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Production of conjugated linoleic acid isomers by dehydration and isomerization of castor bean oil

Villeneuve P., Lago R.C.A., Barouh N., Baréa B., Piombo G., Dupré J.Y., Le Guillou A., Pina M.. 2005. Journal of the American Oil Chemists' Society, 82 (4) : p. 261-269.

DOI: 10.1007/s11746-005-1065-6

The possibility of combining dehydration and isomerization of castor bean oil as a means to obtain CLA as TAG forms was studied. First, dehydration was carried out using various catalysts and reaction parameters. Best results were obtained using phosphoric acid (0.1% w/w) at 280°C for 5 h. Under such conditions, satisfactory proportions of CLA were obtained (54% of total FA) with a majority of 9-cis, 11-trans isomer (61% of total CLA). Other catalysts such as bisulfate-bisulfite, sulfuric acid, tungstic and phosphotungstic acids, or resins and zeolites were also tested. With the exception of resins and zeolites, these catalysts also led to CLA production but in limited amounts in comparison with phosphoric acid. In a second step, an isomerization reaction was carried out to transform the residual nonconjugated linoleic acid also produced during de-hydration into CLA. Using Wilkinson catalyst IRhCI(PPh3)3] in ethanol solvent, dehydrated castor bean oil was isomerized in high yields (>98%), allowing a complete disappearance of non-conjugated linoleic acids. The resulting dehydrated/isomerized oil contained more than 87% CLA with the 9-cis, 11-trans isomer being predominant (40% of CLA fraction). Finally, urea fractionation was also applied on dehydrated/isomerized castor bean oil FA to obtain FFA products containing about 93% CLA.

Mots-clés : ricinus communis; huile de ricin; séchage; isomérisation; catalyseur; acide linoléique; acide gras libre; acide phosphorique

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