Comparison of the Functional Properties of Soy Protein Isolate Films Enhanced by Inorganic Nanoparticles
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Abstract:
Soybean protein isolate (SPI) is a biodegradable biopolymer. However, its application in the packaging industry has been limited by its lack of antibacterial properties, poor mechanical performances, and deficient barrier properties. SPI/nano-ZnO (SZ) and SPI/nano-TiO2 (ST) composite films were prepared herein by the addition of different amounts of nano-ZnO and nano-TiO2 to SPI. Furthermore, various packaging properties of the composite films were compared to identify the nanomaterial more conducive to enhancing the properties of SPI films. The results showed that the dispersity of nano-ZnO in the SPI film solution was superior to that of nano-TiO2. Moreover, Nano-ZnO exhibits better compatibility with SPI and superior synergistic effects. The mechanical performance, barrier properties, and antibacterial properties of SZ composite films were also superior to those of their ST counterparts (P<0.05). Compared to the SPI film, the SZ3 composite film, containing 3% ZnO, showed a higher tensile strength. More specifically, tensile strength increased from 6.64 MPa to 18.33 MPa. Meanwhile, the water vapor permeability (WVP) decreased from 20.63×10-2 to 2.94×10-2 g•mm/(m2•h•kPa), and the oxygen permeability (OP) reduced from 3.32×10-5 to 1.54×10-5 g•m/(m2•d•kPa). In addition, the composite films exhibited excellent antibacterial performance against Escherichia coli and Bacillus cereus, with a more pronounced effect observed as the nanoparticle concentration increased. Thus, both films demonstrated considerable potential in the application of active packaging. Collectively, these results provide a theoretical reference for the improved application of SPI films.
