Preparation and Properties of Soy Protein Isolate/Cotton-Nanocrystalline Cellulose Films

Abstract

This study was performed to estimate the effect of the incorporation of different cotton-nanocrystalline cellulose (C-NCC) contents with soy protein isolate (SPI) films. The results indicated that the C-NCC content had no effect on the thickness of the composite films ( $0.06\pm 0.01\text{mm}$ ), and the optical property of the composite films decreased as the C-NCC contents increased. Water vapor, carbon dioxide, and oxygen permeability decreased with the introduction of C-NCC and started to increase when the peak of 7% C-NCC was reached. Water solubility of the SPI/C-NCC films decreased from 44.46% of the SPI films to 35.36% of the SPI/C-NCC films with 5% C-NCC. The tensile strength (TS) of films increased from 4.25 MPa to 6.02 MPa by increasing the C-NCC content from 0 to 7%. Then, the TS decreased as the C-NCC content was further increased. The trend of the elongation at break was opposite to that of the TS. The results from FTIR and DSC indicated that the addition of C-NCC did not change functional groups of the SPI films, and the glass transition temperature shifted toward a higher temperature as the C-NCC content increased. Hence, the addition of C-NCC enhanced the barrier and mechanical properties of the SPI/C-NCC composite films.