Blueberry anthocyanins-functionalized hydrogel labels for smartphone-assisted real-time visual freshness monitoring...

Given rising consumer demands for meat safety and quality assurance, developing an intuitive, cost-effective, and user-friendly sensor platform for real-time monitoring of perishable meat freshness is important. Herein, this study developed an innovative chitosan/agarose/blueberry anthocyanin (CS/AG/BA) hydrogel label system for visual real-time freshness tracking of perishable proteins through smartphone-assisted colorimetric analysis. Through systematic optimization of CS/AG compositional ratios (3:7-7:3) and pH conditions (2.0-4.0), we identified the CS:AG_3:7-2.0 formulation as exhibiting optimal mechanical properties, water retention capacity, and ammonia sensitivity. The CS/AG/BA hydrogel label exhibited concentration-dependent chromatic transitions, progressively shifting from red to purplish-red and ultimately to blue-purple in response to increasing NH₃ concentrations within the packaged environment. The smart indicator label exhibits distinct color transitions from red to purplish-red and finally to blue-purple when monitoring refrigerated (4 °C) pork and shrimp spoilage. These visually observable color changes demonstrate excellent correlation with standard quality parameters (TVB-N content and pH values), confirming the hydrogel's effectiveness in real-time freshness monitoring. Quantitative analysis established relationships between hydrogel RGB values and standard freshness parameters, enabling both qualitative visual assessment and quantitative evaluation of pork and shrimp quality. This dual-mode sensing platform combines the advantages of simple visual interpretation with smartphone-enabled digital quantification, offering a practical solution for real-time freshness monitoring throughout the cold chain while addressing critical needs for food safety, quality control, and consumer transparency in perishable protein products.