Improving mechanical, barrier, and thermal properties of canola protein-based packaging films using hydrophobically modified nanocrystalline cellulose

Abstract

With the growing concerns on environmental sustainability, there is an emerging interest in biodegradable food packaging materials developed from sustainable sources of biopolymers. Canola protein isolate, the by-product of the canola oil industry, is gaining the attention of researchers and industry due to their high availability at a low cost. Unfortunately, canola protein faces limitations, including poor mechanical properties and high hydrophilicity. Reinforcing the protein matrix with nanocrystalline cellulose (NCC) is a known way of enhancing film properties, but the enhancement is still not enough to compete with petroleum-based packaging. In the current study, we hypothesized that hydrophobically modified NCC (OA-NCC) would increase the properties of the canola protein films compared to unmodified NCC (U-NCC). The objective of this study was to fabricate canola protein films using OA-NCC and U-NCC and characterize them to evaluate the film properties. Oleic acid (OA) was introduced to the surface of NCC, and films were fabricated using U-NCC and OA-NCC (0, 1, 3, 5, 7, 9% of protein (w/w)) by solvent casting method. One-way ANOVA with Tukey test was used for the data analysis. The films reported the highest tensile strength of 3.44 MPa with 3% OA-NCC, where it was only 1.85 MPa for control films. Also, up to 5%, all the films with OA-NCC reported significantly higher tensile strength values than those with the same U-NCC amount. The films with 9% OA-NCC reported the lowest water vapor permeability of the films. From 5%, all the films with OA-NCC reported significantly lower water vapor permeability values than those with the same amount of U-NCC, indicating enhanced barrier properties. Moreover, the thermal stability and flexibility of the films were improved by the addition of nanomaterials. Enhanced film properties could be a result of protein and OA-associated NCC interactions in the polymer matrix.