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LIPID

LIPID. Soluble in non-polar solvents and insoluble in polar solvents. Lipid is not polymers. Lipids: 1. Fatty acids 2. Neutral fats and oils 3. Waxes 4. Phospholipid 5. Sterols 6. Fat soluble vitamins. Fatty Acids. Saturated Fatty Acids. Octanoic Acid. Unsaturated Fatty Acids.

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LIPID

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  1. LIPID Soluble in non-polar solvents and insoluble in polar solvents. Lipid is not polymers. Lipids: 1. Fatty acids 2. Neutral fats and oils 3. Waxes 4. Phospholipid 5. Sterols 6. Fat soluble vitamins

  2. Fatty Acids

  3. Saturated Fatty Acids Octanoic Acid

  4. Unsaturated Fatty Acids 3 - Octenoic Acid 3, 6 - Octadienoic Acid Short hand: 8:1 (D3) 8:2 (D3,6)

  5. Cis And Trans Fatty Acids Cis 9 - Octadecenoic Acid (oleic) Trans 9 - Octadecenoic Acid (elaidic acid)

  6. Polyunsaturated Fatty Acids Linoleic acid: Cis, cis, 9, 12 - Octadecadienoic acid Linolenic acid: Cis, cis, cis 9, 12, 15 - Octadecatrienoic acid Arachidonic acid: Cis, cis, cis, cis 5, 8, 11, 14 - Eicosatetraenoic acid Linoleic Acid Linolenic Acid Arachidonic Acid

  7. Naturally-occurring fatty acids 1. Cis form 2. Not conjugated --- isolated double bond. 3. Even numbered fatty acids.

  8. Common Name Systematic Name Formula Common source CLASSIFICATION OF FATTY ACIDS PRESENT AS GLYCERIDES IN FOOD FATS I. Saturated Fatty Acids Butyric Butanoic CH3(CH2)2COOH butterfat Caproic Hexanoic CH3(CH2)4COOH butterfat, coconut and palm nut oils Caprylic Octanoic CH3(CH2)6COOH coconut and palm nut oils, butterfat Capric Decanoic CH3(CH2)8COOH coconut and palm nut oils, butterfat Lauric Dodecanoic CH3(CH2)10COOH coconut and palm nut oils, butterfat Myristic Tetradecanoic CH3(CH2)12COOH coconut and Palm nut oil, most animal and plant fats Palmitic Hexadecanoic CH3(CH2)14COOH practically all animal and plant fats Stearic Octadecanoic CH3(CH2)16COOH animal fats and minor component of plant fats Arachidic Eicosanoic CH3(CH2)18COOH peanut oil

  9. Common Name Systematic Name Formula Common source Arachidonic 5,8,11,14-Eicosatetraenoic C19H31COOH traces in animal fats II. Unsaturated Fatty Acids A. Monoethenoic Acids Oleic Cis 9-octadecenoic C17H33COOH plant and animal fats Elaidic Trans 9-Octadecenoic C17H33COOH animal fats B. Diethenoic Acids Linoleic 9,12-Octadecadienoic C17H31COOH peanut, linseed, and cottonseed oils C. Triethenoid Acids Linolenic 9,12,15-Octadecatrienoic C17H29COOH linseed and other seed oils Eleostearic 9,11,13-Octadecatrienoic C17H29COOH peanut seed fats D. Tetraethenoid Acids 4,8,12,15-Octadecatetraenoic Moroctic C17H27COOH fish oils

  10. Common Name Systematic Name Formula Common source Arachidonic 5,8,11,14-Eicosatetraenoic C19H31COOH traces in animal fats Common and Systematic Names of Fatty Acids A. Monoethenoic Acids Oleic Cis 9-octadecenoic C17H33COOH plant and animal fats Elaidic Trans 9-Octadecenoic C17H33COOH animal fats B. Diethenoic Acids Linoleic 9,12-Octadecadienoic C17H31COOH peanut, linseed, and cottonseed oils C. Triethenoid Acids Linolenic 9,12,15-Octadecatrienoic C17H29COOH linseed and other seed oils Eleostearic 9,11,13-Octadecatrienoic C17H29COOH peanut seed fats D. Tetraethenoid Acids 4,8,12,15-Octadecatetraenoic Moroctic C17H27COOH fish oils

  11. Melting Points and Solubility in Water of Fatty Acids

  12. Fatty Acids M.P.(0C) mg/100 ml Soluble in H2O C18 70 0.04 CHARACTERISTICS OF FATTY ACIDS C4 - 8  - C6 - 4 970 C8 16 75 C10 31 6 C12 44 0.55 C14 54 0.18 C16 63 0.08

  13. F. A. M. P. (0C) 60 16:0 16:1 1 18:0 63 18:1 16 18:2 -5 18:3 -11 20:0 75 20:4 -50 Effects of Double Bonds on the Melting Points

  14. FAT AND OILS Mostly Triglycerides: Glycerol 3 Fatty Acids

  15. GLYCERIDES Monoglyceride (a - monostearin) Diglyceride (a, a' - distearin) Triglyceride (b - palmityl distearin)

  16. a - oleodipalmitin 1 - oleodipalmitin a - Linoleyldiolein 1 - Linoleyldiolein

  17. FATS AND OILS ARE PRIMARILY TRIGLYCERIDES (97-99%) Vegetable oil - world supply - 68% Cocoa butter - solid fat Oil seeds - liquid oil Animal fat - 28% (from Hogs and Cattle) Marine oil - 4% Whale oil cod liver oil

  18. Fatty Acids Butter Coconut Cottonseed Soybean 18:3 2 8 Fatty Acids (%) of Fats and Oils 4 3 6 3 8 2 6 10 3 6 12 3 44 14 10 18 1 16 26 11 4 12 16:1 7 1 18:0 15 6 3 2 18:1 29 7 18 24 18:2 2 2 53 54

  19. Triglyceride Melting Point (°C) C6 -15 C12 15 C14 33 C16 45 C18 55 C18:1 (cis) -32 C18:1 (trans) 15 MELTING POINTS OF TRIGLYCERIDES

  20. WAXES • Fatty acids + Long chain alcohol • Important in fruits: • Natural protective layer in fruits, vegetables, etc. • Added in some cases for appearance and protection. • Beeswax (myricyl palmitate), Spermaceti (cetyl palmitate)

  21. PHOSPHOLIPID Lecithin (phosphatidyl choline)

  22. STEROLS Male & female sex hormones Bile acids Vitamin D Adrenal corticosteroids Cholesterol

  23. FAT SOLUBLE VITAMINS Vitamin A:

  24. Vitamin D2: Vitamin E:

  25. ANALYTICAL METHODS TO MEASURE THE CONSTANTS OF FATS AND OILS 1. Acid Value 2. Saponification Value 3. Iodine Value 4. Gas Chromatographic Analysis for Fatty Acids 5. Liquid Chromatography 6. Cholesterol Determination

  26. 1. Acid Value Number of mgs of KOH required to neutralize the Free Fatty Acids in 1 g of fat.

  27. 2. Saponification Value Saponification - hydrolysis of ester under alkaline condition.

  28. Fat Saponification # Lard 190-202 Saponification Value of Fats and Oils Milk Fat 210-233 Coconut Oil 250-264 Cotton Seed Oil 189-198 Soybean Oil 189-195

  29. 2. Saponification Value Determination • Saponification # --mgs of KOH required to saponify 1 g of fat. • 1. 5 g in 250 ml Erlenmeyer. • 2. 50 ml KOH in Erlenmeyer. • 3. Boil for saponification. • 4. Titrate with HCl using phenolphthalein. • Conduct blank determination. • B - ml of HCl required by Blank. • S - ml of HCl required by Sample.

  30. 3. Iodine Number Number of iodine (g) absorbed by 100 g of oil. Molecular weight and iodine number can calculate the number of double bonds. 1 g of fat adsorbed 1.5 g of iodine value = 150.

  31. Iodine Value Determination 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

  32. Fatty Acids # of Double-bonds Iodine # Arachidonic Acid 4 320 Iodine Numbers of Triglycerides Palmitoleic Acid 1 95 Oleic Acid 1 86 Linoleic Acid 2 173 Linolenic Acid 3 261

  33. Fat C4 C6 C10 C16 C18 C18:1 C18:2 C18:3 C20:4 6 100 Compositions (%) of Fatty Acids of Fats 1 5 5 20 40 30 2 20 35 40 5 3 10 50 40 4 20 40 40 5 10 20 20 10 20 20

  34. 4. GC Analysis for Fatty Acids 1. Extract fat. 2. Saponify (hydrolysis under basic condition). 3. Prepare methyl ester (CH3ONa). 4. Chromatography methyl ester. 5. Determine peak areas of fatty acids. Fatty acids are identified by retention time. 6. Compare with response curve of standard.

  35. Fatty Acids Methyl Esters: GC condition: 10% DEGS Column (from supelco) Column temperature 200C.

  36. 5. TRIGLYCERIDE ANALYSIS BY LIQUID CHROMATOGRAPHY Soybean Oil Solvent CH3CN/HF Column 84346 (Waters Associates)

  37. Fatty Acid Composition Total Acyl Carbons: Unsaturation Equivalent Carbon Number OS2 54:1 52 Oleate-containing triglycerides in olive oil OL2 54:5 44 O2L 54:4 46 OPL 52:3 46 O3 54:3 48 OSL 54:3 48 O2P 52:2 48 O2S 54:2 50 OPS 52:1 50

  38. 6. CHOLESTEROL DETERMINATION Enzymatic Determination: Cholesterol Oxidase 0-Dianisidine Oxidized 0-Dianisidine (Colorless) (Brown color)At 440 nm

  39. Cholesterol by GLC 1. Prepare cholesterol butyrate. 2. Analyze by GLC. time in GC - 15 min. sensitivity - 10-7 g.

  40. Spectromertic Absorption Standard Curve of Cholesterol Cholesterol by GLC 1. Prepare cholesterol butyrate. 2. Analyze by GLC. time in GC - 15 min. sensitivity - 10-7 g.

  41. LIPID CONTENT ANALYSES 1. Gravimetric Method (1) Wet extraction - Roese Gottliegb & Mojonnier. (2) Dry extraction - Soxhlet Method. 2. Volumetric Methods (Babcock, Gerber Methods)

  42. 1. Gravimetric Method • Wet Extraction - Roese Gottlieb & Mojonnier. •  For Milk: • 1) 10 g milk + 1.25 ml NH4OH mix. solubilizes protein and neutralizes. • 2) + 10 ml EtOH - shake. Begins extraction, prevents gelation of proteins. • 3) + 25 ml Et2O - shake and mix. • 4) + 25 ml petroleum ether, mix and shake. 

  43. (2) Dry Extraction - Soxhlet Method. Sample in thimble is continuously extracted with ether using Soxhlet condenser. After extraction, direct measurement of fat - evaporate ether and weigh the flask. Indirect measurement - dry thimble and weigh thimble and sample.

  44. Soxhlet Method.

  45. 2. Volumetric Method (Babcock, Gerber Methods) • Theory: • Treat sample with H2SO4 or detergent. • Centrifuge to separate fat layer. • Measure the fat content using specially calibrated bottles. • Methods: • 1. Known weight sample. • 2. H2SO4 - digest protein, liquefy fat. • 3. Add H2O so that fat will be in graduated part of bottle. • 4. centrifuge to separate fat from other materials completely.

  46. REACTIONS OF FATS Hydrolytic Rancidity: 1. Triglyceride -> Fatty acids Specially C4 butyric acid (or other short chain fatty acids) are the real problem. 2. By lipase.

  47. LIPID OXIDATION Major flavor problems in food during storage are mainly due to the oxidation of lipid. Lipid Oxidation - free radical reactions. 1. Initiation. 2. Propagation. 3. Termination.

  48. Pentane Formation from Linolenic Acid

  49. ANALYSIS OF FLAVOR QUALITY & STABILITY OF OIL 1. Peroxide Value Peroxide Value = ml of Na2S2O3  N  1000 (milliequivalent peroxide/kg of sample) Grams of Oil

  50. 2.Active Oxygen Method (AOM) Determined the time required to obtain certain peroxide value under specific experimental conditions. The larger the AOM value, the better the flavor stability of the oil.

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