PRESSURIZED LIQUID EXTRACTION OF POLAR AND NONPOLAR LIPIDS IN CORN AND OATS WITH HEXANE, METHYLENE CHLORIDE, ISOPROPANOL, AND ETHANOL

Authors: Moreau, Robert; Powell, Michael; SINGH, VIJAY - UNIV. OF ILLINOIS, URBANA

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2003
Publication Date: 10/10/2003
Citation: Moreau, R.A., Powell, M.J., Singh, V. Pressurized liquid extraction of polar and nonpolar lipids in corn and oats with hexane, methylene chloride, isopropanol, and ethanol. Journal of American Oil Chemists' Society 80:1063-1067.2003.

Interpretive Summary: Vegetable oils are obtained by either crushing seeds or extracting them with solvents such as hexane. Although hexane has been shown to efficiently extract all of the major lipid component in seeds (triacylglycerols), it's efficiency at extracting some of the other valuable components (phytosterols, tocopherols, and glycolipids) has not been rigorously evaluated. In the current study we employed a new instrument, an Accelerated Solvent Extractor, to compare the main chemical components extracted from seeds of corn and oats, with four solvents (hexane, methylene chloride, isopropanol, and ethanol) at two temperatures (40oC and 100oC). The results indicated that for corn, phytosterols were probably the most valuable components and they were optimally extracted with either hexane or methylene chloride at 100oC. However, for oats, there is growing evidence that digalactosyldiacylglycerol is a valuable component, and the highest levels of this component were obtained in the 100oC ethanol extracts. This study demonstrates, for the first time, that optimal conditions for extraction of health-promoting vegetable oils primarily depends on the types of unique phytonutrients components in each type of seed.

Technical Abstract: Samples of freshly ground corn kernels and freshly ground rolled oats were extracted via pressurized liquid extraction (accelerated solvent extraction) using four different organic solvents (hexane, dichloromethane, isopropanol, and ethanol), at two temperatures (40 and 100 o C). Lipid yields from ground corn varied from 2.9 to 5.9 wt%, and from ground oats varied from 5.5 to 6.7 wt%. With ground corn, more lipid was extracted as solvent polarity was increased, and for each individual solvent, more lipid was extracted at 100oC, than at 40oC. With ground oats the same temperature effect was observed, but the solvent polarity effect was more complex. In general, for both corn and oats, methylene chloride extracted the highest levels of each of the nonpolar lipid classes. In general, for both corn and oats, increasing solvent polarity resulted in increasing yields of polar lipids, and for each solvent, more of each lipid class was extracted at 100oC, than at 40oC. Among the lipids in the corn extracts the phytosterols may be the most valuable, and total phytosterols ranged from a low of about 0.6 wt% in the hot ethanol extracts to a high of about 2.1 wt% in the hot hexane and methylene chloride extracts. Total phytosterols in all oat extracts were about 0.1 wt%. Digalactosyldiacylglycerol was the most abundant polar lipid in the oat extracts, and its levels ranged from 1.6 wt% in the cold hexane extracts to a high of 4.3 wt% in the hot ethanol extracts.