Mineral composition of gluten, starch, and water-solubles fractions of wheat flour and its ...

51 Pages·2013·3.57 MB·English

by  Bequette, Robert Keebler.

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DIlRCDOCTiaiANDROTIEtfOF LITSUTORE 1
MATERIALSANDMETHODS 9
HBStJLTSANDDISCUSSION 10
*#H"gQuality • .10
Composition oftheFlourFractions 13
RelationshipBetweenMineralCenpositianendBakingQuality 26
SUMMARYANDCGHCTUSICWS 29
SOOOESTICHSFORFWEUaBWCRE 30
ACKNOWIEDGMHTTS 31
UTSUTORBCITKD 32
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Mineralcomposition ofwheatandflour Is Mnown tovarywith environ-
mentand heredity, finviromcntal factore includeweather, available
nutrients inthe eoiland thephysical ocndttion of the aoil. Beeeen (*)
andBailey (3) harereviewedthaeKtenaivaearlyliterature onthemineral
composition ofwheat and flour, Many of these earlyanalyaesware carried
out en samples ofunknownoriginend frequently information on sM.1, climatic
factore, variety, andbaking qualitywerelacking. Meatresults indicated
thet-italash and composition oftheashvariedgreatly*
Uptake ofavailablenutrientsby thewheatplant is afrected Ifvariolar
and soilnolatureas wallastherelativeratios oftheelements inthe soil
(5). Oraavaa andCarter (17) f'andthatthe totalash in thegrainincreaeed
progressivelyas the amount of irrigationwater Increased. Most ofthe
increaseresulted fromadditionalphosphorus, potassium, calcium, and
magnesiumabsorbedby theplents. In e l.vtcr paper,Qreevec, et. si. (15)
reported thatspringwheat containedgreaterpercentages of totalash,
oalciua,potassium, ircn, phosphorus, »nA sulfurthen winter vheat grown on
theacmesoil• Thiswas assumedtobedueto genetic differencesbetween
the twoclasses ofwheats. Additions of greenmanaracauseda significant
increase in totaleah, caldnm, mdphosphoruspreaamanlybecause ofthe
increaeedavailability oftheseelements. Mo data onbakingquali^rware
reported•
SehrenkandKing (36) reportedthatash sndmineral contentof three
wheatvarietiesgrown for threeyearsat 13 locationswithinthe state of
Kansas variedappreciablyandwere correlated, ingeneral, with available
nutrients inthe eoil. Theavailabilityofnutrients depended onthe rain-
fall sine*high annualrainfall leachedavailablenutrients fromthe soil.
Areas producingwheatwith highmineral contentalsoproducedwheat withhigh
protein. Mineral contentwas influenced greatlyby location,but only
slightlybyvariety. Areasproducinghi<;hmineral content did so consistenly,
Indicating thatdifference© duetorainfall and other environmental factors
durin- the three-year perioddidnotaffectmineral content significantly.
The increasedashcontent ofWestern Kansaswheatswasnet dueto Increases
inMfoneelement, butwas there; nett increases in each of the
major constituents of theash. The change* in ;rdnor element composition
showednodefinitetrendwithrespect to locati .
Ina continuation ofthiswork, Schrcnk (35) studied the effects of
calcium, magnesium, and phosphorus applications on the composition of rain
produced in SoutheasternKansas. Thepercentage cf proteindecreaseddue
to fertiliser treatment, while themineral content of the grain increased.
This suggests thatwhen non-nitrogenous fertiliserswereappliedat these
locationsnitrogen content of the soilbecaeallmitinr factor. The ivost
noticeable effect of soiltreatmentwas the increase inphosphorus content
ofthe grain. Magnesiumdecreasedwhen onlycalcium andphosphoruswere
spplied tothesoil. When these twonutrientsweresupplemented*lth
magnesium,magnesiumalso increased inthegrain.
Informationaccumulatedat the HardWinterWheat Qualitylaboratory
(Finne-, et. el., 12) andrepresentingmanyvarietiesgrown throughout the
GreatPlains, indicates that totalashis controlledbytwofactors. These
arevarietyand environment, themostimportant ofwhich is envirenraent.
Varietyplays aminor role indetermining mineral content ofwholewheat
under field conditions. Conditions that favoraccumulation ofprotein in
thekernelgenerally fevoraccumulation ofminerals.
Significant differences inthemineral copposition ofportione ofthe
wholewheatkernelalsoharebeenmeasured* Morris, et. al. (27), enploying
emicrodissectiontechnique toseparatewholewheatkernels intofractions,
foundevidenceofen increasinggradientInashandproteincontent extending
(xztwordfromthe senter ofthe endosperm. Comparisonoftheashandprotein
contents of thedissectedfractionswiththose ofBuhler flourmillstreams
ofThomesoftwheat showedthatthedissectedfractionwith the lowestash
was identicalwiththeflour streamwiththelowest ash* The flourstreams
withthe highestashwereslightlylowerinashthanthedissected fractions
with thehighestash. Itis knowngenerallythatcationsinfluence dough
behavior and exertamodifying effectontheflourproteins (13, 25).
Severalmethods ofdetermining flourqualitybasedon themeasurementof
physico-chesdealproperties of dispersedflourproteinshavebeen shown to
beaffectedby electrolytes presentinwheatash (MillerandJohnson, ZS)»
Increasingthe saltconcentration ofdough*preparedfor testinginthe
BrabenderSxtsnsograph increasesboththeextensibilityandresistanceto
extensionofdoughs* Weakand strongfloursresponddifferentlytoadded
salt (Fisher, et. al., 13).
Meter containingamediundegree ofhardnessis consideredmoot suit-
able forhexingpurposesas sonsof themineral saltshaveastrengthening
effectonthegluten. Softwaters ere objectionableinbakingbeoauee they
tendtoyieldasoft, stickydough (Pyler, 33). Patentedpreparations
generallyareusedtobringccramercial doughstoamaximumionic strength,
regulatedbythe solubilityofcalcium sulfate.
SullivanendNear (3?) analysed theash of 20wheat samples ofwidely
differentcharacter andoriginandreportedthatmagnoalum contentwas
relateddirectly to thestrengthofwheatsasdeterminedbyprotein
percentageandgluten quality* Theglutenqualityscore wasbased on
physicalproperties ofdoughandwashedgluten. This subjectivemethod
ofevaluatingglutenqualityleavesmuchtobedesired*
DavidsonandShollenberger (6) studied effects onflourbaking quality
of sodiumnitrateappliedat different stagesduring growth of thewheat
plant, Flourprotein, ash, andabsorption, loafvolume,andtotal loafscore
increasedwith increases In length of timefrom seedinguntil sodium
nitratewasapplied. Thehighestflourprotein, ash, andabsorption, and
highestquality loavesresultedfromapplication ofsodiumnitrateat
(Hi, 15) grewwheatinhydroponic solutionsandstudiedthe
effects onbreadscores ofnitrateand chloridesalts sejplisd during the
laterperiod mfplantgrowth* Thequality of flourfromsheetgroanin
cultureewherenitrogenwas suppliedinthefernofmonlawas decidely
inferiorto thatnilled fromwheatgrownincultures suppliedwithnitrogen
inthenitrate fora* Inbothseries, theuse ofcalciumnitrate or chloride
resulted inhigherbreadseoresthandidthe similarsalts ofpotassium,
•odium, andmagnesium. Theuse ofammoniumnitrateresultedin thepoorest
loafproduced fromwheatgrown insolutions containingdifferentnitrate salts.
Semequestion of thevalidityof theseresultsmightberaiseddue to the
inadequacyof thebaking testeusedby Oaricke. Although each samplewas
bakedbybothbasicandstimulated (diastased)methods, in severalcases,
qualityrankings variedbetween bakingmethods* Recentlydevelopedbread-
makingmethods (Finney, 9) eremuchbetterable tomeasurethebreeomeldng
potentialofflours*
IcCalleendWoodford (*3) eaployed theliquidculture technique* of
Ocrlekeandreportedthatlimiting thesupplyofpotaeelua towheatplant*
hadanadverseeffect on thaqualityof trainaa deterpdnadbygluten and
Separation of flourdoughe or flour-waterauBponaiona intothair
andraoonatltution ofthaaa complexestoproduce "synthetic" doughs
hasyieldedeeneideratle informationon factors determining flourquality.
Omfortnnstely, methods ofaskingtheseseparationsharevariedandsomsoftha
data obtainedharebeencontradictor:.', Thagluten complex, however, hasbeen
showntobethemost lasiortsnt substsnee intheflour. Itiereaponsibls
forthe elastic andeeheeiveproperties ofaflourdoughandfor**thethree
^—^,^1
networkwhichisresponsibleforthsohsraoteristio porous
structureofleavenedbreed. Pence, at.al. (30) andSullivan (38) recently
reviewedtheliteratureon thsrole ofwheat flourproteininbaking.
Ksrlyworkers separatedgluten into fractionsbasedonsolubilityIn
various solvents insnatteapttodetermine factorsresponsiblefor the
unusualproperties ofglutenandthereasonsforvariation inproperties of
gluten obtained fromdifferentflours. Thetoostlispcrtantconclusiondrawn
fromthisworkwasthatgluten consistsofmanycomponentsvarying progres-
sive!'insolubilityandotherphysical rr©parties (Killer andJohnson, 2$).
awsnson (hO) discussed the inflaenoeofelectrolytes on ths physical
properties ofdoughsand onflourproteins. DoughsareInflnenoeridirectly
bythekindandsmountof saltpresent,andindirectlyby theireffect onpH.
awrasssinviscosity ofadoughinthepresence ofa saltwaaattributedto
theappropriationof waterbytha saltmolseules orions. Decreasein
viscositywouldbecausedbyadispersing offestonthagluten.
Fewanalyses ofgluten obtainedfromflours ofwidelydifferentdough
characteristics andbaking qualityhare shownsignificant differences in the
—minin orkinds ofaminoacids. Miller, et. el, (26) studied the "micro-
biologioallyapparent'1 lysine, glutamic acid, cjstine,andmethioninecontent
ofwholewheats and foundarelationshipbetweennixingtimeandpercentof
both cystineandMethionineas influencedby environment. No differences
feetovariety wereobserved. Flour frostwheatsamples highin cystine
required the longeet mixing for optimumdoughdevelopment. VWetiamn (hZ)
reportedapositivecorrelationbetween flour strength, asreflectedby
surfacearea of exteneograas, thecystine content offlourproteins,and
total cystine content of theflour. Cystinewas determinedpolarogrsphieally.
Presentevidenceindicates thatvariations inglutenproperties, inpart,
areduetomodifyinginfluencesexertedbythe other doughcomplexes, mainly
thosematerials extractableinwater. Pence, et. al. (23, 29, 31)made
detailed studies ofeffects ofwater-soluble flour components enbaking
behavior. They found that solublepentosans hadlittleeffect on thebaking
performanceofdoughs reconstitutedwithout theuseofthewater-soluble
fraction,ofthe flour, but thehandlingproperties ofthe doughsweremodified
distinctly. Thesepentosans corrected toa large degree the softness, wet
surface, and lack ofnormalstickiness shownindoughsreconstitutedwith only
glutenend starch. Improrewenteinvolume, grain, and texture, however,
thesoluble oomponente of the flourswererequired formaximumperfc
ofallglutene except thatfromadurumwheat, andappearedtobe capable
ofaffecting flourbehaviortosuchen extent thatdifferences or similarities
in gluten characteristics were obscured. Thepentosans ofthe crudealbumin
fraction (non-dialysableportion of thewater-solubles)warereepcnsible for
the shortenednixingtinsofdoughscontaining thisfraction.
«n
ofsolubleproteins foundtoincreasedirectlywith total flour
protein,battherelatione*!?heosneinversewhen theywereexpressedee
perecntagesof totalprotein. Therationofalbuminstoglobulinscontained
by flours veraoorrelated withproteinqualitybeyondtheonepercent level
ofsicnifiosnee. TheauthorepostulatedthatalbuminccepanahtPactIna
benefieialwanner inbreeddou#ujtwhereaa, globulins actinadeleterious
meaner. Theresultant effect ofthetwopreteine isreflectedbytheratio
oftheirsmounte,
MetternendSendetedt (22)reported thattheprincipal factorresponsible
fordeterminingthe"^^rlftf.requirementofwheatflouris mlsrmsnlitils. The
nixingtineofaflooresslengthenedbyremoval oftheweter-eoluble freotlon.
Reiuctt-ptreticn ofthe solublesreversedtideeffect* Themixingrequire*
Meetofafleeralsowasextendedbyincorporatingwaterextractedflour
withanormal floor*
Starchhasbeen showntoexert sonseffectendough propertiesandloaf
qualityslthnasyi these effects ererathersmallcooperedtothosereported
fortheglutenandwater-soluble fractions. AccordingtoSsndstedt, et.el*
(3it)the "eeylodextrin" or "tailingsstarch" fractionofflourisafactor
inabsorptionendexertsitsinfluenceonthehandling charaeteristiesof
flourdoughs. Thisnotorialwasassociatedwithst.lskinosa of
withtenderness efcrumbinthebakedproduct. HarrisendSdbbit (18, 3y)
foundnarfceddifferenoecinthecomparativebakingqualitiesofstarch
preparedirondifferentwheatvarieties* %nthetio floors werepreduosdby
addingthese starches toaconstantglutensubstratea* threeproteinlevels.
PreeentevidenceprovidedbyMatternendasndstedt (22) leadstodoubt
ofthevalidity ofearlyreports ooncorningthepositive offooto of
ladetuminiagdoughcharacteristicsandtreadquality, Sandetedt, et. al.
(31) andHarriaandaUftdt 0$) aeparatedthe glutenandstarchfiroa«
ItooptdsondevelcpnentanddiscardedthevattcrwoolnMaa,
Daacrerecentoork, (8, 22, 37, U3> thefloor ocnpleoeee barebean
bynathodadesignedtoseepdoaghdevelopnontatanlnlaaa, under
thoae conditions, thavater-eolnbleeareneeoseary inreconstitutinga
"eynthetiodoagh" *!ieh willremitinbreadofqualityequaltothatfreea
flour*
Littlela know*about therelativedistributionoftheminerals intha
(operatedIronhydratedfloursandtheirrelationehlp to the
topologicalbehavior offlour, SIOindy, et,el, (7) studiedthe influence
ofvariety, fertilisertaraavaont,andsoilontheproteincontentandmineral
oonpoeitionoftfceet, Hoar, andflour fractlona (gluten, starch,andeater*
solnblss). millngbehaviorandflouryieldveranotaffectednoticeably
aysoildifferencesorfertiliser treetaents. Totalvhoatashaeeaffected
byfertilisertreetawntaandvariedanongvarieties. Theporeonlagoof
epecific elenenteintheashes ofthevheetandthafloor fractionsvaried
greatlyanongvarlstles forsaneelenente. Thereusenoconsistent
relationehlpanongvarietiesend elanental ooapoeitionconparedaaabsolute
aaounteoraaporoentagaaofthaash, Thaanthersconcludedthatacenplex
herediterylirkayiniilprobablyinfluencedopposition ofthaash. Ho
iaforaation onthebaJdagoharaaterlatios ofthese flourewaspiassuied*
Theliteraturesuggeatethatflourandgluten qualityarecontrolledby
afactororfactorsvtdeharesubtileinnature, Che ofthesefactorsabout
vhloh therelalittleinfomation iethaalneral coapoeiticn offlourandits