A dye-incorporated chitosan-based CO2 indicator for monitoring of food quality focusing on makgeolli quality during storage

A chitosan-based CO2 indicator that exhibits a prominent visual change depending on different CO2 levels was developed. The partial pressure of CO2 in the headspace of food packaging can be considered as a quality indicator of makgeolli. For fabrication of a CO2 indicator, 0.3% brilliant blue (BB) was incorporated into chitosan dissolved in a 0.1 M HCl solution, and the pH was subsequently adjusted to 7.0. At the beginning of makgeolli storage, the indicator was opaque because chitosan is insoluble at pH 7.0. With an increase in the CO2 level in the packaging headspace during fermentation, the indicator developed transparency due to dissolution at lower pH values caused by CO2. BB dye encapsulated in flocculated chitosan particles was released. The transparency of the indicator was correlated with the makgeolli quality attribute of titratable acidity over the storage time.