Ⅰ. Introduction 廚中百味油為貴 Ⅱ. Chemical Structure of Lipids 1 2 triacylglycerol ( 三酸甘油酯 ) H 2 C C R1 (FA 1 ) R 2 C CH (FA 2 ) H 2 C C R 3 (FA 3 ) glycerol 甘油 FA=Fatty Acid, 脂肪酸 3 1. Fatty acids 脂肪酸 4 脂肪酸分類架構 脂肪酸 飽和脂肪酸 短碳鏈飽和脂肪酸 牛 ( 體 ) 油 羊油 豬油 奶油 (butter) 等動物油脂, 椰子油 棕櫚油 容易被人體消化吸收 飽和脂肪酸 不飽和脂肪酸 中碳鏈飽和脂肪酸 能誘發較強的食物產能效應, 使能量消耗增加, 有防止脂肪積累的效果 長碳鏈飽和脂肪酸 容易聚集在一起形成油滴, 與血小板作用形成栓塞 短碳鏈飽和脂肪酸 中碳鏈飽和脂肪酸 長碳鏈飽和脂肪酸 單元不飽和脂肪酸 多元不飽和脂肪酸 單元不飽和脂肪酸 ω- 3 系列 油酸 ( 山茶油 橄欖油 棕櫚油 杏仁油 花生油 豬油 ) 胡麻油 ( 亞麻籽油 ) 火麻油 紫蘇油 魚油 海豹油 ω- 3 系列 ω- 6 系列 ω- 6 系列 月見草油 紅花油 葵花籽油 玉米胚芽油 花生油 豬油 牛油 奶油 5 6 1
1-a. Saturation Association of fatty acids in organic solvents alkanoic acids 飽和脂肪酸 CH 3 (CH 2 ) n C H 7 Intermolecular hydrogen bonding (binding energy 38 kj/mole) 8 in aqueous solution C Chain length & melting point (M. P.) C Common Name Systematic Name Carboxylic acid Formula M. P.( ) 2 Acetic acid n-ethanoic CH 3 CH +16.6 短碳鏈脂肪酸 4 Butyric n-butanoic propanecarboxylic CH 3 (CH 2 ) 2 CH -8.0 6 Caproic n-hexanoic pantanecarboxylic CH 3 (CH 2 ) 4 CH -1.5 H R C R C 中碳鏈脂肪酸 8 Caprylic n-ctanoic CH 3 (CH 2 ) 6 CH +16.0 C 2 ~ C 9 pk = 4.75-4.95 9 10 Capric n-decanoic CH 3 (CH 2 ) 8 CH 31.3 12 Lauric n-dodecanoic CH 3 (CH 2 ) 10 CH 43.5 10 C Common Name Systematic Name Formula M. P. ( ) 長碳鏈脂肪酸 14 Myristic n-tetradecanoic CH 3 (CH 2 ) 12 CH 54.4 16 Palmitic n-hexadecanoic CH 3 (CH 2 ) 14 CH 62.9 18 Stearic n-ctadecanoic CH 3 (CH 2 ) 16 CH 69.6 20 Arachidic n-eicosanoic CH 3 (CH 2 ) 18 CH 75.4 22 Behenic n-docosanoic CH 3 (CH 2 ) 20 CH 80.0 24 Lignoceric n-tetracosanoic CH 3 (CH 2 ) 22 CH 84.2 26 Cerotic n-hexacosanoic CH 3 (CH 2 ) 24 CH 87.7 28 Montanic n-ctacosanoic CH 3 (CH 2 ) 26 CH 90.9 30 Melissic n-triacontanoic CH 3 (CH 2 ) 28 CH 93.6 1-b. Unsaturated fatty acids - alkenoic acids 依脂肪酸分子的雙鍵數分 (1) Monoenoic acids (MUFA, 單元不飽和脂肪酸 ) (2) Polyenoic acids/long-chain polyenoic acids: dienoic acids, trienoic acids (PUFA, 多元不飽和脂肪酸 ) 32 Lacceroic n-dotriacontanoic CH 3 (CH 2 ) 30 CH 96.2 11 12 2
依脂肪酸分子的空間結構分 Geometric isomers ( 幾何異構物 ) substitution with 2 alkyl groups on the double bond (1) cis 順式 : naturally occurring cis double bond: oleic acid (2) trans 反式 :thermodynamically stable trans double bond: elaidic acid 13 14 substitution with 3 alkyl groups:r/s system (1) Z 最大的二原子團在 的同一邊 ( 類似 cis) (2) E 最大的二原子團在 的兩側 ( 類似 trans) H C=C H 65 Kcal / mole 脫臭氫化 H C=C H bacteria / biohydrogenation 15 16 trans fat 造成的生理影響 (a). LDL 增加 (b). HDL 下降 (c). 血栓機率增加 (d). 第二型糖尿病風險增加 trans free 1 ounce = 28.3 g < 0.5 g/serving 17 18 3
台灣各類市售食用油反式脂肪及飽和脂肪含量 ( 以每 100 克計 ) 類別 沙拉油調和油橄欖油麻油酥油芥花油奶油豬油葵花油 樣品數 6 13 7 11 7 3 5 3 1 反式脂肪平均含量 ( 範圍 )( 克 ) 1.87 (1.65~2.07) 1.88 (0.68~2.94) 未檢出 * 0.97 (0.15~2.67) 1.72 (0.28~4.09) 2.49 (0.87~3.82) 0.48 (0.00~1.57) 2.53 (0.21~4.10) 1.40 飽和脂肪平均含量 ( 範圍 )( 克 ) 15.4 (14.5~15.9) 14.4 ( 7.4~32.3) 15.4 (14.5~17.0) 15.2( 13.6~16.5) 35.7( 15.0~52.9) 8.3( 6.7~11.7) 29.4( 14.8~49.3) 43.7( 40.7~46.5) 10.3 trans fat 替代方案 (1) 加工方法 (a) blending 混合 (b) fractionation 劃分 (c) interesterification 交酯化 (d) partial hydrogenation 部分氫化 * 偵測極限 :0.01% 19 20 (2) 產品指標 (a) xidative stability 氧化安定性 (b) Hardness 硬度 (c) Mouth feel 口感 同時 CLA 亦增多 21 22 1-c. Conjugated linoleic acid (CLA) 1932 年在牛奶中發現 含量因季節而異 - 冬天少 ; 夏季青草 [CLA] 較多因為季節 : dietary 調控 CLA 具生理功效 1. 抑制癌細胞增生 2. 心血管疾病 3. 調控免疫系統 4. 抑制體脂在 adipocyte 中堆積 改變脂質代謝 23 24 4
1-d. 必需脂肪酸 (essential fatty acids): 人無法自行合成, 必需自食物攝取 ω C 18:2 ω-6, 即 n-6 C 18:3 ω-3, 即 n-3 25 26 n-6 pathway n-3 pathway elongase elongase elongase elongase elongase elongase 27 28 紅血球必需脂肪酸之比例 Content of essential fatty acids in human erythrocyte Fatty acids ( 脂肪酸 ) Control ( 雜食者 ) Vegan ( 全素 ) ω-3 1 0.56 ω-6 0.85 1 ω-3/ω-6 1 0.5 * Platelet has the same trends of fatty acids profile. (Agren et al., 1995) 29 緊迫 病變與脂肪酸組成的改變 Changes of fatty acids in diseases or under stress C18:1 (ω-9) ω- 3 fatty acids ω- 6 fatty acids ω- 3 / ω- 6 ( 本實驗室 ) 30 5
2. 脂肪 2-1. Neutral Lipids 中性脂質 2-1. 中性脂質 三酸甘油酯 2-2. 極性脂質 磷脂質 醣脂質 含硫醣脂質 glycerol + fatty acids triacylglycerol ( 三酸甘油酯 ) CH2H CH2CR1 _ CHH + 3 R CH R2CC _ CH2H 3H2 CH2CR3 31 32 Triacylglcerols (triglycerides) (1) Stereospecific numbering SN system 例 :sn - glycerol - 1 stearate - 2 oleate - 3 myristate mixture glycerol Fischer planar projection 33 34 (2) R/S system H 2 C-C-R 1 排序 :C 多 > C 少 ; 多 > 少 HC-C-R 2 H 2 C-C-R 3 對嗎? R 順時針 S 逆時針 35 36 6
Ⅱ. Lipid classification based on fatty acids components 種類 F.A. 特性 MP 來源 1. Animal fat 含 tri-sat 豬油 C 16:0, C 18:0 高 18:0 16:0 C 18:1, C 18:2 其次 18:2 2. Milk fat C 4-12 有, 但少高反芻動物的乳脂中 C 16:0 18:0 為主 18:1 C 奇數 支鏈 有, 但極少 trans double bonds 高 C 16 C 14 C 短鏈 ( 一般 ) (milk) C 4 37 種類 F.A. 特性 MP 來源 3. Marine oil PUFA 最低 4. Lauric acid ~ 6 氧化後 C 12 40~50% 棕櫚 C 6-10 低椰子 C unsat 少量 C 14:0 C 12:0 80% C 8:0 38 種類 F.A. 特性 MP 來源 5. Vegetable Sat/unsat 高 高 cocoa butter butter tri-sat sharp melting 熱帶植物的種子中 C 18:1 75% Sat Sat 6. leic-linoleic C 18:1 為主 Sn 2 C 18:2 飽和 < 20% 7. Linolenic C18:3 高 飽和 <20% 低 低 棉子油, 玉米油花生油, 麻油, 橄欖油, 葵花油 大豆油 39 2-2. Polar Lipids 極性脂質 : Phospholipids ( 磷脂質 ) Hydrophilic head Hydrophobic tail P - CH 2 CH CH 2 C C FA 1 FA 2 FA=Fatty Acid, 脂肪酸 40 2-2. Classification of Lipids by Biological Functions H 2 C-C-R 1 (storage lipid) (building blocks of biological membrane) HC-C-R 2 - H 2 C-C-P- - - 對嗎? 41 42 7
Sugar Lipid Glycolipid ( 醣脂質 ) H H CH 2 CH CH 2 H H C C H Sulfoglycolipid structure( 含硫醣脂質 ) R 2 -CH CH 2 -CR 1 CH 2 - H CH 2 H H - S 3 X + FA 1 FA 2 FA=Fatty Acid 脂肪酸 43 Glycolipid Sulfoglycolipid 44 sphingolipids sialic acid lactose amide sphingosine fatty acid ceramide 3. Physical Properties of Lipids 1. soluble in organic solvent 2. slightly soluble in water 3. melting point >Rm temp, Fat < Rm temp, il 45 46 4. Biological Properties of Lipids 1. adipose tissue (neutral lipids) 2. supply calorie 3. supply essential fatty acids 4. structural elements of membrane. (phospholipids) 5. anti-tumor agents - in alga1 47 6. antifouling agents - in bivalves, crustacean, octocoral ( 二枚貝 ) ( 甲殼類 ) ( 軟珊瑚 ) 例 : antifouling agent in octocoral 1. sterols ( 固醇類 ) cholesterol sitosterol cholestanol 2. fatty acids 在 C 4~22 中, C 18:3 ; n-9 C 20:5 最有效 ( 日水誌 59(7). 1195~9, 1993) 48 8
cholesterol 芥花油紅花油亞麻籽油 cholestanol sitosterol 49 50 Ⅲ. Physical properties Chemical Structure Composition Application Functionality Physical Properties Molecular Packing 51 A. Thermal properties of lipids 1. melting point - 由 acyl residues in the crystal lattice 而定 a. range - varies with fat composition b. factors- chain length cis-trans forms polymorphism substitutions c. measurements- softening pt cloud pt drop pt melting pt flow pt - lowest T. a fat flows 52 2. titer point - T of solidification, 脂肪酸凝固點 saponification acidification fat + NaH soap f.f.a. cool solidification solidified f.f.a. 3. Cold stability - related to melting/solidification cold test time to develop cloudineess in ice bath salad oil - 5.5 hr mayonnaise ( 美奶滋 ) - hr 53 54 9
Solid fat content 4. thermal stability smoke pt ( 發煙點 ) flash pt ( 閃光點 ) fire pt ( 著火點 ) 5. specific heat relates to the molecular motion increase with sp. heat of liquid = 2 of solid α form > β form polymorphic forms ( 同質多晶型 / 性 ) 55 56 6. heat of combustion Amount of heat liberated/mole : inc. with C 7. Density = 1 specific volume C Heat (cal/g ) 4 5,900 12 8,900 18 9,600 57 Fig. 4.9 Comparison of the melting profile of a pure triacylglycerol and typical edible fat. The edible fat melts over a much wider range of temperatures because it consists of a mixture of many different pure triacylglycerol molecules each with different melting points. 58 B. Consistency crystalline structure H:enthalpy ( 焓 ) D:dilation ( 體積膨脹 ) Dilatometry: 溫度對比體積或密度之影響的測定儀 59 60 10
a. Unit cell b. Space lattice 之安定力 c. Subcell - the smallest spatial unit of repetition along the chain axes 氫鍵 視 angle 疏水性交互作用 61 62 d. Packing types of subcells - 共七種 最主要的三種 : Triclinic (T//) 2 methylene one ethylene in each subcell β Most stable 三斜晶型 Common rthorhombic ( ) Hexagonal (H) chain are randomly 2 ethylene in each subcell oriented, rotation about long axis β α Intermediate stability Least stable 斜方晶型六方晶型 63 2. polymorphism ( 同質多晶性 ): different forms of solid phases of the same chemical composition&liquid phase a. differences between polymorphic forms x ray spacing, sp. vol crystalline forms different long spacing different angle of tilt melting pt 64 b. factors determining the polymorphic forms 1. purity 2. temp 3. rate of cooling 4. presence of crystalline nuclei 5. type of solvent c. characteristics of polymorphic forms of TG 65 66 11
Tab. 4. polymorphic forms & characteristics of monoacid triacylglycerols Characteristics α Form β Form βform Chain packing Hexagonal rthorhombic Triclinic Short Spacing 4.2A 3.8 & 4.2A 4.6A IR spectrum Single band at 720 cm -1 Doublet at 727 & 719cm -1 Density Least Intermediate Most Single band at 717cm -1 Melting pt. Lowest Medium Highest Stability Lowest Highest ccurrence HC below M.P. n-paraffins n-hc Alc Fatty acids Fatty acids Ethyl esters F.a.esters TG 67 monoacid TG: long spacing = 2 chain lengths Molecular arrangement of triacylglycerol crystals 68 mixed TG :long spacing = 3 chain lengths (a) sn2, 碳數較 sn1, 3 長或短, 相差 4C symmetrical TG (b) unsymmetrical TG (c) unsaturated d. transition of polymorphic forms ( 最安定 ) 1 2 3 1 2 β 3 tuning fork β chair 69 mono acid TG trans from quickly β β heterogeneous fats transform more slowly from β to β 70 Melting solid fat index H:enthalpy ( 焓 ) D:dilation ( 體積膨脹 ) Dilatometry: 溫度對比體積或密度之影響的測定儀 71 melting range = x~y at T = t: solid fraction = ab/ac liquid fraction = bc/ac solid fat index (SFI) = solid:liquid Heat content on dilatometric melting curve of a glyceride mixture 72 12
Ⅴ. Chemical Properties A. Lipolysis hydrolytic rancidity B. Autoxidation lipolytic rancidity C. Lipoxygenase (Lipoxidase) catalyze oxygenation (P.337) D. Reversion. E. Polymerization. 73 A. Lipolysis 1. non-enzymatic 2. enzymatica. lipase b. phospholipase A1, A2, B, C, D 74 例.1. milk fat fatty acids, C 4 -C 12 例.2. cottonseed oil. microbial lipase milk lipase selective lipolysis off odor cheese flavor yoghurt flavor FFA. Smoke pt. ( 發煙點 ) (%) ( ) ( ).01 450 232 1.0 320 160 10.0 260 127 100.0 200 93 76 B. Enzymatic hydrolysis of lipid 1. Lipase - triacylglycerol hydrolases 例 :pancreas( 胰 ), 或乳中脂解酶豆類 (beans) 脂解酶水解 1, 2, 3 位置 2. Phospholypases (phospholipid hydrolases) phospholipases A 1, A 2, B, C, D 77 78 13
3. Glycolipid hydrolase mono- 水解 galactosyl - diglycerides 脂肪酸 + 其他 di- 存在於綠色植物中 C. Autoxidation 1. mechanism - free radical R x a. initiation RH K 1 R +H b. propagation R + 2 R +R H K 2 K 3 R RH+R 79 80 c. termination free radicals nonradical products R +R K4 RR R +R K6 RR+ 2 R +R RR R +R K5 RR 2R +2R 2RR+ 2 81 D. General characteristics 1. 抑制 free radical R x 之物質抑制自氧化作用 2. 形成自由基物質 (R ) 催化自氧化作用 3. 形成 RH 4. 光催化 5. 有光及光敏劑 (photosensitizer) 時 ( 如葉綠素及血紅素 ) 2 被活化成 singlet 2 ( 1 2 ), 加速催化形成 R, 縮短誘導期 6. 潛伏期 / 誘導期長, 隨著作用時間延長而加速 82 E. Generalized scheme for autoxidation of lipids 1. Formation of free radicals 2. Formation of hydroperoxides 4. Decomposition/ condensation of aldehydes 6. Formation of dimeric & polymeric cpds. a. 3. Decomposition of hydroperoxides alkoxy radical 5. R x of alkyl & alkoxy radical b. Dimerization between 2 acyl groups in the same triglyceride c. Combination of free radicals to give non-cyclic dimers d. Addition of free radical to a double bond trialkyltrioxanes 83 84 14
F. xidation of unsaturated fatty acids leic acid H Linoleic acid H active methylene 85 86 Linolenic acid H 87 88 G. xidation of saturated lipid- 雖安定 但在空氣中 150 以上之溫度仍可氧化 1. α-position 89 90 15
LX Substrates 2. enzymic pathways of lipid oxidation a. lipolysis to release polyunsaturated fatty acid b. oxidized by lipoxygenase ( 脂氧合酶 ) or cyclooxygenase ( 環氧合酶 ) to form hydroperoxides ( 氫過氧化物 ) 91 I. Factors affecting oxidation 1. fatty acids composition Induction period ( 潛伏期 / 誘導期 ) 由形成自由基 (formation of free radical, R ) 的速率決定 (Ea = 35 Kcal/mol) a. active methylene group 較易形成 R C = C - C - C = C. 93 94 b. No. double bonds 2.[ 2 ] at hi [ 2 ],oxidation rate independent of [ 2 ] at lo [ 2 ],oxidation rate dependent of [ 2 ] c. free > esterified to glycerol d. cis > trans e. conjugated < non conjugated f. saturated F.A unchanged at R.T. 95 96 16
3. T 4. surface area a. in o/w system oxidation rate 2 diffusion into oil phase b. Si prevents 2 diffusion into oil 5. Aw - min rate at monolayer Aw 6. radiation energy - UV, Visible, γ 7. Prooxidant = a. acceleration of hydroperoxide decomposition b. direct reaction with unoxidized substrate 97 c. activation of molecular oxygen to singlet oxygen & H 98 8. 抗氧化劑 - a. 常見之抗氧化劑及作用機制 機制 : (1)R + AH RH + A (2)R + AH 2 RH + AH 或 AH + AH AH 2 (3)R [R-A] R +[R-A] stable product 99 Stable radical intermediate (1) resonance delocalization (2) lack of position suitable for attack by 2 due to steric hindrance of butyl Trolox 100 b. 化學結構與抗氧化性 Potency of antioxidants Ascorbic acid Ascorbyl palmitate 101 102 17
c. synergism - 加乘作用 AH 與 BH 混用效果大於單獨使用 AH 及 BH 之總和與另一種抗氧化劑或 free radical acceptor 混合使用 R + AH RH + A A +BH B + AH d. 103 104 J. Measurement of lipid oxidation 1. 過氧化價 (peroxide value, PV) meq I 2 liberated from KI/kg fat RH + 2KI RH + I 2 + K 2 衛生署 lipophilic balance (HLB) of AH 3. 金屬離子螯合劑, 如 EDTA 或 CaNa 2 鹽 0.10 g/kg 105 I 2 + 2Na 2 S 2 3 2 NaI+ N 2 S 4 6 2. 氧吸收量 ( 2 absorption) meq 2 absorption/kg fat 3. 活性氧法 (Active oxygen method, AM) 98, 2, t to reach specific PV For vegetable oil PV=100, animal fat PV=20 106 4. UV absorption conjugated dienes λ max = 234 nm conjugated trienes λ max = 268 nm 或 369 nm 例 : 於 204 炸油條 時間 A 234 nm 未炸時 1.50 炸 2 h 2.15 炸 5 h 2.47 5. 碘價 (I 2 value) 6. 硫代巴比妥酸 (thiobarbituric acid, TBA test) Alkanal Alkenals 2,4-dienals Malonaldehyde 丙二醛 λ= 450 nm ( 黃色 ) 107 MDA λ= 530nm ( 紅色 ) 108 18
Properties changed in autoxidation 7. 極性物質含量 (Polar material) (1) silica gel chromatography 及 13% ether in hexane 分離油中極性與非極性物質 (2) 當油炸油中極性物質達 27% ( 衛生署規定總含量不得超過 25%) 時, 油品須更換 TBA 109 110 7. 總抗氧化力 (Total Antioxidant capacity ) 以 Trolox equivalent (mm) 表示 8. 血紅素催化亞麻油酸過氧化抑制率 9. DPPH 自由基清除率 α,α-diphenyl-β-picrylhydrazyl 在 517nm 吸光當抗氧化物質將 DPPH 自由基還原時 A 517nm 下降 10. 還原力 1. 為何一種油有油氧化的氣味, 但 TBA 值 0? 2. 在開發一個食品新產品時, 如何選擇抗氧化劑? 111 112 H. 油炸油加熱變化 1. 物理與化學變化 113 114 19
Quality indicator Austria Max frying temp. ( ) 180 180 180 * 180 180 Belgium France Germany Smoke point (min ) 170 170 Free fatty acids (max %) 2.5 Acid value (max) 2.5 2 Polar compounds (max %) 27 25 24 25 25 xidised fatty acids (max %) Dimers and polymers (max %) Viscosity 50 (max mpa.s) of liquid oil Regulation on end of frying life 1 0.7 Italy Netherlands 25 16 37 27 *Relates to automatic chip vending machines. 200 for highly saturated oils. Portugal 115 2001 Wood head Publishing Ltd. 2. 油炸油品質分析方法 (1) 標準方法 酸價 發煙點 極性物質含量 共軛雙烯 (A 232nm ) C 18:2 /C 16:0 (2) 快速方法 - 業務用 介電常數 (dieletric constant) 折射率 (refractive index) 黏度 (viscosity) 116 油炸油含砷烏龍事件的檢驗結果 1. 試驗一 : 油炸油經添加 25% 濾油粉於 60 浸泡 18 小時, 其砷 鉛 銅 汞均未檢出 2. 試驗二 : 油炸油經 10 12 14 16 18 及 20 次之 2% 濾油粉過濾, 其砷 鉛 銅 汞均未檢出 過濾次數砷鉛銅汞 0 N.D. N.D. N.D. N.D. 10 N.D. N.D. N.D. N.D. 12 N.D. N.D. N.D. N.D. 14 N.D. N.D. N.D. N.D. 16 N.D. N.D. N.D. N.D. 18 N.D. N.D. N.D. N.D. 20 N.D. N.D. N.D. N.D. 註 : 砷 鉛 銅 汞之檢出現量均為 0.01 ppm 117 顯色試劑 : 例如 spot test- 依 FFA 含量呈藍 綠 黃監控油脂酸敗 Fritest- 監控 C 基化合物含量 oxifrit test- 依氧化還原電位呈色 118 3. 防止油炸油變質的方法 (1) 提高油脂周轉使用率 (fat turnover rate) 新油添加率 12.5%/h (2) 防止熱氧化 阻斷油炸油表面的空氣如使用矽油 使傳熱面過熱 (T) 使用抗氧化劑 Ⅵ. Processing of fats and oils A. Rendering 提煉 wet/ dry rendering B. Solvent Extraction 溶劑萃取 n-hexane 119 120 20
2. Alkaline Refining 鹼精製 / 脫酸 Neutralization C. Refining / Purification 精煉 / 純化 1. Setting and Degumming 沉澱及去膠 a. To remove phosphatides ie. lecithin and protein b. By mixing with 2-3% H 2 / steam for 1 / 2 hr at 54-71, then separated by centrifugation enclusion emulsion soluble Na-silicate agglomerate filtrate 121 Soap stock hot Residual soap stock centrifuge 122 122 3. Bleaching 脫色 -heating the oil at 85 a. To remove pigment, oxidation products, trace metals. b. By clay (bentonite) chlorophyll (green) charcoal-carotenoids and xanthophyll (red) c. H 2 reduces adsorption of clay, high temp causes darkening by oxidation. d. Bleaching earth is removed by filtration. neutral or acid activated clay FFA=0.05%, PV=0 Adsobtant, bleaching earth 4. Deodorization 脫臭 Specialty il a. To remove volatile odorous cpds, some pigments, chlorinated pesticide ( 如 PCB) b. By vacuum steam steam stripping c. Cufsate is often added to remove faces of pro-oxidant metals. 123 124 Is oxidative stability of oil always improved by refining? Why? 1. Crude cottonseed oil more stable gossypol, tocopherols in crude oil. 2. Toxicants ie. aflatoxin in crude peanut oil & gossypol in crude cottonseed oil are revomed by refining. 125 126 21
5. Winterization 冬化 a. To remove high melting glycerides b. By holding at 5 until crystallization and removal of the solids. D. Modification 1. Hydrogenation 氫化 a. at 140-225 direct addition of H 2 to double bonds of fatty acids b. to change the physical and chemical properties of fats and oils c. Partial hydrogenation - 魚油供作酥油 (shortening) 或人造奶油 (margarine) 127 128 c. Rate of reaction depends on nature of the fats and oils SR trans rate catalyst nature and conc. hi hi hi hi agitation H 2 pressure hi Lo Lo hi temperature hi Lo Lo hi hi hi hi hi SR = selectivity ratio = K 2 /K 3 trans fat d. Selectivity highly unsaturated vs. less unsaturated iso acids / trans acids vs. natural occurring acids / trans acids linoleic K 1 linolenic isolinoleic K 2 oleic K 3 stearic isooleic 129 130 131 Selectivity ratio (SR) = K 2 / K 3 (more selective, more trans, not nutritional) 132 22
Solid content index cis e. catalysts catalyst metal on various support supports aid in orientation of metal metal Ni, Cu, Cu Cr, Pd mechanism 133 134 poisons to catalysts capable of reacting with or adsorbing irreversibly phospholipids water S cpds soaps partial glycerol esters C 2 As mineral acids active site covered 135 2. 交酯化 (Interesterification 或 Transestecification) a. exchange acyl groups among TGs b. calalysts:sn, Pb, Zn, Cd., or their cpds / alkaline metals / alkaline earth metals. CH 3 Na (Sodium methoxide 最常用 ) 136 c. Mechanisms enolate ion formation carbonyl addition R 2 Na R 3 137 138 23
Applications 1. 酥油 (shortening) 2. 人造奶油 (margarine) 3. 包裹用油脂 (coating fat) 4. 熟成 (tempering) 5. 生化柴油 (bio-diesel) 參考資料 http://www.soybean.org.tw/tech6-2.htm 生化柴油 (Bio-diesel)- 生質能源 原料 植物油 動物油 交酯化 長鏈脂肪酸甲脂 烹調廢油 可代替柴油的 環保燃油 應用 直接作用現有柴油引擎, 不需任何修改 生化柴油之製造模式 : 139 140 特點 含有 11% 的氧量 閃火點 (Flash Point) 118 ( 石化柴油 52 ) 硫量 <0.01% 十六烷值 : 50(#1 石化柴油 50, #2 石化柴油 42) 毒性低 生化可分解 可再生 排廢氣味較佳 潤滑性佳 氧量多 不需更換引擎設備, 以代替部分石化柴油 美國及食品藥物管理局 (FDA) 及美國農業部 (USDA) 認可 健康效應 利於環保 另可節省進口石油外匯 生化柴油 (Bio-Diesel) - 廢食用油脂資源化循環圖 141 142 Role of Food Lipids in Flavor a. Physical effects on mouth feel, on volatility of flavor components b. As flavor precursors c. As off-odor precursors. 143 144 24
Cause 1. Rancidity 2. Reversion Factors linolenic, isolenoleic temp Light 2 antioxidant - metallic ions + End products same different PV high low 2n-pentyl furan 3 cis 及 3-trans hexenols - 2 ppm (p.228) odor 豆味 beany 草味 grassy 145 146 25