食品课件化学ch5proteins physical properties

1、alShanghaiJiaoTong1InfluenceofpHonalShanghaiJiaoTong1InfluenceofpHon6InfluenceofpHonMinimum solubility at Solubility is greater atalkaline Solubility and extractability of enhancedby increasingthe ne ectrical5um eractionnthe protein and Protein- protein + water protein-eract by ionic, H-bond On the

2、contrary, hydrophobic eractions promote protein-protein eractions,solubilityProtein solubility index percentageofsolubleprotein presentinacommer proteinorisolates 25-Depends rinsic 内在Extrinsic 外在IonicInfluence ofTemperature (with temperature bet n 0-40 Type of4The physicochemical 物理化学aspects of prot

3、eins and their impact on functionalities in foodsHydrationSolubilitydispersibility分散性wettability 润湿性, swelling, thickening增稠, water absorption, water-holding capacitySurface emulsification, foaming,flavor binding, pigment Hydrodynamic水动力/ RheologicalElasticity弹性,viscosity粘性,cohesiveness粘结性,chewiness

4、, 粘附力, stickiness, gelation, dough formation, texturation3FunctionsofProteinsinFlavor, odor, texture, color Opacity不透turbidity混浊Solubility,dispersibilitygelation, foaming, Viscosity粘稠, 粘附力, aggregation凝聚, gelation凝Comparabilitywith other ingredientsandwith sing2FunctionalProteinsPuJing,Food Chemistr

5、y, Fall 2014 ShanghaiJiaoTong 1alShanghaiJiaoTong2Water binding capacity Measurement pro s Equilibratedry alShanghaiJiaoTong2Water binding capacity Measurement pro s Equilibratedry derin 90-95%relative humidity environment Measure amount ofwatertakenupbythe protein in units ofgwater/ gDough Flavor C

6、lassification of Protein Proteinsmust eractwith other components of thefoodEmulsification, DoughformationWaterabsorption/retention; Swelling;adhe ,dispersibility, protein-hydration Functional9Atypicalindustrialpro sforisolationofsoyproteinfromdefatted soyflour8Influence of pH on Minimum solubility a

7、t Solubility is greater at alkaline Solubility and extractability of enhancedby increasingthe ectrical7alShanghaiJiaoTong3Factors Affecting Gel alShanghaiJiaoTong3Factors Affecting Gel ProteinSalt GelCalcium and FreesulfhydrylTypes of Proteins containing small amounts of nonpolar amino acids (32%)Tr

8、anslucentCoagulum-type Proteins containing large amounts of amino acidsStages of heat-induced waterin WaterProteinunfoldingHydrophobic eraction Definition:Agelisacontinuousnetworkofmacroscopic dimen simmersedinaliquidmediumexhibitingno steady-s e flow.Donkey-Hide Factors Affecting Protein at PI,the

9、least water binding capacity PI,WBCincreasesduetotheincreaseofnetcharge andrepulSalta low concentration (33%)hydroxylamino atype of Water3 Apolaraminoatypeofglu hydrophobic eractions -binding1 Low levelof charged li sand glycoli 4 Higherlevel (about14% of low surface charge residues) of favors forma

10、tion of -low charge molecular 5 Formation ofnew disulfideeasily approach each form hydrogen alShanghaiJiaoTong6ppensonmolecular level during dough Protein Hydrophobic Th alShanghaiJiaoTong6ppensonmolecular level during dough Protein Hydrophobic Th disulfide cross-Entrap starch and3DproteinMolecular

11、UnfoldingofDisulfide New disulfide bonds Native disulfide bonds break ppensonmolecular level during dough Protein Hydrophobic disulfide cross-3DproteinMolecular UnfoldingofProtein One native s Manydenatured ppensonmolecular level during dough Protein 3D protein Molecular Unfoldingof Dough Glutennetw

12、orkinatvariousstagesofDoughat (b)partiallymixedEarly hepro (atabout themiddle of thehydrationalShanghaiJiaoTong7Foamability or foaming alShanghaiJiaoTong7Foamability or foaming The amount oferfa l areaInfluenced by the rate of absorption, flexibility, and Foaming Thestabilityofproteinstabilizefoamag

13、ainstgravi ional and mechanical stressesInfluencedbyRheologicalpropertiesoftheproteinSimilar in some respects to Denaturation of proteinatanair-liquid Hydrophobicgroupsenter theair, hydrophilicamino acidsremain in thewaterProtein-stabilizedfoamsare formedbybubbling,whip a protein solution Factors im

14、portant for protein stabilized NetProtein Establishhydrophobic Higherconcentration favorsTemperature (favored around60LowerFavors hydrophobic Adsorbat erfaceandcontributes tothephysical and rheological ,preventing droplet Abilitytodiffusetowards and adsorbattheElectron Micrographof HomogenizedMilk f

15、at Definitionof Emul oneispresentasdropletst are dispersed throughout the otherThermodynamically unstable mixtures of immiscibleProteinsmaystabilizeemuls Inorderto form and stabilizean ,a proteDiffuseto milk Ex ehydrophobiceractwith 3DProteinnetHydrated flourparticleafterstarch is removedbyenzymatic

16、 alShanghaiJiaoTong8Foaming HighalShanghaiJiaoTong8Foaming HighMWglobularproduce thickadsorbed Aggregation of partially unfolded Hydrophobic, H-bond, electros Adsorb strongly erface viaPolar side chainseract with water withand reduce drainageFoamingAlsocalled as( volume of foam volume of initial liq

17、uid) *100% Overrun=volume of initial liquidFlavor Protein itselfis However, proteins contribute to the flavor of foods Flavor molecules bind to Breakdown Chemical lardFactorsAffectingFoamFormationand Protein Increases stability more n foamSmaller bubbles and stiffer Durationand ensityofAdequate unfolding and Li Impair foaming Specificallysurface-activepolarl s（usually phospha i ) erferewith adsorbedproteinsForhigh fatproducts, mus veone typeofprote o formtheemul another to incorporate airFactorsAffectingFoamFormationand Around PI range, imp