Sensory and motor responses of normal young adults during swallowing of foods with different properties and volumes.

We examined the influence of rheological/textural properties and volumes of test foods on the sensory and motor aspects of swallowing in healthy young adults. Three test foods differing in thickening agent concentration (0.0, 1.5, and 3.0%) were prepared and delivered in different volumes (approximately 3, approximately 5, and approximately 7 ml) to subjects seated on a chair. Viscosity analyses of the 1.5 and 3.0% test foods revealed that they behaved as non-Newtonian fluids and were thixotropic. The 1.5% test food differed from the 3.0% test food in its textural properties (hardness, cohesiveness, and adhesiveness). As determined by a linear model equation method, the thickening agent concentration affected the scores of all six sensory evaluation questions that were answered by the subjects, which suggests that the concentration affected the food properties being evaluated. Consistent with previous reports, thickening agent concentration and test food volume also affected some durational parameters of laryngeal (recorded by a piezoelectric sensor) and suprahyoid muscle (recorded on an electromyogram) motor activity. However, thickening agent concentration and test food volume did not affect the single amplitude parameter of the electromyogram that was measured. The thixotropic property of foods can affect the motor aspect of oropharyngeal swallowing as well as the sensory aspect.