Double bond analysis of dienoic fatty acids in mixtures

Abstract

Mixtures of dienoic fatty acids such as occur in edible hydrogenated fat products cannot be analyzed by current methodology. A method of ozonization, reduction to alcohol fragments by sodium borohydride, gas chromatographic analysis for alcohol, alcohol ester, and internal dialcohol fragments, and computer resolution of a matrix of linear simultaneous equations, is described that gives the analysis of the diene isomers.

Identification of novel octadecadienoic fatty acids in the seaweedCladophora rupestris through oxidative ozonolysis of the alcohols prepared from the acids

“…Prior reduction of carboxyl groups to alcohols is equally satisfactory except for the absence of the C 3 fragment. Low recoveries of C 3 fragment are also reported for the procedure in which the carboxyl ester is retained and the ozonides are reduced to alcohols (10).…”

“…The All,A14-octadecadienoic acid can accumulate in animals (24,25). Reduction of fatty alcohol ozonides to aldehydes and analysis of half-aldehyde, halfsilyl esters is feasible (26), as well as the reduction to alcohols already mentioned (10). The oxidative ozonolysis route which we have evaluated is flexible and convenient and avoids the toxic-reducing agents sometimes used to achieve similar mixed function products (27).…”

Volatile compounds from the triacylglycerol ofcis,cis 9,15‐linoleic acid

“…Lowering the Ln content of SBO by hydrogenation is the principal method used to stabilize SBO (4,5). However, there are isomeric dienes or isolinoleates, formed during hydrogenation of Ln (9)(10)(11)(12)(13) that are considered to be precursors of an undesirable odor (4,5,14-18) described as a "hydrogenation" or "hardened" odor. Keppler et aL (15,16) synthesized and oxidized three of the isomeric dienes with double bonds at carbons 7,15, 8,15 and 9,15 formed by catalytic hydrogenation of methyl linolenat~ They concluded that 6-nonenal caused the hydrogenated odor.…”

Identification of trans-diene isomers in hydrogenated soybean oil by gas chromatography, silver nitrate thin-layer chromatography, and carbon-13 NMR spectroscopy

“…Capillary GC has been used for several years to determine specific fatty acid isomers in foods (Slover and Lanza, 1979; Slover et al, 1985). The determination of the bond positions of fatty acid isomers involves chemical reaction at the point of unsaturation followed by additional chromatography (Johnston et al, 1978;Dutton et al, 1988).trans,trans-18:2 dienes include conjugated, methyleneinterrupted (MI), and other positional isomers of linoleic acid. The irans-9,trans-12-octadecadienoic acid (trans-9,trans-l2-l8:2) isomer has been shown to interfere with linoleic acid metabolism (Anderson et al, 1975;Privett et al, 1977;Hwang and Kinsella, 1979).…”

“…Capillary GC has been used for several years to determine specific fatty acid isomers in foods (Slover and Lanza, 1979; Slover et al, 1985). The determination of the bond positions of fatty acid isomers involves chemical reaction at the point of unsaturation followed by additional chromatography (Johnston et al, 1978;Dutton et al, 1988).…”