Tannic acid-loaded halloysite clay grafted with silver nanoparticles enhanced the mechanical and antimicrobial properties of soy protein isolate films for food-packaging applications

Abstract

Poor mechanical and water barrier properties restrict the applicability of protein-based packaging in high-moisture food commodities. In this study, a nanocomposite (Nc) of tannic acid-loaded halloysite nanotubes grafted with silver nanoparticles was developed as a reinforcement agent to enhance the functional properties of soy protein isolate (SPI)-based films. The 5%- and 10%-Nc incorporation in SPI films significantly (p < 0.05) improved the tensile strength (by 1.94–3.14 fold) and thermal stability (by 5–7%) and reduced water vapor permeability (by 1.28–1.30 fold), oxygen permeability (by 2.72–3.84 fold), and water solubility (by 6.3–9.5 fold). The 5%- and 10% Nc/SPI films showed antioxidant properties (by scavenging 18%−28% of DPPH) and exhibited a 3–5 log10 reduction in multi-drug resistant S. aureus and S. Typhimurium contamination in chicken breast fillets. Although 10% Nc/SPI exhibited silver migration to chicken fillets beyond the acceptable limit contributing to color change, 5% Nc/SPI films enhanced the shelf-life of fillets for 4 days by facilitating a controlled pH, lipid oxidation, and microbial growth with acceptable levels of silver migration. In conclusion, the multifunctionality of Nc in SPI films enables its potential to be an alternative to non-biodegradable and non-eco-friendly polymers.