pH-responsive starch-based bilayer film functionalized with alliin loaded MIL-101 (Fe) for active food packaging

Food packaging films containing antimicrobial reagents play a crucial role in preventing bacterial-induced fruit decay. This study proposes a bilayer film consisting of an internal amino-modified starch hydrophilic layer and an external amino-modified polyvinyl alcohol/polylactic acid hydrophobic layer, embedding alliin@MIL-101(Fe) as an antibacterial agent, utilizing the pH reduction of fruit decay sites to achieve pH-responsive release, enhancing antibacterial performance. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) analyses confirm successful crosslinking between amino and aldehyde groups, resulting in the formation of imine bonds and a mesh-like structure conducive to adsorption. Under acidic conditions, the cumulative release rate of alliin reached 74 % within 36 h. Compared to a simple mixture, the tensile strength of the alliin@MIL/NST-NPVA/PLA film reached 34.771 MPa, and transmittance in the wavelength range of 200-370 nm decreased to 0. The scavenging rate of DPPH free radicals in the film can reach 83 %. In addition, the water vapor permeability and oxygen permeability of the film are approximately 7.62 × 10^-16 [g/ (m²‧24 h‧0.1 mm)] and 6.83 (m²‧24 h‧0.1 MPa), respectively; moisture content and water solubility decreased to 10.99 % and 20.77 %. This composite film extended the shelf life of strawberries from 2 to 7 days, significantly enhancing freshness.