Comparative Study on the Hardness, Adhesiveness, and Cohesiveness of Ingredients on the Basis of IDDSI Levels and Ingredient Selection.

This study aimed to quantitatively characterize hardness, adhesiveness, and cohesiveness of foods commonly consumed by elderly Chinese individuals across International Dysphagia Diet Standardization Initiative (IDDSI) Levels 0-7, to examine within-level heterogeneity among food categories, and to provide practical guidance for texture modification and food substitution in dysphagia diets. Twenty-six representative ingredients frequently consumed by older adults were selected and prepared to IDDSI Levels 0-7 using standardized cooking, blending, and dilution procedures. Texture Profile Analysis (TPA) was applied to measure hardness, adhesiveness, and cohesiveness, in conjunction with IDDSI syringe flow and fork pressure tests for level classification. As texture data were non-normally distributed, differences across IDDSI levels and food categories were analyzed using the Kruskal-Wallis test with Dunn-Bonferroni post hoc correction (α = 0.05). Effect sizes were quantified using Cliff's δ, and within-level interchangeability was evaluated on the basis of Euclidean centroid distance. All three texture parameters differed significantly across IDDSI levels (hardness H = 412.43; adhesiveness H = 238.89; cohesiveness H = 312.76; all p < 0.05). Hardness increased progressively from Level 0 to Level 7, cohesiveness declined accordingly, and adhesiveness exhibited a non-linear pattern with a pronounced peak at intermediate levels (Levels 3-5). Within-level analyses revealed significant category-dependent heterogeneity (p < 0.05). Fiber-rich vegetables and legumes showed higher adhesiveness and lower cohesiveness compared with protein-based foods such as meats and eggs, suggesting a greater potential for oral residue. Interchangeability assessment indicated that foods at Levels 0-2 were largely functionally similar, whereas substantial divergence was observed at Levels 3-6, with centroid distances exceeding 0.60. Instrumental texture analysis demonstrated clear quantitative gradients across IDDSI levels and structured heterogeneity within the same level, confirming that foods sharing an IDDSI classification are not necessarily functionally equivalent. The proposed texture-based substitution framework (centroid distance ≤ 0.60) offers an objective tool for optimizing dysphagia diet design in both clinical and home settings. These findings bridge the IDDSI system with naturally prepared Chinese foods and provide evidence to support culturally adaptable, texture-based dietary management for elderly individuals with swallowing difficulties.