The non-biodegradable and non-renewable nature of plastic packaging has led to increasing interest in packaging materials based on bio-nanocomposites. In this study we investigated nanocomposite materials prepared by casting a mixture of gluten, glutenin and gliadin as the matrix and different concentrations of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-carboxylated cellulose nanocrystals (C.CNC) as the reinforcing agent. The resulting films were characterized for their mechanical, thermal and barrier properties. The mechanical properties of gluten films showed that the breaking elongation (? b ) decreased by 26%, but tensile strength (TS) increased (60%) in the presence of C.CNC, with a maximum at 7.5%.These effects were also reflected in the dynamic mechanical analysis (DMA) results and the storage modulus (E') for all composites containing nanofillers were pushed to a higher level relative to the neat gluten system. The mechanical properties of glutenin showed that the presence of C.CNC (5%) resulted in an increase (58.8%) in TS while at higher contents it tended to decrease because of partial agglomeration of the filler.The reinforcing effect of C.CNCs was also confirmed by DMA where, by adding C.CNC, an increase in E' was detected.Similarly, C.CNC resulted in improved TS and E ? of gliadin films that can be ascribed to the strong interactions between the C.CNC and the matrix. The results obtained from differential scanning calorimetry (DSC) curves indicated that increasing the amount of C.CNC from 0 to 10% showed a minimum at 5% for T g of gluten films, led to an increase in T g of glutenin films from -29.8 to -23.7 °C and indicated an optimum in T g of gliadin films at 5% CNC content. As compared to film without C.CNC, the water vapor permeability (WVP) decreased from 5.02× 10 -6 to 3.21× 10 -6 g/mm.h.kPa for the gluten film containing 7.5% C.CNC; with increasing nanocellulose content, water uptake (WU) of the nanocomposites increased but water solubility (WS) decreased. Although the use of C.CNC reduced the resistance to water vapor permeation and water absorbance of glutenin films, its incorporation up to 5% resulted in composites with the lowest WS. Upon increasing the filler content to 10%, the WVP of gliadin films decreased and reached a minimum value at 7 . 5% concentration. WU decreased with increasing C.CNC content as expected but WS increased. Keywords: Carboxylated cellulose nanocrystals, Gluten, Glutenin, Gliadin, Nanocomposite
