Ph-indicating properties and storage stability of a smart edible film based on nopal-mucilage/gellan gum and red cabbage anthocyanins

Nopal mucilage is a complex polysaccharide with great potential in the preparation of films for food packaging. In this work, a smart edible film was developed with pH-indicating capabilities based on nopal mucilage/gellan gum, and red cabbage anthocyanins (70:20 w/w, and 10%, respectively). Physical properties, appearance, and colorimetric functionality were characterized at a pH range 2.5-5.9. Color stability, measured by CIELAB, was tested with different storage conditions and time, and interpreted by differential tristimulus colorimetry. Results showed films with uniform appearance, flexibility, easyhandling, and excellent color response within the pH range studied. The evolution of color difference (∆E*ab) confirmed that the colorimetric functionality of films was stable at short storage periods (8 days) under natural conditions of sunlight and oxygen exposure, whereas a more extended storage period affected the films. Results showed that the film is an excellent barrier and presents color changes triggered by pH changes.