Konjac glucomannan/xanthan gum film embedding soy protein isolate–tannic acid–iron complexes for blueberry preservation

The development of active food packaging films has become an important area of research because of the increasing demand for extending the shelf life of perishable foods. In this study, we developed a novel active food film comprising konjac glucomannan (KGM) and xanthan gum (XG) embedded with soy protein isolate (SPI)–tannic acid–iron (STFe) complexes. In detail, the STFe complexes were prepared through covalent interactions and polyphenol–metal ion coordination to enhance the functional properties of SPI. The KGM and XG matrix was selected owing to its excellent film-forming properties and ability to generate a stable, flexible, and transparent film. The integration of STFe complexes into the KGM/XG film enhanced the functional properties of the resulting film, which displayed exceptional properties, including barrier effects (water vapor permeability: 4.13 g mm/m 2 day kPa), mechanical strength (tensile strength: 20.30 MPa, elongation at break: 65.24%), ultraviolet-shielding capability (>90%), degradability (5 days in soil), antioxidative (>80%), and antimicrobial (>99%) properties. Additionally, we revealed that the film can effectively prolong the storage period of blueberries and maintain their freshness for 15 days. Thus, this film represents a promising approach to food preservation and suitable for the development of sustainable food packaging.