Enzymatic interesterification: Highlighting the catalytic performance of immobilized enzymes with different analytical methods

Abstract: Enzymatic interesterification is a sustainable modification process: no chemicals, no oil degradation, no side reactions, no induced contaminants and reduced oil losses. This process is generally carried out with immobilized enzymes, in continuous and counter-current mode. The enzyme process is cost-efficient since higher oil yield outweighs the higher operating costs. The catalytic performance of the enzyme is an important parameter to consider since it directly impacts the process cost.

The aim of the study was to evaluate the performance of two immobilized enzymes during the process of interesterification, with different analytical methods. Lab-scale enzymatic interesterification was performed in batch mode using RBD palm oil. The working conditions (enzyme load and reaction temperature) were defined on the basis of an experimental design. The analytical methods involved were DSC, p-NMR, and RP-HPLC.

Enzymatic interesterification was carried out for 25 hours with regular sampling. The DSC melting profiles made it possible to determine the modification of co-crystallization properties as a function of time (high, medium and low melting peaks) for each condition. The solid fat content profile by p-NMR allowed to quantify the changes in melting behavior over time. The triglyceride composition by RP-HPLC of the various withdrawn samples, compared to the theoretically calculated random composition, enabled to calculate degrees of interesterification; these were used to establish reaction kinetics for each of the conditions.

Small variations in catalytic performance of the immobilized enzymes were easily demonstrated with these analytical methods. In the particular case of this study, the significant influence of the enzyme type and of the enzyme load and the neutral effect of temperature was evidently shown.