Fabrication of pH‐Sensitive Smart Indicator Film From Polylactic Acid and Elderberry Anthocyanin for Monitoring Chicken Spoilage

ABSTRACT The objective of this research was to create an environmentally friendly pH‐responsive indicator film using polylactic acid (PLA) polymer, polyethylene glycol (PEG) plasticizer and elderberry anthocyanin‐rich (EBAC) extract for monitoring the quality of chicken breast stored at 5 ± 1°C. The composite films were prepared via solution casting, where PLA, PEG, and EBAC were dissolved in appropriate solvents, mixed thoroughly, and dried at controlled conditions. The influence of varying PLA, PEG, and anthocyanin concentrations as three independent variables on the film's properties was systematically evaluated. Comprehensive analyses employing thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) revealed that the incorporation of PEG and anthocyanin extract into the PLA matrix, particularly at higher concentrations, resulted in a reduction in the film's thermal stability. The results also revealed that the indicator film exhibited consistent homogeneity and uniformity, showing no obvious changes in its structure. Increasing the PLA content resulted in thicker films, increased opacity, and surface hydrophobicity while decreasing swelling and water vapour permeability. Conversely, higher PEG concentrations improved film flexibility and crystallinity. Interestingly, anthocyanin extract primarily influenced water vapour permeability. The indicator's response was assessed by exposing films to various pH buffers (2–11), resulting in a distinct colour shift (pink/purple to dark purple). Additionally, the films exhibited significant sensitivity and rapid colour changes upon exposure to ammonia vapour. To evaluate their efficacy in monitoring chicken spoilage, the films were employed during a 6‐day refrigerated storage period. The indicator transitioned from pink/purple on day 0 to brown/grey on Day 6, demonstrating the potential of these PLA‐anthocyanin‐based films for real‐time monitoring of chicken breast freshness.