Gelatin/carrageenan-based smart packaging film integrated with Cu-metal organic framework for freshness monitoring and shelf-life extension of shrimp

A gelatin/carrageenan (Gel/Car) based antibacterial and pH-responsive intelligent film was developed by incorporating a Cu-metal organic framework (Cu-MOF) and anthocyanins from red cabbage (Brassica oleracea). Cu-MOF and anthocyanin were mixed compatibly with the polymer matrix to form a dense, flexible, and strong film. The film incorporated with 3 wt% Cu-MOF displayed excellent UV-barrier ability (98.5% in the UV-A and 99.9% in the UV-B), strong antioxidant efficacy against ABTS (100%), and DPPH (100%) and exhibited strong antibacterial activity to completely stop the growth of Gram-positive and Gram-negative bacteria after 3 h of incubation. In addition, the film exhibited pH-dependent color change under various pH conditions (pH 2 to 12), and freshness monitoring tests of shrimp demonstrated a qualitative and quantitative color change of the film (decreasing the redness, a-value, from 24.5 to 3.7). In packaging experiments using shrimp, this packaging film delayed the quality change rate of foods during storage and extended the shelf life of these foods. The gelatin/carrageenan-based multifunctional film combined with a Cu-metal organic framework is expected to help visualize food changes before consumption, extend processed foods' shelf life, and significantly reduce food waste problems.