SOLID-LIQUID EXTRACTION OF QUERCETIN FROM ONION SKIN AND CONCENTRATION BY REVERSE OSMOSIS

摘要

Bioflavonoids are high addcd-value products in food and pharmaceutical industries as they have various physiological functions such as anti-oxidation and anti-cancer activity. Quercetin, one of bioflavonoids, is abundant in onion skin which is a waste product in onion processing. In view of quality of quercetin recovered and savings in separation cost, membrane processing can be considered one of the most promising methods. Membrane processing as a downstream processing technique for the recovery of quercetin was investigated. Our objective was to examine operation parameters associated with extraction and membrane processing suitable for partial purification and concentration for quercetin. Ground onion skin (30-100 mesh) was leached with 20 fold mass of solvent having various ethanol concentration. Optimum concentration was found to be 60%. The extract was filtered and the filtrate was centrifuged for 10 min at 10,000 rpm. The supernatant was then used for ultrafiltration with a polyethersulfone membrane of which the molecular weight cut off was 30 kDa. Optimum process parameters were transmembrane pressure of 15 psi and cross flow rate of 1 l/min. In subsequent reverse osmosis, permeate flux decreased from 23 L/ m~2·hr to 16.6 L/ m~2·hr as the concentration factor increased from 1 to 3. Negligible amount of quercetin was found in the permeate during reverse osmosis indicating that quercetin was concentrated in retentate. These results suggest that membrane processing can be successfully used for partial purification and concentration of quercetin from onion skin.