Aqueous extraction of anthocyanins from Hibiscus sabdariffa : Experimental kinetics and modeling

Solid-liquid extraction of anthocyanins from calyces of Hibiscus sabdariffa L. was studied to evaluate the influence of the operating parameters. Solid-to-solvent ratio and particle size had the main impact on anthocyanin extraction efficiency. Maximum yield of anthocyanins (88%) was obtained at 25 °C with the highest solid-to-solvent ratio (1/25). The decrease in the particle size of the calyces from 2 cm to 150 ?m drastically reduced the extraction time. The increase of temperature reduced the extraction time by increasing the diffusion coefficient (3.9 × 10?11-1.35 × 10?10 m2 s?1 between 25 and 90 °C) but did not modify the extraction yield. A simple extraction model that integrated anthocyanin thermo-degradation kinetic was proposed. A good agreement between the predicted results of the models and experimental data was demonstrated. From a solid-to-solvent ratio of 1/5, an extraction yield of 63% and an anthocyanin concentration of 0.3 g L?1 could be obtained in less than 10 min. (Résumé d'auteur