High-performance films fabricated by food protein nanofibrils loaded with vanillin: Mechanism, characterization and bacteriostatic effect

Abstract

A viable platform for food packaging applications has evolved in the form of protein nanofibers with material properties. Through this work, a simple, extensible process of protein for amyloid fibrils formation was proposed. The addition of polyphenol was expected to improve its synergistic antibacterial properties. The isolate protein of soy and whey (SPI and WPI) were selected as model proteins with an acid-heat treatment for 5 h to prepare the nanofibrils. Protein molecules eventually lost their intrinsic structure, which was also followed by aggregation and degeneration. Atomic force microscopy was used to investigate how proteins' spherical and linear shapes changed over time. As the protein unfolded and intermolecular aggregation occurred, circular dichroism (CD) demonstrated that the protein's secondary structure altered from a-helix to β-sheet and random coils. Furthermore, the fibrous protein films' mechanical characteristics were enhanced, particularly the elongation (E) of amyloid SPI films, which increased from 33.50 % to 100.57 %. Additionally, the films' water solubility (WS) and water vapor permeability (WVP) were both decreased. In order to create an antibacterial edible film, vanillin was also added to the fibrous protein solution as a bacteriostatic agent. The results showed that the fibrous protein film demonstrated a great bacteriostatic action and retained good shape. Here we present this simple and efficient method to obtain robust, flexible films, which not only provides a strategy for films with good mechanical properties but also extends their antibacterial by adding a bacteriostatic agent to further provide a new idea for food packaging.