Development of pH-sensitive films based on gelatin/chitosan/nanocellulose and anthocyanins from hawthorn (Crataegus scabrifolia) fruit

In this research, pH-sensitive films were prepared based on gelatin, chitosan, and nanocellulose as film matrix, anthocyanins from hawthorn (Crataegus scabrifolia) fruit (0, 10, 15, and 20%) as natural pigments. The films were evaluated by thickness, moisture content, swelling property, water vapor permeability, mechanical property, UV–Vis light barrier property, microstructure, and color stability of films. The color of hawthorn fruit extract was distinctly different from pH 1 to pH 14. Scanning electron microscope analysis confirmed the biocompatibility between film matrix and hawthorn fruit extract. Fourier transform infrared spectra confirmed the structural changes in polymer matrix and anthocyanins. Furthermore, the pH-sensitive film showed evident color changes from red–purple (fresh), light grey (use soon), to yellow-green (spoiled) when applied to indicate the freshness of shrimp stored under 4 ± 1 °C, before the TVB-N value slowly increased to exceed the limit value (20 mg/100 g) on day 6. The results suggested that the developed films could be used to indicate the changes of food quality.