Structural design of dysphagia-oriented double emulsions via internal-external phase coordination to modulate texture, rheology, and oral lubrication.

Dysphagia is a swallowing disorder that poses serious nutritional and safety challenges for older adults and clinical patients. Traditional thickening techniques negatively affect mouthfeel, resulting in limited tunability of texture and lubrication. In this study, a dual-parameter strategy was developed to form dysphagia-oriented double emulsions (DEs, W1/O/W2). The internal aqueous phase (ϕ = 0.10-0.25) and the external xanthan gum‑sodium alginate matrix (XG: SA = 1:7-9:1) of DEs were modulated. In combination with IDDSI flow and fork-drip tests, texture, rheology, and oral tribology measurements were comprehensively employed to clarify their structure-swallowability relationship. Results showed that increasing ϕ reduced hardness by ∼57% and increased yield stress by ∼180%, generating softer yet cohesive networks with enhanced lubrication (friction coefficient reduced by up to 23%), consistent with rheological changes attributable to altered droplet packing behavior, meeting IDDSI Level 3-4 criteria. Meanwhile, higher XG: SA ratios decreased hardness (∼82%) and apparent viscosity at 50 s-1 (∼69%) while improving springiness (∼43%); notably, at identical low sliding speeds, this group exhibited 44%-78% lower boundary friction compared to the ϕ-modulated group, effectively spanning IDDSI Levels 2-4. Pairwise correlation analysis indicated stronger associations of ϕ with lubrication-related parameters and of XG: SA with texture and elasticity indices, while principal component analysis (explaining 79.8%-84.9% of the variance) supported the overall consistency of these multivariate trends. This study highlighted a structure-function coupling between the internal and external phase design and multiscalar performance of DEs, which provided structural guidance to design texture-modified emulsified foods for IDDSI Level 2-4 diets.