Stabilization of flavylium dye by incorporation into the pore of protonated zeolites

Flavylium dye, a model compound of natural anthocyanin, has a defect that its color stability is very poor. We have complexed the flavylium dye with protonated zeolites and succeeded to enhance both the thermal and chemical stability of the dye. The aqueous dispersion of the flavylium/zeolite complex maintains its color even at 353 K or at pH 9, under which conditions the aqueous solution of the flavylium loses its color immediately. The stability is enhanced when the dye is incorporated into the pore of the zeolites, and a large stabilization effect is obtained by a tight adsorption with a narrow pore, as long as the dye is incorporated into the pore. Because of its enhanced color stability, the flavylium dye incorporated in the zeolite pore can be a candidate for an environmentally friendly coloring material.