Rheological properties of acidic soybean protein gels:: Salt addition effect

The objective of this work was to study rheological properties of acidic soybean protein gels in the presence of sodium and calcium chloride. The viscoelastic properties of acidic gels were affected by the amount and type of the assay salt. The pH 2.75 dispersions prepared with 0.1-0.25 M NaCl behaved as diluted macromolecular or entanglement solutions and were more viscous than elastic. At high ionic strength (2.0 M NaCl), samples were more elastic with a gel-like behavior. A semidiluted macromolecular solutions was observed for dispersions at pH 3.50 with 0.1 M NaCl, while at high salt concentration (0.25-2.0 M) gels were obtained. At pH 2.75 gelation kinetics was different at several NaCl concentrations, while at pH 3.50, first order kinetics was observed. At pH 2.75 and 0.1 M CaCl2, the dispersions behaved as semidiluted macromolecular solutions, while at 0.2 M CaCl2 diluted macromolecular solutions were obtained. A semidiluted solution dynamic spectra for pH 3.50 samples (0.1-0.2 M CaCl2) was observed. Both pH 2.75 and 3.50 gels prepared with several NaCl concentrations were more fragile, hardest and resistant rupture than those obtained with CaCl2. The textural properties of acidic gels were less modified by CaCl2. (C) 1999 Elsevier Science Ltd. All rights reserved.