A naked-eye detection polyvinyl alcohol/cellulose-based pH sensor for intelligent packaging.

Naked-eye detection pH sensor is becoming a powerful tool in food safety monitoring. In this work, a pH sensor was developed by incorporating cellulose modified with acidochromic dye into polyvinyl alcohol (PVA). The results indicated that the dye (up to 170.4 μmol/g) was successfully anchored to cellulose. It was demonstrated that the addition of acidochromic regenerated cellulose (ARC) resulted in enhancement of tensile strength, elongation at break and maximum decomposition temperature by 44 %, 43.6 % and 11 °C, respectively. The pH sensor demonstrated that a visible color change from yellow to brick-red and to purple when placed in solutions of pH = 7, 10 and 12. The pH sensor showed excellent resistance to leaching under strong acidic and alkaline conditions. When applied to spoiled shrimp, an evident color change from yellow to brown was observed, suggesting it could serve as an easy-to-use, non-destructive visual indicator system for real-time food monitoring.