2009 Volume 13 Issue 1 Pages 10-19
The aim of this study was to investigate the usefulness of texture profile analysis (TPA) as a method for measuring the mechanical properties of dysphagia thickening agents. Commercial dysphagia products were dispersed or dissolved in de-ionized water as a solvent and subjected to some physical measurements, including TPA for hardness, adhesiveness, and cohesiveness, shear viscosity using a B-type viscometer, shape retention by the so-called ring method, and strain and frequency dependence of dynamic viscoelasticities to examine the correlation among measurements. Data cross-checking was also carried out among institutions using the same test samples.
Xanthan-gum based products behaved rheologically as weak gels, showing a low degree of frequency dependence of dynamic storage modulus with mechanical loss tangent ranging from 0.1 to 1 throughout the frequencies assessed. Also, hardness and cohesiveness from TPA were hardly altered by table speed or deformation speed. At a table speed of 10 mm/s and reasonable addition levels from an application point of view (i.e., ＜5%), TPA hardness increased from 170 to 1,200 N/m2 with addition level, while cohesiveness was rather constant within 0.7–0.9 regardless of hardness. A positive correlation was evident between hardness and shear viscosity, while a negative correlation was found between hardness and the ring method indication. Essentially the same data were obtained by different institutions for TPA but not for the viscosity.
The results indicate the usefulness of TPA as a mechanical measurement for dysphagia thickening agents, and their mechanical properties can be well described by a hardness-cohesiveness two-dimensional plot. TPA is advantageous over other physical methods in that it is performed using instruments widely used in the food industry and that it shows a good correlation with other conventional methods along with high data reproducibility, contributing to quality control and texture design of dysphagia products.
