Rheological properties of acidic soybean protein gels: Salt addition effect

The objective of this work was to study rheological properties of acidic so ybean protein gels in the presence of sodium and calcium chloride. The visc oelastic 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 behav ed as diluted macromolecular or entanglement solutions and were more viscou s than elastic. At high ionic strength (2.0 M NaCl), samples were more elas tic with a gel-like behavior. A semidiluted macromolecular solutions was ob served for dispersions at pH 3.50 with 0.1 M NaCl, while at high salt conce ntration (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 kin etics 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 macromol ecular 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 re sistant 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.