2009 Lipids Part 1 - On the ultimate composition of simple...

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On the ultimate composition of simple alimentary substances; with some preliminary remarks on the analysis of organised bodies in general Philosophical Transactions of the Royal Society 355 (1827) “The subject of digestion, however, had for a long time occupied my particular attention: and by degrees I had come to the conclusion, that the principal alimentary matters employed by man, and the more perfect animals, might be reduced to three great classes, namely, the saccharine , the oily , and the albuminous “… William Prout (1785-1850)
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Lipids in Foods "Lipids" Two major categories of food lipids: 1. Fatty acids and triglycerides : Account for > 90% of lipids in most foods 2. Other lipids: Sterols (cholesterol, plant sterols) Fat - s oluble pigments (carotenoids, chlorophylls) Fat - soluble vitamins (vitamins A, D, E, K) Essential oils (terpenes) Organic (contain carbon), limited solubility in water Soluble in organic solvents (alcohols, hydrocarbons, chlorocarbons) Slippery consistency (mouth or touch)
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Functional properties of lipids in foods A. Lipids as foods for direct consumption Butter, margarine, spreads, salad oils, chocolate B. Lipids as components or ingredients : Texture modifiers smooth, creamy, slippery mouthfeels Cooking medium (frying, sauteeing oils) Shortening agents in flour-based products Carrier for fat-soluble flavor compounds Coloring agents (chlorophylls, carotenoids) Nutrition Source of calories Source of essential fatty acids Solvent/ carrier for fat-soluble vitamins
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Fatty acids, & lipids containing fatty acids Fatty acids: long chain carboxylic acids CH 3 (CH 2 ) n COOH n = 4 - 24 (even numbers) Most common (foods) : n = 10 - 18   Saturated fatty acids Only single bonds between carbon atoms - C - C - Unsaturated fatty acids One or more carbon-carbon double bonds: - C = C -   " polyunsaturated " : two or more double bonds per fatty acid    " methylene-interrupted " double bonds most common arrangement : - C = C - C - C = C- " conjugated " double bonds -C = C - C = C-
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Fatty acid nomenclature Example (common name): linoleic acid C H 3 CH 2 CH 2 CH 2 CH 2 C H = CHCH 2 C H = CHCH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 C OOH Formal name: octadecadienoic acid "octadeca-" = eighteen (octa=8 + deca=10) "di" = 2 "e noic" = unsaturated (double bond) ["dienoic" = 2 double bonds] Fatty acid notation: ϖ ”, “n” Carbon numbering and double bond location ex.: linoleic acid 18:2 n6 , or 18:2 ϖ 6 (" ϖ " = "omega") 18 = total number of carbon atoms :2 = total number of double bonds n-6 ( ϖ -6) = carbon no. of the double bond nearest the CH 3 end
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                                 C H 3 CH 2 CH 2 CH 2 CH 2 C H = CHCH 2 C H = CHCH 2( CH 2) 5 CH 2 COOH      " ϖ " ("n") carbon  1             6           9  
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2009 Lipids Part 1 - On the ultimate composition of simple...

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