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 Phospholipids Terpenes/Terpenoids Steroids Waxes Primary topics
Oils and Fats Major Component (%95-99) Minor Components (%1-5) Triglycerides Minor Components (%1-5) Triglyceride Derivatives Glycerol Free Fatty Acids Mono- and Diglycerides Non-Triglyceride Derivatives Phospholipids Sterols 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 C - R1 triacylglycerol - R2 - R3 HC H2C OH glycerol HC H2C HO - C O - R1 3 fatty acids + - R3 - R2 +3H20 O R One chiral carbon with 1-3 acyl groups simpler stereochemistry than sugars - C more possible substituents acyl
Triglyceride (b - palmityl distearin) GLYCERIDES Monoglyceride (a - monostearin) Diglyceride (a, a' - distearin) Triglyceride (b - palmityl distearin)
a - oleodipalmitin 1 - oleodipalmitin a - Linoleyldiolein 1 - Linoleyldiolein
Fatty Acids
Fatty Acid Structure R-groups on fatty acid chains are generally linear hydrocarbons, e.g. O CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 H- O - C CH2 CH2 CH2 CH2 CH2 CH2 CH2 which may be more simply represented as O H- O - C
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 consists of 18 carbons with 1 double bond located between the 9th and 10th carbon. O 2 4 6 11 8 13 15 17 - O - C 1 3 5 7 9 10 12 14 16 18
Saturated Fatty Acids Octanoic Acid
Unsaturated Fatty Acids 3 - Octenoic Acid 3, 6 - Octadienoic Acid Short hand: 8:1 (D3) 8:2 (D3,6)
Important Food Fatty Acid Constituents
Chain Lenght – Molecular Weight Fatty Acids Common Name General Formula Formula Mol Weight (g) C 12:0 Lauric CnH2nO2 C12H24O2 200 C 14:0 Myristic C14H28O2 228 C 16:0 Palmitic C16H32O2 256 C 18:0 Stearic 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 mg/100 ml Soluble in H2O Fatty Acids M.P.(0C) C4 - 8 - C6 - 4 970 C8 16 75 C10 31 6 C12 44 0.55 C14 54 0.18 C16 63 0.08 C18 70 0.04
Effects of Double Bonds on the Melting Points 16:0 60 16:1 1 18:0 63 18:1 16 18:2 -5 18:3 -11 20:0 75 F. A. M. P. (0C) 20:4 -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 3 + 3 K+OH - O - R C H2C H2C OH O HC + HC KO - triacylglycerol HC H2C OH glycerol HC H2C C O - R KO - + 3 K+OH - 3 + Potassium salt Similarly; RCOOH + KOH RCOO-K+ + Glycerol MG + KOH RCOOK + Glycerol DG + 2KOH 2RCOOK + Glycerol
Saponification Value 1 mol TG 3 mol KOH required 1 g TG X mol KOH required MWKOH: 56 g = 56000 mg 1 g TG : 1 g / MWTG (g/mol) mol 1 mol TG 3x 56000 mg KOH required 1 g TG / MWTG X mg KOH required
Saponification Value What is the MWTG ? O O O - R1 - R1 C - R C H2C C
Saponification Value Which one’s MW should be taken? O O O - R1 - R1 C HC H2C O C - R1 - R2 HC H2C O C - R HC H2C
Saponification Value The Answer is the Weighted Average MW O O O - R1 HC H2C O C - R1 - R2 HC H2C O C - R HC H2C
Saponification Value Calculation of AMWTG Oil consists of only type Simple Triglyceride O C - R HC H2C
Average Moleculer Weight of FAs in Oil (AMWFA) 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 C - R1 HC H2C O C - R1 - R2 HC H2C O C - R2 HC H2C O C - R1 - R2 HC H2C 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 xi R1 x1 R2 x2 . . RN xN
Saponification Value Milk Fat 210-233 Coconut Oil 250-264 Cotton Seed Oil 189-198 Soybean Oil 189-195 Fat SV 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) Excess unreacted ICl
Theoretical Iodine Value Monoene + I2 Saturated Diene + 2*I2 Saturated Triene +3* I2 Saturated Sample: 100 g basis Assumption: Oil =TG FA xi C16:0 5 C18:0 15 C18:1 15 C18:2 40 C18:3 1 C20:0 3
Theoretical Iodine Value 1 mol C18:1 1 mol I2 (254 g) 15 g C18:1 X (g) I2 1 mol C18:2 2 mol I2 (2x254 g) 40 g C18:2 X (g) I2 Assumption: Oil =TG FA xi C16:0 5 C18:0 15 C18:1 15 C18:2 40 C18:3 1 C20:0 3
Theoretical Iodine Value 1 mol C18:3 3 mol I2 (3x254 g) 1 g C18:3 X (g) I2 Theoritical IV= IV C18:1 + IV C18:2+ IV C18:2 Real IV= 0.95xTheoricital Value