Anthocyanin-based intelligent films and labels for monitoring food freshness and spoilage: A comprehensive review

Maintaining food quality and safety throughout the supply chain remains critical, particularly for perishable commodities. Traditional packaging methods inadequately monitor real-time freshness and preventing food spoilage. Intelligent packaging systems incorporating pH-sensitive colourimetric indicators offer promising solutions. Anthocyanins, water-soluble flavonoid compounds responsible for the red, purple, and blue colours in many plants and stored in cell vacuoles, are natural pigments from fruits, vegetables, and flowers. They have attracted increasing attention due to their pH-responsive properties, non-toxicity, and compatibility with biodegradable polymers. This comprehensive review examines anthocyanin-incorporated intelligent and consumer-friendly films and labels to reduce food waste, enhance safety, and promote environmental sustainability. Anthocyanin types, sources, and intelligent properties, highlighting structural diversity and pH-dependent colour transformation mechanisms are discussed. Sustainable bio-matrices including polysaccharides (chitosan, cellulose, starch, pectin) and proteins are evaluated for supporting anthocyanin functionality. Advanced fabrication strategies from conventional solvent casting to electrospinning and 3D printing and its film performance and commercial viability are also reviewed. Recent applications across fruits, vegetables, dairy products, and muscle foods demonstrate system versatility in providing real-time visual freshness indicators through colour changes correlated with spoilage markers. Despite some progress, considerable challenges from anthocyanin stability, formulation standardization, production scalability, and regulatory approval needs to be solved.