Suspensions of vacuum-freeze dried starch nanoparticles: influence of NaCl on their rheological properties.

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(2)>0.94).