Food Lipids: Chemistry, Nutrition, and Biotechnology

Table 1 Theoretical Triacylglycerol Compositions After Complete
Interesterification of n Fatty Acids (A, B, C, D, . . .) with Molar
Fractions a, b, c, d,...
Type Quantity Proportion
Monoacid (AAA, BBB, . . .) n a 3 , b 3 ,...
Diacid (AAB, AAC, . . .) n(n � 1) 3a 2 b,3a 2 c,...
Triacid (ABC, DEF, . . .)
n(n � 1)(n � 2)
6
6abc, 6def,...
Total
n(n � 1)(n � 2)
6
Source: Adapted from Ref. 11.
SSS, 3.7%
OOO, 3.7%
LLL, 3.7%
SSO, 11.1%
SSL, 11.1%
SOO, 11.1%
SLL, 11.1%
OOL, 11.1%
OLL, 11.1%
SOL, 22.2%
Gavriilidou and Boskou [53] found that a random distribution was obtained
after chemical interesterification of olive oil–tristearin blends. They observed that
trisaturate and triunsaturate proportions decreased markedly, whereas proportions of
SSU and SUU increased (Table 2).
Not all workers agree that chemical interesterification is a purely random process.
Kuksis et al. [54] found that the triacylglycerol composition of rearranged butter
and coconut oils approached random distribution but deviated from true random
distribution, even when experimental error was accounted for. This result was attributed
to differences in the reactivity of the fatty acids and to possibly different esterification
rates of the inner and outer hydroxyl sites on the glycerol backbone.
B. Batch Interesterification
Random interesterification can be accomplished in either batch or continuous mode.
A typical batch reactor (Fig. 7) consists of a reaction vessel fitted with an agitator,
heating/cooling coils, nitrogen sparger, and vacuum pump [3,14,28]. In a batch process,
the raw lipid is heated to 120–150�C under vacuum in the reaction vessel to
remove any trace of moisture [1,29]. As mentioned, moisture and peroxides deactivate
the catalyst. Following the drying step, the mixture is cooled to 70–100�C.
Catalyst is sucked into the reaction vessel and disperses to form a white slurry. The
reaction is allowed to proceed for 30–60 minutes. When completion has been confirmed
by analysis, the catalyst is neutralized in the reaction vessel. Processing losses
can be minimized by using as little catalyst as possible and neutralizing with phosphoric
acid or CO2 prior to addition of water.
C. Continuous Interesterification
During continuous random interesterification, the fat is flash-dried and catalyst is
continuously added. The fat then passes through elongated reactor coils with res-
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