Cellulose-protein biocomposite films with enhanced mechanical and optical properties extend raspberry shelf life

The widespread accumulation of plastic waste has become a major global environmental concern due to its harmful impacts on ecosystems and human health. Consequently, there is growing interest in developing renewable and biodegradable alternatives to conventional petroleum-based plastics. In this study, cellulosic residue from soyhulls (SCR), an underutilized agricultural byproduct, was used to produce biodegradable packaging films. As cellulose films have inherent functional limitations, different proteins (gluten, soy protein isolate, whey protein isolate, and zein) were incorporated into the cellulose matrix to enhance film performance. Results show that protein incorporation significantly increased tensile strength, from 6.30 ± 0.60 MPa for the pure SCR film to 16.22 ± 0.64-32.65 ± 1.07 MPa for the cellulose-protein composite films. Protein incorporation increased water vapor permeability, except for zein, which reduced it from 0.9 ± 0.3 to 0.68 ± 0.05 x 10^-10 g.m^-1s^-1Pa^-1, due to its relatively hydrophobic nature. The SCR-protein films also exhibited enhanced UV-blocking and biodegradability and extended the shelf life of raspberries by 2 additional days compared to conventional plastic films. Overall, these findings demonstrate that combining soyhull-derived cellulose with different proteins improves the mechanical, barrier, optical, and biodegradation properties of cellulose-protein composite films. The outcome highlights the potential of low-value agricultural byproducts for developing biodegradable packaging materials with enhanced performance.