Water soluble lignin extract from ozonation of Miscanthus giganteus for bioactive starch packaging films

Abstract

The development of bio-based packaging materials is a crucial step toward sustainability, with natural additives playing a key role in enhancing their functionality. Due to their brittle structure, starch-based packaging materials require natural plasticizers at optimal concentrations to improve their flexibility and performance. In this study, we hypothesized that a water-soluble lignin derivative, obtained by ozonation of Miscanthus giganteus and exhibiting bioactive properties, could function simultaneously as plasticizer and bioactive agent to obtain active starch-based packaging films. The effects of lignin on mechanical, antioxidant, antimicrobial, UV-blocking properties, and retrogradation of potato starch-based films were examined. Starch-lignin films were prepared with varying lignin concentrations (0%, 5%, 10%, and 20%) using casting method. Increasing lignin content from 0% to 10% reduced Young’s modulus and significantly improved ductility, with elongation rising from 35% to 166%, while 20% lignin inclusion reversed these effects. The phenolic structure of lignin increased the contact angle from 50% to 110% for lignin contents of 0% to 10%, without altering water vapor permeability. X-ray diffraction analysis revealed a reduction in the crystallinity of lignin-containing films. All starch-lignin films exhibited UV-blocking properties. Antioxidant capacity, measured by the β-carotene assay, increased significantly from 0% to 93% with lignin content from 0% to 20%. Moreover, all the films containing lignin demonstrated bactericidal activity, reducing the viability of Escherichia coli and Staphylococcus aureus by 99.9%. Lignin delayed film retrogradation during storage by reducing crystallinity compared to starch-glycerol films. These starch-lignin biofilms show significant potential as sustainable additives for active food packaging applications.

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