Lignin-based oxygen-scavenging films and coatings

The market for active packaging is expected to exhibit constant growth over the next ten years since there is an increased awareness in the areas of food waste as well as food safety and health. A package that scavenges oxygen prevents oxidation of the packaged material and thereby increases the shelf-life and maintains the quality of the packaged food. From a biorefinery perspective it is of interest to create high value-added products out of lignin derivatives. One way of creating an active package would be to integrate an oxygen-scavenging system consisting of lignin and an enzymatic catalyst facilitating oxidation of lignin with concomitant reduction of molecular oxygen to water. This can be achieved by embedding the phenol-oxidizing enzyme laccase together with a lignin derivative in a coating layer inside the package. In this study we investigated the effects on lignin-based oxygen-scavenging systems of industrial-scale fractionation of lignosulfonates through ultrafiltration. While laccase is known to catalyze oxidation and cross-linking of lignosulfonates, the dependence of the reaction on the size distribution of the lignin fragments and the purity of the lignin preparation is not well understood. The efficiency of the enzymatic catalysis and the properties of films and coatings were studied, as well as the extent of cross-linking in the different lignosulfonate fractions.