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The objectives of this study were to examine the effects of mouthful quantities and mechanical properties of gels on natural mastication behaviors using electromyography (EMG). Two types of hydrocolloid gels ( A and K ) with similar fracture loads but different moduli and fracture strains were served to eleven normal women in 3-, 6-, 12-, and 24-g masses in a randomized order. EMG activities from both masseter muscles were recorded during natural mastication. Because of the similar fracture loads, the numbers of chews, total muscle activities, and entire oral processing times were similar for similar masses of both gel types. Prior to the first swallow, the more elastic K gel with a higher fracture strain required higher muscle activities than the brittle A gel, which had higher modulus. Majority of subjects had preferred sides of chewing, but all subjects with or without preferred sides used both masseters during the consumption of gels. Similar effects of masses and types of gels were observed in EMG activities of both sides of masseters. Contributions of the dominant side of chewing were diminished with increasing masses of gels, and the mass dependency on ratio of the dominant side was more pronounced with K gel. More repetitions of smaller masses required greater muscle activities and longer periods for the consumption of 24-g gel portions. Reduction in the masses with an increased number of repetitions necessitated slower eating and more mastication to consume the gel portions. These observations suggest that chewing using both sides is more effective and unconsciously reduces mastication times during the consumption of gels. [ABSTRACT FROM AUTHOR]

This study aimed to elucidate the effects of water volume on flow properties of bolus (passage time and velocities) at the esophagus orifice using ultrasonic pulsed wave Doppler method. Five healthy males and five females were asked to consume 3, 6, 9 and 12 mL water in a single swallow. An ultrasound probe was placed against each subject's neck to observe the flow properties of bolus. The velocity spectra of the bolus at the esophagus orifice were analyzed. Our results revealed that velocity of bolus was easily affected by volume of water, and the passage time and velocities increased as the increase in volume. Practical Applications Ultrasonography, using a medical ultrasound instrument, is an effective method for observing bolus kinematics during swallowing. The velocity spectra of bolus can be visualized for different volume of water using the pulsed wave Doppler method. When a bolus of food is swallowed, aspiration that the bolus partly enters the trachea instead of the esophagus may occur. Water is known to show a high possibility of aspiration. This study revealed that reducing volume of water decreases the passage time and velocities of bolus at the esophageal entrance. Therefore, this technique can be used for designing the texture of food materials for people who experience aspiration or suffocation by food. [ABSTRACT FROM AUTHOR]

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]