A visual indicator based on curcumin with high stability for monitoring the freshness of freshwater shrimp, Macrobrachium rosenbergii

An ink-free printing method of multifunction pH indicator was provided based on agar and polyvinyl alcohol (AP) incorporated with curcumin for monitoring shrimp freshness. The physical properties results showed that the addition of curcumin increased elongation at break of hydrogel films from 47.02% to 68.69% but reduced their water content. The curcumin film showed a greater colorimetric stability at 4 °C which ΔE value was 3.93. The hydrogel film exhibited obvious color changes to ammonia while the electrochemical writing pattern was well-stable acts as a reference. Meanwhile, the intelligent indicator presented the highly color change from yellow to red with the increasing of shrimp storage time. Last but not the least, the printed information not only provides the basic information of packaging (production date, shelf-life, etc.) but also has the reference function for indicators.