Effect of preheating temperature and calcium ions on the properties of cold-set soybean protein gel

To elucidate the effect of preheating temperature and calcium ions on the properties of cold-set soybean protein gel, Ca2+ induced gelation of soybean protein were investigated by theological approaches, electrophoresis analysis, confocal scanning laser microscopy (CSLM) and surface hydrophobicity (S-0). The results showed that, both CaCl2 concentration (20-40 mM) and preheating temperature (80-120 degrees C) took significant influence on the dynamic viscoelasticity of the gel samples. The bands distribution of samples preheated at 120 degrees C were different from the bands distribution of samples preheated below 100 degrees C in denature and native electrophoresis. The CSLM analysis showed that the gel became coarser as the Ca2+ increased. On the other hand, two different kinds of gel were shown under the same Ca2+ concentration: a bead-like structure (below 100 degrees C) and a filamentous structure (above 100 degrees C). According to fractal theory, weak-linked gel (alpha was >0.8) was formed when preheating below 100 degrees C, while a transition gel (alpha = 0.52-0.62) was obtained when preheating over 100 degrees C. All these results suggested that the preheating temperature influence the type of cold-set gel. (C) 2010 Elsevier Ltd. All rights reserved.