Effect of Polysaccharides on Rheological Properties of Soy Protein Isolate Emulsion Gels*

The effects of x-carrageenan (KC), sodium alginate (SA), xanthan gum (XG) and XG/locust bean gum (XG+LG) mixture on rheological properties and microstructure of soy protein isolate (SPI) emulsion gels were investigated. Rheological properties were determined with texture profile analysis, breaking test and creep-recovery curve analysis. KC increased the hardness and instantaneous elastic modulus, and showed the most effectiveness on the gels. While, XG showed the lowest effect on hardness. XG+LG addition gave the maximum in breaking force and deformation at heating from 20 to 60 min. Scanning electron microscope was used to evaluate the changes in the microstructure of SPI-emulsion gels with polysac-charides. Preparations were carried out by critical point drying and cryofracturing methods. The fat droplets in the gels were not thoroughly fixed by glutaraldehyde and it was shown that they were dislodged from the fractured surfaces, leaving vacuoles, These observations also showed a wide variation among emulsion gels with various polysaccharides on a microstructural basis, which may be correlated to rheological properties