Food Lipids: Chemistry, Nutrition, and Biotechnology

Figure 5 Schematic representations of (a) triclinic parallel, (b) orthorhombic perpendicular,
and (c) hexagonal subcells. [Reproduced with permission from The Physicial Chemistry of
Lipids (D. M. Small, ed.), Plenum Press, New York, 1996.]
strated [21]. This trilayer structure occurs when the sn-2 position of the triacylglycerol
contains a fatty acid ester that is either cis-unsaturated or of a chain length
different by four or more carbons from those on the sn-1 and sn-2 positions. Also,
it was predicted that the trilayer structure would arise if the sn-2 position contained
a saturated acyl ester with unsaturated moieties occupying the sn-1 and sn-3 positions
[22]. Figure 7 depicts these varied layered structures.
When unsaturation results in a trans configuration around the carbon–carbon
double bond, the crystal structure exhibits the normal bilayer appearance. The trans
carbon–carbon double bond results in a linear chain configuration, unlike the bent
chain configuration observed in the cis-unsaturated molecule. In fact, trielaidin
(trans-C18:1) has the same polymorphic configuration as tristearin (C18:0) [13],
although the phase transition temperatures of trielaidin are 30�C below that of tri-
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.