Food Lipids: Chemistry, Nutrition, and Biotechnology

Figure 5 Kinetics of interesterification via the carbonyl reaction mechanism (S, SS, SSS
and U, UU, UUU: mono-, di-, and trisaturated and unsaturated, respectively). (Adapted from
Ref. 41.)
ylate is now free to attack other carbonyl carbons and exchange esters intra- and
intermolecularly (Fig. 6). Once this carbanion has been created, the same considerations
as for the usual carbonyl carbon chemistry apply.
VII. RANDOM AND DIRECTED INTERESTERIFICATION
A. Random Interesterification
Interesterification reactions performed at temperatures above the melting point of the
highest melting component in a mixture result in complete randomization of fatty
acids among all triacylglycerols according to the laws of probability [28,51].
The energy differences between the various combinations of triacylglycerols
are insignificant and do not appear to lead to fatty acid selectivity [52]. Hence,
random interesterification is entropically driven (randomization of fatty acids among
all possible triacylglycerol positions) until an equilibrium is reached [41].
In ester–ester interchange, the fatty acid distribution is theoretically fully randomized,
meaning that the resulting triacylglycerol structure can be predicted from
the overall fatty composition of the mixture (Table 1) [11].
In Table 1, a, b, and c are the molar concentrations of fatty acids A, B, and C.
AAA, AAB, and ABC are triacylglycerols composed of one, two, or three different
fatty acids, respectively. For AAB, there are three possible isomers, whereas for ABC
there are six. For example, 1-stearoyl-2-oleoyl-3-linoleoyl glycerol results in the
following fully randomized equilibrium mixture:
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.