Rheological Studies on Gelling Behavior of Soy Protein Isolates

The gelling behavior of soy protein isolate (SPI) dispersions with solid contents 0.8-8.8% was studied by a dynamic fluid rheometer. Strain sweep and frequency sweep measurements showed the dispersions were stable and predominantly elastic at room temperature. Elasticity increased sharply when dispersions were heated. Cooling set was found for dispersions of higher solid contents. For solids contents < 3%, cooling set was not as pronounced; and cooling could result in reduced elasticity when the prior heating was milder. Results suggest SPI changed from an aqueous dispersion to a dispersion consisting of particles embedded in heat-soluble protein sol matrix upon heat treatment, and further underwent a transition into a gel consisting of particles embedded in heat-formed protein gel matrix. Thermoreversibility of elasticity was determined by solids content.