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Determination of Characteristic Shear Rate of a Liquid Bolus through the Pharynx during Swallowing
Author(s) -
Zhu J.F.,
Mizunuma H.,
Michiwaki Y.
Publication year - 2014
Publication title -
journal of texture studies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.593
H-Index - 54
eISSN - 1745-4603
pISSN - 0022-4901
DOI - 10.1111/jtxs.12094
Subject(s) - shear thinning , bolus (digestion) , shear rate , viscosity , rheology , pharynx , shear (geology) , swallowing , materials science , liquid food , chemistry , apparent viscosity , chromatography , analytical chemistry (journal) , anatomy , composite material , medicine , surgery , food science
A method for determining the characteristic shear rates of fluids in the pharynx is advanced here using videofluorography on three healthy subjects. Bolus velocity ( V ) was measured for five N ewtonian fluids (using different concentrations of glucose syrup), with viscosities in the range of 0.0089–0.657 Pa·s, and was expressed as a function of viscosity ( η ). Shear thinning liquid food (with four different thickener concentrations) was also used where the apparent viscosities were adjusted to match the N ewtonian fluid viscosities in the shear rate range of 10–1,000/s. The N ewtonian and shear thinning liquid bolus velocities were both assumed to follow the same function V = F ( η ), which gave the shear thinning liquid characteristic viscosities η c [= F −1 ( V )]. Substituting η c into the rheological model gaveγ ˙ c , the characteristic shear rate dominating bolus flow at the pharynx.γ ˙ cvalues of 120 and 990/s were found at the meso‐ and hypopharynx, respectively, and these were approximately independent of η c (and thickener concentration). V was found to be a function of both the characteristic viscosity and the differences between the individuals tested. Practical Applications The viscosity of liquid foods (e.g., in care homes) can be increased using a thickener, suppressing the effects of swallowing disorders. Thickened liquid food shows viscous shear thinning behavior, and the apparent viscosity depends on shear rate. When the viscosity of the food is adjusted for a patient with a swallowing disorder, the viscosity should be measured at the shear rate that dominates the liquid bolus flow at the pharynx. The measured viscosity is expected to correlate well with the bolus flow characteristics. The new experimental methodology proposed herein can be used to determine the characteristic shear rate at the pharynx.