Fig. 1(B) illustrates the variation

Fig. 1(B) illustrates the variation of the basal reflection d001 with the amount of AN added. Thus, the interlayer spacing at the full adsorption of AN (plateau value, 1.56 nm) was 0.6 nm (subtracting the thickness of 0.96 nm from the basal spacing) (Endo et al., 1988). Considering that the anthocyanin has a planar flavylium skeleton with a glucose moiety, and that the sugar moiety of the anthocyanin is thought to be positioned perpendicular to the flavylium skeleton (Borkowski et al., 2005), this interlayer distance roughly corresponds to the molecular thickness of AN. In addition, the hydrophilic sugar moiety may adsorb water molecules in the interlayer space. A planar molecule such as xanthene dye showed the tendency to be adsorbed parallel to the silicate layer (Endo et al., 1988; Endo and Shimada,
1991). Similarly, the planar flavylium skeleton of AN is expected to have an affinity to the internal surface of KF. Not only the cationic polysaccharide chitosan (Darder et al., 2005) but also non-ionic starch (Wilhelm et al., 2003) was intercalated. Thus, a sugar moiety should also have affinity to the interlayer space. We concluded that AN was adsorbed between the layers of KF with the flavylium skeleton parallel to the clay mineral layer.