Stepwise reinforcement strategy for guar gum/sodium alginate based films: Introduction of carboxylated cellulose nanofibers by different methods and further calcium ion crosslinking

Insufficient mechanical, barrier and water resistance properties of guar gum (GG) films limit their application in food packaging field. Herein, the properties of GG films were enhanced by a stepwise modification strategy. The mechanical and water vapor barrier properties of GG films were initially reinforced by doping with a different type of polysaccharide (sodium alginate; SA). Next, carboxylated cellulose nanofibers (CCN) were introduced as a reinforcing agent to improve film properties via two methods (blending and layer-by-layer (LBL) assembly method). Finally, the water resistance of composite films was further enhanced by calcium ion cross-linking treatment. GG/SA composite films exhibited better mechanical strength and water vapor barrier capacity compared to pristine GG film. In addition, the introduction of CCN, either by blending or LBL method, improved the light barrier, water vapor barrier and tensile strength. The calcium ion cross-linking treatment further enhanced the water vapor barrier, thermal stability, tensile strength and water resistance capacity. The potential applications of GG/SA/CCN films in real food packaging were also explored. In short, this study presents a simple and feasible performance enhancement strategy for GG and other underperforming polysaccharide matrix films, with potential applications in the development of high-performance bio-based food packaging materials.