Enzymatic preparation and facile purification of medium-chain, and medium- and long-chain fatty acid diacylglycerols

High purity diacylglycerols (DAG) rich in medium-chain fatty acid diacylglycerols (MCD) and medium- and long-chain fatty acid diacylglycerols (MLCD) were prepared via the enzymatic esterification of monoacylglycerols (MAG) with caprylic acid followed by molecular distillation (MD), solvent fraction and low-temperature centrifugation. The content of DAG in the crude product was 44.8 ± 0.1%, under the selected esterification conditions, which were MAGs/caprylic acid mole ratio of 1:3, reaction temperature of 65 °C, reaction time of 30 min and enzyme load of 5 wt%. Subsequently, the one-step MD and solvent fraction in methanol/ethanol increased the DAG content to 61.3 ± 0.8%. Eventually, the product containing 86.6 ± 0.6% of DAG with 39.3 ± 1.3% of MCD and 47.3 ± 0.6% of MLCD was obtained by the methanol crystallization at 0 °C with a water content of 9 wt% and a 1:3 ratio of glycerides/methanol (v/v) followed by the centrifugation separation at 0 °C.