06-3月-241

Water06-3月-242

FunctionofwaterPhysicalpropertyofwaterandiceAssociationofhydroneandhydroneStructureofwaterandiceWater-soluteinteractioninfoodWateractivityandfoodstabilitycontents06-3月-243

Keypoints:Interactionofwaterwithionsandionicgroups,withneutralgroups,andwithnonpolarsubstances;wateractivityandtemperaturedependence;moisturesorptionisotherms.Difficultpoints:wateractivityandfoodstability;cagehydrate.06-3月-244

avarietyofappearancewell-roundeddripriverwaterfall06-3月-245

inthreephysicalstateiceWatervapour06-3月-246

Keycomponentoffoods;Dependenceproperties,quality,tastiness,andkeepingtime;Removingharmfulsubstanceinfoodprocessing.1importanceofwater06-3月-247

Physicalenvironment;Carrier;Solvent;Mandatorystandardoffood.1importanceofwater06-3月-248

WatercontentsofvariousfoodsFoodWatercontent(%)Meatpork,raw,compositeofleancutsbeef,raw,retailcutschicken,allclasses,rawmeatwithoutskinfish,muscleproteins53-6050-707465-8106-3月-249

FoodWatercontent(%)Fruitcherries,pearsapples,peaches,grapefruit80-8590VegetablespeaBeets,broccoli,carrots,potatoes74-8085-90Watercontentsofvariousfoods06-3月-2410

Melt(0℃)andboil(100℃)athightemperatures;Largevaluesforpermittivity,surfacetension,heatcapacity,andheatsofphasetransition;High2physicalpropertiesofwaterandice06-3月-2411

Lowvaluefordensityandviscosity;Expandinguponsolidificationandsolvability;Thermalconductivityandthermaldiffusivitiesofwaterislarge.2physicalpropertiesofwaterandice06-3月-2412

3.1thewatermoleculeTwohydrogenatomsapproachthetwosp3bondingorbitalsofoxygen.O-Hcovalentbond:40%partialioniccharacter.3Associationofhydroneandhydrone06-3月-2413

Bondangle:104.5°,near109°28’.O-Hinternucleardistance:0.096nm,Thevanderwaalsradiiforoxygenandhydrogenare0.14nmand0.12nm.3.1thewatermolecule06-3月-2414

thecommonisotopes:16Oand1H,others:17O,18O,2Hand3H,18isotopicvariants.Ionicparticlessuchashydrogenions,hydroxylions,andtheirisotopicvariants.Morethan33chemicalvariantsofHOH.3.1thewatermolecule06-3月-2415

Unsymmetricalchargedistribution;intermolecularattractiveforces,associatewithconsiderabletenacity.Multiplehydrogenbondingonathree-dimensionalbasis.3.2Associationofwatermolecules06-3月-2416

109.472.82Electrostaticeffects.Tetrahedralstructure;Explanationformanyofitsunusualproperties.3.2Associationofwatermolecules06-3月-2417

4.1structureofice:Thedihexagonalbipyramidalclassofthehexagonalsysytem.O-Odistanceis0.276nm,O-Oangleis109°.4structureoficeandwater06-3月-2418

在C軸是單折射，其它方向是雙折射4.1structureofice06-3月-2419

Crystalssymmetry:ninepolymorphismstructure,amorphismorglassystate.Hexagonice:moststability.Theamountandkindofsolutesinfluencethequantity,size,etc.4.1structureofice06-3月-2420

hexagonicecrystal4.1structureofice06-3月-2421

4.1structureofice06-3月-2422

intermolecularhydrogenbondsbeingmomentarilyconcentratedinbulkyclusters-mixturemodelsdistributeduniformlythroughoutthesample-continuummodelsretaininganice-likeorclathrate-typestructure-interstitialmodel4.2structureofwater06-3月-2423

Temperaturedependent;Increaseddensity,maximumat3.98℃;Lowviscosity-highlydynamichydrogen-bondedarrangements.4.2structureofwater06-3月-2424

5.1macroscopiclevelWaterbindingandhydrationAgeneraltendencyforwatertoassociatewithhydrophilicsubstances,includingcellularmaterials.5water-soluteinteractions06-3月-2425

Waterholdingcapacity:theabilityofamatrixofmoleculestophysicallyentraplargeamountsofwaterinamannerthatinhibitsexudation.5.1macroscopiclevel06-3月-2426

Features:notflowfromtissuefoods;easilyremovedduringdrying;easilyconvertedtoiceduringfreezing;asasolvent;restrictedbulkflow;impairmenthasaneffectonfoodquality.5.1macroscopiclevel06-3月-2427

categoriesofwaterinfoods食品中的水鄰近水構(gòu)成水體相水結(jié)合水自由水截留水多層水06-3月-2428

boundwater:waterthatexiststhevicinityofsolutesandothernonaqueousconstituents.theequilibriumwatercontentofasampleatsomeappropriatetemperatureandlowrelativehumiditynotcontributetopermittivityathighfrequenciesnotfreezeat-40℃orlower;5.2boundwater06-3月-2429

notasasolventforadditionalsolutes;linebroadeninginexperimentsinvolvingprotonnuclearmagneticresonance.existsinthevicinityofsolutesandothernonaqueoussubstances.5.2boundwater06-3月-2430

constitutionalwater

結(jié)合最強(qiáng)的水，已成為非水物質(zhì)的整體部分vicinalwater

占據(jù)著非水成分的大多數(shù)親水基團(tuán)的第一層位置multilayerwater

占有第一層中剩下的位置以及形成了鄰近水外的幾層5.2boundwater06-3月-2431

5.3water-soluteinteractions溶質(zhì)和水混合時(shí)會(huì)同時(shí)改變這兩個(gè)成分的性質(zhì)。親水溶質(zhì)改變鄰近水的結(jié)構(gòu)和疏水性水會(huì)改變親水溶質(zhì)的反應(yīng)性和結(jié)構(gòu)溶質(zhì)的疏水基團(tuán)優(yōu)先選擇非水環(huán)境06-3月-2432

類(lèi)型實(shí)例相互作用強(qiáng)度(與水-水氫鍵比)偶極-離子水-游離離子較大水-有機(jī)分子上的帶電基團(tuán)偶極-偶極水-蛋白質(zhì)NH近乎相等水-蛋白質(zhì)CO水-側(cè)鏈OH疏水水合水＋R→R(水合的)

較小(ΔG>0)疏水相互作用R(水合的)＋R(水合的)→R2(水合的)＋H20不可比(疏水相互作用；ΔG＜0)5.3water-soluteinteractions06-3月-2433

水和簡(jiǎn)單的離子產(chǎn)生偶極-離子相互作用。5.4interactionofwaterwithionicgroups06-3月-2434

凈結(jié)構(gòu)形成效應(yīng)(formingeffect)

小離子或多價(jià)離子產(chǎn)生強(qiáng)電場(chǎng)，大多是帶正電荷的離子；如Li+,Na+,H3O+,Ca2+,Ba2+,Mg2+,Al3+,F-,OH-

。具有比純水較低的流動(dòng)性和較緊密的堆積。5.4interactionofwaterwithionicgroups06-3月-2435

凈結(jié)構(gòu)破壞效應(yīng)(breakingeffect)大離子和單價(jià)離子產(chǎn)生較弱電場(chǎng)，大多是負(fù)離子和大的正離子，如K+,Cs+,NH4+,Cl-,Br-,I-,NO3-,BrO3-,IO3-,ClO4-。具有比純水較好的流動(dòng)性。5.4interactionofwaterwithionicgroups06-3月-2436

通過(guò)水合能力，改變水的結(jié)構(gòu)；影響水的介電常數(shù)；決定膠體粒子周?chē)p電層的厚度；離子的種類(lèi)和數(shù)量也影響蛋白質(zhì)的構(gòu)象和膠體的穩(wěn)定性。5.4interactionofwaterwithionicgroups06-3月-2437

能形成氫鍵的溶質(zhì)會(huì)促進(jìn)（至少不會(huì)破壞）純水的正常結(jié)構(gòu).溶質(zhì)氫鍵部位的分布和定向在幾何上與水不相容時(shí)對(duì)水結(jié)構(gòu)具有破壞作用，如尿素——顯著破壞效應(yīng).5.5interactionofwaterwithhydrophilicsolutes06-3月-2438

不改變總氫鍵數(shù)，對(duì)水的凈結(jié)構(gòu)沒(méi)有大影響.能與水形成氫鍵的基團(tuán)：-OH、-NH2、-CO、?；啺被?在生物大分子的兩個(gè)部位或兩個(gè)大分子之間可形成由幾個(gè)水分子構(gòu)成的水橋.5.5interactionofwaterwithhydrophilicsolutes06-3月-2439

木瓜蛋白酶主鏈單元之間的三分子水橋5.5interactionofwaterwithhydrophilicsolutes06-3月-2440

疏水水合作用（hydrophobichydration）

△G=△H－T△S＞0△S＜0H2O＋R→R(水合)5.6interactionofwaterwithnonpolarsubstances06-3月-2441

疏水相互作用(hydrophobicinteraction)△G＜0熱力學(xué)有利R(水合)＋R(水合)→R2(水合)＋H2O5.6interactionofwaterwithnonpolarsubstances06-3月-2442

籠狀水合物：“主體”物質(zhì)-水；“客體”物質(zhì)-低相對(duì)分子質(zhì)量的化合物締合對(duì)蛋白質(zhì)功能性質(zhì)的影響：為蛋白質(zhì)的折疊提供主要推動(dòng)力；維持蛋白質(zhì)四級(jí)結(jié)構(gòu)；疏水基團(tuán)處在蛋白質(zhì)分子的內(nèi)部。5.6interactionofwaterwithnonpolarsubstances06-3月-2443

雙親分子的特征：一個(gè)分子中同時(shí)存在親水和疏水基團(tuán).雙親分子的膠團(tuán)：雙親分子在水（分散介質(zhì)）中形成大分子聚集體.水與親水部位的締合導(dǎo)致雙親分子的表觀“增溶”5.7interactionofwaterwithparentsmolecule06-3月-2444

6.1WaterContentVarioustypesoffoodwiththesamewatercontentdiffersignificantlyinperishability.Thus,watercontentaloneisnotareliableindicatorofperishability.6WateractivityandFoodstability06-3月-2445

Awwasdevelopedtoaccountfortheintensitywithwhichwaterassociateswithvariousnonaqueousconstituents.Awcorrelateswithratesofmicrobialgrowthandmanydegradativereactions.6.1Watercontent06-3月-2446

6.2DefinitionofWaterActivityAw=f/f0,fisthefugacityofthesolventandf0isthefugacityofthepuresolvent.Atlowpressures,thedifferencebetweenf/f0andp/p0islessthan1%,sodefiningAw≈p/p0,purewater:p=p0,Aw=1;infood,pislessthanp0,soAw<1.06-3月-2447

p/p0iseasytomeasure→measurerelativehumidity.RVPisrelatedtopercentequilibriumrelativehumidity(ERH)oftheproductenvironmentasfollows:RVP=p/p0=%ERH/100.6.2DefinitionofWaterActivity06-3月-2448

ERHisapropertyoftheatmosphereinequilibriumwiththesample.Theequationrelationshipisanequalityonlyifequilibriumhasbeenestablished.Withfoods,Awisanapproximation.6.2DefinitionofWaterActivity06-3月-2449

Knowledgeoffreezingpointdepressionandelectrichygrometers.Aw=n1/(n1+n2)n2=GΔTf/(1000Kf)G-qualityofsolventΔTf-freezingpointdepression(℃)Kf-constant1.866.3MeasurementmethodsofAw06-3月-2450

Relativehumidityintheclosedchamberforatimesufficienttoachieveapparentequilibrium.Theprecisionisabout±0.02.06-3月-2451

HygroPalm

Aw1HygroLab

Aw206-3月-2452

AwfeelerSoftware06-3月-2453

TheClausius-Clapeyronequation:dlnAw/d(1/T)=-ΔH/R,T-absolutetemperature,R-thegasconstant,ΔH-isostericnetheatofsorptionatthewatercontentofthesample.6.4TemperatureDependence06-3月-2454

AplotoflnAw-1/T(atconstantwatercontent)shouldbelinear.PlotsoflnAw-1/Tgenerallyexhibitsharpbreakswiththeonsetoficeformation.6.4TemperatureDependence06-3月-2455

Atsubfreezingtemperatures:Aw=pff/p0(scw)=Pice/P0(scw),

wherepffisthepartialpressureofwaterinpartiallyfrozenfood,p0(scw)isthevaporpressureofpuresupercooledwater,andpiceisthevaporpressureofpureice.6.4TemperatureDependence06-3月-2456

TwodistinctionsbetweenAwvaluesatabove-andbelow-freezingtemperatures:First,atabove-freezingT,Awisafunctionofsamplecompositionandtemperature,withtheformerfactorpredominating.AtsubfreezingT,AwbecomesindependentofsamplecompositionanddependssolelyonT.6.4TemperatureDependence06-3月-2457

So,Awvaluesatsubfreezingtemperaturesarefarlessvaluableindicatorsofphysicalandchemicalevents;andknowledgeofAwatasubfreezingtemperaturecannotbeusedtopredictAwatanabove-freezingtemperature.6.4TemperatureDependence06-3月-2458

Second,Awabove-freezingtemperatureindicatetheavailablewatercontentofthesample,anddescribethefoodstability,whereas,Awsubfreezingtemperaturecannot.6.4TemperatureDependence06-3月-2459

Inaproductat-15℃,Aw=0.80,microorganismswillnotgrowandchemicalreactionswilloccurslowly.However,at20℃,andAw=0.80,chemicalreactionswilloccurrapidlyandsomemicroorganismswillgrowatmoderaterates.6.4TemperatureDependence06-3月-2460

Definition:

AplotofwatercontentoffoodversusAwatconstanttemperature.Determination:

Addingwatertopreviouslydriedsamples,thatisresorptionisotherms.Isothermswithasigmoidalshapeformostfoods.6.5MoistureSorption

Isotherms(MSI)06-3月-2461

AJ-typeisothermsforfoodssuchasfruits,confections,andcoffeeextractthatcontainlargeamountsofsugarandothersmall,solublemoleculesandarenotrichinpolymericmaterials.6.5MoistureSorption

Isotherms(MSI)06-3月-2462

多層水構(gòu)成水體相水鄰近水06-3月-2463

ThepropertiesofwaterfromZoneⅠ:constitutionalwater;0~0.07gH2O/gdrymatter;Aw:0~0.25；unfreezableat-40℃,noabilitytodissolvesolutes,andnoeffectonthesolid.stability,variousrateofreactionisverylow.06-3月-2464

ThepropertiesofwaterfromZoneⅡRange:0.07~0.38gH2O/gdrymatter,Aw=0.25~0.85Lessmobilethanbulkwater;Mostofitisunfreezableat-40℃;Causeincipientswellingofthesolidmatrix.WaterinZonesⅠandⅡconstituteslessthan5%06-3月-2465

Thepropertiesofwaterfrom

ZoneⅢ>0.40g/gdrymatter;Aw=0.85~0.99Bulkwaterisphysicallyentrapped;Dissolutionanddilutionaction;Freezableandsolvent;Chemicalreactionandmicroorganismsisrapid;Constitutemorethan95%ofthetotalwater.06-3月-2466

TemperatureDependenceAtconstantwatercontent,T↑,Aw↑;AwconstantT↑,watercontent↓Hysteresis:

Isothermpreparedbyresorptiondoesnotbesuperimposableonisothermpreparedbydesorption06-3月-2467

06-3月-2468

resorption:additionofwatertoadrysampledesorption:dryaftermakesamplesopsaturationHysteresisloopAtangivenAw,thewatercontentofthesamplewillbegreaterduringdesorptionthanduringresorption.06-3月-2469

AppleDrypork06-3月-2470

ThemeaningofHysteresisAtAw=0.75～0.84,lipidoxidationinstrainedmeatfromchickenandporkproceedsmuchmorerapidlybydesorption.Stopthegrowthofmicroorganisms,thelowerAwbydesorption.06-3月-2471

Duringdesorption,thewatercontentatthefirst-encounteredrateminimumisthe“BETmonolayer”watercontent.Aw：0～BET,therateoflipidoxidationdecreases;overdryingofsamples;lessthanoptimumstability.6.6WaterActivityand

FoodStability06-3月-2472

Reasons:waterbindingtohydroperoxides,hinderingtheprogressofoxidation;waterhydratingmetalionsreducescatalyzeeffectivenessofoxidation.6.6WaterActivityand

FoodStability06-3月-2473

Aw＞BET,

increasingratesofoxidation.Reasons:wateracceleratesoxidationbyincreasingthesolubilityofoxygenandbyallowingmacromoleculestoswell,therebyexposingmorecatalyticsites.6.6WaterActivityand

FoodStability06-3月-2474

Aw＞0.80,retardratesofoxidation,andthedilutionofcatalystsreducestheireffectiveness.Reasons:first,anincreaseinwatercontentcanresultinproductinhibition.Second,waterwilldiluterate-enhancingconstituentsanddecreasethereactionrate.6.6WaterActivityand

FoodStability06-3月-2475

1.StructurecharacterofwatermoleculeA水是呈四面體的網(wǎng)狀結(jié)構(gòu)；

B水分子間的氫鍵網(wǎng)絡(luò)是動(dòng)態(tài)的；

C水分子氫鍵鍵合程度取決于溫度。2.Associationofhydroneandhydrone

由于每個(gè)水分子具有相等數(shù)目的氫鍵供體和受體，能夠在三維空間形成氫鍵網(wǎng)絡(luò)結(jié)構(gòu)。3.StructureoficeBriefSummary06-3月-2476

冰是由水分子有序排列成的冰晶，有多種晶型，其中六方形冰晶是最穩(wěn)定的。4.Structuremodelofwater

混和模型、連續(xù)模型、填隙模型5.Categoriesandpropertiesofboundwater結(jié)合水多層水鄰近水構(gòu)成水06-3月-2477

6Bulk-phasewater

距離非水位置最遠(yuǎn)，水-水氫鍵最多。與稀鹽水溶液中水的性質(zhì)相似，特點(diǎn)：能結(jié)冰，但冰點(diǎn)有所下降；溶解溶質(zhì)的能力強(qiáng)，干燥時(shí)易除去；與純水分子平均運(yùn)動(dòng)接近；適于微生物生長(zhǎng)和大多數(shù)化學(xué)反應(yīng)易引起食品的酸敗變質(zhì)，但與食品的風(fēng)味和功能性緊密相關(guān)。06-3月-2478

7Water-soluteinteractions

與離子基團(tuán)、中性基團(tuán)、非極性基團(tuán)、雙親分子的相互作用。8Definitionofwateractivity

某種食品在密閉容器中達(dá)到平衡狀態(tài)時(shí)的水蒸汽分壓；與同一溫度下純水的飽和蒸汽壓之比。06-3月-2479

9DefinitionofMSIandhysteresis

在恒定溫度下，食品中的水分含量與水分活度的關(guān)系曲線。水分回吸與解吸等溫線之間的不一致就稱(chēng)為滯后現(xiàn)象。06-3月-2480

KeyWords水和冰的結(jié)構(gòu)：structureofwaterandice構(gòu)成水:constitutionalwater鄰近水:vicinalwater多層水:multilayerwater體相水:bulk-phasewater06-3月-2481

水分活度:wateractivity吸著等溫線:moisturesorptionisotherms疏水水合:hydrophobichydration疏水相互:hydrophobicinteraction籠形水合物:clathratehydrates滯后現(xiàn)象:hysteresis06-3月-2482

ChapterTwoQuestions1.水在食品中的重要性？2.在溫差相等的情況下，為什么生物組織的冷凍速度比解凍速度更快？3.在同一類(lèi)分子中為什么水的結(jié)構(gòu)最穩(wěn)定？4.持水力、結(jié)合水、水結(jié)合和水合的含義是什么？5.水與不同溶質(zhì)之間的相互作用有什么特點(diǎn)？06-3月-2483

IntroductionMonosaccharide:structure,physicalproperty,chemicalpropertyOligosaccharide:maltose,lactose,sucrosePolysaccharide:starch,cellulose,alginatejelly,plantpolysaccharide,microorganismpolysaccharide.Contents06-3月-2484

Keypoints:

mechanismandmeaningofmaillardreaction;maltose;lactoseintoleranceresults;propertiesandapplicationofpolysaccharide.Difficultypoints:

mechanismandmeaningofmaillardreaction;structureandpropertiesofstarchandcellose.06-3月-2485

1Introduction1.1conceptionCn(H2O)m,incorrectness.Containingpolyhydricaldehyde,ketone,condensationpolymer,andramification.06-3月-2486

1.2classificationMonosaccharide:

notbebrokendowntolowermolecularweightcarbohydratesbyhydrolysis.Oligosaccharide:

contains2to20sugarunitsjoinedbyglycosidicbonds.Polysaccharide:

arepolymersofmonosaccharides.06-3月-2487

linearchainandbranchedchainpolysaccharide.structural,storage,andantigenpolysaccharide.plant,animalandmicrobialpolysaccharide.1.2classification06-3月-2488

FruitD-glucoseD-fructosesucroseApple1.176.043.78Grape6.867.842.26Peach0.911.186.92Pear0.956.771.61Cherry6.497.380.22Strawberry2.092.401.03Freecarbohydrateinfruits06-3月-2489

VegetableD-glucoseD-fructosesucroseBeet0.180.166.11Carrot0.850.854.24Cucumber0.870.860.06Lettuce0.070.160.07Onion2.071.090.89Spinach0.090.040.06Sweetcorn0.340.313.03Tomato1.121.340.01Freecarbohydrateinvegetables06-3月-2490

2monosaccharide2.1structurechiralcarbonatoms,intwodifferentspatialconfigurations.Acyclicstructure

aldose:C2andC4epimerism;ketoses:C5epimerism.06-3月-2491

D-sugar:thehydroxylgrouponthehighestnumberedchiralcarbonatompositionedonright-handside;L-sugar:left-handside.aldoseketoses2406-3月-2492

Ringforms:-C=O+-OHhemiacetalorhemigetal,furanoseorpyranosering.2.1structureofmonosaccharide06-3月-2493

C-1:thehydroxyllocatebelowtheringisαform,anduptheringisβform.06-3月-2494

Glucopyranose:chairandboatform;chairformismorestability.chair

boat2.1structureofmonosaccharide06-3月-2495

2.1structureofmonosaccharide06-3月-2496

2.2physicalpropertymutamerism;Solubility:increasingfollowingtemperature;atthesametemperature,fructoseismosteasytosoluble.Hygroscopic:softenbread,cake,andpanocha.1monosaccharide06-3月-2497

Crystallinity:sucrose>glucose>fructoseandinvertsugar>starchsyrupViscosity:glucoseandfructose<sucrose<starchsyrupantioxidationcryoscopic2.2physicalproperty06-3月-2498

1與堿的作用：?jiǎn)翁窃趬A性溶液易異構(gòu)化和分解。影響因素：糖的種類(lèi)和結(jié)構(gòu)、堿的種類(lèi)和濃度、作用的溫度和時(shí)間等有關(guān)。2.3chemicalproperty06-3月-2499

06-3月-24100

2與酸的作用：酸+糖

低聚糖2.3chemicalproperty戊糖強(qiáng)酸酮糖糠醛+5-羥甲基糠醛06-3月-24101

3氧化還原作用：Ｄ-葡萄糖在葡萄糖氧化酶的作用下，氧化成Ｄ-葡萄糖酸。用于測(cè)定食品、生物材料、血液中D-葡萄糖含量；制造D-葡萄糖酸及其內(nèi)酯。2.3chemicalproperty06-3月-24102

2.3chemicalproperty06-3月-24103

所有單糖都是還原糖。分子中的游離羰基易被還原成醇。

D-葡萄糖D-葡萄糖醇（又稱(chēng)山梨醇）

D-果糖山梨醇+甘露醇

D-木糖木糖醇在糖果中，木糖醇可代替蔗糖，防齲齒。2.3chemicalproperty06-3月-24104

4glycosideshemiacetalformofsugarsreactwith-OH、-NH2、-SHtoproduceafullacetal.Furannucleusandpyranoidring.aglycone:alcoholicgroup.2.3chemicalproperty06-3月-24105

O-glycoside:OHaglyconeN-glycoside:NH2S-glycoside:SH06-3月-24106

5hydroxylgroupestersandethersEsters:

carboxylate:phosphate,acetate,sucrosefattyacidester,sulfate.Sucroseesterisagoodemulsifier.2.3chemicalproperty06-3月-24107

ethersPolysaccharidesareetherifiedtomodifytheirpropertiesandmoreuseful.Hydroxypropylethersofcelluloseandhydroxypropylethersofstarch.3,6-anhydroringfoundinredseaweedpolysaccharides.2.3chemicalproperty06-3月-24108

62.3chemicalproperty06-3月-24109

6nonenzymicbrowningMaillardreaction:reactionbetweenreducingsugars,mainlyD-glucose,andafreeaminoacidorafreeaminogroupofanaminoacidthatispartofaproteinchain.2.3chemicalproperty06-3月-24110

Threeprimaryelements:nitrogen-containingcompounds,reducingsugars,andwater.Characters:producingflavorandcolor.Desirable:milkchocolateflavor,candyflavor;Undesirable:nutritionloss,noxious,andmutagenesismaterial.2.3chemicalproperty06-3月-24111

Maillardreactionprocess還原糖會(huì)與胺反應(yīng)生成葡基胺,溶液為無(wú)色，重排得到1-氨基-1-脫氧-D果糖衍生物。

2.3chemicalproperty06-3月-24112

若反應(yīng)pH≤5反應(yīng)繼續(xù)，得到5-羥甲基-2-呋喃甲醛（HMF）；若pH＞5，活性環(huán)狀物(HMF)快速聚合，生成含氮的不溶性深暗色物質(zhì)。食品中脫色要在色素形成之前加入還原劑。2.3chemicalproperty06-3月-24113

06-3月-24114

06-3月-24115

Maillard反應(yīng)最適條件：褐變程度：D-木糖＞L-阿拉伯糖＞己糖＞二糖酮糖在褐變中：D-果糖＜D-葡萄糖中等水分含量pH7.8~9.2（偏堿性）金屬離子：Cu與Fe促進(jìn)褐變，F(xiàn)e+3

＞Fe+22.3chemicalproperty06-3月-24116

抑制Maillard反應(yīng)的方法稀釋或降低水分含量降低pH降低溫度除去一種作用物：加入葡萄糖轉(zhuǎn)化酶，除去糖，減少褐變色素形成早期加入還原劑（亞硫酸鹽）2.3chemicalproperty06-3月-24117

7caramelizationHeatingofcarbohydratesandreducingsugarwithoutnitrogen-containingcompoundseffectsacomplexgroupofreactions.2.3chemicalproperty06-3月-24118

Acidiccaramelcolor：pH2-4.5,usedincolasoftdrinks,negativecharges.Bakedcaramelcolor:

pH4.2-4.8,usedinbakedgoods,syrups,positivecharges.Beercaramelcolor:

pH3-4,usedinbeerandotheralcoholicbeverages,positivecharges.2.3chemicalproperty06-3月-24119

葡萄糖(C6H12O6)：無(wú)色晶體或白色粉末，易溶于水。葡萄糖以水果和蜂蜜中的含量為多。工業(yè)生產(chǎn)中從玉米和馬鈴薯中的淀粉制取。食品中用于生產(chǎn)面包、糖果、糕點(diǎn)、飲料等。2.4幾種主要的單糖06-3月-24120

果糖(C6H12O6)：白色晶體或粉末，是最甜的糖，易溶于水、乙醇和乙醚。存于水果、蜂蜜中，菊粉水解制取。06-3月-24121

工業(yè)上：用淀粉水解制備葡萄糖，經(jīng)固定化葡萄糖異構(gòu)酶轉(zhuǎn)化為轉(zhuǎn)化糖，含有42％果糖、58％葡萄糖，商業(yè)上稱(chēng)果葡糖漿或高果糖漿，甜度與蔗糖相當(dāng)，具有天然蜂蜜香味，生產(chǎn)成本低，廣泛用于飲料和糖果糕點(diǎn)等食品工業(yè)。06-3月-24122

3低聚糖3.1低聚糖的性質(zhì)褐變反應(yīng)相對(duì)單糖反應(yīng)程度較小，麥芽糖、異麥芽糖均可發(fā)生美拉德褐變褐變的中間產(chǎn)物有明顯的抗氧化作用。高溫下低聚糖能發(fā)生焦糖化反應(yīng)。06-3月-24123

發(fā)酵性酵母不能利用乳糖乳酸菌可發(fā)酵葡萄糖、果糖、蔗糖、麥芽糖，發(fā)酵乳糖產(chǎn)生乳酸。黏度黏度相比:低聚糖>蔗糖>單糖。糖漿的粘度可使熬煮的糖膏有好的可塑性。3.1低聚糖的性質(zhì)06-3月-24124

結(jié)晶、吸濕性蔗糖易結(jié)晶，晶體粗大。淀粉糖漿是葡萄糖、低聚糖和糊精的混合物，不能結(jié)晶，并可防止蔗糖結(jié)晶。應(yīng)用于硬糖生產(chǎn)；制作糖衣材料。3.1低聚糖的性質(zhì)06-3月-24125

1麥芽糖（maltose)由兩分子的吡喃葡萄糖通過(guò)α-1，4糖苷鍵結(jié)合而成的雙糖。麥芽糖(α-D-吡喃葡萄糖-(14)-D-吡喃葡糖苷)143.2重要的低聚糖06-3月-24126

無(wú)色或白色晶體；屬于還原性雙糖；易溶于水，微溶于乙醇；能被酵母發(fā)酵。3.2重要的低聚糖06-3月-24127

存在于麥芽、花粉、花蜜、樹(shù)蜜及大豆植株的葉柄、莖和根部。是淀粉在β-淀粉酶作用下的最終產(chǎn)物。在食品生產(chǎn)中常用作營(yíng)養(yǎng)劑、溫和的甜味劑。3.2重要的低聚糖06-3月-24128

2乳糖β-吡喃半乳糖和D-吡喃葡萄糖以β-1,4糖苷鍵結(jié)合而成。3.2重要的低聚糖06-3月-24129

白色或乳黃色結(jié)晶；溶解度?。惶鸲鹊?蔗糖的1/6)；具有還原性。牛乳中4.6-5.0%，人乳中5-7%。3.2重要的低聚糖06-3月-24130

乳糖促進(jìn)腸道吸收和鈣的保留。D-葡萄糖和D-半乳糖快速吸收并進(jìn)入血液LactoseD-glucoseD-galactose+lactase3.2重要的低聚糖06-3月-24131

乳糖不耐癥：攝入的乳糖僅部分水解，即部分被消化，或不是全部水解3.2重要的低聚糖乳糖D-葡萄糖D-半乳糖+細(xì)菌β-半乳糖苷酶L-乳酸細(xì)菌發(fā)酵06-3月-24132

如果缺少乳糖酶，乳糖保留在小腸腸腔內(nèi)，會(huì)產(chǎn)生腹脹和痙攣。液體保留和腸蠕動(dòng)增加引起腹瀉，發(fā)酵產(chǎn)生的氣體引起脹氣和痙攣。有無(wú)乳糖酶受基因的控制3.2重要的低聚糖06-3月-24133

兩種方法克服：一是通過(guò)發(fā)酵除去乳糖，二是加入乳糖酶減少乳中乳糖。乳糖在植物界較少見(jiàn)。用于嬰幼兒營(yíng)養(yǎng)食品、乳制品、烘烤制品3.2重要的低聚糖06-3月-24134

3.2重要的低聚糖3蔗糖(sucrose)一分子α-D-吡喃葡萄糖和一分子β-D-呋喃果糖

頭頭相連(12)，α，β-1，2糖苷鍵。α-D-吡喃葡萄糖β-D-呋喃果糖1206-3月-24135

非還原性二糖；具有吸濕性和溶解性；很甜，溶于水，難溶于乙醇；蔗糖水解后的水溶液具有旋光性，水解液被稱(chēng)為轉(zhuǎn)化糖。3.2重要的低聚糖06-3月-24136

用作食品甜味劑高濃度的蔗糖溶液抑制細(xì)菌生長(zhǎng)，醫(yī)藥上用作防腐劑和抗氧劑。存在于植物的果實(shí)、根、莖、葉、花及種子內(nèi)。3.2重要的低聚糖06-3月-24137

1低聚果糖（fructooligosaccharide,FOS)組成：蔗糖中的D-果糖與1～3個(gè)果糖以β-2,1糖苷鍵連接成的蔗果三糖、蔗果四糖、蔗果五糖及其混合物。結(jié)構(gòu)：G(葡)+G-F(蔗)+G-F-F(蔗果三糖)+G-F-F-F(蔗果四糖)+G-F-F-F-F(蔗果五糖)分子式為G-F-Fn，n=1～3glucose,fructose3.3功能性低聚糖06-3月-24138

蔗糖果糖21β2,1糖苷鍵06-3月-24139

低聚果糖的生理活性增殖雙歧桿菌；防止齲齒；難水解，是一種低熱量糖；水溶性食物纖維;抑制腐敗菌，維護(hù)腸道健康；不易使血糖升高.3.3功能性低聚糖06-3月-24140

分布低聚果糖存在于天然植物中，如香蕉、蜂蜜、大蒜、西紅柿、洋蔥等目前工業(yè)上利用微生物中具有果糖轉(zhuǎn)移活性的酶作用于蔗糖來(lái)得到低聚果糖3.3功能性低聚糖06-3月-24141

應(yīng)用新型食品甜味劑或功能性食品配料，淀粉食品、乳制品、乳酸飲料；美容產(chǎn)品、護(hù)膚品；醫(yī)藥和保健品。3.3功能性低聚糖06-3月-24142

2低聚木糖(xylooligosaccharide)由2～7個(gè)木糖以β-1,4糖苷鍵連接木二糖含量越高，低聚木糖的產(chǎn)品質(zhì)量越高。3.3功能性低聚糖06-3月-24143

特性：較高的耐熱和耐酸性；高選擇性增殖雙歧桿菌；代謝不依賴(lài)胰島素，適合糖尿病、肥胖癥、高血壓等患者食用；抗齲齒。3.3功能性低聚糖06-3月-24144

應(yīng)用：醫(yī)藥保健品：腸胃功能失調(diào)、糖尿病、高血壓、肥胖癥等患者食品:焙烤食品、調(diào)味品、甜品點(diǎn)心；飲料類(lèi)：酸奶、乳酸菌、碳酸飲料；綠色飼料添加劑。3.3功能性低聚糖06-3月-24145

低聚木糖的生產(chǎn)原料：玉米芯、棉籽殼、富含半纖維素的植物兩步：提取木聚糖；木聚糖酶水解內(nèi)切木聚糖酶、β-1,4木糖苷酶水解木聚糖，后者水解木二糖，有不利影響。菌株篩選（產(chǎn)木聚糖酶酶活高的）。3.3功能性低聚糖06-3月-24146

4Polysaccharides4.1Structure

Composedofglycosylunitsinlinearorbranchedarrangements.MosthaveDPsintherange200~3000,onlyafewlessthan100.06-3月-24147

4.1StructureHomoglycans:cellulose、starchamyloseandstarchamylopectin.Heteroglycan:algins、guarandlocustbeangums.06-3月-24148

4.2Properties

1Solubility:hydroxylgroupandtheringoxygenatomcanformhydrogenbondswithwater.Witheverysugarunithavingthecapacitytoholdwatermoleculesavidly,glycanspossessastrongaffinityforwaterandreadilyhydrate.4Polysaccharides06-3月-24149

Thewaterofhydrationthatishydrogen-bondedtowillnotfreezeandsolvatespolysaccharidemolecules.Polysaccharidesdonotdepressthefreezingpointofwatersignificantly,arecryostabilizersratherthancryoprotectants.4.2Properties06-3月-24150

Carbohydratesareeffectiveinprotectingfoodproductsstoredatfreezertemperaturesfromdestructivechangesintextureandstructure.4.2Properties06-3月-24151

Highlyorderedpolysaccharidespossessorientationandcrystallinity.Certainlinearhomoglycans,haveflat,ribbon-likestructures.Suchlinearchainsundergohydrogenbondingwitheachothersoastoformcrystallites,calledfringedmicelles,separatedbyamorphousregions.06-3月-24152

Crystallitesoflinearchainsgivecellulosefibers,theirgreatstrength,insolubility,andresistancetobreakdown.4.2Properties06-3月-24153

Mostpolysaccharidesarenotsocrystallineastoimpartwaterinsolubility,butarereadilyhydratedanddissolved.4.2Properties06-3月-24154

Water-solubleandmodifiedpolysaccharidesareknownasgumsorhydrocolloids,whicharesoldaspowdersofvaryingparticlesize.4.2Properties06-3月-24155

2viscosityandstabilityPolysaccharidesareusedtothickenorgelaqueoussolutionsandcontroltheflowpropertiesandtexturesofliquidfoodandbeverageproductsandthedeformationpropertiesofsemisolidfoods.4.2Properties06-3月-24156

Atconcentrationsof0.25~0.5%.Theviscosityisafunctionofthesizeandshapeofitsmoleculesandtheconformationstheyadoptinthesolvent.4.2Properties06-3月-24157

Disorderedorrandomcoilstatesinsolution.Somebeingcompact,someexpanded.Linearpolysaccharidesproducehighlyviscous,branchedpolysaccharidesproducemuchlowerviscosity.4.2Properties06-3月-24158

4.2Properties06-3月-24159

Flowbehaviorisdeterminedbythesize,shape,easeofdeformation,andpresenceandmagnitudeofchargesonthesehydratedmoleculesandaggregates.IncreaseinTresultsinadecreaseinviscosity.4.2Properties06-3月-24160

3gelsAgelisacontinuous,three-dimensionalnetworkconsistsofpolymermoleculesorfibrilsformedfrompolymermoleculesjoinedinjunctionzonesbyhydrogenbonding,4.2Properties06-3月-24161

hydrophobicassociations,ioniccrossbridges,entanglements,orcovalentbonds,andtheliquidphaseisanaqueoussolutionoflow-molecular-weightsolutesandportionsofpolymerchains.4.2Properties06-3月-24162

06-3月-24163

Choiceofaspecificgumforapplicationdependsontheviscosityorgelstrength,rheology,pHofthesystem,temperatures,interactionswithotheringredients,textureetc.Functionasabinder,bodyingagent,bulkingagent,crystallizationinhibitoretc.4.2Properties06-3月-24164

4polysaccharidehydrolysisHydrolysisofglycosidicbondscanbecatalyzedbyacidsorenzymeswiththeeffectofreducingviscosity.Hydrolysisoccursmostreadilyduringthermalprocessing,4.2Properties06-3月-24165

sousingmoreofthegumintheformulationtocompensateforbreakdown.Enzyme-catalyzedhydrolysisarecontrolled