Functional properties of hydrothermally cooked soy protein products

The effects of hydrothermal cooking on the functional properties of defatte d soy flour, aqueous alcohol washed soy protein concentrate, and soy protei n isolate were determined in samples that were treated at 154 degreesC by i nfusing steam under pressure for 11, 19, 30, and 42 s, and then spray dried . Hydrothermal cooking increased the nitrogen solubility index (NSI) of the concentrate from 15 to 56% and altered the solubility profile from a flat profile to one more typical of native soy protein. Hydrothermal cooking als o improved foaming and emulsifying properties of the concentrate. For isola te, hydrothermal cooking also improved NSI and foaming and emulsifying prop erties, although the improvements were less dramatic than with concentrate. NSI and emulsifying properties of the flour were improved by some processi ng conditions, but foaming properties were not improved by hydrothermal coo king. Dramatically increased protein solubility of concentrate and modestly improved protein solubilities of flour and isolate by hydrothermal cooking , which will also inactivate trypsin inhibitors and microorganism's, have c onsiderable practical significance to protein ingredient manufacturers and those who use these ingredients in foods and industrial products.