Relationship between the rheological properties of thickener solutions and their velocity through the pharynx as measured by the ultrasonic pulse Doppler method.

The dependence of the dynamic viscoelastic parameters of carboxymethylcellulose (CMC), xanthan gum, and guar gum solutions on the angular frequency (omega) was compared with that of their viscosity (mu) on the shear rate (gamma). In addition, the effect of these rheological properties on the maximum velocity through the pharynx, V(max), as measured by the ultrasonic pulse Doppler method, was investigated. The CMC and guar gum solutions examined were taken as a dilute solution and a true polymer solution, respectively. The xanthan gum solution was taken as a weak gel above 0.5% and a true polymer solution below 0.2%. The maximum velocity, V(max), of the thickener solutions correlated well with mu, the dynamic viscosity eta', and the complex viscosity eta(*), especially those measured at gamma or omega of 20-30 s(-1) (or rad/s) and above, suggesting that mu, eta', and eta(*) are suitable indexes for care foods of the liquid type for dysphagic patients.