Physicochemical characteristics of decolorized zein-based composite films and their utilization in developing dual-channel pH-responsive labels incorporating carbon dots and anthocyanins

This study developed a dual-channel pH indicator utilizing hydrophobin to enhance the compromised structural integrity of bio-based pH indicator films affected by moisture, while also addressing the limitations in pH response sensitivity and stability associated with single-mode detection. This indicator facilitates stable and real-time pH monitoring under daylight and ultraviolet illumination, incorporating zein with anthocyanins and carbon dots. To reduce interference from the inherent coloration of zein on colorimetric performance, activated carbon was utilized for decolorization, and the adsorption kinetics, along with optimal operational conditions, were systematically examined. The findings demonstrated that decolorization attained equilibrium after 5 h at 55 °C. Composite film analysis experiments revealed that the incorporation of anthocyanin and carbon dots improved matrix compatibility through hydrogen bonding interactions, leading to a denser microstructure and thereby enhancing the thermal stability and water insolubility of the composite film. The label demonstrated a sensitive and distinct dual-channel response, with color difference ( ΔE  > 5) across various pH conditions, confirming excellent color response capability. This study effectively developed a zein-based intelligent indicator label, exhibiting high sensitivity and reliability in detecting pH variations, indicating significant potential for monitoring the spoilage of perishable foods such as seafood and dairy products.