Production of diacylglycerol-enriched oil by glycerolysis of soybean oil using a bubble column reactor in a solvent-free system

Abstract

In this study, diacylglycerol-enriched soybean oil (DESO) was synthesized through Lipozyme 435-catalyzed glycerolysis of soybean oil (SO) in a solvent-free system using a modified bubble column reactor. The effects of enzyme load, mole ratio of glycerol to soybean oil, reaction temperature, gas flow and reaction time on DAG production were investigated. The selected conditions were established as being enzyme load of 4 wt% (mass of substrates), glycerol/soybean oil mole ratio of 20:1, reaction temperature of 80℃, gas flow of 10.6 cm/min, and a reaction time of 2.5 h, obtaining the DAG content of 49.4±0.5 wt%. The reusability of Lipozyme 435 was evaluated by monitoring the contents of DAG, monoacylglycerol (MAG) and triacylglycerol (TAG) in 10 consecutive runs. After purified by one-step molecular distillation, the DAG content of 63.5±0.3 wt% was achieved in DESO. The mole ratio of 1, 3-DAG to 1, 2-DAG was 2:1 and the fatty acid composition had no significant difference from that of soybean oil. However, the thermal properties of DESO and SO had considerable differences. Polymorphic form of DESO were mainly the β form and minor amounts of the β ′ form. Granular aggregation and round-shaped crystals were detected in DESO.