Comparison of linoleic and conjugated linoleic acids in enzymatic acidolysis of tristearin

The acyl incorporation and migration of linoleic and conjugated linoleic acids in enzymatic acidolysis were compared in a solvent-free system. Two systems were used in the Lipozyme RM IM-catalyzed acidolysis at 60C temperature and 5% by weight enzyme load (based on substrates). One included tristearin (SSS) and linoleic (L) or conjugated linoleic (cL) acids (1:6, mol/mol).

The other was between tristearin and the mixture of linoleic and conjugated linoleic acids (1:3:3, mol/mol/mol). Acyl incorporation and migration together with triacylglycerol composition of the products were monitored with gas chromatography, pancreatic lipase hydrolysis, and high performance liquid chromatography.

Both acyl incorporation and migration of linoleic acid were faster than those of conjugated linoleic acid. At 5 h reaction, there were 13.0% LLL, 46.5% LSL, 27.7% LSS, and 5.6% SSS in the product for a system between tristearin and linoleic acid; whereas there were 2.4% cLcLcL, 10.4% cLScL, 50.9% cLSS, and 36.2% SSS in the product for a system between tristearin and conjugated linoleic acid.

The results suggest that linoleic acid was more reactive than conjugated linoleic acid in the enzymatic acidolysis probably because of the rigid structure of the latter.