Consumer liking of freeze-dried probiotic powders during oral processing: sensory evaluation with complementary 3D facial expression analysis and insights from rheology and volatile profiles

The relationships between oral perception, consumer liking and physicochemical properties of direct-to-mouth freeze-dried probiotic powders remain poorly understood. Consumer testing at approximately 2 and 10 s, quantitative descriptive analysis (QDA), and three-dimensional facial expression analysis were used to compare the sensory and facial responses elicited by three probiotic powders, XZ35, PH21, and FS09. Complementary measurements characterized dry particle size, rheology in artificial saliva and volatile profiles. Overall liking did not differ significantly at 2 seconds. At 10 seconds, XZ35 and FS09 scored higher than PH21 (6.13 and 5.73 versus 4.60; nine-point scale). QDA characterized XZ35 by greater sweetness and lower clumpiness and oral drying sensation. Multiple factor analysis associated XZ35 with favorable liking-related attributes and higher arousal estimated from facial expressions at both stages. Volatile profiling detected 70 compounds, and XZ35 and PH21 showed higher relative ester abundance than FS09 after water and artificial saliva treatments. PH21 had the largest median particle diameter (147.3 micrometers) and highest graininess ratings from trained assessors, whereas FS09 had the smallest particles (74.15 micrometers). All suspensions showed predominantly viscous behavior, with FS09 exhibiting the greatest viscoelasticity and hysteresis. These findings may guide improvements in flavor and mouthfeel to enhance consumer acceptance of freeze-dried probiotic powders.