A novel edible colorant lake prepared with CaCO3 and Monascus pigments: lake characterization and mechanism study

Monascus pigments (MPs) were adsorbed using calcium carbonate to produce CaCO3-MPs lakes. The fundamental properties and formation mechanism of the lakes were investigated. Results indicated that CaCO3 displayed a high enough affinity for the MPs to form colorant lakes, while the MPs tended to transform the CaCO3 crystals from calcite to vaterite. The adsorption of MPs by CaCO3 followed the Freundlich isothermal model with n value higher than 1, confirming it as physical adsorption. The ΔG0 (-29 to ∼-33 kJ/mol) and ΔH0(30-55 kJ/mol) indicated that lake formation was a spontaneous and endothermic process. UV/Vis spectroscopic analysis verified the complex formation between Ca2+ and MPs via physical bonding, suggesting a possible attraction between the Ca2+ and glutamate residues of the MPs. EDS showed that the MPs were trapped inside the particles. FTIR spectroscopy and XPS further confirmed that the physical bonding was the primary driving force behind the lake formation.