Color stabilization of cyanidin-3-glucoside-based dyes by encapsulation with biocompatible PEGylated phospholipid micelles

Anthocyanins color stabilization is a constant concern of the scientific community which has been searching different approaches since encapsulation technology to development of new host-guest systems. In this work, the interaction between a biocompatible self-assembled system (PEGylated phospholipid micelles) and two anthocyanin dyes was studied by UV–Vis, stopped-flow, NMR and DLS. Overall, the results obtained clearly showed a superior stabilization and intensification effect on the colored species of anthocyanin dyes in the presence of PEGylated phospholipid micelles. The red flavylium cation of cyanidin-3-glucoside was preferentially encapsulated by the negatively charged micelles rather than the colorless hemiketal species resulting in an increase of absorbance of the solution color in 36% at pH 3.5. The thermodynamic constants were also modulated in the presence of the micelles, namely the hydration constant (pK_h) and the apparent acidic equilibrium constant (pK'_a) increased in 0.5–0.6 pH units. In the case of the anthocyanin lipophilic pigment, it was observed an increase in the mole fraction of blue quinoidal base concomitantly with the decrease of the hemiketal species from pH above 6 (circa 40%) displaying stable bluish colored solutions. The tuning and color stabilization of anthocyanin-based dyes using this biocompatible system envisage novel applications such as colorimetric sensors for food packaging.