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1、脂 质,Lipid,Main Contents,Unsaturated fatty acids Antioxidants Complex lipids and derivative lipids Fat substitute Modification of lipids,1. Unsaturated fatty acids,An 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 is monou
2、nsaturated 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 more d
3、ouble bonds in the fatty acid) the more vulnerable it is to lipid peroxidation.,Unsaturated fatty acids,从甲基端开始的第一个碳原子称为碳。从碳开始计数，按第一个发生双键的碳原子数分类。 单不饱和：n-7，n-9 多不饱和：n-3，n-6 n-3：-亚麻酸，EPA，DHA n-6：亚油酸，-亚麻酸，花生四烯酸 在膳食中n-3和n-6脂肪酸应各有一定比例, ,Two types of triglyceriders,热门不饱和脂肪酸,Linoleic acid (-亚麻酸),-亚麻酸属于n-3系列
4、，其第一个双键从甲基端第3个碳原子开始。 CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH,Linolenic acid (-亚麻酸),-亚麻酸属于n-6系列，其第一个双键从甲基端第6个碳原子开始。 CH3(CH2)4CH=CHCH2CH=CHCH2CH=CH(CH2)4COOH,EPA （-3，20：5） DHA（-3，22：6）,海洋鱼油EPADHA为2030 DHA是大脑灰质的重要成分,EPA治疗和预防心血管疾病。 在生物体内可由-亚麻酸转化而来。,EPA and DHA,It is obtained in the human diet by eating oi
5、ly fish or fish oil e.g., cod liver, herring, mackerel, salmon, menhaden and sardine. It is also found in human breast milk.,2.1 Classification Natural Antioxidants and Synthetic Antioxidants,自由基清除剂 1O2淬灭剂 金属螯合剂 氧清除剂,ROOH分解剂 酶抑制剂 酶抗氧化剂 紫外线吸收剂,2. Antioxidants,2.2 Antioxidation mechanism,1）Singlet oxy
6、gen and -carotene,Physical quenching 1 O2 + 1Car 3 O2 + 3Car 3 O2 + 1Car + heat kq = 5 *1010 M-1S-1 Chemical quenching 1 O2 + 1Car Car-O2 kq = 80 M-1S-1,Carotene and peroxyl radicals,Scavenger for alkyl radicals,ROO.+ Car ROO- + Car+.,Electron transfer,Carotene and peroxyl radicals,ROO+ Car ROO-Car
7、Low oxygen concentration: ROO+ ROO-Car ROO-Car-OOR Antioxidative effect Carotene is consumed irreversible High oxygen concentration: O2 + ROO-Car ROO-Car-OO Prooxidative effect Carotene is consumed irreversible,2） ROOH Decomposition,ROOH ROH R 2S+ROOH R 2S = O+ ROH R 2S=O+ROOH R 2SO2+ ROH,3） Enzyme
8、systems,Superoxide dismutase, catalase and peroxiredoxins,2.3 common antioxidants 1)Natural Antioxidants 酚类：vitamin E、 Tocopherol生育酚、Sesamol芝麻酚 Carotenoids （类胡萝卜素） 氨基酸和肽类：glutathione 酶类：superoxide dismutase (SOD) 、catalase、 peroxidases 其它：vitamin C,生育酚（Tocopherols）,抗氧化活性: 特点： 耐热、耐光和安全性高，可用在油炸油中。,茶多酚
9、 (Tea Polyphenols) EGCG(表没食子儿茶素没食子酸酯）, EGC,ECG, EC。 L-抗坏血酸(L-Ascorbic Acid) 水溶性抗氧化剂 清除氧 有螯合剂的作用 还原某些氧化产物 保护巯基-SH不被氧化,2) Synthetic Antioxidants,3-叔丁基茴香醚(3-BHA) 2-叔丁基茴香醚(2-BHA) 2,6-二叔丁基.对甲基苯(BHT),没食子酸丙酯 (PG) 2,6-二叔丁基.对苯二酚(TBHQ) 2,4,5-三羟基苯丁酮(THBP),BHA 脂溶性、耐热、遇Mn+不着色、能抗微生物；有酚的气味，BHA有一定的毒性。 BHT 无BHA那种异味，
10、价廉，抗氧化能力强。 PG 抗氧化性能优于BHT和BHA；但口感不好，遇金属离子着色。 D-异抗坏血酸及其钠盐,1. Lecithin （卵磷脂） Phospholipids(磷脂): include glycerol phospholipids and non-glycerol phospholipids Lecithin glycerol phospholipids,Complex Lipids and Derivative Lipids,Structure of Lecithin,Structure of Phospholipids,R1为饱和脂肪酸， R2为不饱和脂肪酸,R3= -H为
11、磷脂酸 (phosphatidic acid,PA) R3= -CH2CH2N+(CH3)3 为磷脂酰胆碱 (phosphatidyl choline, PC) R3= - CH2CH2NH2 为磷脂酰乙醇胺 (phosphatidyl ethanolamine, PE ),为磷脂酰肌醇 (phosphatidyl inositol, PI),O,H,O,H,O,H,O,H,H,O,Phospholipid,R3=,Lecithins function 构成生物膜的成分 参与脂肪的代谢 健脑、增强记忆力 乳化剂 抗氧化剂,2. Cholesterol（胆固醇）,植物固醇：如麦角固醇、豆固醇、谷
12、固醇 动物固醇： 胆固醇,an organic chemical substance classified as a waxy steroid of fat. It is an essential structural component of mammalian cell membranes.,Cholesterol function,Cholesterol is required to build and maintain membranes; Within the cell membrane, cholesterol also functions in intracellular tra
13、nsport, cell signaling and nerve conduction; Within cells, cholesterol is the precursor molecule in several biochemical pathways. too much cholesterol can clog arteries and lead to heart disease.,Fat substitute,a food product with the same functions, stability, physical, and chemical characteristics
14、 as regular fat, with fewer kilocalories per gram than fat. They are utilized in the production of low fat and low calorie foods.,Categories of fat substitutes based on composition,脂肪替代物,脂肪替代品(oil and fat substitute) 以脂质和合成脂肪酸酯为基质。 蔗糖脂肪酸聚酯和山梨醇聚酯是已经应用的脂肪替代品。 蔗糖脂肪酸聚酯为蔗糖与68个脂肪酸通过酯基团转移或酯交换而形成的蔗糖酯的混合物，不能
15、为人体提供能量。 山梨醇聚酯是山梨醇与脂肪酸形成的三、四及五酯，可提供的热量仅为4.2kJ/g，远比甘油三酯的39.58kJ/g低。 脂肪模拟品 以蛋白质和碳水化合物为基质。 如植物胶、改性淀粉、某些纤维素等经加工形成。,Modification of lipids, Modify physical characteristics (melting point) Modify chemical properties (oxidation, rancidity) Functional properties (emulsifier) Special characteristics (deep fr
16、ying oil) Remove unwanted lipids (trans isomers) . IMPROVE THEIR USEFULLNESS,Why do we want to modify fats and lipids,Components in fats and lipids, TAGs (triacylglycerols) DAGs MAGs Phospholipids Pigments Sterols FFA Fatty alcohols Vitamins Antioxidants,Processes for modification of fat and lipids, Hydrogenat
