Sources, stability, encapsulation and application of natural pigments in foods

In recent years, the replacement of synthetic colorants with natural ones has attracted increasing consumers' and market interest. Natural colorants include different groups of pigments, many of which possess also pronounced biological potential. This review addresses the main issues related to the use of natural pigments in foods, starting from the sources available in nature, their chemical properties, stabilization processes, and applications in real foods, as discussed in the scientific literature reported in the main databases relevant to this topic (Scopus, Web of Science, PubMed, ScienceDirect, and Google Scholar). Notably, several natural pigments are available to cover different needs in terms of hues and intensities, and whose use is permitted in foods by the main regulatory agencies. However, their use is still frequently limited by their higher price and lower stability than synthetic counterparts. This review discusses in detail the main sources for natural pigments, focusing on the recent trends towards those more economically favorable, such as microbial sources and agro-industrial residues. It also examines the most suitable stabilization systems to protect the highly reactive and unstable molecules of natural pigments from negative physical and chemical changes, as well as to minimize the interactions with food systems.