LAUSR

Abstract In this work, two kinds of water-soluble chitosan derivatives (succinylated chitosan and hydroxypropyl chitosan) were used as substrates to prepare indicator label for detecting CO2 concentration. The mixed-dyes of bromocresol blue and methyl red indicators were investigated and the results of SEM test revealed that the mixed indicator could be uniformly dispersed in the transparent membranes. The color differences of the indicator label under different environmental conditions (humidity and temperature) were highly correlated with the CO2 concentration. The values of label membranes' color difference ( δ E ) showed a good linear relationship with the CO2 content. Subsequently, these label membranes were successfully applied to reveal the evolution of the CO2 content in fruit packaging to indicate the freshness of fruit. Therefore, these chitosan derivative-based indicator label membranes assume a promising application prospect in the future.