Novel color stability and colorimetry-enhanced intelligent CO₂ indicators by metal complexation of anthocyanins for monitoring chicken freshness

This study aims to improve the color stability of anthocyanins and develop a CO₂-sensitive indicator based on black goji anthocyanin (BGA) extract. Although the BGA extracts showed distinct color changes, such as red–purple–blue, their intrinsic color diminished after 24 h. A metal complexation method was used for the high color stability of BGA. BGA extracts were chelated with various concentrations of Al³⁺ [0 – 20% (w/w)]. It showed high color stability and strong intensity in a dose-dependent manner. A CO₂-sensitive indicator sachet was developed using hydroxypropyl methylcellulose hydrogel, based on 5% (w/w) Al³⁺-BGA complexes. The indicator was applied to the chicken breast and detected its spoilage after 3 days with its changing color to greyish blue, due to the microbial growth to 7.00 log CFU/g. These results demonstrated the possibility of chelated anthocyanin complexes as indicating dyes and the ability to monitor the food quality changes through noticeable color changes.