Effect of anthocyanin indicator addition on cellulose nanocrystals/gellan gum‐based intelligent packaging films

Food spoilage often causes a change in pH inside the package. As a type of intelligent packaging, pH freshness indication packaging, with its simplicity, sensitivity, and efficiency, can monitor food quality and inform consumers promptly. In this study, Clitoria ternatea anthocyanin (CT) was added to gellan gum (GG), glycerol and cellulose nanocrystal (CNC) matrix to prepare a pH-sensitive indicator film. The addition of CT disrupted the network structure, forming a new hydrogen bond and a smooth and continuous cross-section of the film, giving the film excellent mechanical properties. The addition of CNC locked the CT firmly into the indicator film while improving the film's water resistance. Anthocyanin improved the light-blocking ability of the film and gave an excellent pH response to the indicator film. The pH response tests showed a significant color change in the film at pH in the range of 3–12 when anthocyanin was added at 20% and 30%, suggesting the potential application of the developed intelligent indicator film in monitoring food freshness. Novelty impact statement Excellent mechanical properties (Tensile strength: 33.47 MPa; Elongation at break: 27.12%), even with the addition of anthocyanins. High water contact angle (88.4°) provided excellent moisture resistance to the film. Excellent pH responsiveness and new ideas for real-time material monitoring of food packaging.