Proof-of-concept study of chitosan-based carbon dioxide indicator for food packaging applications

► Partial pressure of carbon dioxide (CO2) indicates quality in some packaged food product. ► Chitosan-based CO2 indicator is designed to detect freshness of packaged food. ► CO2 dissolved in water lowers pH by formed H2CO3. ► Opaque CO2 indicator develops transparency due to chitosan dissolution at lowered pH. ► Addition of 2-amino 2-methyl 1-propanol enhances resolution on optical transition.