現(xiàn)代食品化學(xué)研究進(jìn)展4脂質(zhì)-2

脂質(zhì)LipidMainContentsUnsaturatedfattyacids

AntioxidantsComplexlipidsandderivativelipidsFatsubstituteModificationoflipids1.UnsaturatedfattyacidsAnunsaturatedfatisafatorfattyacidinwhichthereisatleastonedoublebondwithinthefattyacidchain.Afatmoleculeismonounsaturatedifitcontainsonedoublebond,andpolyunsaturatedifitcontainsmorethanonedoublebond.Incellularmetabolism,unsaturatedfatmoleculescontainsomewhatlessenergythananequivalentamountofsaturatedfat.Thegreaterthedegreeofunsaturationinafattyacid(i.e.,themoredoublebondsinthefattyacid)themorevulnerableitistolipidperoxidation.Unsaturatedfattyacids從甲基端開始的第一個(gè)碳原子稱為ω碳。從ω碳開始計(jì)數(shù)，按第一個(gè)發(fā)生雙鍵的碳原子數(shù)分類。單不飽和：n-7，n-9多不飽和：n-3，n-6

n-3：α-亞麻酸，EPA，DHA

n-6：亞油酸，γ-亞麻酸，花生四烯酸

在膳食中n-3和n-6脂肪酸應(yīng)各有一定比例TwotypesoftriglyceridersStearicacid硬脂酸Palmiticacid軟脂酸熱門不飽和脂肪酸Linoleicacid(α-亞麻酸)α-亞麻酸屬于n-3系列，其第一個(gè)雙鍵從甲基端第3個(gè)碳原子開始。CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOHLinolenicacid(γ-亞麻酸)γ-亞麻酸屬于n-6系列，其第一個(gè)雙鍵從甲基端第6個(gè)碳原子開始。CH3(CH2)4CH=CHCH2CH=CHCH2CH=CH(CH2)4COOHEPA（ω-3，20：5）

DHA（ω-3，22：6）海洋魚油EPA＋DHA為20～30％DHA是大腦灰質(zhì)的重要成分,EPA治療和預(yù)防心血管疾病。在生物體內(nèi)可由α-亞麻酸轉(zhuǎn)化而來。EPA

andDHAItisobtainedinthehumandietbyeatingoilyfishorfishoil—e.g.,codliver,herring,mackerel,salmon,menhadenandsardine.Itisalsofoundinhumanbreastmilk.2.1Classification

NaturalAntioxidantsandSyntheticAntioxidants自由基清除劑1O2淬滅劑金屬螯合劑氧清除劑ROOH分解劑酶抑制劑酶抗氧化劑紫外線吸收劑2.Antioxidants2.2Antioxidationmechanism1）Singletoxygenandβ-carotenePhysicalquenching

1O2

+1Car→3O2+3Car→3O2+1Car+heatkq=5*1010

M-1S-1Chemicalquenching

1O2

+1Car→Car-O2kq=80M-1S-1CaroteneandperoxylradicalsScavengerforalkylradicalsROO.+Car→ROO-+Car+.ElectrontransferCaroteneandperoxylradicalsROO·+Car→ROO-Car·Lowoxygenconcentration:

ROO·+ROO-Car·→ROO-Car-OORAntioxidativeeffectCaroteneisconsumedirreversibleHighoxygenconcentration:

O2+ROO-Car·→ROO-Car-OO·ProoxidativeeffectCaroteneisconsumedirreversible2）ROOHDecomposition

ROOHROH

R'2S+ROOHR'2S=O+ROHR'2S=O+ROOHR'2SO2+ROH3）

EnzymesystemsSuperoxidedismutase,catalaseandperoxiredoxins2.3commonantioxidants1)NaturalAntioxidants

?

酚類：vitaminE、

Tocopherol生育酚、Sesamol芝麻酚

?Carotenoids（類胡蘿卜素）

?

氨基酸和肽類：glutathione

?酶類：superoxidedismutase(SOD)、catalase、

peroxidases

?

其它：vitaminC生育酚（Tocopherols）

R1R2R3CH3CH3CH3CH3HCH3γHCH3CH3HHCH3抗氧化活性:δ>>>特點(diǎn)：耐熱、耐光和安全性高，可用在油炸油中。茶多酚(TeaPolyphenols)EGCG(表沒食子兒茶素沒食子酸酯）,EGC,ECG,EC。L-抗壞血酸(L-AscorbicAcid)

水溶性抗氧化劑

?

清除氧

?

有螯合劑的作用

?

還原某些氧化產(chǎn)物

?

保護(hù)巰基-SH不被氧化2)

SyntheticAntioxidants3-叔丁基茴香醚(3-BHA)2-叔丁基茴香醚(2-BHA)2,6-二叔丁基.對甲基苯(BHT)沒食子酸丙酯

(PG)2,6-二叔丁基.對苯二酚(TBHQ)2,4,5-三羥基苯丁酮(THBP)BHA

脂溶性、耐熱、遇Mn+不著色、能抗微生物；有酚的氣味，BHA有一定的毒性。BHT

無BHA那種異味，價(jià)廉，抗氧化能力強(qiáng)。PG

抗氧化性能優(yōu)于BHT和BHA；但口感不好，遇金屬離子著色。D-異抗壞血酸及其鈉鹽

1.Lecithin（卵磷脂）Phospholipids(磷脂):includeglycerolphospholipidsandnon-glycerolphospholipidsLecithin→glycerolphospholipidsComplexLipidsandDerivativeLipids

StructureofLecithinStructureofPhospholipidsR1為飽和脂肪酸，

R2為不飽和脂肪酸

R3=-H為磷脂酸

(phosphatidicacid,PA)R3=-CH2CH2N+(CH3)3

為磷脂酰膽堿

(phosphatidylcholine,PC)R3=-CH2CH2NH2

為磷脂酰乙醇胺

(phosphatidylethanolamine,PE)為磷脂酰肌醇

(phosphatidylinositol,PI)OHOHOHOHHOPhospholipidR3=Lecithin’sfunction?

構(gòu)成生物膜的成分

?

參與脂肪的代謝

?

健腦、增強(qiáng)記憶力

?

乳化劑

?

抗氧化劑

2.Cholesterol（膽固醇）植物固醇：如麥角固醇、豆固醇、谷固醇動物固醇：膽固醇anorganicchemicalsubstanceclassifiedasawaxysteroidoffat.Itisanessentialstructuralcomponentofmammaliancellmembranes.Cholesterol

functionCholesterolisrequiredtobuildandmaintainmembranes;Withinthecellmembrane,cholesterolalsofunctionsinintracellulartransport,cellsignalingandnerveconduction;Withincells,cholesterolistheprecursormoleculeinseveralbiochemicalpathways.toomuchcholesterolcanclogarteriesandleadtoheartdisease.Fatsubstituteafoodproductwiththesamefunctions,stability,physical,andchemicalcharacteristicsasregularfat,withfewerkilocaloriespergramthanfat.Theyareutilizedintheproductionoflowfatandlowcaloriefoods.CategoryTypeandexampleFunctionCarbohydrate-basedCellulose(Avicel)Dextrins,modifiedstarches(Stellar)Fruit-basedfibre(WonderSlim)Grain-basedfibre(Betatrim)Hydrocolloidgums(Kelgum)Maltodextrin(Maltrin)Pectin(Grinsted)Binder,body,bulk,flavor,moistureretention,mouthfeelProtein-basedMicroparticulateproteinModifiedwheyproteinconcentrate(Dairy-Lo)Mouthfeel,water-binding,reducesyneresisFat-basedAlteredtriglycerides(Caprenin)Sucrosepolyesters(Olean)Emulsion,mouthfeelCombinationCarbohydrateandprotein(Mimix)Carbohydrateandfat(Optamax)Flavour,texture,mouthfeel,waterretentionCategoriesoffatsubstitutesbasedoncomposition脂肪替代物脂肪替代品(oilandfatsubstitute)

以脂質(zhì)和合成脂肪酸酯為基質(zhì)。蔗糖脂肪酸聚酯和山梨醇聚酯是已經(jīng)應(yīng)用的脂肪替代品。蔗糖脂肪酸聚酯為蔗糖與6～8個(gè)脂肪酸通過酯基團(tuán)轉(zhuǎn)移或酯交換而形成的蔗糖酯的混合物，不能為人體提供能量。山梨醇聚酯是山梨醇與脂肪酸形成的三、四及五酯，可提供的熱量僅為4.2kJ/g，遠(yuǎn)比甘油三酯的39.58kJ/g低。脂肪模擬品以蛋白質(zhì)和碳水化合物為基質(zhì)。

如植物膠、改性淀粉、某些纖維素等經(jīng)加工形成。Modificationoflipids?Modifyphysicalcharacteristics(meltingpoint)?Modifychemicalproperties(oxidation,rancidity)?Functionalproperties(emulsifier)?Specialcharacteristics(deepfryingoil)?Removeunwantedlipids(transisomers)?….?…IMPROVETHEIRUSEFULLNESSWhydowewanttomodifyfatsandlipidsComponentsinfatsandlipids?TAGs(triacylglycerols)?DAGs?MAGs?Phospholipids?Pigments?Sterols?FFA?Fattyalcohols?Vitamins?AntioxidantsProcessesformodificationoffatandlipids?Hydrogenation(加氫)?Fractionation（分餾）?Blending（混合）?Interesterification（酯交換）?Hydrolysisandesterification（水解和酯化）Hydrogenation?Purpose:Convertingliquidoilsintosemisolidorplasticfatsforspecificfoodapplications(meltingpoint)?Improvetheoxidativestabilitytomaintainthesensoryproperties

foranextendedperiodoftime?Thereactionimply:Hydrogen(H2),unsaturatedoil,andcatalyst

(nickel,cupper,noblemetalsdependingonreactionspecificity,extent

oftrans-isomerformationanddurationofactivityandcost)Hydrogenationcontinued…Threeprocessesoccurssimultanously:?Saturationofdoublebondswithhydrogens?Cis-transisomerization?MigrationofdoublebondsFractionation?Purpose?Separationoffatsandoilswithdifferentmeltingpoints?Margarines,Shortenings,Saladoils,Fryingoils?SeparationofDAGsandMAGs?Themajorprocessesemployedtofatsandoils:?Dryfractionation?Graduallycoolingoftheoiluntilfractionalcrystallizationofhighmelting

TAGs?Solventfractionation?Crystallizationofdesiredfatfractionsolubilizedinasuitablesolvent

(value-addedproductslikeMCT-oils,andothers)?Aqueousdetergentfractionation?5%sodiumlaurylsulfate(SDS)addedtoseparateliquidoleinfrom

solidstearinfractionBlending?Purpose:?Obtainproductswithspecifiedfattyacidcomposition,consistencyandstabilityrequirements?Margarines,Shortenings,Saladoils,Fryingoils?Consistencydefinedby:?Fattyacidcomposition,SFI,iodinevalue,meltingpoint?ProcessemployphysicalblendingofMCTandLCTforspecificnutritionalcomposition(healthissues)Interesterification?Purpose:?ModifythephysicalandfunctionalpropertiesofTAGmixtures?ExchangeofacylgroupsbetweentwoTAGs?Twotypesofinteresterification:?Chemical:RandomremovaloffattyacidsfromTAGs,shuffling,and

randomreplacementonthenewTAGs?Enzymatic:Highsubstratespecificityorstereospecifity,mildreaction