pH-responsive color indicator films based on methylcellulose/chitosan nanofiber and barberry anthocyanins for real-time monitoring of meat freshness.

A new pH-responsive color indicator film was prepared by blending barberry anthocyanin (BA) with methylcellulose (MC)/chitosan nanofiber (ChNF) composite film. The addition of ChNF and BA increased the mechanical and water barrier properties but reduced the UV-vis light transmittance of the composite film. Anthocyanin showed proper compatibility with the composite film. The color indicator film showed an apparent color change in response to pH changes and ammonia gas, being suitable for indicating the change in food pH, the formation of volatile nitrogen compounds, and food decay. The color indicator film changed clearly from reddish-pink to pale peach and finally to yellow when exposed to different pH buffers. However, in response to ammonia vapor, the color changed from pink to pale green and yellow. Besides, the color indicator film exhibited remarkable antioxidant activity. Therefore, the pH-sensing color indicator film can be used as a smart indicator for real-time freshness monitoring of meat and seafood products.