Make your packaging colorful and multifunctional: The molecular interaction and properties characterization of natural colorant-based films and their applications in food industry

Great attentions have been paid on the safety and quality of food products, leading to emerging innovations in food packaging industry. The natural colorants with eco-friendly and multi-functional properties are widely integrated into packaging films. And the natural colorant-based film can not only protect food from surrounding environment, but also behave indicator and active functions as a promising component for novel food packaging. This review provides a thoroughly insight into recent advances in natural colorant-based food packaging. Main 7 kinds of natural pigments were critically summarized. The molecular interaction between natural colorants and bio-polymers was investigated. Meanwhile, the influences of molecular interaction on physical and functional properties of natural colorant-based films were clearly discussed. Additionally, the applications of natural colorant-based film in terms of indicator and active food packaging were systematically summed. Furthermore, the major bottlenecks and future prospects were also illustrated for the further application of natural colorant-based film. The molecular interactions which were varied due to different charged natures of natural colorants, exerted significant influences on film physical properties, including structural, mechanical, hydrophobic, thermal and oxygen permeability properties. The natural colorant-based film which exhibited great pH-responsive, active and barrier characteristics, was suitable for the freshness monitoring and maintenance of food products, being regarded as indicator and active food packaging. Nevertheless, further studies focusing on the stabilization modification of colorants as well as the commercial production method of natural colorant-based films are critically needed.