Abstract
The aim of this study was to investigate the encapsulation of natural food dyes incorporated into liposomes in terms of particle size, rheological and colour properties, zeta potential, and encapsulation efficiency. The liposomes contained dye substances of anthocyanins from freeze-dried raspberry powder (R), copper complexes of chlorophyllins (C), or commercial-grade β-carotene (B). The phospholipid envelope was composed of sunflower lecithin and carboxymethylcellulose sodium salt as a surface stabilizer treated by high-pressure homogenization. The median particle diameter of R and C systems fluctuated around 200 nm, while B systems showed a broader range of 165-405 nm. The rheological results demonstrated a specific flow behaviour pattern dependent on the rotational shear applied, indicating a flow-induced structural change in the dispersions. Samples were characterized by a translucent profile with relatively high lightness, accompanied by a hue angle (h*) typical of the dye encapsulated. The zeta potential was approx. -30 mV, showing electrokinetically stabilized dispersions. The encapsulation efficiency (EE) varied significantly, with the highest EE observed for anthocyanins, ranging from 36.17 to 84.61%. The chlorophyll encapsulation was the least effective, determined in the range between 1.82 and 16.03%. Based on the suitability index, optimal liposomal formulations were evaluated by means of the Central Composite Design (CCD).