Facile strategy for improvement properties of whey protein isolate/walnut oil bio-packaging films: Using modified cellulose nanofibers.

This work aims to explore the addition impact of surface modified cellulose nanofibers (CNF) with poly (methyl methacrylate) (PMMA), CNF-g-PMMA, on the required properties of whey protein isolate (WPI)/walnut oil (WNO) films for packaging applications. WPI/WNO films containing 15 wt% WNO were selected for CNF incorporation. The addition effects of different quantities of unmodified and modified CNF (CNF and MCNF) on mechanical strength, fracture surface morphology, hydrophobicity, water vapor permeability (WVP), water uptake, and transparency of bionanocomposite films were studied. Fracture surface was observed by Scanning electron microscopy (SEM). The maximum ultimate tensile strength (UTS) was obtained to be 9 ± 0.11 and 10.38 ± 0.16 MPa, respectively, at 7.5 wt% of both CNF and MCNF. Compared with WPI/WNO unfilled films, while CNF increased the hydrophilicity of the films, MCNF resulted in more hydrophobic films. In addition, 51% and 64% improvement in water vapor barrier features of CNF and MCNF-loaded films was observed, respectively. The similar trend was occurred for the water uptake behavior. In the case of film transparency, MCNF-loaded films were opaque with 18.12% light transmittance (600 nm wavelength). Generally, WPI films including 15 wt% of WNO and 7.5 wt% MCNF shows promising potential as bio-packaging films.