Development of Eco-friendly Soy Protein Isolate Films with High Mechanical Properties through HNTs, PVA, and PTGE Synergism Effect

Xiaorong Liu,Chusheng Qi,Ruyuan Song,Jianzhang Li,Shifeng Zhang,Wei Zhang

doi:10.1038/srep44289

Abstract

This study was to develop novel soy protein isolate-based films for packaging using halloysite nanotubes (HNTs), poly-vinyl alcohol (PVA), and 1,2,3-propanetriol-diglycidyl-ether (PTGE). The structural, crystallinity, opacity, micromorphology, and thermal stability of the resultant SPI/HNTs/PVA/PTGE film were analyzed by the Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), UV-Vis spectrophotometry, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). The SPI/HNTs/PVA/PTGE film illustrated that HNTs were uniformly dispersed in the SPI matrix and the thermal stability of the film was enhanced. Furthermore, the tensile strength (TS) of the SPI/HNTs/PVA/PTGE film was increased by 329.3% and the elongation at the break (EB) remained unchanged. The water absorption (WA) and the moisture content (MC) were decreased by 5.1% and 10.4%, respectively, compared to the unmodified film. The results highlighted the synergistic effects of SPI, HNTs, PVA, and PTGE on the mechanical properties, water resistance, and thermal stability of SPI films, which showed excellent strength and flexibility. In short, SPI films prepared from HNTs, PVA, and PTGE showed considerable potential as packaging materials.

Highlights

The use of epoxide compounds has been explored
Compared with original halloysite nanotubes (HNTs), the characteristic peaks at 3692, 3620, and 1032 cm−1 of the HNTs nanoparticles remained in the SPI/HNTs and SPI/HNTs/Poly-vinyl alcohol (PVA)/PTGE films, suggesting that the structure of HNTs was not changed in resultant films[33]
The UV/Vis spectra of SPI-based films are shown in Fig. 3b, where it was clear that the transparency of SPI/PVA/PTGE/HNTs film was lower than both neat SPI film and SPI/PTGE film but higher than both SPI/PVA film and SPI/HNTs film

Summary

Introduction

The use of epoxide compounds has been explored. The results that an epoxide compound such as 1,2,3-pro panetriol-diglycidyl-ether (PTGE) or epoxidized soybean oil (EPO) can significantly enhance the mechanical properties of SPI-based composites[5]. The novel nanocomposite films that combined the advantages of SPI, HNTs, PVA, and PTGE were prepared via the casting method and the mechanical properties, water resistance, chemical structures, micromorphology, opacity, crystallinity, and thermal stability of the resultant films were thoroughly investigated. As the XRD pattern of the SPI/HNTs/PVA/PTGE film shown, three additional peaks at around 2θ= 12.2°, 19.9° and 25° were observed, corresponding to the crystalline structure of HNTs. This result indicated that HNTs was uniformly dispersed in the SPI matrix and the crystal structure of HNTs was not altered[26,37].

Results

Conclusion