食品课件化学ch4lipid

1、PuJing,PuJing, FoodShanghai JiaoTong University Fall2014FOOD RolesofFoodEnergy Carrierof fat soluble Hormone and cell Nerve Thermal insulation of Mouth Main flavorsource of TextureofEmulsifying Moldreleasing and anti-spatteringAgent(i.e.2MajorMajorlipidFattyacids anic solvents, but are not soluble i

2、n water Mostly made up of C, andO SomeP,Nand Fats: SolidatRT, Mostlyfromanimal Oils: LiquidatRT,Mostlyfromplant Fatty Neutralfats Fat solublevitamins4Fatty Fatty Structuresoffattyacids Saturated & Unsaturated 5Structure of Fatty OR C Acid #1 Polar End - Hydrophilic Non-polar End = Hydrophobic (Fat-s

3、oluble 6Saturated&Saturated&Unsaturatedfatty Saturated Fatty 87OCH3 CH2 CH2 CH2 CH2 21C Unsaturated Fatty 8CHO7CH65CH2 CH432CH1C 87O3CH2 CH2 C 7 8Nomenclature命Nomenclature命名法of CommonStearic acid Systematic name (IUPAC Octadecanoic Abbreviation (simple numerical Positionofdoublebonds( , andnIUPAC: I

4、nternationalUnion of PureandAppliedSaturated& Unsaturatedfatty Saturated Fatty 3OCH3 CH2 CH2 CH2 CH2 Octanoic 21C Unsaturated Fatty CH7CH 6543CH2 CH2CH 1C 3- Octenoic 8:1 873CH2 CH2 3,6 - Octadienoic 2CH2 C 82O1PositionPositionofdouble Cis/trans-x Thedoublebondislocatedonthexthcarbon-carbon bond, co

5、unting from the carboxyl terminusH C 10 18:1 O(CH2)7 C -x Adoublebond is located on the xth carbon-carboncountingfrom the methyl carbon end of the 18 1-GeometricConfigurationofDouble HCH3(CH2)7 H OCCis-9 - Octadecenoic CH3(CH2)7 C HTrans-9 -Octadecenoic18:1cis- (CH2)7 C OHelaidic 18:1trans-Cisconfig

6、urationisthenaturalconfigurationofdoublebonds in unsaturated fatty acids.If more than onedouble bond: cis,cis-9,12or cis-Polyunsaturated fattyPolyunsaturated fatty Polyunsaturatedfatty 2ormorecisdouble Allcis-9,12, 15octadecatrienoic=18:3,9=Polyunsaturated fatty Conjugated fatty 9(Z),11(E),13(E)-Oct

7、adecatrienoic Acid =18:3, cis, trans, trans-General information General information of Conjugated linoleic acids 共轭亚油酸(CLA)CLA: natural food Health benefits of anticarcinogenesis, cholesterol lowing, antioxidant, signal transduction, immunomodulating effectsMechanism of CLAs beneficial effects is no

8、t Neutral Cholesterol & cholesterol Triacylglycerol Triacylglycerol HC HC HC +OHO C R HO C R HO C OHC O C OHC O C + 3 OHC O C 3 Fatty H2C OH HC OHOHC O C (CH2)16OHC O C (CH2)16CH3 HC OH OHC O C (CH2)16Monoacylglycerol (Monoglyceride) Diacylglycerol OHC O C (CH)CH(OHC O C (CH)CHHC O C (CH)Triacylglyc

9、erol Most common in sn-1,3-disteariol-2-palmito-sn: stereospecific Monoacylglycerol Monoacylglycerol Triacylglycerol 33six-carbon rings +1five-carbon ring + 1aliphatic Cholesterol isthemajorsterolfound inanimalto increase risk for cardiovascular diseases.Plant sterols (phytoserols) decrease the abso

10、rption of cholesterol from diet. H3C 2033Fatty 17 H3C polar head & 2 hydrocarbon Lecithin (3-sn-Phospholipids磷polar head & 2 hydrocarbon Lecithin(3-sn-phosph OO C OR C O H2C ON CH3 +CH2 Phosphatidic 胆Saturated Fatty Saturated Fatty MP:meltingFattyFatty a + Long chain Natural poec layerinfruits veget

11、ables Added in some cases for appearance and oecTerpenesFats Fats World Vegetable oil AnimalMarine FattyAcids(%)ofFatsFattyCoconut 436382636347163272228Melting Melting Longerchain fattyacidspackbetterthanshortMPlong Saturatedfattyacids packbetterthanunsaturated MPsat. Trans fatty acids pack better t

12、han MPtrans. Hydrogenation increasing the MP:melting Systematic Trivial 4 88 -7 6 116-3 8 144 16 9 172 31 200 44 228 53 256 63 margaric 270 61 284 69 312 75 340 79 368 84 )Polyunsaturated fatty acids )Polyunsaturated fatty acids Systematic g- 22 5(n-18 3(n- -4,7,10,13,16-docos ntaenoic -Monounsatura

13、ted fatty Systematic TrivialShorthand Molecular MP(14 1(n-14 1(n-14 1(n-16 1(n-18 1(n-181(n- 18 1(n-18 4(n-20 4(n-20 1(n- 20 5(n-gon 20 1(n-7,10,13,16,19-docos 22 5(n-22 1(n-4,7,10,13,16,19-22 6(n-22 1(n-Polymorphic Polymorphic Polymorphicforms多晶形arecrystallinephasesofthesame chemical composition th

14、at differ among themselves in structure but yield identical liquid phases upon melting.Fatty acids, temperature, rate of cooling, presence of crystalline nuclei, and type of solvent Polymorphic transformation 多晶型转变 :Transformation of the fat crystals into other polymorphic forms.with higher melting

15、points(more stable)Chocolatebloom (fat Chocolate bloom (fat bloom): caused Polymorphic transformation low melting point, less stable to high melting point, more stable Melted chocolate fat （cocoa butter可可脂）migrates to the surface and recrystallizes重结晶 upon coolingTempering processing回火过程: cocoa butt

16、er-sugar-cocoa powder mixture 50C, seeding with the stable crystal “seedsslowlycrystallizingitas2629Candthenslowly Otherwise, unstable crystal forms will form initially and these are likely to melt, migrate,and transform to more stable formsMilk Milk An emulsion is a mixture of two or more immiscibl

17、e -a substance which stabilizesemulsion,frequentlyaMilk fat FatFatMilk isan oil-in-wateremulsion, with the fat globules dispersed in werelefttostand,however,the Homogenization均质Three factorscontribute to thisenhanced stability of homogenized a decrease in the mean diameterof the fat adecrease in the

18、 size distributionof the fatan increase in density of theglobules (bringing them closer to 40 continuousphase) owingto theadsorption of aHomogenizationHomogenizationonfat15 Homogenization of milk prevents this creaming by decreasing 41 diameter and size distribution of the fat Chemical TypesTypesofE

19、xtremepH Saponification皂化(baseAcid Commercialfryingoilsarefilteredonaregularbasiswithabsorbentwhichcan bind and remove free fatty acidsEnzymatic hydrolysis Change Desirable Yogurtand Contribute flavors to cheese, milk,Undesirable hydrolytic rancidityCause off-flavorsin frying foods,milks,fruitsand R

20、educe oxidative stability, cause foaming, reduce smoke point Smokepoint thetemperatureatwhichanoilbeginstoLipolysis脂Lipolysis脂Hydrolysis of ester bonds in lipids results in liberation of free fatty acids-by lipase脂肪酶Release of short-chain fatty Undesirable hydrolytic Desirable Yogurtand the control

21、mechanism is destroyed during the processing and storage when raw living material isused for foods theyeTriglyceride Fatty CH2 OC (CH2)2 CH2 CLipolysis Lipolysis + SEP + E Interesterification酯交Definition Rearrange fatty acids so erandomlyamongtriacylglycerolmoleculesofFatty acids distribution patter

22、ns of natural fats limit their industrialapplicationInteresterification gives a triacylglycerol profile different from the original lipidIncreasing consistency of lipids fat + new Manufacture of shortenings起酥Lard(want10%tri-saturatedglycerides)-directed AdditionAddition of hydrogen across double Imp

23、ortant in fats ls Liquid fatssemi-solid fats or convert soft fats into firmer fatImproves oxidative Ni,CisSaturated TransTrans Trans fattyReferto triglycerides containing unsaturated fatty acidstransFound in partially hydrogenated fats or FDA adopted new food LabelgiveweightoftransThe regulationallo

24、ws trans fatlevels ofless than 0.5 实施的预包装食品营通则 transfatsTransfatlevelsof03g/100gwillbelabeledasClinic Trans fatty acids andtransfat and heart Epidemiological studies suggest a stronger positive association between TFAs and risk of ischemic heart disease (IHD) than that between saturated fat and IHD

25、4 studies involving 145,000for6-14years (Ann Nutr Matab, 2004, 48:61)TFAs and Positive association was found between level of TFAs in adipose tissue and the incidence of breast and colon cancers,but not of the prostate cancer (Mansour et al , 2001, Eu J Clin Nutri, 55:59)TFAs and The Nursess Health

26、Study,involving 84,204 women for 14 years,showed the positive association between increased TFAs intake and risk of type-2 TransfatTransfatinfatty acids ranging 0-32% of total fatty acidscrackers (1-13 g trans Fr 100 g cracker); Hard margarineandsoftmargarinecontained40-17%transFat in Total FLabel：

27、shortening（起酥油）， margarine（人造黄油）, hydrogenated lipid （氢化油）Bubble LipidEffects of Lipid FlavorQuality Rancid flavoroxidative Changes ofcolor and Consumer EconomicNutritional Quality Essential Fatty Health Growth Heart Activation Activation Energy 活化能for Chemical Activation ProteinNonenzymaticBrowning

28、Reaction Enzyme Catalyzed Reaction10-Lipid 15MechanismsoflipidFree radical species can vary greatly in theirHydroxyl radical (OH)high energy, can oxidize any other form radical with low energy, so theyare much capableof attacking molecules (e g FreeFreeradicalR+R+ROO+ROOH + R+R + ROO Initiation of a

29、utooxidation occurs when hydrogen atomat-methylene亚甲基groupindoublebondsof unsaturated fatty acids is removed to form radical(R)R +Initiation Initiation Oxygen raised to excited state （1O2）by Promoted bypigments Inactivebyblanching(shortenergyOxygen raised to excited state by enzymes Oxygenraisedtoex

30、citedstatebymetalions(e g Fe,Naturallyinfood, orfrommetalUsingchelatingagents(egEDTA)toAntioxidant Antioxidant Mechanismof Oxidationand 12 11 CH3 (CH2)3 CH2 CH CH CH2 CH2 CH2 CH2 Initiation Reactiveoxygen species (eg 1O) - 12 10 CH3 (CH2)4 C H C H CCHCCH2 Oxygen + OConjugated diene 共轭双键, and Electro

31、n spin resonance 电子13 12 11 (CH2)4 CH CH CH CH2 CH2 CH2 R O+ HFrom+ H 3stabilizationantioxidant RROROORHROHO. O.Preventive Preventive Superoxide dismutaseCatalase 过氧化氢Glutathione peroxidase 谷胱甘肽Singlet oxygen quencher 单线态氧促灭Transition metal chelators (EDTA) 过渡金属螯合Radical 基清除Preventive antioxidants m

32、inimize the formation of initiating Antioxidant SuperoxideAnion (O) + Catalase过氧化氢H2O+Glutathione Peroxidase asH H O O C N C C N HC Glutathione谷胱甘肽L-glutamicacidL-cysteine酸andGSH (Glutathion) + H2O2 Glutathion Oxidase GSSH + Singlet Singlet Oxygen Quenching 淬灭of1O2 +3O2 + Prooxidant activity 促氧化作用 o

33、f transition 过渡金RH+Fe R.+H+ +FeMetalMetalIons EDTA ComplexEthylene Diamine Tetraacetic carboxylateand two amine groups氨基据了解，乙二胺四乙酸二钠是强效螯合剂,有很高稳定常数，能与碱金属以外的绝大多数金属离子生成稳定的络合物，消除金属离子或由其引起的有害作用，抑制水煮食品的水混浊,防止食品氧化变色，从而起到抗氧化、护色、防腐的作用,使产品质量稳定，是极为广泛使用的护色剂、品质改良剂和抗氧化剂，防腐保鲜剂。广泛应用于水果、蔬菜制品、奶制品、饮料、肉制品、果脯、酱料的保鲜、护色，也

34、应用于油脂、香精的抗氧化。但其对眼睛、皮肤、粘膜和上呼吸道有刺激作用。公告称，本次监共抽取样品128组，合格120组，不合格8Synthetic Synthetic Butylatedhydroxyanisole Butylatedhydroxytoluene O OC (C H)OOO COOCHPropyl Tertiary butylhydroquionone Natural Vitamin -QuercetinAnthocyaninRadical scavenging antioxidants break free radical chain reaction by donating

35、hydrogen to free radicalsFood Food Antioxidants as Freeradical Reactive oxygen Metal Regenerators for other antioxidant Factorsinfluencingtherateoflipid Fatty acid composition, number, position and geometry of double bonds affect the rateSaturated triglycerides are stableat room Unsaturated fatty ac

36、ids are promotion of lipid oxidation Relative rates of oxidationArachidonic linolenic linoleic oleic=402010Fish oil (polyunsaturated fatty acids) isvery Free fattyacids react fasterthanConjugated double bonds are less reactive than non-conjugated FactorsFactorsinfluencingtherateofoxidation Oxygen co

37、ncentration Proportional to lipid oxidatio low oxygen pressureOxygenLow film 性TherateofoxidationincreaseastemperatureisWaterMostunderverylowAw(02) Randicityisamajorproblemin dehydratefoodsMetal Usemetalchelators VisibleandUVlightaresourceofenergytoinitiateAntioxidants （BHT, etc NaturalQualitativeAci

38、d Acid Number of mgs of KOH required to neutralize the Free Fatty Acids in 1 g of fat.RCOOH + ROO-K + AVml of KOH x M x Weight of = mg of Acid Thefreefattyacidcontentinagoodsoybeanoilshouldbelessthan orequalto0 05 % Theaveragemolecular weightoffreefattyacids of the oil is 280 which is the molecular

39、weight of linoleic acidWhatisumacid valueof thegood soybean acidvalueis03? Theaveragemolecularweightoffreefattyacids of the oil is 280AcidAcid005%in1gramis05mgfattyacidin1gramofoil 56 mg of KOH reacts with 280 mg of RCOOH 280mgofRCOOH/56 mgofKOH =5 1The0 1mgKOHreactswith0 5mgAcidValueis0 What isthe

40、content (%) of free fatty acids of soybean oil if the acid value is 0 3?Acid value 0 3 means that 0 3 mg KOH is required to react with the free fatty acid in1g (1000mg) of oilThe56mgKOHreactswith280mgfreefattyacid, 56 =1 1mg KOH reactswith5 mg free fattyThe 03mgKOHreactswith15mgoffreefattyacidin1 gramoil15mgfreefattyacid/1000mgoilx100(%)=015Saponification Saponification Saponification - Hydrolysisof ester (triglyceride) under alkaline condition.Definition : mgs of KOH required to saponify 1 g of OHC O C HC O C OHC O C HC O+ 3 HC OH + 3 R C O-HC Saponification C