Bionanocomposites Utilizing Agro‐Waste Nanocellulose and Starch Matrix Incorporating Anthocyanin Extracted From Hibiscus Flowers: Efficacy as pH Sensitive Packaging Films

pH-sensitive films are the current trend in food packaging as the change in the food material can be easily identified visually from them. In this study, we developed an intelligent, biodegradable thin film using starch and nanocellulose (NC), reinforced with anthocyanin pigment extracted from fresh Hibiscus flowers. The anthocyanin was isolated through a nonthermal extraction method using an ethanol–water mixture. The anthocyanin extraction followed a nonthermal process using alcohol–water mixture. Evaluation of the efficacy of Hibiscus flower extract (HFE) as a precursor for the development of pH-sensitive films was done by mixing it with different buffer solutions having pH between 2 and 12. NC, obtained from agro-waste pineapple leaves via steam explosion, served as a reinforcing agent. Incorporation of NC and HFE significantly improved the mechanical and thermal properties of the films, increasing tensile strength from 7.13 to 15.27 MPa and enhancing thermal degradation temperature from 230 to 250°C. X-ray diffraction (XRD) analysis revealed increased crystallinity due to NC addition. Furthermore, the films exhibited clear and distinct color changes across the pH spectrum, attributed to the structural transformation of anthocyanins. The correlation between pH of buffer solution and color of S/NC/HFE film suggested that the developed starch-based films have a great potential application as pH indicator for intelligent food packaging.