Gellan gum: A new member in the dysphagia thickener family

In this study, gellan gum (GG) (0.075–0.3 wt%) is proposed as a new dysphagia thickener and compared against commercial starch-based thickeners (modified starch with or without gums, 5 wt%) and xanthan gum (XG, 0.5–1.0 wt%) using apparent viscosity, oral tribology using polydimethylsiloxane (PDMS) ball-on-disc set up and ζ-potential measurements. The measurements were conducted in presence of artificial saliva containing mucin with or without α-amylase at 37 °C. Viscosity results suggested that the commercial starch-based thickeners behaved like water in orally relevant shear, largely associated with the hydrolysis of modified starch by α-amylase, while, XG and GG showed no responsiveness to α-amylase. In the case of oral tribology, artificial saliva containing mucin adsorbed to the PDMS surfaces reducing friction as compared to water. The increase in boundary friction coefficients in commercial starch-based thickeners was likely associated with α-amylase-induced hydrolysis, increasing the PDMS-PDMS asperity contacts. Interestingly, the tribological behaviour of XG and GG was dictated mainly by viscous lubrication. However, in simulated oral conditions, the increase in friction coefficients in presence of XG and GG was influenced by depletion of artificial saliva from the PDMS surfaces due to electrostatic interaction between the gums and mucin. A combination of rheological and tribological techniques in orally relevant conditions appears as a reliable approach to understand the potential of GG (0.3 wt%) to act as a dysphagia thickener that offers similar mechanical properties as XG (1.0 wt%) at a lower concentration. Extensional viscosity measurement of GG is needed to understand its applications in dysphagia management.