The viscoelastic property and scaling behavior of acid (glucono-delta-lactone)-induced soy protein isolate (SPI) gels were investigated at various ionic strengths (0-800 mM) and five protein concentrations ranging between 4% and 8% (w/w). The infinite storage modulus (G '(infinity)) and the gelation start time (t(g))which indicate the progress of gelation process exhibited strong ionic strength dependence. The storage modulus and critical strain were found to exhibit a power-law relationship with protein concentration. Rheological analysis and confocal laser scanning microscopy (CLSM) analysis were applied to estimate the fractal dimensions (D-f) of the gels and the values were found to vary between 2.319 and 2.729. The comparison of the rheological methods and the CLSM image analysis method showed that the Shih, Shih, Kim, Liu, and Aksay (1990) model was better suited in estimating the D-f value of acid-induced SPI gel system. (C) 2012 Elsevier Ltd. All rights reserved.
The effect of addition of NaCl on rheological properties of suspensions containing vacuum freeze dried starch nanoparticles was studied. These starch nanoparticles were produced through high pressure homogenization and emulsion cross-linking technique. Rheological properties such as continuous shear viscosity, storage and loss moduli and creep-recovery were measured. The presence of NaCl at concentration (5-15%, w/v) increased viscosity marginally (p > 0.05) while at 20% (w/v) it significantly (p < 0.05) increased viscosity. The presence of NaCl enhanced heat stability and weakened gelling capacity of suspensions. NaCl concentration below 15% (w/v) marginally (p > 0.05) increased the storage and loss moduli of suspensions. At 20% (w/v), NaCl increased both moduli significantly (p < 0.05) within frequency range tested (0.1-10 rad/s). Creep-recovery behavior was affected by NaCl and recovery rate was the highest (98.6%) at 20% (w/v) NaCl. The Cross, Power Law and Burgers' models followed experimental shear viscosity, storage and loss moduli and creep-recovery data reasonably well ((R