Food Lipids: Chemistry, Nutrition, and Biotechnology

of saturated fatty acids (e.g., myristic, palmitic, stearic) have high melting points and
are generally solid at ambient temperature, whereas triacylglycerols consisting of
unsaturated (monoene, polyene) fatty acids (e.g., oleic, linoleic, linolenic) are usually
liquid at room temperature. Butterfat, for example, contains �70% saturated fatty
acids, whereas many vegetable oils contain almost exclusively unsaturated fatty acids
[4,8].
The fatty acid distribution within naturally occurring triacylglycerols is not random
[9,10]. The taxonomic patterns of vegetable oils consist of triacylglycerols obeying the
1,3 random-2-random distribution, with saturated fatty acids being located almost exclusively
at the 1,3-positions of triacylglycerols [8,11,12]. Conversely, fats from the
animal kingdom (tallow, lard etc.) are quite saturated at the sn-2 position [13].
The industrial applicability of a given fat is limited by its nonrandom distribution,
which imparts a given set of physical and chemical properties. The objective
of modification strategies, such as chemical interesterification, is the creation from
natural fats of triacylglycerol species with new and desirable physical, chemical, and
functional properties [14].
III. A BRIEF HISTORY
Interesterification reactions have been knowingly performed since the mid-1800s.
The first published mention was by Pelouze and Gélis [15]. Duffy [16] performed
an alcoholysis reaction between tristearin and ethanol. Later, Friedel and Crafts [17]
generated an equilibrium interchange between ethyl benzoate and amyl acetate. Glyceride
rearrangement was also reported by Grün [18], Van Loon [19,20], and Barsky
[21]. The first publication demonstrating the chemical interesterification of edible
lipids was presented by Normann [22]. Chemical interesterification has been industrially
viable in the food industry since the 1940s, to improve the spreadability and
baking properties of lard [23,24]. In the 1970s, there was renewed interest in this
process, particularly as a hydrogenation replacement for the manufacture of zerotrans
margarines. Today it plays a key role in the production of low-calorie fat
replacers, such as Proctor and Gamble’s Olestra and Nabisco’s Salatrim or Benefat
[25,26].
IV. THE FOUR FACES OF INTERESTERIFICATION
Excellent reviews in the area of chemical interesterification include Sreenivasan [1],
Rozenaal [11], Kaufmann et al. [27], Going [28], Hustedt [29], and Marangoni and
Rousseau [30].
Interesterification can be divided into four classes of reactions: acidolysis, alcoholysis,
glycerolysis, and transesterification [28,31,32].
Acidolysis involves the reaction of a fatty acid and a triacylglycerol. Reactions
can produce an equilibrium mixture of reactants and products or can be driven to
completion by physically removing one of the reaction products. For example, coconut
oil and stearic acid can be reacted to partially replace the short chain fatty
acids of coconut oil with higher melting stearic acid [28].
Alcoholysis involves the reaction of a triacylglycerol and an alcohol and has
several commercial applications, primarily the production of monoacylglycerols and
diacylglycerols. Alcoholysis must be avoided in the interesterification of food lipids,
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.