Preparation of Lake Pigment from Calcium Carbonate and Cyanidin-3-O-Glucoside: Structural Characterization and...

To explore potential strategies for improving the applicability of cyanidin-3-O-glucoside (C3G) and to avoid the health risks associated with the in vivo accumulation of aluminum by intake of traditional aluminum-based lake pigments, food-grade CaCO₃ was used as a matrix to prepare two types of edible lake pigments, namely C3G-CaCO₃ and MA-CaCO₃, via coprecipitation method using purified cyanidin-3-O-glucoside (C3G) and non-purified mulberry anthocyanins (MA). The effect of pH on adsorption was systematically investigated, and various characterization methods were used to analyze the physicochemical properties and formation mechanism of lake pigments. The results showed that pH 9.5 was the optimal condition for CaCO₃ to adsorb MA. The introduction of C3G altered the particle size, surface charge, and other characteristics of CaCO₃ without changing its calcite crystal form. The adsorption of MA and C3G on the CaCO₃ surface was multilayer physical adsorption, dominated by the Freundlich model. The isothermal adsorption results showed that CaCO₃ exhibited a higher adsorption capacity for C3G than for MA at equivalent equilibrium concentrations, demonstrating C3G's superior binding affinity. C3G primarily binds to calcium carbonate through surface adsorption, with possible partial diffusion of molecules into the matrix, without forming new chemical bonds, and slightly regulated the thermal stability of CaCO₃. This study successfully constructed a lake pigment system based on CaCO₃, systematically elucidated its adsorption behavior and structural characteristics toward anthocyanins, and provided a material foundation for the further application of this type of carrier in the food sector.