Roles of Polysaccharides in the Colloidal Behavior of Thaumatin and the Sweetness Perception

Effects of polysaccharides (pectin, λ-carrageenan, and sodium alginate) on the colloidal behavior and sweetness perception of thaumatin were investigated. Turbidity and zeta potential were measured to map pH-dependent transition regions of polysaccharide-thaumatin complexes. Particle size, secondary structure changes, and molecular docking simulations were analyzed to assess phase behavior and binding interactions of complexes at different conditions. Results showed that polysaccharide type influenced surface charge and complexation strength. At protein-rich mixing ratios, λ-carrageenan-thaumatin and sodium alginate-thaumatin systems exhibited bimodal turbidity profiles, whereas pectin-thaumatin systems showed a single turbidity maximum. FTIR revealed secondary structure redistribution in selected complexes: β-sheet increased from 29.95% (thaumatin) to 33.56% (G11) and 35.19% (H14), while β-turn decreased from 25.22 to 14.65 and 14.16%. Docking of repeating units suggested association with basic surface patches (-6.7/-5.9/-5.5 kcal mol^-1 for pectin/λ-carrageenan/sodium alginate). Sensory analysis showed ratio-dependent sweetness suppression, most evident in the early and late phases of perception, supporting sugar-reduced formulation design.