Soy derived materials such as soy milk, soy flour, soy concentrates, and soy protein isolates, are deflavored by adjusting the pH of an aqueous composition of such soy derived materials to about 9 to about 12 to solubilize the soy proteins and to release the flavoring compounds and thereafter passing the pH-adjusted composition to an ultrafiltration membrane having a molecular weight cutoff up to about 50,000 Daltons under conditions at which the flavoring compounds pass through the membrane, leaving the retained soy material with improved flavor.