Soybean protein dispersions at acid pH. Thermal and rheological properties

The influence of pH, protein concentration, and ionic strength, on rheologi cal properties of thermally treated acidic soy protein dispersions, was stu died. Structural changes due to pH effect and thermal treatment were analiz ed. DSC-thermograms at pH 3.5 showed a shoulder at 74.11+/-0.16 degrees C t hat could be attributed to both beta-conglycinin and the hexameric form of glycinin; and a peak at 81.88+/-0.29 degrees C corresponding to 11S dodecam eric form. At pH 2.75 one endotherm corresponded to denaturation of beta-co nglycinin. The acidic dispersions presented pseudoplastic behavior with eta (app) values higher than those at pH 8.0. At pH 3.50 the eta(app) was highe r than at pH 2.75. The maximum viscoelasticiy was obtained with addition of 0.1 and 0.25M NaCl in the dispersions of pH 3.50 and 2.75, respectively. T he increase in viscoelasticity was enhanced by the formation of 11S native fraction dimers.