Corrigendum to "Challenges to assumptions regarding oral shear rate during oral processing and swallowing based on sensory testing with thickened liquids" [Food Hydrocolloids 84C (2018) 173-180].

[This corrects the article PMC6367734.].

Modulation of Tongue Pressure According to Liquid Flow Properties in Healthy Swallowing.

Purpose During swallowing, the tongue generates the primary propulsive forces that transport material through the oral cavity toward the pharynx. Previous literature suggests that higher tongue pressure amplitudes are generated for extremely thick liquids compared with thin liquids. The purpose of this study was to collect detailed information about the modulation of tongue pressure amplitude and timing across the range from thin to moderately thick liquids. Method Tongue pressure patterns were measured in 38 healthy adults (aged under 60 years) during swallowing with 4 levels of progressively thicker liquid consistency (International Dysphagia Diet Standardisation Initiative, Levels 0 = thin, 1 = slightly thick, 2 = mildly thick, and 3 = moderately thick). Stimuli with matching gravity flow (measured using the International Dysphagia Diet Standardisation Initiative Flow Test; Cichero et al., 2017 ; Hanson, 2016 ) were prepared both with/without barium (20% weight per volume concentration) and thickened with starch and xanthan gum thickeners. Results After controlling for variations in sip volume, thicker liquids were found to elicit significantly higher amplitudes of peak tongue pressure and a pattern of higher (i.e., steeper) pressure rise and decay slopes (change in pressure per unit time). Explorations across stimuli with similar flow but prepared with different thickeners and with/without barium revealed very few differences in tongue pressure, with the exception of significantly higher pressure amplitudes and rise slopes for nonbarium, starch-thickened slightly and mildly thick liquids. Conclusions There was no evidence that the addition of barium led to systematic differences in tongue pressure parameters across liquids with closely matched gravity flow. Additionally, no significant differences in tongue pressure parameters were found across thickening agents. Supplemental Material https://doi.org/10.23641/asha.7616537.

Sensory characteristics of liquids thickened with commercial thickeners to levels specified in the International Dysphagia Diet Standardization Initiative (IDDSI) framework.

Sensory characteristics are important for the acceptance of thickened liquids, but those of liquids thickened to the new standards put forth by the International Dysphagia Diet Standardization Initiative (IDDSI) are unknown. This research sought to identify and rate the perception of important sensory properties of liquids thickened to levels specified in the IDDSI framework. Samples were made with water, with and without added barium sulfate, and were thickened with a cornstarch or xanthan gum based thickener. Samples were characterized using projective mapping/ultra-flash profiling to identify important sample attributes, and then with trained descriptive analysis panels to characterize those attributes in non-barium and barium thickened liquids. Three main groups of attributes were observed. Taste and flavor attributes decreased in intensity with increasing thickener. Thickener specific attributes included graininess and chalkiness for the cornstarch thickened samples, and slipperiness for the xanthan gum samples. Within the same type of thickener, ratings of thickness-related attributes (perceived viscosity, adhesiveness, manipulation, and swallowing) at different IDDSI levels were significantly different from each other. However, in non-barium samples, cornstarch samples were perceived as thicker than xanthan gum samples even though they had similar apparent viscosities at 50 s-1. On the other hand, the two thickeners had similar perceived thickness in the barium samples even though the apparent viscosities of cornstarch samples were higher than those of the xanthan gum samples. In conclusion, IDDSI levels can be distinguished based on sensory properties, but these properties may be affected by the type of thickener and medium being thickened.

Challenges to assumptions regarding oral shear rate during oral processing and swallowing based on sensory testing with thickened liquids.

For people with dysphagia, or difficulty swallowing, thickened liquids are used to slow bolus flow to make them easier to control. For these liquids, the oral shear rate of 50 s-1 has been adopted as the standard at which viscosity measurements are taken. However, there is evidence to suggest that other shear rates may be more appropriate to model the processes in the mouth and throat. This research compared the sensory and rheological properties of xanthan gum, guar gum, and carboxymethyl cellulose thickened liquids that had been matched for apparent viscosity at 50 s-1 to assess the validity of the current shear rate standard. Properties of gums were observed at various viscosity levels based on the International Dysphagia Diet Standardisation Initiative (IDDSI) framework. Textural sensory characteristics of samples were quantified using magnitude estimation scaling and a trained descriptive panel, while rheological measurements were taken at shear rates of 1 to 1000 s-1. Perceived slipperiness of the gums was found to be driven by thickness level at low viscosity levels, but affected by the shear thinning behavior of the gums at higher viscosity levels. Although the liquids had been matched for apparent viscosity at 50 s-1, panelists could distinguish both the perceived viscosities of the gums and their ease of swallowing, suggesting that 50 s-1 is neither appropriate to model the oral nor pharyngeal shear rates. A single oral shear rate could not be predicted from the data, and it is proposed that panelists evaluated oral viscosity using different methods at different viscosity levels. Based on the sensory data, the pharyngeal shear rate during swallowing appears to lie above 50 s-1.