ARS | Publication request: Purification of 1,2-diacylglycerols from vegetable oils: comparison of molecular distillation and liquid CO2 extraction

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 23, 2008
Publication Date: March 20, 2008
Citation: Compton, D.L., Laszlo, J.A., Eller, F.J., Taylor, S.L. 2008. Purification of 1,2-diacylglycerols from vegetable oils: comparison of molecular distillation and liquid CO2 extraction. Industrial Crops and Products. 28(2):113-121.

Interpretive Summary: The goal of our project is to develop new, environmentally benign methods to convert soybean oil produced in the U.S. to new, value-added uses, such as nutritional, industrial and cosmetic ingredients. Soybean oil consists of a glycerol backbone with three attached fatty acid groups. We have developed an environmentally-friendly method to exchange one or two of the fatty acid groups of the soybean oil for another natural plant component, ferulic acid. These patented ferulic acid modified vegetable oils, called SoyScreen(TM), have shown promise as active ingredients in anti-aging and skin-rejuvenating cosmetic formulations. To increase production capacity of SoyScreen(TM) while reducing production costs, we have investigated the process of removing one fatty acid group prior to attaching the ferulic acid. The removal of one fatty acid group from soybean oil results in an oil called 1,2-diacylglycerol (1,2-DAG). The current investigation was to find the best method for purifying 1,2-DAG without forming the 1,3-DAG isomer, which is not a good starting material for SoyScreen(TM) synthesis. Additionally, we determined which purification method was gentlest on the 1,2-DAG by monitoring discoloration and formation of free fatty acid impurities. This information will aid in the scale-up of SoyScreen(TM) production and process optimizations. New, value added uses for vegetable oils, such as SoyScreen(TM), are beneficial to producers by increasing the value of their commodity crops. Determining the best method for purifying 1,2-DAG will be of use to others researching the development of modified vegetable oils for commercial use.

Technical Abstract: High oleic sunflower oil and soybean oil were partially deacylated by enzyme-catalyzed propanolysis using Lipozyme TL IM to form 1,2-diacyl-sn-glycerols (1,2-DAG) in 40% yields. 1,2-DAG are of interest as potential regiospecific intermediates in the synthesis of structured lipids for cosmeceutical and nutraceutical applications. Two purification techniques were examined to determine which was the most efficient at removing the fatty acid propyl ester (FAPE) byproducts, while limiting the spontaneous acyl migration of the 1,2-DAG to 1,3-diacyl-sn-glycerols (1,3-MAG) and adversely affecting the physical properties of the 1,2-DAG and FAPE. Molecular distillation of the partially deacylated vegetable oils was examined at temperatures ranging from 120 to 220°C. Molecular distillation at 220°C removed 77% of the FAPE byproduct, but caused significant acyl migration. Additionally, the acid values and Lovibond color of the partially deacylated vegetable oils were deleteriously affected. The purity of the FAPE, contaminated by co-distillation of di-and monoacylglycerol species as monitored by viscosity values and 1H NMR, was also compromised by the high temperature distillation. Distillations at lower temperatures improved the physical properties of the partially deacylated vegetable oils and the purity of the FAPE, but at the sacrifice of the efficiency of FAPE removal. The mild condition of the liquid CO2 extraction afforded the most efficient removal of the FAPE, 96%, while causing no appreciable acyl migration, and resulted in acid values and Lovibond colors comparable to those obtained at the lowest molecular distillation temperatures studied.