fusarium spp. infection and dOn content

ThelevelsofFusariumspp.infectionandDONcontentintheindividualgrainsamplesaresum-marisedinTable2,wherethedifferencesarevisiblebetweentheindividualyears,experimentalvariant,andcultivars.In2008,theinfectiongradewasevi-dentlyhigherthanin2009.Itwasmostlikelyduetotheclimaticconditionsduringwheatflowering,whichwerefavourableforafastdevelopmentofFusariuminoculuminthatyear.

ThereareconflictingreportsonthecorrelationbetweentheFusariuminfectiongradeandDONcontent.SomeauthorsdidnotconfirmpositivecorrelationbetweentheinfectiongradeandDONcontent(Kushiro2008;Garciaet al.2009) whileothersfoundahighpositivesignificantcorrela-tion(Snijders2004).Nevertheless,inthecaseofastronginfectionpressureevokedbyartificialinoculationisitpossibletosupposealsoahighDONcontent.

Inourstudy,wefoundthehighestaveragecon-tentofdeoxynivalenol(DON)ingrainforvariantsVIIandVIIIwiththehighestintensityofinfection(Table3).ThesedetectedaveragevaluesofDON(3023,resp.4003μg/kg)exceededconsiderablythelimitpermittedforthefoodgrain,nevertheless,sointensiveinfectionenablesaverygooddistinc-tionoftheeffectofFusariumspp.infestationonthewheatcharacteristics.SignificantdifferenceswereobservedbetweenDONcontentsofthein-dividualvariants(I–IIIandVII–VIII)aswellasbetweenthetwomonitoredyearsbutnotbetweenthecultivars.

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Effect of Fusarium spp. infection on mixolab parameters

TheaveragevaluesofMixolabcharacteristicsforspecificvariants,years,andwheatcultivarsandtheirstatisticalcomparisonsareshowninTable3.Visiblevariationswerefoundbetweenthevariants,years,aswellascultivars.

ThevalueofdoughtorqueforparameterC2representsthedoughstrengthdecreasesfromvariantsIandIItothemostinfectedvariantVIII.Itisinaccordancewiththevaluesofthetechno-logicalcharacteristicsrelatingtoproteinlikewetglutenandZelenysedimentationindex.

Aswaspredictedfromthevaluesofthefallingnumber,MixolabparametersC3andC4whichimplythestarchdamagewereagaintheworstforvariantVIII.Thedoughwithsuchresultsisusu-allystickierandcanhaveapoorbakingquality(Dexteret al.1985).Inourcase,thelowvalueofMixolabcharacteristicC5forthisvariant,whichrepresentstherateofretrogradation,verifiestheworsequalityofthestarchpartofthewheatgrain(Collaret al.2006).Thefinalbreadfromsuchdoughmayhaveasimilarvalueoftheloafvol-umebutitispossibletoanticipateundesirablechangesoftheshape(Nightingaleet al.1999),asconfirmedbyourresults(Figure2).

Table2.Fusariuminfectiongradeofwheatsamples(PCRassayusingspecificprimers)andindividualDONcontentingrain

Variant Cultivar2008 2009

F. culmorum F. graminearum DONcontent(µg/kg) F. culmorum F. graminearum DONcontent

(µg/kg)

IMeritto + – n.d. + – 148Akteur + – 12 + – 148Eurofit – – n.d. + – 54

IIMeritto ++ + 266 + + 111Akteur ++ – 151 + – 117Eurofit ++ – 211 – + 4

IIIMeritto ++ – 337 + – 117Akteur ++ + 756 + – 174Eurofit ++ – 324 – – 502

IVMeritto + – 638 + – 436Akteur +++ + 1695 ++ – 2148Eurofit + – 578 + – 271

VMeritto ++ – 2324 + – 1114Akteur ++ – 2433 + – 764Eurofit ++ – 1489 + – 994

VIMeritto ++ + 2443 + – 727Akteur ++ – 3556 + – 1418Eurofit ++ + 2388 + – 294

VIIMeritto +++ + 6146 ++ + 664Akteur +++ + 6304 ++ + 632Eurofit ++ + 3889 ++ + 1053

VIIIMeritto +++ + 7335 ++ + 1700Akteur +++ + 5747 ++ + 1568Eurofit ++ – 6595 ++ – 1053

+samplepositive(lowinfectiongrade);++samplepositive(mediuminfectiongrade);+++samplepositive(highinfectiongrade);–samplenegative;LOQ(DON)=5µg/kg;n.d.–nondetected

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Mixolabdistinguishedsensitivelythevariationsamongthebakingqualityofthecultivarsandalsotheshiftsinthecharacteristicsintheindividualyears(Figure3).Accordingtothefigurethecultivarskepttheirfeaturesincompliancewiththeirqualitygroup.Thehigherqualitycultivars,AkteurandEu-rofit,overtoppedtheworsequalitycultivarMerittoinbothyearsmonitored.In2008,whenFusariumspp.infectionwashigher,therewasaclearshiftinthecurvestoaworsebakingqualitythanin2009.Higherdifferenceswererecordedforthestarchpartofthewheatgrain,whichcouldhavebeencausedbyanearlyhydrolysisofdamagedstarchinmoreinfectedgrains(Barreraet al.2007).

ThesensitivityofMixolabdetectionofsinglevariantswithadifferentintensityofFusariumspp.

contaminationisdemonstratedonthecultivarEu-rofit(Figure4).ClearlyshownistheeffectoftheintensityofFusariumspp.infectiononrheologicalcharacteristicsandtheshiftofindividualcurves.VariantsIandIIwiththelowestintensityofinfectiondisplayedthebeststabilityandthelowestdeclineofthecurveintheproteinpart.Inthestarchpartthehighestincreaseofviscositywasobservedwhichindicatedundamagedstarchgrains. Onthecontrary,variantsVIIandVIIIshowedaconsiderablefallofdoughconsistency,whichdenotesinferiorqualityofgluten,andaworsecourseofthecurveinthestarchpart.Thisresultisinagreementwiththelowfallingnumbersofthesevariants.Thelastpartofthecurvealsoshowedthesmallestincreaseasaresultofthelowviscosityofthedough(Grant1998).

Table3.AveragevaluesofMixolabcharacteristicsandDONcontentforindividualvariants,yearsandwheatcultivars

C2(nm) C3(nm) C4(nm) C5(nm) C1C2(nm) C3C4(nm) C5C4(nm) DS(min) DON(µg/kg)

I 0.46cd 2.04c 1.76bc 2.44bc 0.66ab 0.29a 0.68bc 7.8ab 40.7a

II 0.47d 2.06c 1.80c 2.55c 0.63b 0.26a 0.76c 8.2b 162.9a

III 0.44bcd 2.00bc 1.65abc 2.28abc 0.66ab 0.35a 0.63abc 7.6ab 312.2a

IV 0.40abc 1.93abc 1.62abc 2.27abc 0.69abc 0.31a 0.64abc 7.2ab 961.0ab

V 0.39abc 1.90ab 1.53abc 2.13ab 0.71abc 0.36a 0.6abc 6.3a 1519.7ab

VI 0.37ab 1.84a 1.47a 1.94a 0.73bc 0.37a 0.48ab 6.7a 1804.3abc

VII 0.36a 1.86ab 1.51ab 1.93a 0.74bc 0.35a 0.42a 6.1a 3022.8bc

VIII 0.35a 1.81a 1.43a 1.91a 0.75c 0.38a 0.49ab 6.3a 4002.7c

2008 0.37a 1.81a 1.45a 1.97a 0.74b 0.36a 0.52a 6.5a 2317.4b

2009 0.44b 2.05b 1.74b 2.39b 0.65a 0.31a 0.65b 7.5b 639.2a

EUROFIT 0.43a 2.03a 1.75a 2.31b 0.68a 0.28a 0.57b 7.8a 1175.7a

AKTEUR 0.42a 2.01a 1.73a 2.54c 0.68a 0.28a 0.81c 8.4a 1727.6a

MERITTO 0.37b 1.75b 1.31b 1.69a 0.72b 0.44b 0.38a 5.0b 1531.6a

ValueswithdifferentlettercombinationsarestatisticallysignificantatP ≤0.05(probabilityoferrormax.5%);LOQ(DON)=5µg/kg;C2–proteinweakening;C3–starchgelatinization;C4-stabilityofgel;C5–starchretrogradation;C1C2–fallofproteinstrength;C3C4–diastaticactivity;C5C4–anti-stallingeffect;DS–stabilityofthedoughbeforeweakening

Figure2.TreatedvariantIandinfectedvariantVII–cultivarAkteur(in2008)

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Changes in technological and baking characteristics

TheeffectofFusariumspp.infectionwasvis-ibleinbothproteinandstarchpartsofthewheatgrainandmarkedlyinfluencedthetechnologicalcharacteristicsofthegrain(Table4).SomeauthorsmentionedanincreaseofproteincontentaftertheFusariumspp.contamination(Boyacioğlu&Hettiarachchy1995),butothers, forex-ampleDexteret al.(1997)andGärtneret al.(2008),mentionedaslightdecreaseofit.Inourcase,slightdecreaseoccurredofproteinandwetglutencontentsinthemostinfectedvariantVIIIincomparisonwithvariantsIandII.TheZelenysedimentationindexmeasurestheswellingpo-tentialofthekernelprotein.Meyeret al.(1986)andGärtneret al.(2008)observedgeneralre-ductionofZelenyindexinwheatgrainsafterFHB

infection.Thisindicatesthatalthoughthetotalamountofproteinremainsquitestable,theinfec-tionmayalteritsquality.AccordingtoHareland(2003),fungalinfectionisexpectedtoincreasethedegradationofstarchduetothepresenceofenzymessuchasα-amylaseinthekernelswhichismeasurablebymeansofthefallingnumber.Thesefindingsareinaccordancewithourresults–ZSandFNshoweddistinctivelydecreasedvaluesintheinoculatedvariants(theworstvaluesforvari-antVIII).Anincreaseofashcontentofflourwasrecordedintheartificiallyinoculatedvariants.Ashismainlycomposedofmineralsoftheseedcoat(branandaleurone).Theproportionofashinflouristhereforeanindicatorofitspurity,asincreasingashcontentindicatesanalterationinthekernelseedcoat–volumeratio.Itispossibletoassociatethisobservationwiththepresenceofshrivelled,misshapenfusarium-infectedkernels

Figure3.Mixolabcurvesforindividualcultivarsin2008and2009(variantVIII)

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Figure 4. Mixolab curvesforcultivarEurofitin2008(variantsI–VIII)

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( Jones&Mirocha1999).Thisobservationisprobablyinconnectionwiththelowervaluesoftheflouryieldwithmoreinfectedvariantswhichwasalsoconfirmedbyourresults.Likewise,theloafvolumesandratiosbetweentheheightanddiameterofbreadhadadescendingtendencywithprogressiveinfectionandDONcontent.TheseresultsareinagreementwiththoseofDexteret al. (1996),whoreportedcleardeteriorationofbreadmakingqualityowingtohighFusarium spp.contamination.

relationship between mixolab parameters, dOn content, technological and baking

characteristics

HighlysignificantnegativecorrelationswerefoundbetweenthevaluesofMixolabindividualpoints(C2,C3,C4,C5)andDONcontentindicat-ingtheintensityofFusariumspp.contamination.ThisshowsahighresponseofMixolabtothechangesofwheatgraincausedbyFusariumspp.infection(Table5).

ThesignificantrelationsfoundbetweenMixolabcharacteristicsandstandardtechnologicalparam-eters,especiallyZSandFN,confirmedthealready

publishedknowledge(Ozturket al.2008;Codinăet al.2010).HighlysignificantcorrelationswerealsofoundbetweenMixolabandflourcharacter-istics(flouryield;ashcontent)aswellasbetweenMixolabandbakingparameters(LV;ratioofH/D).AccordingtoourpresumptionthehighervaluesofMixolabparametersC2toC5showedpositiverelationswiththebakingcharacteristicswhereastheincreasingdifferencesC1C2andC3C4indicateddeteriorationofthebreadmakingquality.

COnCLUsiOn

ThehighsensitivityofMixolabsystemformoni-toringthechangesinrheologicalcharacteristicsofwinterwheatwithdifferentintensitiesofFusariumspp.contaminationwasconfirmedinourstudy.IncreasingintensityofFusariumspp.contamina-tionworsenedrheologicalqualityandhencetookupanegativeeffectonproteinandmainlyonthestarchpartofMixolabcurves.Theevaluatedwheatcultivarskeptthebreadmakingqualityaccordingtotheirqualityclassificationnotwithstandingtheinfectiongradeoftheindividualcultivars.

HighcorrelationswerefoundbetweenMixolabcharacteristicsandthestandardtechnologicalparam-

Table4.Averagevaluesofqualitycharacteristicsforindividualvariants(I-thelowest;VIII-thehighestgradeofDONcontent),yearsandwheatcultivars

CP(%) WG(%) ZS(ml) FN(s) LV(ml) H/D FY(%) AC(%)

I 15.0ab 32.2ab 57.0b 365.3cd 272.9c 0.62bc 65.79ab 0.59b

II 15.3b 33.2b 56.7b 380.0d 275.5c 0.66c 65.57ab 0.59b

III 14.7ab 31.7ab 49.7a 330.2bcd 259.9bc 0.60bc 66.66b 0.60b

IV 14.6ab 31.5ab 46.8a 303.0abc 250.2ab 0.60bc 65.62ab 0.68a

V 14.8ab 31.9ab 47.7a 298.2ab 246.1ab 0.57abc 65.01ab 0.69a

VI 14.6ab 31.5ab 47.7a 290.3ab 246.8ab 0.54abc 65.56ab 0.69a

VII 14.7ab 31.7ab 45.2a 270.5ab 237.8a 0.49ab 63.51a 0.70a

VIII 14.5a 31.2a 44.2a 257.7ab 235.7a 0.45a 64.94ab 0.71a

2008 14.9b 31.5a 53.2b 297.2a 249.1a 0.52a 62.54a 0.64b

2009 14.7a 32.2b 45.5a 326.6b 257.1b 0.61b 68.12b 0.67a

EUROFIT 15.1b 32.8a 51.1a 305.1a 258.8a 0.57a 66.17b 0.65a

AKTEUR 15.6c 33.5a 52.2a 332.4a 255.1a 0.57a 67.47b 0.66a

MERITTO 13.7a 29.3b 44.8b 298.2b 245.5b 0.56a 62.36a 0.66a

ValueswithdifferentlettercombinationsarestatisticallysignificantatP≤0.05(probabilityoferrormax.5%);CP–crudeprotein;WG–wetgluten;ZS–Zelenysedimentation;FN-fallingnumber;LV–loafvolume;H/D–rateofheightanddiameterofbread;FY–flouryield;AC–ashcontentofflour

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Table5.Correlationsamongtheevaluatedparameters

CP WG ZS FN LV H/D FY AC

C2 0.37** 0.53** 0.35** 0.80** 0.75** 0.77** 0.68** –0.72**

C3 0.51** 0.68** 0.23 0.64** 0.64** 0.66** 0.83** –0.56**

C4 0.58** 0.71** 0.30* 0.58** 0.62** 0.59** 0.74** –0.50**

C5 0.65** 0.75** 0.36* 0.69** 0.62** 0.61** 0.80** –0.54**

C1C2 –0.27 –0.45** –0.18 –0.75** –0.65** –0.75** –0.69** 0.66**

C3C4 –0.54** –0.59** –0.34* –0.36* –0.46** –0.36* –0.44** 0.28*

C5C4 0.62** 0.66** 0.37** 0.69** 0.50** 0.51** 0.72** –0.48**

DS 0.75** 0.81** 0.47** 0.59** 0.59** 0.48** 0.68** –0.50**

DON –0.04 –0.19 –0.18 –0.77** –0.72** –0.85** –0.51** 0.71**

*correlationsignificantatP≤0.05(probabilityoferrormax.5%);**correlationsignificantatP≤0.01(probabilityoferrormax.1%);C2–proteinweakening;C3–starchgelatinisation;C4–stabilityofgel;C5–starchretrogradation;C1C2–fallofproteinstrength;C3C4–diastaticactivity;C5C4–anti-stallingeffect;DS–stabilityofthedoughbeforeweakening;DON–DONcontent;CP–crudeprotein;WG–wetgluten;ZS–Zelenysedimentation;LV–loafvolume;H/D–rateofheightanddiameterofbread;FY–flouryield;AC–ashcontent

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ReceivedforpublicationNovember4,2010AcceptedaftercorrectionsApril4,2011

Corresponding author:

Ing.LudmilaPapoušková,Výzkumnýústavrostlinnévýroby,Odborgenetiky,šlechtěníakvalityprodukce,Drnovská507,16106Praha,Českárepublikatel.:+420233022395,e-mail:[email protected]

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