Relationship between Syringe Flow Measurements and Viscosity of Nectar-Thick Beverages for Dysphagia Management

Commercial cold beverages thickened with a xanthan gum (XG)-based food thickener were examined at different thickness levels by using the simple, cost-effective syringe flow test (SFT) developed by the International Dysphagia Diet Standardization Initiative (IDDSI). We prepared cold thickened beverage (CTB) samples with different thickener concentrations and measured them by extrapolating the viscosity range (51-350 mPa·s) for nectar-like consistency. CTBs were also measured via the line-spread test (LST), and the flow distance value (cm) by LST and the volume remaining (mL) in the syringe by SFT was correlated with the apparent viscosity (η₅₀). Plots comparing η₅₀ with SFT or LST values showed good exponential relationships between the measurements. The SFT showed a better relationship (R² = 0.928) than LST (R² = 0.825), indicating that the former can predict the viscosity better in the range for nectar-like consistency. In particular, the SFT showed a significant difference (R² = 0.964) compared to the LST (R² = 0.709) for thickened protein-based beverages. These results suggest that the SFT using the IDDSI methodology is a more suitable instrument than the LST for accurately evaluating the viscosity of XG-based CTBs with nectar-like consistency.