2. The Lipids Triglycerides Phospholipids Sterols Copyright 2005 Wadsworth Group, a division of Thomson Learning

3. Lipids (C,H,O) Triglycerides (Neutral lipids) –Fats and oils 95% of the lipids in food 99% of the lipids stored in the body Fats – solid at room temperature (70F or 25C) Oils – liquid at room temperature Phospholipids Sterols Lipids include the fat soluble vitamins Copyright 2005 Wadsworth Group, a division of Thomson Learning

4. Fatty Acids and Triglycerides Copyright 2005 Wadsworth Group, a division of Thomson Learning Triglycerides are made up of –Glycerol –Fatty acids Glycerol

5. Copyright 2005 Wadsworth Group, a division of Thomson Learning Condensation of Glycerol & Fatty Acids to Form a Triglyceride

6. Fatty Acids and Triglycerides glycerol + 3 fatty acids  triglyceride + H 2 O Copyright 2005 Wadsworth Group, a division of Thomson Learning

7. Fatty Acids Fatty acids –Fatty acids are long unbranched chains of carbon atoms with attached hydrogens and other groups. –A carboxyl (-COOH) group at one end gives the molecule its acidic properties. –Most naturally occurring fatty acids contain an even number of carbon atoms in their backbone chains. (Few with odd numbers are found in all organisms, but they are a minor fraction of the total) –Length Various lengths most important are 12-24 Tables C-1 and C-2 in Appendix C –Saturated vs. unsaturated Copyright 2005 Wadsworth Group, a division of Thomson Learning

8. Fatty Acids Fatty acids –Length Various lengths - most important are 12-24 Except for butyric and caproic (4 and 6 carbons) longer lengths (18 and above) are characteristic of animal fats. Length affects softness (see later) Tables C-1 and C-2 in Appendix C –Saturated vs. unsaturated Copyright 2005 Wadsworth Group, a division of Thomson Learning

9. Fatty Acids Organic acids –Example: acetic acid Copyright 2005 Wadsworth Group, a division of Thomson Learning

10. Fatty Acids Length of carbon chain Copyright 2005 Wadsworth Group, a division of Thomson Learning Stearic acid – 18-carbon, saturated Simplified structure

11. Fatty Acids Degree of saturation –Saturated fatty acid Has all the Hydrogen needed to satisfy all four bonds of each carbon –Monounsaturated fatty acid Has two hydrogens less causing a double bond to form –Polyunsaturated fatty acid Has four or more hydrogens less causing two or more double bonds Point of saturation –Location of the double bonds (see below) Copyright 2005 Wadsworth Group, a division of Thomson Learning

13. An impossible chemical structure Oleic acid – 18-carbon, monounsaturated Linoleic acid – 18-carbon, polyunsaturated

14. Fatty Acids Location of double bonds –Omega number Omega-3 fatty acid Omega-6 fatty acid Copyright 2005 Wadsworth Group, a division of Thomson Learning

15. Omega-3 and Omega-6 Fatty Acids Compared

16. A Mixed Triglyceride This mixed triglyceride includes a saturated fatty acid, a mono- unsaturated fatty acid, and a polyunsaturated fatty acid.

17. Triglycerides Degree of unsaturation revisited –Firmness Polyunsaturated fats are liquids at room temperature Many animal fats are saturated e.g. butter There are plant oils that are saturated e.g. coconut oil, palm oil, cocoa butter (tropical oils) But these tend to have shorter carbon chains so they are softer than animal fats (longer chain lengths) Saturated and unsaturated fatty acids contents of various foods – See Appendix H Copyright 2005 Wadsworth Group, a division of Thomson Learning

18. Triglycerides Degree of unsaturation revisited –Stability Oxidation –Exposure to oxygen breaks down all fats (rancidity) –Double bonds are unstable –More saturated fats are more stable –Saturated>Monounsaturated>Polyunsaturated Methods to overcome oxidation –Seal in airtight, nonmetallic containers, protect from light, refrigerate – Add Antioxidants – Hydrogenation Copyright 2005 Wadsworth Group, a division of Thomson Learning

20. Triglycerides Degree of unsaturation revisited –Hydrogenation Makes fats more stable Makes food taste better (pie crusts and puddings) –Cis vs. trans-fatty acids Trans-fatty acids behave more like saturated fatty acids in the body Copyright 2005 Wadsworth Group, a division of Thomson Learning

21. Hydrogenation

22. Copyright 2005 Wadsworth Group, a division of Thomson Learning Cis- and Trans-Fatty Acids Compared

23. Phospholipids Copyright 2005 Wadsworth Group, a division of Thomson Learning

24. Lipids Hydrophobic vs. hydrophilic –For something to be soluble in water (and therefore hydrophilic) it must have a charge –Fatty acids and triglycerides don’t have any charges (hence the name neutral lipids) –Phospholipids have charge from the phosphate group so they have a hydrophilic end and a hydrophobic end Copyright 2005 Wadsworth Group, a division of Thomson Learning

25. Phospholipids Phospholipids in foods Roles of phospholipids –Plasma membrane –Emulsifiers Copyright 2005 Wadsworth Group, a division of Thomson Learning