Enzymatic re-esterification of lower glycerides from soybean oil with conjugated linoleic acid (CLA)

Abstract

New structured lipids essentially free of saturated fatty acids and rich in essential fatty acids and CLA were prepared from soybean oil using a selective enzymatic procedure of synthesis. Saturated fatty acids originally present in the oil were selectively removed in a selective alcoholysis step. Enzymatic re-esterification with conjugated linoleic acid (CLA) of lower glycerides (di- and monoglycerides) obtained from soybean oil was studied using several commercially available lipases. Higher maximum reaction conversions were obtained with the free acid form of CLA than with the corresponding ethyl ester. Reactions with Novozym 435 were fastest, producing 84% diacylglycerols (DAG) in 0.5 h of reaction at 60 degrees C. For Lipozyme RM IM the maximum yields of triacylglycerols (TAG) were achieved at 60 degrees C (43% in 4.5 h) and 25 degrees C (43% TAG in 7 h). The dominant species in DAG-rich products were LnL and LL. TAG-rich products obtained with Lipozyme RM IM had LLL and LLO/OLO as their predominant TAG. Quantitative conversions to DAG were obtained in 3-4.5 h with 10% (w/w) Lipase G 50 at 60 degrees C and a molar ratio of free CLA to hydroxyl groups of 5:1.