Lipids

1. Lipids

2. Properties of Lipids • Do not readily dissolve in water • Fats are solid at room temperature • Oils are liquid at room temperature • Energy dense (9 kcal /gm)

3. Three Groups of Lipids • Triglycerides: the main form of lipids in food and body (storage) • Phospholipids • Sterols

4. Triglyceride (TG) Structure • Contain Carbons (C), Hydrogens (H), Oxygens (O) • Glycerol + 3 fatty acids

5. (Ester bond) Glycerol + 3 FA’s Triglyceride + 3 H20 Triglycerides H H--C--OH H--C--OH H--C--OH H O HO-C-R O HO-C-R O HO-C-R H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H R + H2O + R + H20 R + H20

6. esterification desterfication Triglycerides H H--C--OH H--C--OH H--C--OH H Fatty Acid Fatty Acid Fatty Acid H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H Fatty Acid + Fatty Acid Fatty Acid

7. Phospholipid • Built on a glycerol backbone • Has at least one fatty acid replaced with phosphorus compound • Found in body • Synthesized by the body as needed

8. Phospholipid Structure

9. Functions of Phospholipids • Make up cell membrane • Emulsifier • Bile acids • Lecithins • Improves food products

10. Hydrophilic end (attracts water) Hydrophobic end (attracts lipid) Emulsifier

11. Emulsification

12. Cholesterol • Most common sterol • A multi-ringed structure • Does not have a glycerol backbone • Waxy substance • Do not readily dissolve in water • Cholesterol is a sterol

13. Cholesterol Structure

14. Dietary Sources of Cholesterol • Found in animal products only • Never found in plants • However ↑ saturated fat intake ↑ serum cholesterol

15. Serum (blood) Cholesterol • Dietary cholesterol • Endogenous cholesterol • Made in liver • Increases with increased SFA intake

16. Functions of Cholesterol • Essential component of cell membrane • Produced by the liver • Found only in animal products • Forms important hormones • Estrogen, testosterone, vitamin D • Precursor to bile acids

17. Fatty Acids • Simplest form of lipids • Common to most lipids, in the body and in foods • Chain of 4-26 carbons bonded together, flanked by hydrogens • Alpha end: is an acid • Omega end: a methyl group • Fats in foods are generally fatty acid mixtures

18. Differences in Fatty Acids • Number of carbons • Degree of saturation • Number of single or double bonds in carbon chain • Saturated • Monounsaturated • Polyunsaturated • Point of first unsaturated bond • Omega-3 • Omega-6

19. omega end alpha end stearic acid (C18:0) Fatty Acid Structure H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

20. Saturated Fatty Acids (SFA) • All the bonds between carbons are single connections and the carbons are filled with hydrogen • Foods containing primarily saturated fats tend to be solid at room temperature • Medium chain (coconut oil) and short-chain saturated fatty acids (dairy fat) may be liquid

21. Saturated Fatty Acids • Don’t spoil easily, therefore longer shelf life • High intakes of sfa are associated with an increased risk of cardiovascular disease

22. Sources of SFA • Animal fats (meat, dairy) • Tropical oils (coconut and palm oil) • Hydrogenated fats

23. omega end alpha end degree of saturation: single carbon bond stearic acid: C18:0 Saturated Fatty Acid Structure H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

24. Monunsaturated Fatty Acids (MFA) • One double bond between the carbons (missing hydrogens) • Liquid at room temperature • Easily oxidized → becomes rancid • Double bonds are weak points • Easily broken by oxygen (oxidized)

25. Monounsaturated Fatty Acids • Canola, olive, peanut oil contain a high percentage of monounsaturated fatty acids • MFA decreases CVD risk

26. omega end alpha end One double bond ω-9 C18:1 Monounsaturated Fatty Acid Structure H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

27. Polyunsaturated Fatty Acids (PUFA) • More than one double bond between the carbons • Liquid at room temperature • Easily oxidized • Polyunsaturated fat decreases CVD risk when substituted for SFA

28. Polyunsaturated Fatty Acids • Corn, soybean, sunflower, and safflower oils are rich in polyunsaturated fatty acids (PUFA)

29. omega end alpha end > 2 double bonds Polyunsaturated Fatty Acid Structure (Fig. 5-1-C) H H H H H H H H H H H H H O H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

30. Fatty Acid Profiles in Foods

31. Hydrogenation of Fatty Acids • Addition of H to C=C double bonds • Breaks double bonds • Formation of trans fatty acid (similar to shape of saturated fatty acid)

32. Hydrogenation of Fatty Acids • Process used to solidify an oil • Resistant to oxidation • Increases shelf life • Can be reused longer in frying • However resulting trans fatty acids are associated with ↑ CVD risk

33. Cis and Trans Fatty Acid

34. Health Dangers of Trans Fatty Acids • Raises LDL • Lowers HDL • Increases risk for heart disease • Current intake is~3% of total kcals • Soon to be on food labels

35. Sources of Trans Fatty Acid • Stick margarine • Shortening • Crackers • Hydrogenated fats • Deep-fried foods • High fat baked goods • Non-dairy creamers

36. Rancidity • Decomposed oils • Breakdown of the C=C double bonds by ultraviolet rays, &/or O2 • Yields unpleasant odor and flavor • PUFA more susceptible • Limits shelf life

37. Prevention of Rancidity • Hydrogenation • Addition of vitamin E • Addition of Butylated hydroxyanisol (BHA) and Butylated hydroxytolune (BHT)

38. Functions of Fats • Provide essential fatty acids • Provide energy (muscles and many organs burn fat) • Supply fat soluble vitamins • Satiety • Texture and flavor

39. Essential Fatty Acids • Body can only make double bonds after the 9th carbon from the omega end • Needed for immune function, vision, cell membrane, and production of hormone-like compounds

40. omega end alpha end 1st double bond is located on the 3rd carbon from the omega end Essential Fatty Acid- Omega-3 (alpha-linolenic acid) H H H H H H H H H H H H H H H H H O H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H

41. Omega-3 Fatty Acid • Primarily from fish oil • Also found in canola or soybean oil • Recommend intake of ~2 servings of fish per week

42. omega end alpha end 1st double bond is located on the 6th carbon from the omega end Essential Fatty Acid- Omega-6 (alpha-linoleic acid) H H H H H H H H H H H H H O H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

43. Omega-6 Fatty Acid • Found in vegetable oils • Only need ~ 1 tablespoon a day

44. Essential Fatty Acids Omega-3 Omega 6 Alpha-linolenic acid Linolenic acid DHA EPA Arachidonic Acid (docosahexanoic (eicosapentaenoic acid) acid)

45. Effects of Essential Fatty Acids • Archidonic acid (Omega-6 ) • increase blood clotting • increase inflammatory responses • DHA, EPA (Omega-3) • decrease blood clotting • reduces heart attack • excess may cause hemorrhagic stroke • large amounts may decrease inflammation pain with rheumatoid arthritis

46. Signs and Symptoms of Essential Fatty Acids Deficiency • Flaky, itchy skin • Diarrhea • Infections • Retarded growth and wound healing • Anemia

47. Functions of Body Fat • Energy store • Adipose cells • 1 pound fat = 3500 calories • Insulation • Subcutaneous fat • Protection • Internal organs

48. Lipids in Foods

49. Hidden Fat • Look on the Nutrition Facts • Look on the lists of ingredients • Control portion size

50. Reduced Fat Foods • Sugar is commonly added in place of fat • Check calorie content