Anthocyanin Films in Freshness Assessment of Minced Fish

Introduction. Smart food packaging that alerts consumers to spoilt food by changing color is based on affordable and biodegradable raw materials. The research objective was to develop films from anionic polysaccharides and anthocyanin pigment that can be used as a freshness indicator of minced fish. Study objects and methods. The study featured frozen black currant berries (Ríbes nígrum), polysaccharide-based anthocyanin films, and minced fish. Extracts of anthocyanin pigment and films based on agar, kappa-carrageenan, chitosan, starch, and anthocyanin pigments were analyzed by IR spectroscopy. Results and its discussion. Anionic polysaccharides, i.e. agar and kappa-carrageenan, demonstrated good film-forming properties. Films based on 1.5% agar and 2% kappa-carrageenan showed elasticity, resilience, plasticity, and sufficient resistance to mechanical deformation. Neutral polysaccharide starch and cationic polysaccharide chitosan appeared to have no such qualities. An IR spectral analysis revealed chemical interactions between polysaccharide and anthocyanin molecules. It indicated the electrostatic nature of the polyelectrolyte complexes of the anthocyanin pigment with anionic polysaccharides. A film based on 1.5% agar fortified with anthocyanin pigment was used as a test-system for analyzing the quality of fish. The minced fish samples were wrapped in the anthocyanin film and left for 2–7 min to register the color change of the film. When the anthocyanin film came in contact with fresh fish, the color of the film did not change even after prolonged contact. When the film came into contact with spoilt fish, the color of the film began to change after 2 min of contact. When the contact time reached 7 min, the film turned blue. Conclusion. The type of polysaccharide and the interaction between polysaccharides and anthocyanin pigment had a significant effect on film formation. Anionic polysaccharides demonstrated the best results. Electrostatic interactions between anionic polysaccharides and anthocyanin pigments produced stable polyelectrolyte complexes. The new smart films were able to determine the quality of minced fish.