現(xiàn)代食品化學(xué)研究進(jìn)展 4脂質(zhì)-2

1、LipidMain ContentsMain ContentsFUnsaturated fatty acidsF AntioxidantsFComplex lipids and derivative lipidsFFat substituteFModification of lipids1. Unsaturated fatty acidsAn unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fat molecule i

2、s monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond. In cellular metabolism, unsaturated fat molecules contain somewhat less energy than an equivalent amount of saturated fat. The greater the degree of unsaturation in a fatty acid (i.e., the

3、 more double bonds in the fatty acid) the more vulnerable it is to lipid peroxidation.Unsaturated fatty acids從甲基端開(kāi)始的第一個(gè)碳原子稱為碳。從碳開(kāi)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：-亞麻酸，EPA，DHA n-6：亞油酸，-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Two types of triglyceridersTwo types of triglyceridersStearic acid硬脂

4、酸硬脂酸Palmitic acid軟軟脂酸脂酸C16:0C18:0C16:1 -7系列脂肪酸油酸C18:1C18:2C18:3C18:3 -3 -6 -9系列脂肪酸 -6亞油酸 -亞麻酸 -亞麻酸C20:3C20:4C22:4C22:5C22:6 -6 -6二高 -亞麻酸花生四烯酸C18:4 -3 -3C20:5 -3 -3C20:4EPADHA -6系列脂肪酸 -3系列脂肪酸Linoleic acid (-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(kāi)始。 CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOHLinolenic acid (-亞麻酸)-亞麻酸屬

5、于n-6系列，其第一個(gè)雙鍵從甲基端第6個(gè)碳原子開(kāi)始。 CH3(CH2)4CH=CHCH2CH=CHCH2CH=CH(CH2)4COOH EPA EPA （-3-3，2020：5 5） DHADHA（-3-3，2222：6 6）海洋魚(yú)油海洋魚(yú)油EPADHA為為2030DHA是大腦灰質(zhì)的重要成分是大腦灰質(zhì)的重要成分,EPA治療和預(yù)防心血管疾病。治療和預(yù)防心血管疾病。在生物體內(nèi)可由在生物體內(nèi)可由-亞麻酸轉(zhuǎn)化而來(lái)。亞麻酸轉(zhuǎn)化而來(lái)。EPA and DHAIt is obtained in the human diet by eating oily fish or fish oil e.g., cod l

6、iver, herring, mackerel, salmon, menhaden and sardine. It is also found in human breast milk.2.1 Classification Natural Antioxidants and Synthetic Antioxidants自由基清除劑自由基清除劑1 1O O2 2淬滅劑淬滅劑金屬螯合劑金屬螯合劑氧清除劑氧清除劑ROOHROOH分解劑分解劑酶抑制劑酶抑制劑酶抗氧化劑酶抗氧化劑 紫外線吸收劑紫外線吸收劑2. Antioxidants2.2 Antioxidation mechanism1）Singlet

7、 oxygen and -carotenePhysical quenching 1 O2 + 1Car 3 O2 + 3Car 3 O2 + 1Car + heat kq = 5 *1010 M-1S-1Chemical quenching 1 O2 + 1Car Car-O2 kq = 80 M-1S-1Carotene and peroxyl radicalsScavenger for alkyl radicalsROO.+ Car ROO- + Car+.Electron transferCarotene and peroxyl radicalsROO+ Car ROO-CarLow o

8、xygen concentration: ROO+ ROO-Car ROO-Car-OOR Antioxidative effect Carotene is consumed irreversibleHigh oxygen concentration: O2 + ROO-Car ROO-Car-OO Prooxidative effect Carotene is consumed irreversible2） ROOH Decomposition ROOH ROH R 2S+ROOH R 2S = O+ ROH R 2S=O+ROOH R 2SO2+ ROH3） Enzyme systemsS

9、uperoxide dismutase, catalase and peroxiredoxins2.3 common antioxidants1)Natural Antioxidants 酚類：vitamin E、 Tocopherol生育酚、Sesamol芝麻酚 Carotenoids （類胡蘿卜素） 氨基酸和肽類：glutathione 酶類：superoxide dismutase (SOD) 、catalase、 peroxidases 其它：vitamin C生育酚（生育酚（Tocopherols）OR1HOR2R3CH3CH3CH3CH3CH3 R1R2R3CH3CH3CH3CH3

10、HCH3HCH3CH3HHCH3抗氧化活性抗氧化活性: : 特點(diǎn)：特點(diǎn)：耐熱、耐光和安耐熱、耐光和安全性高，可用在全性高，可用在油炸油中。油炸油中。茶多酚茶多酚 (Tea Polyphenols)EGCGEGCG( (表沒(méi)食子兒茶素沒(méi)食子酸酯）表沒(méi)食子兒茶素沒(méi)食子酸酯）, EGC,ECG, EC, EGC,ECG, EC。 L-抗壞血酸抗壞血酸(L-Ascorbic Acid) 水溶性抗氧化劑水溶性抗氧化劑 清除氧清除氧 有螯合劑的作用有螯合劑的作用 還原某些氧化產(chǎn)物還原某些氧化產(chǎn)物 保護(hù)巰基保護(hù)巰基-SH-SH不被氧化不被氧化2) Synthetic AntioxidantsOHC(CH3)

11、3OCH3OHC(CH3)3OCH3OHC(CH3)3CH3(CH3)3C3-叔丁基茴香醚叔丁基茴香醚(3-BHA) 2-叔丁基茴香醚叔丁基茴香醚(2-BHA) 2,6-二叔丁基二叔丁基.對(duì)甲基苯對(duì)甲基苯(BHT)OHCOOC3H7OHC(CH3)3OHCOC3H7OHOHOHOHHO沒(méi)食子酸丙酯沒(méi)食子酸丙酯 (PG) 2,6-二叔丁基二叔丁基.對(duì)苯二酚對(duì)苯二酚(TBHQ) 2,4,5-三羥基苯丁酮三羥基苯丁酮(THBP) BHABHA 脂溶性、耐熱、遇脂溶性、耐熱、遇M Mn+n+不著色、能抗微生物；有不著色、能抗微生物；有酚的氣味，酚的氣味，BHABHA有一定的毒性。有一定的毒性。BHT

12、BHT 無(wú)無(wú)BHABHA那種異味，價(jià)廉，抗氧化能力強(qiáng)。那種異味，價(jià)廉，抗氧化能力強(qiáng)。PGPG 抗氧化性能優(yōu)于抗氧化性能優(yōu)于BHTBHT和和BHABHA；但口感不好，遇金；但口感不好，遇金屬離子著色。屬離子著色。D-D-異抗壞血酸及其鈉鹽異抗壞血酸及其鈉鹽 1. Lecithin （卵磷脂）Phospholipids(磷脂): include glycerol phospholipids and non-glycerol phospholipidsLecithin glycerol phospholipidsComplex Lipids and Derivative Lipids Structu

13、re of Lecithin Structure of Phospholipids R2COOCHCH2OCOR1CH2OPOR3OOR1為飽和脂肪酸為飽和脂肪酸， R2為不飽和脂肪酸為不飽和脂肪酸 R3= -H為磷脂酸為磷脂酸 (phosphatidic acid,PA)R3= -CH2CH2N+(CH3)3 為磷脂酰膽堿為磷脂酰膽堿 (phosphatidyl choline, PC) R3= - CH2CH2NH2 為磷脂酰乙醇胺為磷脂酰乙醇胺 (phosphatidyl ethanolamine, PE ) 為磷脂酰肌醇為磷脂酰肌醇 (phosphatidyl inositol, PI

14、)O HO HO HO H HOPhospholipidR3= Lecithins function 構(gòu)成生物膜的成分構(gòu)成生物膜的成分 參與脂肪的代謝參與脂肪的代謝 健腦、增強(qiáng)記憶力健腦、增強(qiáng)記憶力 乳化劑乳化劑 抗氧化劑抗氧化劑 2. Cholesterol（膽固醇）（膽固醇）植物固醇：如麥角固醇、豆固醇、谷固醇動(dòng)物固醇： 膽固醇an organic chemical substance classified as a waxy steroid of fat. It is an essential structural component of mammalian cell membrane

15、s.CholesterolCholesterol functionfunctionCholesterol is required to build and maintain membranes;Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling and nerve conduction;Within cells, cholesterol is the precursor molecule in several biochemical pathways.to

16、o much cholesterol can clog arteries and lead to heart disease.Fat substitutea food product with the same functions, stability, physical, and chemical characteristics as regular fat, with fewer kilocalories per gram than fat. They are utilized in the production of low fat and low calorie foods.Categ

17、oryCategoryType and exampleType and exampleFunctionFunctionCarbohydrate-basedCellulose (Avicel)Dextrins, modified starches (Stellar)Fruit-based fibre (WonderSlim)Grain-based fibre (Betatrim)Hydrocolloid gums (Kelgum)Maltodextrin (Maltrin)Pectin (Grinsted)Binder, body, bulk, flavor, moisture retentio

18、n, mouth feelProtein-basedMicroparticulate proteinModified whey protein concentrate (Dairy-Lo)Mouth feel, water-binding, reduce syneresisFat-basedAltered triglycerides (Caprenin)Sucrose polyesters (Olean)Emulsion, mouth feelCombinationCarbohydrate and protein (Mimix)Carbohydrate and fat (Optamax)Fla

19、vour, texture, mouth feel, water retentionCategories of fat substitutes based on composition脂肪替代品脂肪替代品( (oil and fat substitute) 以脂質(zhì)以脂質(zhì)和合成脂肪酸酯為和合成脂肪酸酯為基質(zhì)?；|(zhì)。蔗糖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。蔗糖蔗糖脂肪酸聚酯為蔗糖與脂肪酸聚酯為蔗糖與6 68 8個(gè)脂肪酸通過(guò)酯基團(tuán)轉(zhuǎn)移或酯交換而形個(gè)脂肪酸通過(guò)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成的蔗糖酯的混合物，不能為

20、人體提供能量。山梨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?jī)H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?jī)H為為4.2kJ/g4.2kJ/g，遠(yuǎn)比甘油三酯的，遠(yuǎn)比甘油三酯的39.58kJ/g39.58kJ/g低低。脂肪脂肪模擬品模擬品 以蛋白質(zhì)和碳水化合物為以蛋白質(zhì)和碳水化合物為基質(zhì)。基質(zhì)。 如如植物膠、改性淀粉、某些纖維素等經(jīng)加工形成。植物膠、改性淀粉、某些纖維素等經(jīng)加工形成。Modification of lipids Modify physical characteristics (melting point) Modify chemical propertie

21、s (oxidation, rancidity) Functional properties (emulsifier) Special characteristics (deep frying oil) Remove unwanted lipids (trans isomers) . IMPROVE THEIR USEFULLNESSWhy do we want to modify fats and lipidsComponents in fats and lipids TAGs (triacylglycerols) DAGs MAGs Phospholipids Pigments Stero

22、ls FFA Fatty alcohols Vitamins AntioxidantsProcesses for modification of fat and lipids Hydrogenation(加氫) Fractionation（分餾） Blending（混合） Interesterification（酯交換） Hydrolysis and esterification（水解和酯化）Hydrogenation Purpose: Converting liquid oils into semisolid or plastic fats for specific food applica

23、tions (melting point) Improve the oxidative stability to maintain the sensory properties for an extended period of time The reaction imply: Hydrogen (H2), unsaturated oil, and catalyst (nickel, cupper, noble metals depending on reaction specificity, extent of trans-isomer formation and duration of a

24、ctivity and cost)Hydrogenation continuedThree processes occurs simultanously: Saturation of double bonds with hydrogens Cis-trans isomerization Migration of double bondsFractionation Purpose Separation of fats and oils with different melting points Margarines, Shortenings, Salad oils, Frying oils Se

25、paration of DAGs and MAGs The major processes employed to fats and oils: Dry fractionation Gradually cooling of the oil until fractional crystallization of high melting TAGs Solvent fractionation Crystallization of desired fat fraction solubilized in a suitable solvent (value-added products like MCT

26、-oils, and others) Aqueous detergent fractionation 5% sodium lauryl sulfate (SDS) added to separate liquid olein from solid stearin fractionBlending Purpose: Obtain products with specified fatty acid composition, consistency and stability requirements Margarines, Shortenings, Salad oils, Frying oils

27、 Consistency defined by: Fatty acid composition, SFI, iodine value, melting point Process employ physical blending of MCT and LCT for specificnutritional composition (health issues)Interesterification Purpose: Modify the physical and functional properties of TAG mixtures Exchange of acyl groups between two TAGs Two types of interesterification: Ch