Intelligent carrageenan-based composite films containing color indicator-loaded nanoparticles for monitoring fish freshness

Recently, intelligent packaging integrated with natural colorants has garnered interest for its capability to assess the freshness of stored food and delay its spoilage. However, the poor dispersibility and stability of natural pigments limit their application. This study addresses these issues by encapsulating natural pigments in core-shell protein-polysaccharide nanoparticles to enhance their stability and dispersibility. Using curcumin and anthocyanin as examples, pigment-loaded nanoparticles were synthesized using antisolvent precipitation to create zein particles, which were then coated with chondroitin sulfate through electrostatic layer-by-layer deposition. This method produced spherical anionic nanoparticles with high encapsulation efficiency (Curcumin: 91.93 %, Anthocyanin: 85.85 %). These nanoparticles were incorporated into carrageenan-based composite films, which acted as freshness indicators and preservatives. The films' color shifted from green-brown ( L =33.47, a =9.46, b =11.09) to red-brown ( L =22.80, a =13.83, b =2.11) with increasing nanoparticle concentration (from 20 % to 40 % w/v), and their uniform microstructure demonstrated good compatibility with the biopolymer matrix. The films were tested as freshness indicators and preservatives for packaged fish, showing improved freshness detection and preservation effectiveness with higher nanoparticle content. These biodegradable materials are expected to be intelligent packaging solutions for the food sector.