Soy protein isolate (SPI)-based materials are abundant, biocompatible, renewable, and biodegradable. In order to improve the tensile strength (TS) of SPI films, we prepared a novel composite film modified with microcrystalline cellulose (MCC) and metal nanoclusters (NCs) in this study. The effects of the modification of MCC on the properties of SPI-Cu NCs and SPI-Zn NCs films were investigated. Attenuated total reflectance-Fourier transformed infrared spectroscopy analyses and X-ray diffraction patterns characterized the strong interactions and reduction of the crystalline structure of the composite films. Scanning electron microscopy (SEM) showed the enhanced cross-linked and entangled structure of modified films. Compared with an untreated SPI film, the tensile strength of the SPI-MCC-Cu and SPI-MCC-Zn films increased from 2.91 to 13.95 and 6.52 MPa, respectively. Moreover, the results also indicated their favorable water resistance with a higher water contact angle. Meanwhile, the composite films exhibited increased initial degradation temperatures, demonstrating their higher thermostability. The results suggested that MCC could effectively improve the performance of SPI-NCs films, which would provide a novel preparation method for environmentally friendly SPI-based films in the applications of packaging materials.
Keywords: metal nanoclusters; microcrystalline cellulose; nanocomposite film; soy protein isolate; tensile strength.