Dysphagia-friendly high internal phase emulsions stabilized by whey protein isolate-tamarind gum Maillard conjugates: rheological behavior, IDDSI compliance and stability.

To address the limitations of current dysphagia management strategies, this study developed high internal phase emulsions (HIPEs) stabilized by whey protein isolate (WPI)-tamarind gum (TG) Maillard conjugates (WPI-TG-C) for application as Food for Special Medical Purpose (FSMP). Physicochemical characterizations and FTIR spectroscopy confirmed the successful conjugation, which endowed the WPI-TG-C with a higher negative ζ-potential and enhanced antioxidant capacity. Furthermore, CD and intrinsic fluorescence spectroscopy revealed marked protein unfolding, evidenced by a significant decrease in α-helix content (from 19.42% to 7.61%) and a concomitant increase in β-sheet domains (from 25.50% to 47.72%), leading to a looser tertiary structure. CLSM and particle size analysis indicated that WPI-TG-C increased the thickness and density of the oil-water interfacial film of the HIPEs. At 3 wt%, it enabled a homogeneous, defect-free emulsion network with smaller particle sizes, providing sufficient interfacial coverage. Rheological, tribological, and textural analyses showed that the optimized HIPEs exhibited shear-thinning behavior and dominant elasticity, characterized by high hardness and low adhesiveness, which facilitates bolus transport. Notably, the HIPEs showed strong pH dependence. HIPEs prepared at pH 3, 4, and 7 met IDDSI Level 4/5 criteria, whereas the pH 5 sample was unstable near the isoelectric point, with the D4,3 increasing to 7.74 μm. After heating at 80 °C for 30 min, HIPEs at pH 3 and 4 retained IDDSI compliance, while the pH 7 formulation showed phase separation. Moreover, HIPEs exhibit good storage stability and oxidative stability. Overall, WPI-TG-C-stabilized HIPEs provide a stable and antioxidant-rich platform for developing dysphagia-oriented FSMPs.