Phycoerythrin adsorbed easily to synthetic hectorite when the clay was admixed with the pigment solution. In contrast, its adsorption on natural montmorillonite was difficult; addition of a salt to the solution was necessary to obtain the composite. In addition, as hectorite is a synthetic product, which is more transparent than montmorillonite, its composite was more vivid. These findings indicate that hectorite is preferable as the host of the pigment.
The resulting composites, especially hectorite composites, were vivid red powders that exhibited fluorescence. Furthermore, heat and light fastness, which are serious drawbacks of phycoerythrin, were improved by adsorption of the pigment.