Empirical Evaluation of Cellulose Nanocrystal Reinforcement on the Properties of Chitosan-Based Biopolymer Films for Antibacterial Packaging Applications

Biopolymer packaging films combining the inherent antimicrobial activity of chitosan with the reinforcing capability of cellulose nanocrystals represent a promising development in functional sustainable packaging. This study empirically evaluates the effect of cellulose nanocrystal loading on the mechanical, barrier, and antibacterial properties of chitosan-based films, assessing their potential for fresh food packaging applications in Nigerian retail markets. Cellulose nanocrystals were isolated from sugarcane bagasse generated at a processing facility in Kwara State, North Central Nigeria. Chitosan-cellulose nanocrystal composite films were prepared by solvent casting at nanocrystal loadings of 1, 3, 5, and 7 percent by weight, with glycerol as plasticiser. Tensile properties, oxygen transmission rate, water vapour transmission rate, contact angle, and antimicrobial activity against Staphylococcus aureus and Escherichia coli by disc diffusion and colony count reduction methods were evaluated. Results demonstrate that 5 percent cellulose nanocrystal loading improved tensile strength from 31 to 68 MPa, an increase of 119 percent, and reduced oxygen transmission rate by 46 percent compared to neat chitosan films. Water vapour transmission rate declined from 1240 to 810 g/m2/day at 5 percent loading. Antimicrobial activity was retained in composite films, with greater than 99 percent bacterial reduction maintained for all nanocrystal loadings. Contact angle increased from 62 to 74 degrees with nanocrystal addition, indicating moderate hydrophobicity improvement. Film transparency declined marginally with increasing loading but remained adequate for food visibility applications. The study validates cellulose nanocrystal-chitosan composite films as biobased functional packaging materials and recommends fresh produce pilot packaging trials in Nigerian refrigerated supply chains. Keywords: cellulose nanocrystal, chitosan, biopolymer film, antibacterial packaging, sugarcane bagasse