Starch-based cryogels incorporating cobalt chloride as colorimetric moisture sensors for food packaging

Biodegradable colorimetric sensors capable of quantitatively correlating humidity with food quality under real storage conditions remain scarce. Here, we developed starch-based cryogels with varying amounts of cobalt chloride (CoCl₂) and investigated their performance as moisture sensors. We evaluated their color response to humidity (18, 60, 99%) with standard color values and image analysis. Cryogels with 20% CoCl₂ showed the highest humidity sensitivity, indicated by b* value shifts with rapid and visually detectable responses. CoCl₂ also increased water absorption, confirming its hygroscopic behavior. Image analysis provided an instrument-free and practical approach for humidity monitoring. Further tests at 45% and 75% humidity and in real packaging (polypropylene, polyethylene, and gelatin-wrapped crackers) showed a strong quantitative correlation between the b* value, internal humidity, and cracker texture. These findings highlight the potential of starch-based cryogels as scalable, instrument-free sensors for intelligent and sustainable food packaging systems.