Identification and Quantitation of Reaction Intermediates and Residuals in Lipase-Catalyzed Transesterified Oils by HPLC

A high-performance liquid chromatography (HPLC) unit equipped with size exclusion column and a refractive index detector was used for simultaneous monitoring, identification, and quantitation of the reaction components from lipase-catalyzed transesterification of three oils. The procedure simultaneously separated and detected the unreacted triacylglycerols (TAG), diacyl-, and monoacyl-glycerol (DAG and MAG) co-products, residual alcohol as well as free fatty acid (FFA) based on retention times. The chromatograms showed well separated and resolved peaks. The elution of the components from the transesterification reaction in increasing order was: TAG < DAG < FFA < MAG. Generally, higher alcohol ratios decreased the conversion of TAG in all the oils studied with between 14% and 94% of TAG remaining at all the treatment combinations. Higher amount of salmon skin oil (SSO) TAG was generally converted to DAG than Rothsay composite (RC) and olive oil (OO) TAG. Relatively higher amount of OO DAG was converted to MAG than SSO and RC with only 5-14% DAG remaining in OO. RC and OO generally accumulated less MAG, and this was reflected as lower MAG levels in RC (< 6%) and OO (< 14%) compared with SSO (< 27%). For the various treatment combinations and the three oils used in this study, the least amount of FFA was recorded in transesterified OO with a maximum of approximately 4%. This HPLC method can be used as a simple and fast technique to analyze the reaction components and products of transesterification reactions without the need for additional derivatization steps.