Directed interesterification, using

Directed interesterification, using sodium methoxide or
ethoxide or sodium/potassium alloy as a catalyst, can be
used to turn cottonseed oil into solid fat at room temperature (Young, 1980). Wiedermann and co-workers
(Wiedermann, Weiss, Jacobson, & Mattil, 1961) worked
on the chemical IE of lard, which has a tendency to
formbetacrystals. With chemical IE, modified lard with
beta-primecrystal form was obtained. Wiedermann and
coworkers (Wiedermann et al., 1961) found that final
product characteristic depended heavily on the time and
temperature relationships used in the treatment.
Cocoa butter TAGs are high in stearic acid, which
have a sharp melting profile at 37

C(Fig. 3). Cocoa
butter fat melts in the mouth to give a cooling sensation
and a smoother mouth-appeal effect. Palm oil TAGs are
high in palmitic acid and have a melting point of 23

C.
Therefore, palm oil is liquid at room temperature.
Conversion of some common lauric fats (such as palm
oil) into cocoa-butter fat substitute can be achieved by
interesterification. A process is reported in which chemical IE is employed to convert lauric fats into confectioners’ fats (Brown et al., 1970; Gillies, 1974). The
process involves the IE of lauric fats with alkyl fatty
acid esters (fatty acids having 12, 14, and 16 carbon
atoms) at temperature between 80

C and 140

C. The
following equation illustrates the process:
Lauric fatþAlkyl estersðÞ !New TAG
þNew alkyl esters
The IE is carried out using an alkali metal alkoxide as
catalyst, such as sodium methylate.Gleason (1960)also
reported a process for manufacture of an improved cake
shortening utilizing IE of lard with itaconic acid (propylenedicarboxylic acid). Cakes baked using such
shortening have a fine uniform texture with an increase
in crumb volume.
Many studies have been done on the chemical IE and
enzymatic IE of the TAGs that affect the hardness and
spreadability of fat systems (Foglia, Petruso, & Feairheller, 1993; Forssell, Kervinen, Lappi, Linko, Suortti,
& Poutanen, 1992; Lee & Akoh, 1997; Marangoni &
Rousseau, 1998; Moussata & Akoh, 1998; Rousseau,
1996; Rousseau, Forestiere, Hill, & Marangoni, 1996;
Rousseau & Marangoni, 1998; Seriburi & Akoh, 1998).
TAGs containing mixtures of short, medium, and
long chain fatty acids attached to the glycerol backbone
for specific functionality are called structured lipids (SL)
(Haumann, 1997). Their first food use has been in the
confectionary industry. Enzymatic IE, because of substrate specificity, is widely used for producing SL. Several factors have prompted the increasing interest in
structured lipids. SL offer metabolic advantages in
chronic health conditions such as impaired gastrointestinal functions, liver disease or congestive heart
failure and infants with food allergies and digestive
problems. SL has also been used as a valuable
component in designing infant formula, beverages,
snack bars, confectionary products, and supplements
for non-clinical uses, such as for maintaining health or
bodybuilding (Haumann, 1997). Softly (Softly, Huang,
Finley, Petershein, Yarger, Chrysam et al., 1994)
worked on IE of hydrogenated vegetable oils to form
Salatrim. Salatrim is a family of structured TAGs containing at least one short chain fatty acid and at least
one long chain fatty acid (e.g. stearate) on each glycerol
molecule. Because of its chemical design, Salatrim provides five calories per gram, versus the nine calories per
gram of typical fats (Haumann, 1997). Salatrim is prepared by IE of hydrogenated vegetable oils, such as soy
or canola, with triacetin and/or tripropionin and/or tributyrin.Lee and Akoh (1997)used two immobilized
lipases (IM 60 fromRhizomucor mieheiand SP 435 from
Candida antarctica) to synthesize a number of SL.
Native lard consists of grainy crystals with large
spherulitic aggregates. Chemical IE of native lard results
in fine crystals and reduced fat spherulite aggregates
(Rousseau, Hill et al., 1996). IE of lard–canola oil
(LCO) mixtures leads to reduced spherulite and lowdensity aggregate formation. This has a direct effect on
the hardness index (HI) of these fat blends. It was
reported by the Marangoni group (Marangoni & Rousseau, 1998) that the hardness index of lard and LCO
increased after IE. Marangoni and Rousseau (1998)
reported that the G
0 (Elastic modulus) of all LCO
blends increased as a result of IE; while G
0
of palm oil
and soybean oil (POSBO) blends was not affected by IE.
A lot of work has been done on the enzymatic IE of
palm oil blends (Kurashige, Matsuzaki, & Takahashi,
1993). This results in improvement in the handling
properties of the palm oil at low temperatures. Palm oil
was blended with either canola or soybean oil and these
blended oils were then modified by enzymatic selective
IE utilizing an immobilized lipase that had 1, 3- positional specificity (Kurashige et al., 1993). They reported
that enzymatic IE lowered the SFC of the treated blend.
No such effect was reported when a similar blend was
subjected to chemical IE. Therefore, it was concluded
that enzymatic IE is a useful treatment to improve the
fluidity of blends of palm and canola oil.
By employing IE, the manufacturing industry may be
able to achieve freedom from hydrogenation odor and
trans-fatty acids in the final product. Lard and high
oleic sunflower oil (Trisun) were interesterified at 55

C
for 24h with SP 435 lipase (obtained from Candida
antartica) to produce plastic fats (Seriburi & Akoh,
1998).Seriburi and Akoh (1998)reported that 60:40 (w/
w) ratio of lard to Trisun had the widest plastic range
(from 3 to 26

C). Their study demonstrated that enzymatic interesterification of saturated fat (lard) with an
unsaturated vegetable oil (Trisun) can be used as an