Anthocyanin and thyme oil embedded carrageenan-PVA towards bioactive and pH-sensitive food-packaging materials

Consumer interest in smart food packaging is rapidly growing due to its ability to monitor food quality in real time. These packages not only track changes in the product but also help prevent microbial growth, extending food shelf life and safety. A prime example is anthocyanin-containing packaging, which visually indicates pH changes through color shifts. We herein illustrate this approach by designing biocompatible and biodegradable packaging containing anthocyanin and thyme oil entrapping bio-based carrageenan (CR) blended with polyvinylalcool (PVA) films. Incorporating thyme oil and anthocyanin into carrageenan/polyvinyl alcohol (CR/PVA) films has significantly enhanced the desired mechanical properties of the biodegradable packaging. Specifically, flexibility increased by 20 % compared to the pristine CR/PVA film. Moreover, the physical properties of the films improved, with a reduction in water vapor permeability (WVP) from 1.74 to 1.30 and an increase in the water contact angle (WCA) from 60.5° to 89.5°, indicating enhanced hydrophobicity. Additionally, the resulting films exhibited substantial antimicrobial potential particularly against Escherichia coli and Staphylococcus aureus, along with strong antioxidant properties, surpassing the performance of the original CR/PVA films. The incorporation of anthocyanin endowed the films with high pH sensitivity, enabling effective visual detection of pH changes. Stability tests showed that anthocyanins degrade under temperature and light exposure. However, their incorporation into CR/PVA films significantly improved stability by reducing degradation. This enhancement highlights their potential for smart, protective food packaging.