Natural pigments in clean-label foods: A matrix-guided critical review of sources, stability, biofunctionality, regulation, and industrial applications.

The transition toward clean-label food formulation has increased interest in natural pigments as alternatives to synthetic dyes, but industrial replacement requires more than confirming natural origin or initial color intensity. This matrix-guided critical review evaluates anthocyanins, carotenoids, chlorophylls, betalains, and selected emerging microbial and algal pigment platforms by integrating sources, physicochemical behavior, degradation pathways, biofunctional relevance, stabilization strategies, regulatory status, techno-economic feasibility, and food-matrix compatibility. Particular emphasis is placed on how pH, oxygen, temperature, light, metals, proteins, lipids, polysaccharides, processing intensity, and storage conditions determine color retention in real foods. The review compares pigment suitability across acidic aqueous, protein-rich, polysaccharide-rich and high-solids, lipid-rich and emulsion-based, and responsive polymeric matrices, with representative applications in beverages, dairy systems, confectionery, bakery products, edible oils, and intelligent packaging. Recent advances in green extraction, enzyme-assisted recovery, agro-industrial by-product valorization, encapsulation, emulsion-based delivery, microbial pigment production, and predictive formulation are discussed with attention to scale-up and clean-label constraints. A semi-quantitative decision-oriented framework is proposed to connect pigment chemistry with matrix conditions, processing tolerance, labeling feasibility, and commercial scalability. Regulatory distinctions among color additives, coloring foods, encapsulated pigment systems, and pigments from microbial or novel production routes are also considered. Overall, this review argues that the successful use of natural pigments in clean-label foods should be approached as a matrix-specific formulation and regulatory-design problem rather than as a universal substitution strategy.