Food Lipids: Chemistry, Nutrition, and Biotechnology

esterification of butterfat at 40�C produced an increase in the solid fat content below
15�C and a decrease in the solid fat content above 15�C (Fig. 2).
In another study, lipase-catalyzed transesterification of butter increased the relative
proportion of C36 and C40 to C48 saturated triacylglycerols, as well as triunsaturated
triacylglycerols (15). The resulting product had a 114% greater solid fat
content at 20�C than the starting butter, with the solid fat content increasing from
22% to 46%. In general, lipase-catalyzed transesterification produces fat with a
slightly lower solid fat content compared with chemical interesterification. This is
attributed to contamination by monoacylglycerols, diacylglycerols, and free fatty
acids, which are produced in the early stages of transesterification (8,13). Kalo et al.
(13) compared lipase-catalyzed transesterification to chemical interesterification of
butter. He found that the solid fat content of butter increased from 41.2% to 42.2%
at 20�C using lipase-catalyzed transesterification, whereas chemical interesterification
produced butter with a solid fat content of 57.8% at 20�C. Transesterification has
also been used to improve the textural properties of tallow and rapeseed oil mixtures
as well as in the development of cocoa butter equivalents (16,17). Forsell et al. (18)
found that transesterification of a tallow and rapeseed oil blend decreased the solid
fat content and melting point. The extent of melting point reduction was dependent
on the mass fraction of the two lipid components. With a mass fraction of tallow to
rapeseed oil of 0.8, the melting point was reduced by 6�C, whereas a mass fraction
of 0.5 produced a 12�C decrease in melting point. A decrease in the solid fat content
has also been observed upon transesterification between palm oil and canola oil, due
to a decrease in the level of triunsaturated triacylglycerols (19).
The attractiveness of cocoa butter to the chocolate and confectionary industry
is based on the limited diversity of triacylglycerols in this fat, which gives it a unique,
narrow melting range of 29–43�C. Chocolate can contain 30% cocoa butter, meaning
that this fat determines the crystallization and melting properties of the chocolate.
At 26�C, cocoa butter is hard and brittle, but when eaten it melts completely in the
mouth with a smooth, cool sensation. The major triacylglycerols in cocoa butter
Figure 2 Solid fat content versus temperature profiles for native and enzymatically interesterified
butterfat in the absence of solvent using lipase from Pseudomonas fluorescens.
Nontransesterified butterfat, (�); transesterified butterfat, (●). (From Ref. 13.)
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.