Food Biotechnology Dr. Kamal E. M. Elkahlout Food Biochemistry 2 Lipids

1. Food BiotechnologyDr. Kamal E. M. ElkahloutFood Biochemistry 2 Lipids

2. Lipids: Fats & Oils

3. Characteristics of Lipids • Lipids are composed of C, H, O • long hydrocarbon chain • Do not form polymers • big molecules made of smaller subunits • not a continuing chain fat

4. Why do humanslike fatty foods? Fats store energy • Long HC chain • polar or non-polar? • hydrophilic or hydrophobic? • Function: • energy storage • very rich • 2x carbohydrates • cushion organs • insulates body • think whale blubber!

5. Classification Many ways of classifying lipids: Structural characteristics Neutral fats – found in subcutaneous tissue and around organs Phospholipids – chief component of cell membranes Steroids – cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones Fat-soluble vitamins – vitamins A, E, and K Eicosanoids – DHA (docosahexaenoic acid), EPA (eicosapentaenoic acid) (sources of omega 3,6 & 9) Waxes

6. Fatty Acids • Long-chain carboxylic acids • Insoluble in water • Typically 12-18 carbon atoms (even number) • Some contain double bonds corn oil contains 86% unsaturated fatty acids and 14% saturated fatty acids

7. Fatty Acid Structure • Carboxyl group (COOH) forms the acid. • “R” group is a hydrocarbon chain.

8. Fatty Acids • The Length of the Carbon Chain • long-chain, medium-chain, short-chain • The Degree of Unsaturation • saturated, unsaturated, monounsaturated, polyunsaturated • The Location of Double Bonds • omega-3 fatty acid, omega-6 fatty acid

9. The Length of the Carbon Chain Short-chain Fatty Acid (less than 6 carbons) Medium-chain Fatty Acid (6-10 carbons) Long-chain Fatty Acid (12 or more carbons)

10. Unsaturated Fatty Acid Saturated Fatty Acid

11. Saturated and Unsaturated Fatty Acids Saturated = C–C bonds Unsaturated = one or more C=C bonds

12. Properties of SaturatedFatty Acids • Contain only single C–C bonds • Closely packed • Strong attractions between chains • High melting points • Solids at room temperature

13. Properties of UnsaturatedFatty Acids • Contain one or more double C=C bonds • Nonlinear chains do not allow molecules to pack closely • Few interactions between chains • Low melting points • Liquids at room temperature

14. Structures Saturated fatty acids • Fit closely in regular pattern Unsaturated fatty acids • Cis double bonds

15. Fatty Acids are Key Building Blocks • Saturated Fatty Acid • All single bonds between carbons

16. Monounsaturated Fatty Acid(MUFA) • One carbon-carbon double bond

17. Polyunsaturated Fatty Acid(PUFA) • More than one carbon-carbon double bond

18. Location of Double Bonds • PUFA are identified by position of the double bond nearest the methyl end (CH3) of the carbon chain; this is described as a omega number; • If PUFA has first double bond : • 3 carbons away from the methyl end=omega 3 FA • 6 carbons from methyl end=omega 6 FA

19. Omega-3 Omega-6

20. Degree of Unsaturation • Firmness • saturated vs. unsaturated • Stability • oxidation, antioxidants • Hydrogenation • advantages, disadvantages • Trans-Fatty Acids • from hydrogenation

21. Cis and Trans fats isomerisation of cis to trans occurs under extreme conditions of hydrogenation double bonds in fatty acids are almost always cis, which causes bends in the carbon chain. these bends do not allow the close packing and attractions of saturated fatty acids. Therefore, most unsaturated fatty acids are liquid at room temperature. Cis-9-octadecenoic acid(Oleic acid) Trans-9-octadecenoic acid(Elaidic acid)

22. Hydrogenation Process liquid hardens by hydrogenation (addition of hydrogen) reduce the degree of unsaturation briefly, oils are exposed to hydrogen gas at high tempt (2-10 atm, 160-220 0C) in the presence of 0.01-0.2% fine divided nicklel

23. Saturated vs. unsaturated saturated unsaturated 

24. 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

25. 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

26. 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

27. 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

28. 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

30. Lipid Formation Glycerol Fatty Acid

31. GLYCERIDES Monoglyceridea Diglyceride Triglyceride

32. Triglycerides • Structure • Glycerol + 3 fatty acids • Functions • Energy source • 9 kcals per gram • Form of stored energy in adipose tissue • Insulation and protection • Carrier of fat-soluble vitamins • Sensory properties in food

33. FAT AND OILS Mostly Triglycerides:

34. Triglycerides • Food sources • fats and oils • butter, margarine, meat, baked goods, snack foods, salad dressings, dairy products, nuts, seeds • Sources of omega-3 fatty acids • Soybean, canola, walnut, flaxseed oils • Salmon, tuna, mackerel • Sources of omega-6 fatty acids • Vegetable oils

35. 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

36. Learning Check How would the melting point of stearic acid compare to the melting points of oleic acid and linoleic acid? Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain. stearic acid (18 C) saturated oleic acid (18 C) one double bond linoleic acid (18 C) two double bonds

37. Phospholipids • Structure • Glycerol + 2 fatty acids + phosphate group • Functions • Component of cell membranes • Lipid transport as part of lipoproteins • Emulsifiers • Phosphatidylcholine • Food sources • Egg yolks, liver, soybeans, peanuts

38. Phospholipids • Hydrophobic or hydrophilic? • fatty acid tails = hydrophobic • PO4 = hydrophilic head • dual “personality” It likes water & also pushes it away! interaction with H2O is complex & very important!

39. A Phospholipid

40. Steroids • ex: cholesterol, sex hormones • 4 fused C rings • different steroids created by attachingdifferentfunctional groups to rings cholesterol

41. Sterols: Cholesterol • Functions • Component of cell membranes • Precursor to other substances • Sterol hormones • Vitamin D • Bile acids • Synthesis • Made mainly in the liver • Food sources • Found only in animal foods

42. 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)

43. FAT SOLUBLE VITAMINS (A,D,E,K) Vitamin A:

44. Vitamin D2: Vitamin E:

45. Deterioration of Fats Rancidity • Is the chemical deterioration of fats • Are of two types • Oxidative rancidity • Hydrolytic rancidity

46. Oxidative rancidity • A hydrogen on the fatty acid molecule is displaced by energy(heat or light) to give free radical. • Molecular oxygen can unite with the carbon that carries the free radical and form a peroxide. • The energy from this activated peroxide can displace a hydrogen from another unsaturated fatty acid. • The displaced hydrogen unites with the activated peroxide to form a hydroxide. • The hydro-peroxide is very unstable and can decompose into compounds with shorter carbon chains. These include ketones, aldehydes and fatty acids that are volatile and contribute to off flavoures.

47. Oxidative Rancidity

48. Catalysts Salt and trace metals Bacteria and molds Water Light Prevention Addition of chelators Use of antioxidants Air tight storage.

49. Hydrolytic Rancidity • Is the reaction between a triglyceride and 3 water molecule to give a glycerol and 3 free fatty acids.

50. Catalysts : Heat Fat splitting enzymes called lipases. Prevention Keep moisture level low Inert gas packaging sterilization