Colorimetric chitosan/polyvinyl alcohol composite membrane incorporated with anthocyanins as pH indicator for monitoring fish freshness

Abstract During storage, food undergoes transformations, often producing volatile nitrogen compounds known as total volatile basic nitrogen (TVB‐N), which serves as an indicator of food freshness. In this study, chitosan (CTS) was blended with polyvinyl alcohol (PVA) and incorporated with anthocyanins (ACNs) to monitor the quality changes in fish fillets over different time intervals. The results demonstrated that the presence of PVA in the CTS membrane enhanced light transmittance and reduced water absorption due to the reinforcement of the membrane structure through chemical interactions. In the freshness monitoring experiments, the CTS/PVA membranes exhibited an improved value of total color difference (Δ E ), facilitating better detection of pH changes of the surrounding environment. Moreover, the Δ E value of the CTS/PVA film was observed to be quite similar to the value at pH 9 after 24 h and at pH 11 after 36 h when the fish fillet was stored at 25°C. In contrast, the Δ E value of the CTS/PVA film closely matched the value at pH 11 after 96 h of storage at 4°C. Additionally, the correlation between the generated TVB‐N and the Δ E values indicated a higher correlation coefficient ( R 2 ) for the composite membranes compared to the pristine CTS or PVA membranes.