(20)-18、大豆分離蛋白的功能（二）

Chapter6Vegetableproteinprocessing知識點1IsolatedSoyProteinFunctionalProperties23.EmulsificationOneoftheprimaryfunctionsofisolatedsoyproteinsistheirabilitytoformstableemulsionsinavarietyoffoodsystems,includingcreamsoups(奶油稀湯),meatandmeatanalogemulsions(肉糜),dairyanalogs,andotherhigh-fatfoodsystems.Thedefinitionofanemulsionisadispersionorsuspensionoftwoimmiscibleliquids.34.WaterBindingMostconventionalfoodsystemscontainatleast50%wateranduptoasmuchas95%water.Goodwaterbindingisessentialinthesefoodproducts.Formulatedfoodproductsthathavepoorwaterholdingcapacityorfat-bindingpropertieshavethetendencytoloseliquidduringthecookingandfreezingprocesses,whichresultsinincreasedcostsofproductionforthemanufacturer.44.WaterBindingCompositionandconformationalstructureofproteinshavebothbeensuggestedtoplayamajorroleinwater-holdingcapacityofaparticularprotein.Waterheldwithinaproteinstructure,suchasagel,isgenerallycategorizedintothefollowingtwogroups:(a)waterthatisboundtotheproteinmoleculeandisnotavailableasasolvent,and(b)trappedwaterwithinaproteinmatrix,whichisconsideredretainedwater.54.WaterBindingBoundwateristhoughttobelargelydependentonphysiochemicalpropertiesincludingaminoacidtype,pH,andionicconcentration;retainedwaterisaffectedmorebythestructuralintegrityoftheproteinmatrixsuchasporosity.Mostproteins,includingisolatedsoyproteins,bindtheleastamountofwaterattheirisoelectricpoint.Thisisthoughttobetheresultofprotonation質(zhì)子化作用ofthecarboxylgroups羧基andenhancedhydrophobicinteractionbetweentheproteinmolecules.65.ViscosityViscosityofasolutionisrelatedtothesolution’sresistancetoflowunderanappliedforce.Thereareseveralfactorsrelatedtoproteinsthatinfluencetheviscosityofasolutionorfoodsystem,includingshape,size,hydrodynamic水力的size(volumeorsizeuponhydration),andflexibilityoftheproteinstructure.75.ViscosityIsolatedsoyproteinscanhaveasignificantinfluenceontheviscosityoffoodsystems.Viscosityofisolatedsoyproteinscanbemodifiedthroughenzymemodification,theuseofreducingagents,orjetcookingandflashcoolingconditions.Proteaseenzymemodificationandreducingagentsareusedtoreducetheviscosityofisolates,whereasjetcookingandflashcoolingcanbeusedtosignificantlyincreaseviscosities.86.DispersibilityTheproteindispersibilityindex(PDI)

isanofficialmethodoftheAmericanOilChemists’Societyandhastraditionally

beenusedtomeasurethesolubilityofsoyflourproducts.Dispersibilityinrelationtotheincorporationofproteinsintoasolutionorsuspension,ingeneral,isdefinedastheeasewithwhichaproteinpowdercanbedispersedintoanaqueoussystem.FromTable7.1,itcaneasilybeseenthatdispersibilityandsolubilityaregenerallyinverselyrelated.96.DispersibilityAhighlysolubleproteinwillabsorbwaterquicklyatthesurface,whichcausestheproteintoformlumpsorballsthataredryinthecenter.Onceformed,theselumpsorballsareverydifficulttobreakdownandeliminatewithouthighshearsimilartothatachievedthroughhomogenization.107.FoamingandWhipping（攪打起泡性）Thefoodindustry’slargestusesofprotein-basedfoamsareintheapplicationareasofmeringues（蛋白與糖的混合物）,mousses（奶油凍）,whippedtoppings（人造稠黃油）,beer,andavarietyofotherwhippedproducts（攪打產(chǎn)品）.Traditionalisolatedsoyproteinshavelimitedfoamingorwhippingcharacteristics.Solubleisolatedsoyproteinsexhibitsomefoamingcapacitybutvirtuallynofoamstability.117.FoamingandWhippingThefoamingcharacteristicsofisolatedsoyproteinscanbesignificantlyimprovedbytheuseofproteinfractionation（分餾）orenzymemodification.Thespecializedisol