Rheological study of dispersions prepared with modified soybean protein isolates

Structural modifications of modified soy protein isolates (SPI) were distin guished by rheological behavior. SPI were prepared by acidic (pH 2.5) and t hermal-acidic treatment without (pH 1.6) and with neutralization (pH 8.0). Dynamic properties of dispersions were determined through the variation of storage and loss moduli with frequency, and loss tangent behavior was analy zed. Changes in viscoelastic parameters with protein concentration (10-12% wt/vol) and time of heating (15-60 min) were also determined. Flow properti es of dispersions were estimated through apparent viscosity and flow and co nsistency index measurements. Rheological behavior of dispersions was compa red with those found by experiment with commercial mayonnaise, mustard, and salad dressing. The analysis of rheological parameters showed that thermal ly treated isolates formed dispersions with high elastic modulus and consis tency index with a structure mainly stabilized by hydrophobic interactions, although no gelation process after cooling was observed. From the rheologi cal point of view, it was deduced that thermally treated isolates could be used as ingredients in the formulation of salad dressings. The alkaline sam ple would be more versatile because, depending on protein concentration and thermal treatment, the consistency of its dispersions was like that in sal ad dressing, or similar to those of mustard and mayonnaise.