Natural Pigment-Based pH/Gas-Sensitive Intelligent Packaging Film for Freshness Monitoring of Meat and Seafood: Influencing Factors, Technological Advances, and Future Perspectives

Intelligent packaging films (IPFs) with pH/gas sensitivity are used in the food industry to monitor food freshness and shelf-life, ensure consumer safety, and reduce economic loss. Nevertheless, the sensitivity of pH/gas-sensitive natural pigment-based IPFs has been affected by various factors such as pH, storage temperature, relative humidity (RH), gas and pigment concentration, UV-light, and film composition and microstructure, which influence the freshness monitoring of meat and seafood. Therefore, this review focused on the various factors influencing the pH/gas sensitivity of natural pigment-based IPFs as well as the technological advances, and future perspectives for freshness monitoring of meat and seafood. Our review unveiled that encapsulation, crosslinking, 3D-printing, and electrospinning are promising techniques to enhance color stability, barrier properties, sensitive pigment retention, and indicator sensitivity of IPFs. Besides, several co-materials in IPFs, such as co-pigments, nanofillers, essential oils, etc. can boost their desired properties. Furthermore, nanofillers, such as graphene oxide, carbon quantum dots, cellulose nanocrystals, etc. can enhance the barrier and gas sensitivity of IPFs. Further research is needed to achieve high pH/gas-sensitive IPFs stability under different storage temperatures, RH, and light conditions, and release kinetics of sensitive pigment for meats and seafood products.