Natural betalains supported on γ-alumina: A wide family of stable pigments

Natural betalain chromophores, extracted from bougainvillea flowers, were stabilised on different surfaces of γ-alumina matrices. This strategy was used to produce a family of hybrid pigments including one yellow and several purple hues. Both textural and structural parameters of γ-alumina were identified as important factors to stabilise the chromophores. Particularly, a high amount of coordinative unsaturated sites of aluminium, high surface specific areas and pore diameters as high as 15 nm are suitable to stabilise the purple chromophores.