Development and Characterization of Chitosan and Alginate Films Containing Kraft and Organosolv Lignin Nanoparticles for Active Food Packaging

This study examines the effects of kraft and organosolv lignin nanoparticles on chitosan- and sodium alginate-based films designed for active food packaging. Glycerol-plasticized films containing chestnut extract and different nanolignin concentrations were evaluated for their properties and activities. Alginate films generally showed higher tensile strength, reaching 109.35 MPa with 0.2 g of kraft nanolignin, whereas chitosan films provided a better water-vapor barrier, with a minimum permeability of 0.031 mg·µm·Pa−1·s−1·m−2 at 0.02 g of kraft nanolignin. Kraft nanolignin exhibited smaller characteristic structures and produced finer surface features. Organosolv nanolignin formed larger aggregates and generally reduced water absorption. All films decreased light transmission and exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus, with kraft-containing formulations showing the strongest overall inhibition. Spectroscopic, structural, and thermal analyses confirmed intermolecular interactions and slightly improved thermal stability after nanolignin incorporation. All formulations underwent hydrolytic mass loss in phosphate-buffered saline. These findings demonstrate that the matrix, nanolignin type, and concentration can be selected to tailor film properties for specific food-packaging applications.