ARS | Publication request: Synthesis and physical properties of symmetrical and non-symmetrical triacylglycerols containing two palmitic fatty acids

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2007
Publication Date: January 11, 2008
Citation: Adlof, R.O., List, G.R. 2008. Synthesis and physical properties of symmetrical and non-symmetrical triacylglycerols containing two palmitic fatty acids. Journal of the American Oil Chemists' Society. 85:99-104.

Interpretive Summary: The sensory property of "graininess" found in margarines and spreads is primarily due to the structure of the fats in them, specifically the fats containing palmitic and oleic acids. Over the past 25 years, a number of trans-related economic, health and consumer-driven factors have resulted in such alternatives as blending of oils or interesterification (chemical mixing of the fats), alternatives which can also effect the mouth feel of the final product(s). These methods, however, change the structure and interactions of the oil fats and, when used in margarines/spreads, the physical properties/mouth feel 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 seven palmitic acid-containing triglycerides, highly pure and in multi-gram quantities, and studied such physical properties as melting ranges, crystallization, and the amounts of crystals present at different temperatures. This data is expected to provide a better understanding how fat structures relate to such sensory properties as "mouth feel", and to allow producers to prepare more consumer-acceptable products for local and export markets.

Technical Abstract: Both the amounts of and specific structures of the triacylglycerols (TAG) present in the oil phase of a margarine or spread are considered responsible for such properties as its spreadability, resistance to water/oil loss, and melting characteristics. A series of symmetrical and non-symmetrical TAG isomers containing palmitic (P; 16:0) acid and either oleic (O; 9c-18:1), elaidic (E; 9t-18:1), linoleic (L; 9c,12c-18:2) or linolenic (Ln; 9c,12c,15c-18:3) fatty acids was synthesized as part of a study relating TAG structure with such characteristics as melting range, drop points, and other crystalline properties, 1,3-dipalmitoylglycrol (1,3P-DAG) was prepared in multigram quantities by partial glycerolysis (glycerol/p-toluenesulfonic acid) of tripalmitin (PPP), isolated by silica gel chromatography, with final purification (structural purity >98%) by crystallization from acetone. The 1,3P-DAG was esterified with either O, L, Ln to prepare the symmetrical TAG isomers POP, PLP and PLnP, and the 1(3)-MAG precursors O- E-, L-, and Ln-MAG with P acid to prepare the non-symmetrical TAG isomers OPP, EPP, LPP and LnPP, respectively. The TAG isomers were synthesized in multi-gram (3-5g) quantities (80-90% yields), >95% chemical and 97-99% structural purities, and their drop point, solid fat content and melting point values determined.