Food Lipids: Chemistry, Nutrition, and Biotechnology

and unsaturation of the esterified fats, as with normal lipids [98]. It can be exchanged
for fats in products such as ice cream, margarine, cheese, and baked goods, and it
can be blended with vegetable oil.
XI. OXIDATIVE STABILITY
The many advantages of chemical interesterification have been discussed in detail.
Many authors have shown, however, that chemical interesterification can negatively
influence the oxidative stability of fats and oils. Lau et al. [99] demonstrated that
randomized corn oil oxidized three to four times faster than native corn oil. They
concluded that the triacylglycerol structure probably was implicated, but the mechanisms
remained unclear. Lo and Handel [61] showed that interesterified blends of
soybean oil and beef tallow were more unstable following interesterification.
Gavriilidou and Boskou [100] examined the effects of chemical interesterification
on the autoxidative stability of an 80% olive oil–20% tristearin blend. The
randomized fats were less stable than the native mixtures (Fig. 17). Addition of BHT
stabilized the fats, resulting in a peroxide value similar to that for commercially
processed hydrogenated vegetable oil used in margarine.
An important contribution to the literature was made by Zalewski and Gaddis
[101], who investigated the effect of transesterification of lard on stability, antioxidant
efficiency, and rancidity development. Interesterification of lard did not affect
its resistance to oxidation, but changes in oxidative stability due to tocopherol decomposition
and the formation of reducing substances were noted. In the absence of
antioxidants, both interesterified and native lard had similar peroxide values. Furthermore,
because of the position of unsaturated fatty acids at 1,3-positions or randomization
toward the 2-position in pork fat triacylglycerols, there was no appreciable
effect on initiation of oxidation and autoxidation rates.
Figure 17 Change in peroxide value of an 80%:20% olive oil–tristearin blend before and
after interesterification: �, native blend; ●, randomized blend; ▫, hydrogenated blend; �, randomized
blend � BHT. (Adapted from Ref. 100.)
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.