Development and characterization of pH-sensitive and antioxidant edible films based on mung bean protein enriched with Echium amoenum anthocyanins

A novel active packaging system was developed based on mung bean protein incorporated with Echium amoenum extract. Different amounts of anthocyanin-rich extract (0, 2.5, 5, 7.5, and 10% v/v) were added to the film-forming solutions and the films were characterized. The addition of anthocyanins increased the film thickness, water solubility, and water vapor permeability; however, the moisture content of the film was decreased. The tensile strength and elongation at break of films were also enhanced significantly by the addition of anthocyanins-rich extract. The color parameters (L*, a*, and b*) indicated remarkable changes after the incorporation of extract into the films. The scanning electron microscopy was utilized to investigate the surface and cross-sectional areas of the active films. The structural changes resulted from enriching with extract were studied by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The antioxidant activity as well as the total phenolic content of active films was improved after the incorporation of anthocyanin-rich extract. Moreover, the antimicrobial activity of active films on E. coli and S. aureus revealed that anthocyanin-containing films could inhibit bacterial growth. The film samples containing extract also showed different colors under different pH conditions. These findings suggested that these types of antioxidant films can be applied for food packaging application.