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No of double bonds the greater the lower the mp 2

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Unformatted text preview: cids or TAGs go Can fatty acids or TAGs go RANCID? Olive oil and butter All dietary fats contain a mixture of saturated and unsaturated fats If exposed too long to air, they become rancid Due to oxidative cleavage of double bonds (only) forming shorter chain aldehydes and carboxylic acids (saturated fats do not) • Melting point is affected by: 1. no. of double bonds – the greater the lower the MP) 2. chain length – the lower the lower the MP Naturally occurring saturated fatty acids Carbon Carbon s 12 CH3(CH2)10COOH Melting pt 44.2 CH3(CH2)12COOH 53.9 16 CH3(CH2)14COOH 63.1 18 CH3(CH2)16COOH 69.6 20 CH3(CH2)18COOH 76.6 14 Structure Fatty acid composition of 3 food fats The higher the proportion of long chain (C16 & C18) saturated fatty acids in butter (than olive oil) increases its melting point, beef fat ­ higher proportion of long chain saturated fatty acids Triacylglycerols (TAGs) Triacylglycerols (TAGs) A glycerol backbone. Hydroxyls at C1 & C2 are esterified to fatty acids. Polar hydroxyls and polar carboxylates bound in the ester linkage TAGs are nonpolar hydrophobic CH2OH H C CH2OH glycerol Formation of an ester: O OH O R'OH + HO­C­R" R'­O­C­R'' + H2O Triacylglycerols (TAGs) Triacylglycerols (TAGs) Neutral and water insoluble fat STORE in plant and animal cells (not in membranes) 3 fatty acids ester linked to glycerol – simple (same fatty acids) – mixed (different fatty acids) H O diacylglycerols, monoacylglycerols HCOC HCOC HC O OC...
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