(20)-18、大豆分离蛋白的功能（二）

Chapter6Vegetableproteinprocessing知识点1IsolatedSoyProteinFunctionalProperties23.EmulsificationOneoftheprimaryfunctionsofisolatedsoyproteinsistheirabilitytoformstableemulsionsinavarietyoffoodsystems,includingcreamsoups(奶油稀汤),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质子化作用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（搅打起泡性）Thefoodindustry’slargestusesofprotein-basedfoamsareintheapplicationareasofmeringues（蛋白与糖的混合物）,mousses（奶油冻）,whippedtoppings（人造稠黄油）,beer,andavarietyofotherwhippedproducts（搅打产品）.Traditionalisolatedsoyproteinshavelimitedfoamingorwhippingcharacteristics.Solubleisolatedsoyproteinsexhibitsomefoamingcapacitybutvirtuallynofoamstability.117.FoamingandWhippingThefoamingcharacteristicsofisolatedsoyproteinscanbesignificantlyimprovedbytheuseofproteinfractionation（分馏）orenzymemodification.Thespecializedisol