This study proposes a novel approach for developing smart, biodegradable, and pH-sensitive films using poly(lactic acid) (PLA) and hybrid pH indicator systems. Natural dyes-anthocyanins, alizarin (A), and hematoxylin (HEM)- were selected for their diverse pH-responsive behaviors and molecular structures, and subsequently immobilized on mineral supports to create robust, eco-conscious additives for packaging applications. The resulting hybrid pigments imparted pH-responsiveness and good biodegradation sensitivity to the PLA films, while improving gas barrier properties and reducing flammability. The films exhibited strong colorimetric responses (ΔE ≥ 3 within 5 min) upon exposure to HCl vapor. Additionally, their effectiveness in monitoring milk spoilage was successfully demonstrated. These findings highlight a sustainable strategy for producing multifunctional packaging materials with real-time freshness monitoring capability.
Szadkowski et al. (Fri,) studied this question.