pH-responsive gellan gum-based double-layer film doped with Centella asiatica extract for real-time monitoring of chicken breast freshness.

In this research, intelligent double-layer films were prepared using modified grape skin anthocyanin (MGSA)-betanin (BL)-shikonin (SKN)-gellan gum (GG) as the internal indicator layer and sodium carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA)-gelatin-Centella asiatica extract (CAE) as the external antimicrobial protective layer. The successful preparation of double-layer films can be revealed by scanning electron microscopy, FT-IR spectroscopy and X-ray diffraction measurements. The mechanical properties, water content, water solubility, and water vapor resistance of films with CAE showed significant enhancement compared to inner layer film and film without CAE. The double-layer films exhibited sensitive pH responsiveness. The presence of the outer layer significantly improved the antioxidant and antimicrobial properties of the inner film. When the films were applied to chicken breast, it was found that the dual-layer films not only allowed for real-time monitoring of the freshness of the chicken breasts, but also successfully extended the shelf-life of the chicken breasts by 1 day compared to the blank group and the single-layer film. Therefore, the double-layer film developed in this study has great potential for monitoring and preserving active intelligent packaging of meat foods.