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Hydrogenation of a menhaden oil: II. Formation and evolution of the C 20 dienoic and trienoic fatty acids as a function of the degree of hydrogenation
Author(s) -
Sebedio J L.,
Ackmam R. G.
Publication year - 1983
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02669971
Subject(s) - chemistry , double bond , polyunsaturated fatty acid , methylene , thin layer chromatography , fatty acid , gas chromatography , hexane , organic chemistry , silver nitrate , ozonolysis , cis–trans isomerism , adduct , menhaden , medicinal chemistry , chromatography , fish oil , fishery , fish <actinopterygii> , biology
To complement studies on monoethylenic fatty acids produced from the major polyunsaturated fatty acid (20:5A5,8,11,14,17) during hydrogenation of a menhaden oil of iodine value (IV) 159, the C 10 dienoic and trienoic fatty acid isomers of partially hydro‐genated menhaden oils (PHMO) of IV 131.5, 96.5 and 85.5 were isolated by a combination of preparative gas liquid chromatography (GLC), mercuric adduct fractionation, and silver nitrate thin layer chromatography (AgNO 3 ‐TLC). The 20:2 fatty acid methyl esters of the three PHMO samples were transformed to the corresponding alcohols and ozonized in BF 3 ‐MeOH, followed by GLC analysis of the ozonolysis fragments. During the hydrogenation process, re‐sidual ethylenic bonds in the 20:2 isomers tend to migrate both towards the carboxyl group and towards the methyl end of the molecule. The hydrazine reaction results revealed that the trans ethylenic bonds in the 20:2 and 20:3 isomers were distributed all along the the carbon chain, but the cis ethylenic bonds were more localized in the Δ11,Δ14 and Δ17 positions of the preexisting major menhaden oil component 20:5Δ5,8,11,14,17. Iatroscan analyses on AgNO 3 ‐chromarods revealed that, as a result of the hydrogenation process, almost half of the 20:2 isomers were non‐methylene‐interrupted cis, trans/trans, cis structures.