Rheological characterization of thickened beverages used in the treatment of dysphagia

Dysphagia is a difficulty in eating and swallowing of solid and/or liquid foods. Thickened beverages are traditionally used in the clinical treatment of dysphagia to liquids. The objectives of this study were to evaluate the rheology of clinically efficient cold thickened beverages and relate them to the consistency groups (traditionally recognized as nectar, honey and pudding). Rheological tests were carried out at the serving temperature of 8 degrees C using a rotational viscometer using a pre-established upward and downward shearing sequence. Rheological parameters such as consistency coefficient, flow behavior index, yield stress and apparent viscosity were computed. All beverages tested demonstrated a shear-thinning pseudoplastic flow behavior with yield stress, and were best fitted to the Herschel-Bulkley model. Yet, the correlation coefficient between the consistency coefficient and the Bostwick consistency levels (nectar, honey and pudding) was found to be poor (0.6-0.7). The apparent viscosity and the Bostwick consistency levels showed slightly better correlation coefficients (0.73-0.83). At each Bostwick consistency level, the yield stress, consistency coefficient and apparent viscosity values were found different (p < 0.05). The apparent viscosity values (average +/- SD) were 615 +/- 260 mPa s for the nectar, 1480 +/- 790 mPa s for the honey and 3340 +/- 1240 mPa s for the pudding consistency. (c) 2005 Elsevier Ltd. All rights reserved.