食品化學 Food Chemistry 碳水化合物 Carbohydrate 鄭心嫻教授 (96) 1 Food Chemistry Fennema OR 2 1
一 重點 1. 以化學角度説明食物中組成與色香味之相關 2. 單醣 多醣種類及其衍生物之認識 3. 單醣性質 結構 分類方法及在食品中的應用 4. 瞭解寡醣和多醣的理化性質 生理功能以及在食品加工中的應用 5. 幾種重要多醣的結構 性質及其在食品加工和儲藏中的作用 3 二 前言 They are, widely available, and. As natural component as added ingredients in food Nontoxic They are also > 90% of the dry matter of plants. 4 2
Many different structures, size Exhibit a variety of and properties. 5 Modification Chemical and modification Improving their properties and their use 6 3
Cx(H2O)n 碳水化合物 Living organisms do not have this simple empirical formula ( ) Oligosaccharides ( ) Polysaccharides ( ) 7 例外 : Cx(H2O)n 非醣類 : (HCHO) (CH3COOH) (C H3CHOHCOOH) 8 4
Monosaccharides (simple sugars) are carbohydrate molecules that cannot be down to simpler carbohydrate molecules by. They can be joined to form larger structures (oligosaccharides and polysaccharides) 9 Lower molecular weight carbohydrates are often obtained by depolymerization ( ) of the natural polymers 10 5
Starch, lactose, sucrose Hydrolysis Digestible depolymerization D-glucose, D-fructose 11 三 分類 D-glucose is both a alcohol and an aldehyde. It is classified as an, a designation for sugars containing an aldehyde group. The ending signifies a sugar; --signifies an aldehyde group 12 6
Table Classification of Monosaccharides --------------------------------------------------------------- Kind of group Number of ----------------------------------------- Carbon atoms ---------------------------------------------------------------- 3 Tri Tri 4 Tetrose Tetrulose 5 Pentose Pentulose 6 Hexose Hexulose 7 Heptose Heptulsoe 8 Octose Octulose 9 Nonose Nonulose 13 ----------------------------------------------------------------- 依結構分 : 1. Monosaccharides pentoses : arabinose xylose ribose hexoses : fructose sorbose glucose galactose mannose 14 7
(1) 五碳醣 pentosan (a) L- 阿拉伯糖 (L- arabinose) a. 為多醣膠質 果膠質 半纖維素 (hemicellulose) 的基本組成分 存在蘋果 葡萄 柚子等 b. 稀 水解 果肉 L- (b) D- 核糖 (D- ribose) 構成維生素 B 2 (riboflavin) 及細胞中 (ribose nucleic acid, RNA) (c) D- 木糖 (D-xylose) a. 存於 之細胞半纖維素,(wood sugar) b. 甘蔗渣 稻穀酸水解 酵母菌 ( 去葡萄糖 ) D- c. 不能分解 不產生熱能 ( 肥胖 糖尿病適用 ) 15 (2) 六碳醣 (a) D- 葡萄糖 (D- glucose) a. 澱粉 纖維素 肝醣等的 單位 b. 與果糖以 狀態存在葡萄 無花果中 c. 在 代謝及 產生上, 很重要 d. 水解澱粉 D- e. 甜度為 之 65~75% f. 有食物 功能 (>170 成為焦糖 caramel) (b) D- 果糖 (D-fructose) a. 為 (levurotation) 又稱左旋糖 b. 與 糖以游離狀態存在果實中 ( 蘋果 梨 ) c. 水解菊糖 D- 16 8
(c) D,L- 半乳糖 (D,L- galactose) a. 以 狀態存在 b. 水解 棉子糖得 D- 半乳糖 c. 洋菜中有 L - 半乳糖 (d) D- 甘露糖 (D-mannose ) 聚甘露糖存在膠質植物甘露糖醇存在 菌類 17 2. Oligosaccharides lactose ( -galactose + glucose), 16%sucrose sweet maltose ( -glucose + glucose), 33%sucrose sweet sucrose ( -glucose + -fructose) ( 不具 ) (table sugar) 18 9
3. Polysaccharides (1) homopolysaccharides pentosans xylan( 聚木糖 ), arabinan, hexosans glucosans( 聚葡萄糖 ), starch cellulose, glycogen fructosan (inulin ) (2) heteropolysaccharides gum pectins 19 四 單醣結構 1. 開鏈式 (open-chain form), (Fisher-Tollens formula) a. aldoses ( ) CHO (CHOH) n CH 2 OH 甘油醛, n = 1, D-, L- form b. ketoses ( ) CH 2 OH C O (CHOH) n CH 2 OH 20 10
c. uronic acid ( ) CHO (CHOH)n COOH d. sugar alcohol ( ) CH2OH (CHOH)n CH2OH 21 e. aldonic acid ( ) COOH (CHOH) n CH 2 OH f. aldaric acid ( ) COOH (CHOH) n COOH 22 11
g. amino sugar ( ) CHO H C NH 2 (CHOH) n CH 2 OH 23 醛醣 (, D-glyceraldehyde) CHO H C OH CH 2 OH (1) chiral ; asymmetric carbon atom 原子 (2) enantiomer ; mirror image isomer 物 (3)D-form (-OH 基在其 ) ( 自然界存在多醣 ) L-form (-OH 基在其左邊 ) 24 12
Wedges 楔形 Dashes - 不對稱 25 Chiral carbon atom 原子 different groups attached to them The two different arrangements of the four groups in space (configurations ) are nonsuperimposable( 他物上 ) mirror images of each other. Chemical bones ( 鍵 ): covalent bond ( 鍵 ) ionic bond ( 離子鍵 ) coordinate bond ( 配位鍵 ) 26 13
aldehyde group Hydroxyl group Hydroxyl group Hydroxyl group Hydroxyl group Hydroxyl group 開環 27 L-glucose: D-glucose has a molecular mirror ( 鏡像 )image, termed the L form, 28 14
Chiral carbon atom 原子 Each chiral carbon atom has a mirror image, there are arrangements for these atoms. Six-carbon aldose are 2 4 or different arrangements of the carbon atoms (containing secondary hydroxyl groups). (8 L-form; 8 D-form) 29 C-5 right-hand D-sugar (Shorthand way---rosanoff method) 30 15
31 D-glucose is the only free usually present in natural foods, and then only in small amounts 32 16
C-5 left-hand L-sugar L-sugar less in nature than the D-forms Two L-sugar found in food L- ; L- As units in carbohydrate (polysaccharides) 33 34 (Fischer projection) 17
HOCH 異構化 35 2. 環狀式 (cyclic form) (Haworth formula) 醛基或酮基 醇類 (hemiacetal) (acetal) e.g. 葡萄糖 (Fig. 9) -CHO 基 -OH 基 ( 第四 C 或第五 C) glucofuranose glucopyranose ( 五元環 )( ) ( 六元環 )( ) 36 18
Carbonyl ( )groups of aldehydes (ketone) are reactive and easily undergo nucleophilic ( )attach by the oxygen atom of a hydroxyl group to produce a hemiacetal. ( ) The hydroxyl group of a hemiacetal can react further (by condensation) with a hydroxy group of an alcohol to produce an Acetal ( ) (Fig. 6) 37 Carbonyl groups C=O Ketone group Aldehyde group Nucleophile ( ) 離子或分子能提供一對電子給原子核而形成共價鍵者稱之 Electrophile ( ) 接受電子之原子核稱之 38 19
39 Hemiacetal formation can occur within the same aldose or ketose sugar molecule wherein the function reacts with one of its own properly positioned groups (Fig.7) 40 20
半縮醛 ( 乙醛和醇化合反應的生成物 ). 41 C1 碳 anomeric carbon atom 42 21
如何證明 D-glucose 開鏈式結構形式不存在 (1) 開鏈式 D-glucose 具 -CHO 基 但無 -CHO 基的 Schiff 反應 加成反應 也不易被 (2) 應以其他結構形式存在 43 (3) 環狀式使第一碳原子亦成為 碳原子 異構物 (anomer) or 異構物 (optical isomer) -form -form ( 醛醣與酮醣相同 ) 44 22
3. 構形式 (conformation form) 結構化學之進展 非 Haworth formula 之 六元環 : 形 (chair form) 形 (boat form) 五元環 : 形 (envelope) 形 (twist) 45 C-4 Bulky groups, CH2OH; OH C-1 46 23
4 C1 C-4 is raised slightly the plane C-1 is positioned slightly the plane 47 24