κ-Carrageenan based bio-nanocomposite films containing soy protein and nanocellulose: mechanical and thermal characteristics

The present study aims to formulate packaging films using refined carrageenan (RC) and semi refined carrageenan (SRC) containing soy protein (SP) and nanocellulose (NC). The solvent casting method was adopted for film development. Different concentrations of soy protein (0.2, 0.4 and 0.6%, w/w), RC and SRC (2% w/w) and nanocellulose (2% w/w) were used and the morphological, mechanical and thermal properties of films were evaluated. The results indicated an increase in thickness of SRC film than RC films, possibly due to the insoluble residual solid particles (cellulose, minerals). A greater tensile strength of RC/NC/SP0.4 films (36.5 MPa) were observed compared to SRC/NC/SP0.4 films (19.7 MPa). The SEM images of SRC composite films showed a rougher surface contour than RC composite films. The water vapour transmission rate (WVTR) in RC films was high (1677 g m-2 24 h-1) while WVTR reduced considerably to 50% in RC/NC/SP films. The RC based films were transparent while a yellowish hue was observed for SRC films possibly due to the glucan, insoluble aromatic compounds, and minerals. In the FTIR analysis minor changes in peak intensity was observed in RC and SRC films. The addition of nanocellulose improved the heat stability of the RC composite films. The RC-based nanocomposite film proved to be superior to SRC films and would be a very promising material in improving the shelf-life of foods. Therefore, being eco-friendly, renewable, sustainable and natural, these would have potential as smart packaging material.