Time course of the esterification reaction. (A) The time course of esterification degree and acid value. Chromatography performed at various time points (time point 1, 0 hour; time point 2, 1 hour; time point 3, 1.5 hours; time point 4, 2 hours; time point 5, 3 hours; time point 6, 12 hours). (B) Time course of the composition of oil phase during the esterification reaction. Thin layer chromatography analysis of (top to bottom) fatty acid ethyl esters and fatty acids. The reaction system comprised 2.82 g of fatty acid and 580 μl of ethanol added in a three-step manner to 0.33 g of immobilized lipase at 30°C for 5 hours and spun at 190 rpm.