KINETIC MODELING OF INTERESTERIFICATION REACTIONS CATALYZED BY IMMOBILIZED LIPASE

Kinetic data for lipase-catalyzed interesterification reactions betwee n free fatty acids and triglycerides were collected and the dynamics o f the interesterification reactions were successfully modeled using tw o rate expressions requiring a total of five adjustable parameters. On e rate expression describes the disappearance of the free fatty acid ( octanoic or linolenic acid), and the second describes the rate of rele ase of fatty acid residues from the triglycerides (olive oil or milkfa t). This model is able to account for the effects of the concentration of all chemical species participating in interesterification througho ut the entire reaction. When the data for both milkfat and olive oil w ere subjected to nonlinear regression analyses using the same mathemat ical model, the parameter estimates for both systems were comparable. In addition to reproducing the tendencies observed experimentally, sim ulations of the interesterification system under a variety of initial conditions provided insight into the effects of several reaction varia bles which could not be examined experimentally. Among the most signif icant findings of the simulation work are (1) there is a limit beyond which increasing the initial concentration of water produces no furthe r increase in the initial rate of the interesterification reaction; (2 ) an increase in the initial concentration of lower glycerides produce s a concomitant increase in the rate of the interesterification reacti on; (3) the free fatty acids inhibit the rate of hydrolysis of the fat ty acid residues of the triglycerides; (4) there is a limit beyond whi ch increasing the initial concentration of triglycerides produces no s ignificant increase in the rate of either the hydrolysis reaction or t he interesterification reaction. (C) 1994 John Wiley & Sons, Inc.