Non-toxic hybrid pigments: Sequestering betanidin chromophores on inorganic matrices

Betalain was extracted from bougainvillea flower. Alumina, layered double hydroxides (LDHs) and zeolites were tested as adsorbents of the chromophore. Gamma alumina stabilized betalains over a long period. The adsorption sites which stabilized the chromophores were elucidated by nuclear magnetic resonance. Although the oxides obtained by calcination of LDHs retain betalains, they were oxidized within 20 h or react with Zn2+ of the calcined LDH. No betalain was adsorbed in zeolite X because of the too small pores.