Purification of Soybean Isoflavones from Soy Sauce Residue by Ultrafiltration

The extraction of soybean isoflavones from the soy sauce residue which is the byproduct of soy sauce process is of great significance to improve the utilization of the soy sauce residue. Ultrafiltration (UF) membrane with molecular weight cutoff of 20 kDa was used to purify the extraction of isoflavones. The effects of ultrafiltration pressure, ultrafiltration temperature, feeding velocity, feed concentration and the feed pH on the membrane flux and rejection were analyzed. And then the membrane was cleaned. After purifying the crude soybean isoflavones from the soy sauce reside, the content of isoflavones in the freeze-dried powder was up to 6.27%.