A polysaccharide smart packaging materials: Anthocyanin microcapsules synergized with nanosilver co-filled gellan gum/sodium alginate film for monitoring chilled mutton freshness.

Recently, smart packaging based on biopolymers and natural anthocyanins as pH-sensitive indicators have played a key role in food safety. However, anthocyanin migration phenomenon and poor stability limit its application in smart packaging. In this study, we constructed a pH sensitive purple potato anthocyanin microcapsules (PAM) using gum arabic and maltodextrin as wall materials. PAM and nanosilver co-filled gellan gum/sodium alginate-based indicator film (GS/Ag-PAM) were prepared for monitoring chilled mutton freshness. Results showed that microencapsulation enhanced the structural stability, antioxidant and antibacterial properties of anthocyanins. The incorporation of PAM and nanosilver enhanced the mechanical properties, barrier properties, thermal stability, and oxidation resistance of the film. The components of the indicator film had good biocompatibility and biosafety. Among them, GS/Ag-PAM 2 showed the highest TS, the lowest OP, and a tight and neat cross-section. When the indicator film was exposed to ammonia, its color gradually changed from purplish red to blue-green and finally to blue. The freshness of chilled mutton reached a state of sub-fresh and spoilage on days 4 and 8, respectively. Correspondingly, the color of the indicator film GS/Ag-PAM changed from purple to grey-green and dark blue. Therefore, GS/Ag-PAM indicator film have good prospects for monitoring the freshness of packaged meat.