|Lee, Ki-Teak - FORMER ARS EMPLOYEE|
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 20, 2002
Publication Date: N/A
Interpretive Summary: Very popular among consumers are low-fat containing foods because of their perceived health benefits. To manufacture low-calorie foods producers often remove the fat or use fat substitutes in place of traditional fats. Such low-fat products, however, do not have the same textural and flavor characteristics or nutritional value as their full-fat counterparts. Most natural fats and oils contain long-chain fatty acids, which accounts for their high calorie content. On the other hand, natural medium- and short- chain fatty acids are lower in calorie content. Accordingly, one way to address the problems associated with fat substitutes is to use reduced- calorie structured lipids that contain a mixture of medium-chain and long- chain fatty acids. Currently a chemical process, which limits their usefulness as fat substitutes, is used to produce this class of fat substitutes. Ways are needed, therefore, to tailor-make these low-calorie structured lipids in more directed and wholesome ways to expand their usage. In this paper we describe how nature's catalysts, enzymes, can be used to design and prepare low-calorie structured lipids in a defined manner that takes optimal advantage of the short-chain and long-chain fatty acids used in making them. With this technology, food processors can lower the fat calorie content of food products by changing the structure of natural fats and oils used in foods without loss of their flavor and textural properties.
Technical Abstract: Mixed medium and long-chain triacylglycerol (MLCT) structured lipids (SL) intended as low-calorie triacylglycerol products were synthesized by either lipase-catalyzed or chemical syntheses. In the lipase-catalyzed reactions, stearic acid was selectively incorporated at the 1 and 3 positions of tributyrin using a 1,3-positionally selective lipase (Rhizomucor meihei). At 10% of lipase (w/w of substrates), the acidolysis reaction reached equilibrium within 3 to 6 h at 70 C depending on the substrate mole ratio used. After purification and isolation by column chromatography, the MLCT products were analyzed by high performance liquid chromatography (HPLC), which showed the MLCT were composed of two types of triacylglycerols (TAG). One MLCT species contained two butyryl and one stearoyl acyl residues (MML- TAG, 45% to 85%) and the second MLCT contained one butyryl and two stearoyl acyl residues (LML-TAG, 14% to 55%) the ratio of which depended on the molar ratio of substrates used. For the chemical reaction, tributyrin was transesterified with methyl stearate using sodium methoxide as catalyst (0.25% w/w of substrates). HPLC analysis of the MLCT product showed that > 98% of the TAG species were either MML-TAG or MLL-TAG species, depending upon the mole ratio of reactants used in transesterification. The purified MLCT products were further analyzed by differential scanning calorimetry to compare their crystallization patterns.