Abstract
Purpose: The use of commercial thickeners is prevalent when treating dysphagic persons. Defining thickness levels and the physical characteristics of each level have not been standardized. This study was done to establish three levels of thickness (mildly thick, moderately thick, and very thick) comparing a sensory evaluation to a Line Spread Test (LST) and viscosity measurements.
Methods: Six thickeners (1 starch, 1 guar gum and 4 xanthan gums) were used in this study. Twenty four thickened liquids were made using 4 concentration levels of 6 thickeners. These materials were served to 42 clinicians who have managed dysphagia more than 5 years for a sensory evaluation. They were asked to categorize each sample into one of five numerical categories (1: thinner than “mildly thick”, 2: mildly thick, 3: moderately thick, 4: very thick, and 5: thicker than “very thick”). Averaged evaluation data for each of 24 thickened liquids were calculated. Viscosity was measured using an E-type viscometer at 50 s-1 shear velocity. The same materials were measured with a LST. Correlation of averaged sensory evaluation data with objective viscosity and LST values were analyzed by calculating Pearson's correlation coefficient (r) and a coefficient of determination of regression line (R2). Three categories of thickened liquids by xanthan gum (mildly, moderately and very thick) were chosen to investigate the ranges of viscosity and LST value equivalent to each level of thickness.
Results and Discussion: A strong positive correlation existed between averaged sensory evaluation categories and actual objective viscosity (r＝0.769, R2 ＝0.9183). A strong negative correlation existed between averaged sensory evaluation data and the LST values (r＝－0.942, R2 ＝0.8812). There was a negative correlation between objective viscosity measurements and the LST values (r＝－0.630, R2 ＝0.7264). The objective viscosity measurements and the LST values of level 1 liquids ranged from 55 mPa・s to 100 mPa・s and from 43 mm to 40 mm, respectively. Those of level 2 liquids ranged from 150 mPa・s to 260 mPa・s and from 38 mm to 34 mm, respectively. Those of level 3 liquid ranged from 400 mPa・s to 450 mPa・s and from 32 mm to 30 mm, respectively. Strong correlations between the sensory evaluation, objective viscosity measurements and LST values supports the effectiveness of objective viscosity measurements using E-type viscometer at 50 s-1 shear velocity and LST values in verifying physical characteristics of the thickened liquids.
