Chemistry Reference
In-Depth Information
passedthroughanion-exchangecolumn;andevaporatedtogiveasyrupcontaining42%fructose,
53%glucose,and5%morecomplexsugars.This42%HFCSisconvertedto90%HFCSbysize
exclusion chromatographic columns. The 90% syrup is blended with 42% syrup to give a 55%
HFCS(1.2timesassweetassucrose)(Alexander1998).Allsyrupsarethenreinedbyevaporation,
ion exchange, and vacuum ilters to give inished HFCSs. Part of the 42% syrup is concentrated
andsoldas42%HFCS(71%-80%drysubstance).Thisissimilarfor55%HFCS(77%drysub-
stance).Someofthe90%HFCSisblendedwithalcoholandevaporatedtogive90%HFCS(90%
drysubstance).Thenitiscrystallizedwithfructosecrystals,centrifuged,dried,andcooledtogive
crystallinefructose.
8.17 BISCUItS
Theeffectofsugarondoughbehaviorisanimportantfactorinbiscuitmaking.Inexcess,sugar
causesasofteningofthedough,aresultinpartofcompetitionbetweentheaddedsugarandthe
availability of water in the system (Bure 1980). Using a Farinograph, Olewnik and Kulp (1984)
observedthatanincreaseinthesugarconcentrationinacookiedoughreducesitsconsistencyand
cohesion.Mizukoshi(1985)studiedtheeffectofvaryingsugarcontentonshearmodulusmeasured
during cake baking while keeping the proportion of other ingredients constant. He showed that
below20%sugarhasnoeffectonshearmodulus;whereas,anincreasefrom30%to40%reducesit
appreciably,revealingtheexistenceofathresholdvalueassociatedwiththevariationofsugarcon-
tentintheformula.Vettern(1984)studiedtheeffectsofsugarquantityanditsgrainsizeonbiscuit
spreading.Theconclusionwasthatainegrainsizeandahighconcentrationofsugarcontributed
toasigniicantspreadingofthebiscuit.Sucroseactsasahardeningagentbycrystallizingasthe
cookiecools,whichmakestheproductcrisp.However,atmoderateamounts,itactsasasoftener,
becauseoftheabilityofsucrosetoretainwater(Schanot1981).Sugarmakesthecookedproduct
fragilebecauseitcontrolshydrationandtendstodispersetheproteinandstarchmolecules,thereby
preventingtheformationofacontinuousmass(BeanandSetser1992).
Theadditionofsugartotheformuladecreasesdoughviscosityandrelaxationtime.Itpromotes
biscuitlengthandreducesthicknessandweight.Biscuitsthatarerichinsugararecharacterizedby
ahighlycohesivestructureandacrisptexture(Maache-Rezzougetal.1998).
8.18 FrOZeN DeSSertS
Frozendessertsaremadebyfreezingaliquidmixtureofsugarwithcream,milk,fruitjuices,or
purees.Intheliquidmixture,thedissolvedsugar'sabilitytoattractandholdwaterdiminishesthe
wateravailableforwatercrystallizationduringfreezing.Asaresult,theFPoftheliquidmixtureis
lowered.Becauseless“free”waterisavailable,theicecrystalsthatformtendtobesmaller(Smith
1990).
As part of the liquid mixture begins to freeze, the sugar in the remaining unfrozen solution
becomesmoreconcentrated,furtherloweringtheFPoftheremainingunfrozensolution.Therefore,
atemperaturemuchlowerthantheFPoftheliquidmixtureisusedtoensurerapid,consistentcool-
ing.ThiscombinationoflowerFPprovidedbythedissolvedsugarandacolderthanfreezingtem-
peratureproducesafrozenproductwithtinyicecrystals.Tinyicecrystalsgivethefrozendessertits
smooth,creamytexture.Largecrystalsareundesirablebecausetheyimpartagrittyorsandytexture
inthefrozendessert.Hardeningandstorageoffrozendessertsaretheinalstepstoachievinga
high-qualityfrozendessert(Smith1990).
HFCS,ifusedasanalternativesweetener,lowerstheFPtwiceasmuchassugardoes,which
producesanicytexture.
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