Characterization and Evaluation of the Ag+-Loaded Soy Protein Isolate-Based Bactericidal Film-Forming Dispersion and Films

This study aims to prepare bactericidal films developed from soy protein isolate (SPI) based film-forming dispersions (FFDs) for use in the food and medical fields. The FFD and films were prepared after the incorporation of different concentrations of AgNO3 as a bactericidal agent. The transparency, tensile strength, and antimicrobial features were evaluated. Structural characterizations were also performed by Fourier transform infrared spectroscopy, scanning electron microscope, and atomic force microscopy analysis. Results showed that the opacity of these FFD was greatly decreased after the incorporation of AgNO3. The SPI-5 film has the largest tensile strength (P < 0.05) compared with that of the other ones. Micro structural imaging analysis showed an increase in the surface irregularities with the addition of AgNO3. The minimum inhibitory concentration of AgNO3 was 336 mu g/mL FFD for both Escherichia coli ATCC 25923 and Staphylococcus aureus ATCC 25922. The SPI-AgNO3 films developed from the FFD with the minimal AgNO3 concentration at 336 mu g/mL FFD also showed bactericidal effects for both the strains. These results may prove promising for the use of SPI-AgNO3 films in the food or medical industries.