Smart <scp>pH</scp> ‐Indicating Films Based on Anthocyanin‐Functionalized Bacterial Cellulose

ABSTRACT This study aimed to develop an intelligent ammonia‐responsive packaging film by functionalizing bacterial cellulose (BC) with purple potato anthocyanin extract (PPE), aiming to achieve reversible sensing capacity and practical application in food monitoring. Films were prepared with PPE loadings of 0.1%, 0.3%, and 0.5% (w/v) and characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and x‐ray photoelectron spectroscopy (XPS), and then systematically evaluated for their comprehensive properties and colorimetric behavior. SEM analysis confirmed the uniform dispersion of PPE, while FTIR and XPS spectroscopy verified its successful incorporation into the BC matrix. Films with different PPE loadings exhibited concentration‐dependent colorimetric behavior across the pH range of 2–12. Among all formulations, BC/PPE0.1% was identified as the optimal composition due to its balanced mechanical properties and significantly faster ammonia response compared to other loadings. This optimal film showed excellent reversible sensing capability, with a detection limit of 0.01 M. It was also successfully applied to monitor pork freshness at 25°C, where spoilage‐induced color changes provided a clear visual signal. This work establishes BC/PPE0.1% as a promising stimuli‐responsive biomaterial, positioning it as a reliable visual indicator for detecting freshness failure in the cold chain, such as during the transportation of high‐value meats.