Transcript Slayt 1
OIL AND FAT TECHNOLOGY 1st WEEK Food Lipids • Definition:Nonpolar, hydrophobic, poorly water soluble components which are soluble in organic solvents such as alkanes (e.g. hexane) • Includes fats: solid at room temperature oils: liquid at room temperature • Definition based on physical properties Triglycerides Fatty Acids Primary topics Phospholipids Terpenes/Terpenoids Steroids Waxes Oils and Fats Major Component (%95-99) Minor Components (%1-5) Triglycerides Triglyceride Derivatives Non-Triglyceride Derivatives Glycerol Phospholipids Free Fatty Acids Sterols Mono- and Diglycerides Pigments Vitamins Antioxidants Oxidation Products Trace Metals Hydrocarbons Triglyceride Structure •Food fats/oils are primarily triacylglycerols, commonly called triglycerides. –3 fatty acid chains on a glycerol backbone O H2C OH HC OH 3 fatty acids O + OH glycerol HO - H2C C - R2 HO - O C - R1 O O C - R2 O C - R1 HC HO H2C O O C - R3 –One chiral carbon with 1-3 acyl groups –simpler stereochemistry than sugars –more possible substituents +3H20 H2C O C - R3 triacylglycerol O -C R acyl GLYCERIDES H2 C HC H2 C O OH OH O O C (CH2)16CH3 H2 C O C HC OH O H2 C O C Diglyceride (a, a' - distearin) Monoglyceride (a - monostearin) O H2 C HC H2 C O C O O C O (CH2 )16 CH3 ( C18 ) (CH2 )14 CH3 (C16 ) O C (CH2 )16 CH3 (C18 ) Triglyceride (b - palmityl distearin) (CH2 )16CH3 (CH2 )16CH3 Oleic P almitic OP P P almitic a - oleodipalmitin 1 - oleodipalmitin Linoleic Oleic LOO Oleic a - Linoleyldiolein 1 - Linoleyldiolein Fatty Acids O R C OH #1 Carbon O R C OH Acid Group Polar End - Hydrophilic End Non-polar End - Hydrophobic End (Fat-soluble tail) Fatty Acid Structure • R-groups on fatty acid chains are generally linear hydrocarbons, e.g. O H- O - CH2 C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 which may be more simply represented as H- O - O C CH2 CH2 CH2 CH2 CH3 CH2 Fatty Acid Chain Representation • The symbol followed by the carbon number is used to indicate the position of the double bond E.g. 18:19 O -O- C 2 1 4 3 6 5 11 8 7 9 10 13 12 15 14 consists of 18 carbons with 1 double bond located between the 9th and 10th carbon. 17 16 18 Saturated Fatty Acids 8 7 CH3 CH2 O 5 3 4 6 2 1 CH2 CH2 CH2 CH2 CH2 C Octanoic Acid OH Unsaturated Fatty Acids 8 CH3 7 CH2 5 6 CH2 CH2 4 CH2 O 3 2 1 CH2 CH2 C OH 3 - Octenoic Acid 8 7 CH3 CH2 O 5 3 4 6 2 1 CH2 CH2 CH2 CH2 CH2 C 3, 6 - Octadienoic Acid Short hand: 8:1 (3) 8:2 (3,6) OH Important Food Fatty Acid Constituents Abbreviation S ystematic Name Common Name S ymbol 4:0 Butanoic Butyric B 6:0 Hexanoic Caproic H 8:0 Octanoic Caprylic Oc 10:0 Decanoic Capric D 12:0 Dodecanoic Lauric La 14:0 Tetradecanoic Myristic M 16:0 Hexadecanoic Palmitic P 18:0 Octadecanoic S tearic St 18:1 9-Octadecenoic Oleic O 18:2 9,12 9,12-Octadecadienoic Linoleic L 18:3 9,12,15-Octadecatrienoic Linolenic Ln 20:0 Eicosanoic Arachadic A 20:4 5,8,11,14-Eicosatetraenoic Arachadonic An 22:1 13-Docosenoic Erucic E Chain Lenght – Molecular Weight Fatty Acids Common Name General Formula Formula CnH2nO2 C12H24O2 Mol Weight (g) 200 C 12:0 Lauric C 14:0 Myristic CnH2nO2 C14H28O2 228 C 16:0 Palmitic CnH2nO2 C16H32O2 256 C 18:0 Stearic CnH2nO2 C18H36O2 284 C 18:1 Oleic CnH2n-2O2 C18H34O2 282 C 18:2 Linoleic CnH2n-4O2 C18H32O2 280 C 18:3 Linolenic CnH2n-6O2 C18H30O2 278 Melting Points and Solubility in Water of Fatty Acids Fatty Acids M.P.(0C) mg/100 ml Soluble in H2O C4 -8 - C6 -4 970 C8 16 75 C10 31 6 C12 44 0.55 C14 54 0.18 Melt ing P oint Solubility in H O2 C16 63 0.08 C18 70 0.04 Chain Lengt h Effects of Double Bonds on the Melting Points F. A. 16:0 16:1 M. P . 18:0 18:1 18:2 18:3 20:0 20:4 # Do uble bon ds M. P. (0C) 60 1 63 16 -5 -11 75 -50 Triglycerides differ from each other in regard to • Number of Carbon Atoms in fatty acid chains • Number of double bonds • Isomerization • Distribution of FA on glycerol backbone Analytical Methods • Saponification Value • Iodine Value • Gas Chromatographic Analysis for Fatty Acids • Liquid Chromatography Saponification Value Saponification - hydrolysis of ester under alkaline condition. The saponification value of an oil or fat is defined as the number of mg of potassium hydroxide (KOH) required to neutralize the fatty acids resulting from the complete hydrolysis of 1 g of the sample. Saponification Value O O C- R O HC O C- R + O H2C O C - R triacylglycerol H2C 3 K+OH - H2C OH HC OH H2C OH glycerol O + 3 KO - Potassium salt Similarly; RCOOH + KOH C-R RCOO-K+ + Glycerol MG + KOH RCOOK + Glycerol DG + 2KOH 2RCOOK + Glycerol Saponification Value 1 mol TG 1 g TG 3 mol KOH required X mol KOH required MWKOH: 56 g = 56000 mg 1 g TG : 1 g / MWTG (g/mol) mol 1 mol TG 1 g TG / MWTG 3x 56000 mg KOH required X mg KOH required 168000 X SN MWTG Saponification Value 168000 X SV MWTG • What is the MWTG ? H2C HC H2C O O O C- R O O C- R O O C-R O C - R1 O O C- R1 O O C - R2 H2C HC H2C O H2C HC H2C O C - R1 O O C- R2 O O C - R3 Saponification Value 168000 X SV MWTG • Which one’s MW should be taken? H2C HC H2C O O O C- R O O C- R O O C-R O C - R1 O O C- R1 O O C - R2 H2C HC H2C O H2C HC H2C O C - R1 O O C- R2 O O C - R3 Saponification Value 168000 X SV AMWTG • The Answer is the Weighted Average MW H2C HC H2C O O O C- R O O C- R O O C-R O C - R1 O O C- R1 O O C - R2 H2C HC H2C O H2C HC H2C O C - R1 O O C- R2 O O C - R3 Saponification Value Calculation of AMWTG Oil consists of only type Simple Triglyceride O H2C HC H2C O C- R O O C- R O O C-R AMWTG 41 3 (MWFAR - 1) Saponification Value Calculation of AMWTG Oil consists of Simple and Mixed type Triglyceride with two fatty acids R1 (%90 w/w) and R2 (%10 w/w) O O O O H2C O C - R1 O H2C O C - R1 O H2C O C - R2 O H2C O C - R1 O HC O C- R1 O HC O C- R1 O HC O C- R2 O HC O C- R2 O H2C O C - R1 H2C O C - R2 H2C O C - R2 H2C O C - R2 AMWTG 41 3 [(x R1 MWFAR1 x R 2 MWFAR 2 ) -1] Average Moleculer Weight of FAs in Oil (AMWFA) Saponification Value Generalized Calculation of AMWTG Oil consists of Simple and Mixed type Triglyceride with N fatty acids FA R1 R2 . . RN AMWTG 41 3 [( xi x1 x2 . . xN N i 1 x R i MWFAR i ) - 1] Saponification Value 168000 SV AMWTG 41 [3 ( Fat 168000 N i 1 x R i MWFA R i 1)] SV Milk Fat 210-233 Coconut Oil 250-264 Cotton Seed Oil 189-198 Soybean Oil 189-195 Lard 190-202 Iodine Number • The iodine value of an oil or fat is defined as the mass of iodine absorbed by 100 g of the sample. • The unsaturated fatty acid residues of the glycerides react with iodine, and thus the iodine value indicates the degree of unsaturation of the fatty acid residues of the glycerides. • It is constant for a particular oil or fat, but depends on the method used. Animal fats (butter, dripping, lard) 30 - 70 Iodine Value • Non-drying oils (olive, almond) 80 - 110 Iodine Value • Semi-drying oils (cottonseed, sesame, soya) 80 - 140 Iodine Value • Drying oils (linseed, sunflower) 120 - 200 Iodine Value • The iodine value is often most useful in identifying the source of an oil. Generally, the higher iodine values indicate oils and the lower values fats. Iodine values are normally determined using Wigs or Hanus methods. Determination of Iodine Number Iodine Value = (ml of Na2S2O3 volume for blank - ml of Na2S2O3 volume for sample) N of Na2S2O3 0.127g/meq 100 Weight of Sample (g) CH CH CH Cl + ICl Iodine chloride Excess unreacted ICl I Cl I2 + + KI 2 Na2 S2 O3 KCl + Na2 S4 O6 I2 + 2 NaI CH I Theoretical Iodine Value • Monoene + I2 • Diene + 2*I2 • Triene +3* I2 Saturated Saturated Saturated Assumption: Oil =TG Sample: 100 g basis FA C16:0 C18:0 C18:1 C18:2 C18:3 C20:0 xi 5 15 15 40 1 3 Theoretical Iodine Value 1 mol C18:1 15 g C18:1 1 mol I2 (254 g) X (g) I2 15 254 IVC18:1 282 1 mol C18:2 40 g C18:2 IVC18:2 Assumption: Oil =TG FA C16:0 C18:0 C18:1 C18:2 C18:3 C20:0 2 mol I2 (2x254 g) X (g) I2 40 2 254 280 xi 5 15 15 40 1 3 Theoretical Iodine Value 1 mol C18:3 1 g C18:3 3 mol I2 (3x254 g) X (g) I2 IVC18:3 1 3 254 276 Theoritical IV= IV C18:1 + IV C18:2+ IV C18:2 Real IV= 0.95xTheoricital Value