Protein isolates of faba bean and soybean, obtained using waste effluents of potato as protein extrahent, and water or 86% ethanol or 2% ascorbic acid for washing coagulum, were investigated. Both the use of 86% ethanol and 2% ascorbic acid lowered the solubility of isolates (approx. 1.7–11.9%), stronger protein denaturation being caused by ethanol. Although the use of waste effluents of potato increased trypsin inhibitors activity compared with the use of water, applying ethanol or ascorbic acid washing considerably lowered this activity. The use of 86% ethanol also caused an elimination of approx. 60% phytates from soybean isolates and a little less from faba bean ones. Ascorbic acid eliminated these undesirable compounds only to a small extent. In the case of 86% ethanol the organoleptic properties of isolates were found to have been improved. The isolates were of lighter colour and they were completely devoid of the leguminous taste.