Particle size and surface morphology of plant protein powders determine the sensory perception of grittiness in liquid matrices

• Plant protein powder particles were assessed in conditions relevant to liquid foods • The trend between instrumental particle size and its sensory perception is non-linear • Particle surface morphology was quantified using visual assessment of SEM images • Surface morphology determines the sensory perception for particles <200 µm (D90) • These results are valuable for developing plant-based liquid dairy alternatives Plant protein powders are used in liquid dairy alternatives, but their low solubility may cause gritty texture defects. We investigated the factors influencing the sensory perception of particle size in 18 commercial plant protein powders—chickpea, fava bean, mung bean, oat, pea, soy, and wheat—in heat-treated water dispersions at native pH or pH 4.5, conditions relevant to end applications. We measured particle size distribution using laser diffraction and compared it with a sensory assessment. We also used scanning electron microscopy to visualize particles and developed a unique method to quantify surface morphology attributes by visually grading images with a sensory panel, obtaining particle angularity, surface roughness, and heterogeneity characteristics. The results showed that sample preparation significantly influenced particle size distribution and there was no correlation between instrumental results in the dry and liquid state. Particle sizes (D90) in water dispersions at native pH ranged 75–375 μm, which increased to 73–493 µm at pH 4.5; soy and wheat particles formed large clumps of 1–2 mm. We observed a linear relationship between D90 and sensorially perceived particle size for particles over 200 μm. For smaller particles, the perceived sensory size was instead explained by particle angularity and surface roughness. Small, round, and smooth particles were imperceptible, while rough and angular particles of the same size were detected by the sensory panel. These findings emphasize the importance of both particle size and surface morphology in causing gritty textures, offering insights for improving plant-based dairy alternatives.