Self-assembly of colloidal lignin nanosphere particles blended with chitosan composite coated bagasse paper: An eco-friendly food packaging with antimicrobial properties

Chitosan/lignin nanocomposites were coated on bagasse paper surface to improve antimicrobial packaging. A commercial softwood kraft lignin was selected and purified by fractionation process using organic solvent. The aliphatic, phenolic and carboxylic hydroxyl groups of commercial softwood lignin and fractionated lignin were investigated using 31P NMR spectroscopy. For lignin nanosphere particles (LNPs) preparation, the fractionated lignin was dissolved in organic solvent (acetone), then the deionized water was added under ultrasonic mixing. The size of LNPs were approximately 40–500 nm. Chitosan solutions were mixed with 6–33 wt% of LNPs. The mixture was then spread over the bagasse paper surface. The papers coated with chitosan/LNPs were dehydrated at 40 °C for 48 h. For food packaging applications, the antibacterial activity of the paper packaging coated with chitosan/LNPs was more successful and effective against gram-positive bacteria (such as Staphylococcus aureus, S. aureus) and gram-negative bacteria (such as Escherichia coli, E. coli) compared with the bagasse paper without any coating. The antimicrobial activity of all papers coated with chitosan/LNPs for S. aureus and E. coli was above 2 log CFU/cm2 which are acceptable for antimicrobial efficacy and the percent reduction of bacteria was nearly 100%. In addition, this evident of chitosan/LNPs nanocomposites showed a synergistic effect enhancing the antimicrobial efficiency on the paper surface. The morphology, wettability and overall migration of paper coated with chitosan/LNPs samples were also explored.