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United States Department of Agriculture

Agricultural Research Service

Title: Synthesis and Analysis of Some Non-Symmetrical Disaturated/monounsaturated Triacylglycerols for Use in the Study of Food Oil Systems

Authors
item Adlof, Richard
item List, Gary

Submitted to: American Oil Chemists' Society Meeting
Publication Type: Proceedings
Publication Acceptance Date: November 29, 2001
Publication Date: N/A

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 developed methods to prepare the larger amounts of these fats, in >98% purity, required for testing, and also a rapid method for their analysis. A better understanding of fat structure as related to such consumer-oriented concepts as "looks," "spreadability" and "mouth feel," is expected to allow producers to more easily prepare consumer-acceptable products for local and export markets.

Technical Abstract: Symmetrical disaturated triacylglycerols (TAGs) of the SUS configuration, where S = stearic acid (18:0) and U = unsaturated [oleic (O; 9c-18:1), linoleic (L; 9c,12c-18:2), or linolenic (Ln; 9c,12c,15c- 18:3)] fatty acids, are important components providing functionality to interesterified fat blends and structurally modified oils. The presence, however, of non-symmetrical TAGs of SSU configuration can significantly change melting point and solid fat content profiles. To characterize the physical properties of some non-symmetrical disaturated TAGs, our group prepared multi-gram quantities of TAGs having the SSU configuration. The reaction sequence was analogous to the synthesis we developed for preparation of symmetrical SUS TAGs. Stearic acid was transesterified to tristearin, and the TAG (SSS) converted to a mixture of 1,3 and 1,2 diacylglycerols (DAGs). The DAGs were isolated by silica column chromatography and the 1,3-DAGs removed by crystallization from acetone. The enriched 1,2-DAGs (80% 1,2-isomers, 20% 1,3-isomers) were then esterified with the appropriate fatty acid to form the non- symmetrical TAGs. Silver resin or silver nitrate impregnated silica gel chromatography was utilized to fractionate the symmetrical and non- symmetrical TAGs. SSO, SSL and SSLn were prepared in purities of >98% by this procedure. The DG intermediates and TAG final products were analyzed by silver ion HPLC to determine isomeric purities.

Last Modified: 9/20/2014
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