Aroma-driven salivary secretion modulates mouthfeel by restructuring the bolus in a matrix-dependent manner: evidence...

Aroma is a central factor in food perception, yet the physiological pathways linking olfaction to mouthfeel remain poorly understood. This study investigated how aroma-associated salivary responses relate to texture perception and oral bolus properties in two dairy matrices: milk, a low-viscosity emulsion, and yogurt, a viscoelastic gel. A three-stage design was applied: consumer evaluation (CATA and ranking, N = 120) to establish aroma-related mouthfeel differentiation; trained-panel descriptive analysis (n = 12) under Normal, Nose-Clip, and Orthonasal Stimulation conditions to assess olfactory input; and characterization of saliva and expectorated boluses. Four intensity-matched aromas spanning distinct semantic categories (vanilla, lemon, rose, and mint) were tested. Lemon-flavored samples were perceived as significantly thinner than vanilla-flavored samples across both matrices; this discrimination was abolished by nasal occlusion and reproduced by orthonasal aroma delivery alone. Lemon aroma provoked the strongest cephalic-phase salivary response, increasing flow rate by 95.6%, while MUC5B and Ca²⁺ decreased by ∼25% and ∼23%, respectively; extensional integrity (capillary breakup time) declined by ∼73%. During oral processing, lemon-associated salivary changes coincided with matrix-specific bolus restructuring: yogurt gels fragmented and lost viscosity, while milk proteins aggregated into larger particles (+34%), yet the lemon milk bolus was still perceived as the thinnest. This divergence suggests that perceived thinning in milk also reflected aroma-associated semantic cues. These findings support saliva as a biophysical link between olfaction and mouthfeel, and show that similar salivary responses were associated with divergent bolus outcomes depending on the food matrix, with implications for texture design in liquid and semi-solid foods.