Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 13, 2007
Publication Date: June 19, 2007
Citation: Adlof, R.O., List, G.R. 2007. Synthesis and characterization of EOE and EEO, triacylglycerols containing elaidic and oleic fatty acids. Journal of the American Oil Chemists' Society. 84:427-431. Interpretive Summary: Spreadability, melting at body temperature and similar properties of margarines and spreads are primarily due to the structure of the fats in them. Hydrogenation of vegetable oils has traditionally been used to raise the melting point of margarines and spreads, but this method also produces trans fats. Over the past 25 years, a number of trans-related economic, health and consumer-driven factors have resulted in such alternatives to hydrogenation as interesterification and/or blending of oils. These methods, however, change the structure and interactions of the oil fats and, when used in margarines/spreads, the physical properties of those products. Until now, the lack of pure samples of these fats has hindered research to measure their physical properties and interactions. Our group synthesized two isomers (EOE and EEO, where E is elaidic acid (a trans fatty acid) and O is oleic acid (a cis fatty acid), highly pure and in multi-gram quantities, and studied how they melted. They also discovered that the trans bond acts more like a saturated fat. A better understanding of fat structure as related to such consumer-oriented concepts as "looks," "spreadability" and "mouthfeel," is expected to allow producers to more-easily prepare consumer-acceptable products for local and export markets.
Technical Abstract: Symmetrical and non-symmetrical triacylglycerols (TAG) containing oleic (O; 9c-18:1) and elaidic (E; 9t-18:1) acids were required as part of a study relating the physical characteristics and functionality of trans-containing TAG with the mouth feel, taste characteristics and related characteristics desired by consumers in frying oils and pastries. To replace the trans isomers in frying oils - a significant part of frying oils prepared by partial hydrogenation of vegetable oils - without loss of the sensory properties desired by consumers, required the initiation of a study relating the structure trans-containing TAG with such characteristics as melting range, drop points, and other crystalline properties. The thermodynamically more-stable 1(3)-monoacylglycerol (MAG) and 1,3-diacylglycerol (DAG) precursors were utilized to prepare highly pure samples of the TAG structural isomers EEO and EOE, respectively. Elaidic acid was esterified to trielaidin (EEE), and the EEE partially converted (glycerol/p-toluenesulfonic acid) to a mixture containing ca. 40% DAG (the 1,3- and 1,2-isomers). The DAG fraction was separated by silica gel chromatography, the 1,3EE-DAG isomer isolated (structural purity >98%) by crystallization from acetone, and the DAG esterified with oleic acid to yield EOE. The 1(3)E-MAG (purchased commercially) was esterified to prepare OEE. Both syntheses yielded multi-gram quantities of EOE and EEO, in 80-85% yield, and with structural purities >99%. By careful selection of the thermodynamically more-stable MAG or DAG precursors, multi-gram quantities of the symmetrical EOE and non-symmetrical EEO isomers could be readily synthesized and their drop point, melting point values determined.