Enzyme-assisted process for DAG synthesis in edible oils

Abstract

This study deals with the enzymatic synthesis of diacylglycerols in rapeseed oil by the esterification of free fatty acids and monoacylglycerols. As enzymatic reactions are influenced by many factors, a statistical design of experiments was conducted to investigate the enrichment of diacylglycerols, systematically. Simultaneously, the investigated method contributes to the refining process, as the amount of free fatty acids could be reduced significantly from 2% to 0.3%. Utilizing an immobilized lipase from Rhizomucormiehei, a maximum diacylglycerol content of 23% was obtained, after optimization. By washing with iso-propanol and hexane the immobilised lipase could be reused in 14 consecutive batches. In addition, glycerol was proven to be an alternative to MAG as acyl-group acceptor. However, the diacylglycerol enrichment was not accomplished in the same yields as for monoacylglycerols. Summarizing, the present study revealed the potential of an enzymatic diacylglycerol synthesis in edible oils as a suitable alternative to conventional processes also enabling the reduction of free fatty acids in crude oils.

Keywords: Diacylglycerols; Enzymatic esterification; Lipase; Oil refining; d-Optimal design.