Rheological and Tribological Properties of Tara Gum‐Thickened Lentil Soups at Selected IDDSI Levels for Dysphagia Management

ABSTRACT This study evaluated the application of a tara gum‐based commercial thickener to formulate texture‐modified lentil soups across International Dysphagia Diet Standardization Initiative (IDDSI) Levels 1–4 for dysphagia management, characterizing their rheological and tribological properties at 5°C, 25°C, and 37°C. The thickened soups exhibited distinct non‐Newtonian, shear‐thinning, and thixotropic flow behaviors demonstrating an enhancement in structural strength with increasing thickener concentration. The steady‐flow behavior was described well by both the Herschel–Bulkley and Carreau models, where gradual increases in yield stress, zero‐shear viscosity, and thixotropy reflected reinforced structural integrity. Oscillatory rheological analysis identified distinct gel points (G′ = G″), with the crossover frequencies decreasing as the IDDSI level increased, indicating a high degree of polymer chain entanglement and the formation of a stronger network. For IDDSI diet Levels 1–3, the Han plot demonstrated excellent linearity, whereas the Cox–Merz rule showed reasonable agreement at low frequencies and shear rates (0.1–1 Hz/s −1 ). This correlation suggests comparable structural responses under both oscillatory and steady shear deformation. Tribological measurements via Stribeck curve revealed that the soups predominantly operated within mixed and hydrodynamic lubrication regimes, with insignificant changes in the coefficient of friction across IDDSI Levels 1–3, which indicates their favorable oral lubrication characteristics. Overall, the formulation tested at 37°C for IDDSI Levels 1–3 exhibited the highest structural stability and polymer compatibility. These findings indicate that serving the soups at body temperature may provide superior rheological performance and potentially facilitate safer and more efficient swallowing for individuals with dysphagia.