Food Lipids: Chemistry, Nutrition, and Biotechnology

Figure 5 Lipase-catalyzed glycerolysis reaction between glycerol and a triacylglycerol to
produce monoacylglycerols.
Glycerolysis is the exchange of acyl groups between glycerol and a triacylglycerol
to produce monoacylglycerols, diacylglycerols, and triacylglycerols. There
are several ways to produce monoacylglycerols, which are of great importance in
the food industry as surface-active agents and emulsifiers. Monoacylglycerols can be
produced by ester exchange between triacylglycerols and glycerols, or by free fatty
acids and glycerol, although only the former reaction is termed glycerolysis (Fig. 5).
Glycerolysis is usually performed using nonspecific lipases, giving a wide range of
reaction products (Fig. 6).
High yields in lipase-catalyzed monoacylglycerol synthesis are achieved by
temperature-induced crystallization of newly formed monoacylglycerols from the reaction
mixture. This pushes the equilibrium of the reaction toward increased monoacylglycerol
production. Glycerolysis of lipids containing saturated monoacylglycerols
in the reaction product mixture, since they crystallize at lower temperatures
than unsaturated monoacylglycerols (35). Pseudomonas fluorescens and Chromobacterium
viscosum have been shown to have high glycerolysis activity (36). In glycerolysis
reactions, T c is defined as the critical temperature below which monoacylglycerols
formed by glycerolysis crystallize out of the reaction mixture. Removal of
monoacylglycerols from the reaction mixture pushes the equilibrium of the reaction
toward increased monoacylglycerol production. Vegetable oils with low melting
points due to the presence of long chain unsaturated fatty acids have a much lower
Figure 6 Products of a nonspecific lipase-catalyzed glycerolysis reaction between glycerol
and 1,3-dipalmitoyl-2-oleoyl-glycerol.
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