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This study aimed to elucidate the effects of food bolus volume on tongue movement at the initiation of swallowing using ultrasonography. Four healthy women were asked to consume 3- and 6-mL spoon-served different food samples (hard gel, soft gel, sol and water) in one swallow each and in their natural manner of eating. An ultrasound probe was positioned under each person's chin to produce coronal images of the tongue. The up-down movement of the dorsal surface of the tongue was observed in the M-mode. The grooving depth for 6 mL of gels and water was greater than that for 3 mL. The duration of grooving for 6 mL of gels was longer than that for 3 mL. The velocity of descending and ascending grooving was not significantly different between the volumes for each food sample, and the velocity of descending grooving was greater than that of ascending grooving. Practical Applications Ultrasonography, using a medical ultrasound instrument, is an effective method for observing tongue movement during the oral phase of swallowing. The M-mode can visualize the kinematics of the dorsal surface of the tongue and bolus passing from the tongue to the pharynx at the initiation of swallowing. Different kinematics of tongue movement can be observed for different volumes of food bolus, mechanical properties and individuals. This technique can be used for designing the texture of food materials for the elderly and infants who experience aspiration or suffocation by food. [ABSTRACT FROM AUTHOR]

The cervical auscultation method was applied to investigate sounds generated while swallowing various foods with different consistencies, including water, yogurt, and konjac jelly. Dynamic viscoelasticity, viscosity, and compression or penetration force of yogurt and konjac jelly were measured. The yogurt was fractured by the tongue while swallowing, whereas konjac jelly was not. Significant differences were detected in the durations of the swallowing sound component, generated by food bolus flow through the pharynx. The root mean square amplitude of the component that was attributed to the water flow was significantly higher than that for the flow of other food samples. No significant differences were detected in the duration of sound components appearing before and after the bolus flow or in the total duration among the food samples. Scattered or heterogeneous food bolus flow appeared to significantly reflect the duration of swallowing sounds, generated by the food flow. Practical Applications Nursing-care foods are in much demand in the expanding elderly society. Ease in swallowing is an important factor for such foods and it is strongly correlated to food texture. Our results indicated significant differences in the duration and amplitude of swallowing sounds, generated by food bolus flow through the pharynx. Because the swallowing sounds depend on the food texture, monitoring such sounds can aid in designing and evaluating the foods to ease swallowing. The method used in this study is noninvasive and cost effective and is therefore practical for use in the food industry. The dependence of the swallowing sounds on human subjects can be analyzed if the data from a greater number of subjects are gathered. [ABSTRACT FROM AUTHOR]