Hydroxyl-crosslinked polyvinyl alcohol films reinforced with nanocellulose and tea polyphenols for antibacterial preservation of dried tofu.

Conventional plastic packaging and chemical preservatives pose risks to both the environment and human health. Consequently, increasing research efforts are directed toward the development of environmentally friendly, non-toxic, and safe packaging materials. In this study, a polyvinyl alcohol (PVA) / pullulan (PUL) / soy hull nanocellulose (SHNC) composite film incorporating 2 % (w/w) tea polyphenols (TP) was prepared. The composite film exhibited a smooth and dense structure, with hydrogen bonding as the primary intermolecular force. It demonstrated a tensile strength of 52.62 MPa and an elongation at break of 321.45 %. Additionally, the composite film showed enhanced ultraviolet-blocking properties and thermal stability. When immersed in water at 100 °C for 10 min, the film exhibited a dissolution rate of up to 90 %. Notably, it extended the shelf life of dried tofu to 16 days and effectively reduced total volatile basic nitrogen and total viable count levels. The antimicrobial mechanism of the TP-loaded film involved inhibiting Escherichia coli growth by disrupting the bacterial cell membrane, impairing cytoplasmic metabolism, and suppressing protein synthesis. These findings suggest that the PVA/PUL/SHNC/TP composite film holds promise as a sustainable food packaging material.