Nonlinear and intensity-dependent enhancement of sweetness perception as a function of redness: Behavioral and EEG evidence for visual–gustatory cross-modal integration

Reducing sugar while maintaining perceived sweetness is a major challenge in beverage reformulation. This study systematically quantified the relationship between red color intensity and sweetness perception and evaluated its potential as a sensory compensation strategy. Forty participants assessed sucrose solutions (2.5–10.0% w / v ) combined with graded redness levels under controlled conditions. Behavioral results demonstrated a nonlinear inverted U-shaped enhancement effect, with medium redness producing the greatest sweetness increase, particularly under low-sweetness conditions (maximum relative increase: 26.48%). The enhancement effect decreased as baseline sweetness increased, indicating clear intensity dependency. Objective neural measurements provided correlative evidence supporting the perceptual findings, reflecting the cognitive evaluation of the observed modulation effect. These results establish a quantifiable dose–response relationship between redness and sweetness perception and identify an optimal redness range for sweetness compensation. The findings provide practical guidance for color-based strategies in sugar-reduced beverage formulation.