pH-triggered bilayer film based on carboxymethyl cellulose/zein/Eudragit L100 with purple cabbage anthocyanin for monitoring pork freshness.

A novel pH-triggered bilayer film was composed of zein (Z), carboxymethylcellulose (CMC), Eudragit L100 (L100), and purple cabbage anthocyanin (PCA), followed by casting for monitoring pork freshness during storage at 4 °C and 25 °C. This bilayer film was employed to encapsulate anthocyanins, preventing anthocyanins oxidation and photodegradation. Additionally, under pH 6, this film ruptures and releases anthocyanins, inducing a sudden color change in the indicator film, significantly reducing errors in freshness indications. Notably, the ZCLP8% film had excellent stability and pH response properties. The performance of the ZCLP8% film in monitoring pork freshness was evaluated. When the concentration of pork TVB-N reached 15.59 mg/100 g (pH = 6.35), the bilayer film was ruptured, and the release rate of PCA was 85.52 %, which was a significant change in the color of the bilayer film compared with that at pH = 5. Therefore, this work addresses the limitation that anthocyanin-based intelligent films are subject to judgment errors when applied, opening new possibilities for food freshness differentiation monitoring.