Soy protein-based films incorporated with cellulose nanocrystals and pine needle extract for active packaging

Soy protein-based films have some interesting properties of being biodegradable, biocompatible, and inexpensive. However, their weak mechanical property and high sensitivity to moisture are major hindrances to using this protein-based film for food packaging applications. This study aimed to develop soy protein-based films incorporated with cellulose nanocrystals (CNCs) and Cedrus deodara pine needle extract (PNE). The physical property, barrier capacity, and antioxidant ability of the films were evaluated and the films were further characterized using a release test, Fourier transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy. The results show that the addition of CNCs lowered the moisture content of the film samples by disrupting the hydrogen bonds between N-H groups of soy proteins and water molecules. The filling effect of CNCs caused a decrease in elongation at break and an increase in tensile strength. When a high content of PNE (5-10%) was incorporated in the films, the water vapor permeability was decreased due to the reduction of hydrophilic domains in the film matrix. Moreover, the PNE-added films contained phenolic compounds and displayed strong antioxidant activities. These results demonstrate that CNCs and PNE can significantly enhance the mechanical property, antioxidant ability, and water vapor barrier capacity of soy protein-based films that can be used as an active food packaging material.