Abstract: The integration of ultra-filtration and reverse osmosis membrane technology can provide a protection effect on Hibiscus sabdariffa pigments and improve their quality during purification and condensation process at room temperature. The optimal separation process conditions were ultra-filtration pressure of 0.3 MPa, filtration temperature of 30 ℃, flow rate of 1.375 m/s and material/liquid ratio of 1:4. Under the optimal separation conditions, the separation rates of pectin and pigment were over 96% and 90%, respectively. The permeate was condensed to 20 °Bx by reverse osmosis at 4.5 MPa and 30 ℃. The membrane cleaning method discussed in this paper can provide a promising method for separating and concentrating Hibiscus sabdariffa pigments and other natural pigments.

Key words: Hibiscus sabdariffa L, ultra-filtration, reverse osmosis, membrane cleaning