COMPOSITION AND FUNCTIONAL-PROPERTIES OF PROTEIN ISOLATES OBTAINED FROM COMMERCIAL LEGUMES GROWN IN NORTHERN SPAIN

Pea (Pisum sativum), faba bean (Vicia faba) and soybean (Glycine max) seeds were characterized, and protein isolates were prepared following an isoelectric point precipitation procedure. Soybean seeds showed th e highest protein content (36.7%) and carbohydrate was the major const ituent in the pea (59.4%) and the faba bean seeds (52.1%). Protein con tents were higher than 80% in all the protein isolates. The amino acid contents in the protein isolates were, in general, higher than those in their own starting seeds. The antinutritional factor contents were reduced after the protein isolate preparation. The highest reductions achieved for tannins were 95% in the faba bean protein isolate, and fo r phytates (45%) and trypsin inhibitor activity (46%) in the pea prote in isolate. Haemagglutinating activity was not detected in any of the protein isolates. Minimum solubility values were observed at a pH rang e between 4.0 and 6.0, and maximal solubilities were obtained at basic pH values. The faba bean protein isolate showed the highest water and oil absorption capacities, and the best gelling properties. The soybe an protein isolate had the best foam expansion capacity. Thus, the pro tein isolates had an improvement in some of the characteristics compar ed to their original seeds with lower contents in tannins, phytates an d haemagglutinating activity, but had weak functional properties.