Sayaka Ishihara

Tongue pressure modulation for initial gel consistency in a different oral strategy.

Background In the recent hyper-aged societies of developed countries, the market for soft diets for patients with dysphagia has been growing and numerous jelly-type foods have become available. However, interrelationships between the biomechanics of oral strategies and jelly texture remain unclear. The present study investigated the influence of the initial consistency of jelly on tongue motor kinetics in different oral strategies by measuring tongue pressure against the hard palate. Methods Jellies created as a mixture of deacylated gellan gum and psyllium seed gum with different initial consistencies (hard, medium or soft) were prepared as test foods. Tongue pressure production while ingesting 5 ml of jelly using different oral strategies (Squeezing or Mastication) was recorded in eight healthy volunteers using an ultra-thin sensor sheet system. Maximal magnitude, duration and total integrated values (tongue work) of tongue pressure for size reduction and swallowing in each strategy were compared among initial consistencies of jelly, and between Squeezing and Mastication. Results In Squeezing, the tongue performed more work for size reduction with increasing initial consistency of jelly by modulating both the magnitude and duration of tongue pressure over a wide area of hard palate, but tongue work for swallowing increased at the posterior-median and circumferential parts by modulating only the magnitude of tongue pressure. Conversely, in Mastication, the tongue performed more work for size reduction with increasing initial consistency of jelly by modulating both magnitude and duration of tongue pressure mainly at the posterior part of the hard palate, but tongue work as well as other tongue pressure parameters for swallowing showed no differences by type of jelly. Conclusions These results reveal fine modulations in tongue-palate contact according to the initial consistency of jelly and oral strategies.

Molecular structures of gellan gum imaged with atomic force microscopy in relation to the rheological behavior in aqueous systems in the presence or absence of various cations.

Aqueous solutions of gellan gum with comparable molecular masses but with different acyl contents were investigated by atomic force microscopy and rheological measurements in the presence or absence of various cations. For a high-acyl sample, no continuous network structures were identified microscopically, except in the presence of Ca (2+), where structural inhomogeneity was the highest in terms of the height distribution of molecular assemblies. Rheological thermal hysteresis between sol-gel transitions was detected in the presence of K (+) and Ca (2+), particularly Ca (2+). The storage modulus at 20 degrees C was larger in the order Na (+) < Ca (2+) < K (+). For a low-acyl sample, continuous network structures were identified in the presence of each cation, involving greater thermal hysteresis than the corresponding data for the high-acyl sample. Structural homogeneity was the highest in the presence of K (+). Thermal hysteresis and elasticity of the system were discussed in terms of continuousness and homogeneity of network structures.

Electromyography analysis of natural mastication behavior using varying mouthful quantities of two types of gels

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.

Pressure distribution-based texture sensing by using a simple artificial mastication system.

This paper proposes a novel texture sensing method for nursing-care gel by using an artificial mastication system, in which not only mechanical characteristics but also geometrical ones are objectively and quantitatively evaluated. When human masticates gel food, she or he perceives the changes of the shape and contact force simultaneously. Based on the impressions, they evaluate the texture. For reproducing such a procedure, the pressure distribution of gel is measured in the simple artificial mastication, and the information associated to both the geometrical and mechanical characteristics is simultaneously acquired. The relationship between the value of sensory evaluation (i.e. impression human perceives), and the pressure distribution data is numerically modeled by applying the image texture analysis. Experimental results show that the proposed method succeeds in estimating the values of sensory evaluation of nine kinds of gel with the coefficient of determination greater than 0.93.

Functions of Gum Arabic and Soybean Soluble Polysaccharide in Cooked Rice as a Texture Modifier

The textural properties of cooked rice were investigated in the presence and the absence of gum arabic (GA) and soybean soluble polysaccharide (SSPS). SSPS was more effective in increasing the hardness and in decreasing the stickiness of the rice grains than GA. For both polysaccharides, the increase in hardness was more apparent in the whole body than at the periphery, whereas the decrease in stickiness was more apparent at the periphery than in the whole body. SSPS was more effective in retarding the gelatinization of rice starch and in lowering the elastic characters of the glutinous layer (the materials leached out of the rice grains during cooking) along with a decrease in the amount of amylopectin leached. The textural hardness of cooked rice was determined by the degree of starch gelatinization, whereas the textural stickiness was related to the rheological characters of the glutinous layer and the leaching profile of the starch components.

Food texture sensing by using an imitation tongue with variable elasticity

This paper proposes a texture sensing system based on a biomimetic approach for nursing-care gel foods. The proposed system is equipped with an imitation tongue that can reproduce the elastic behavior of human tongue. First, we introduce the imitation tongue with a variable elasticity mechanism in the artificial mastication model. In this study, using a prototype of the imitation tongue, we verify that it can reproduce the elasticity of human tongue from the relaxed state to the contracted state. Then, we show that the pressure distribution in the artificial mastication of gel food changes clearly with respect to the elasticity of the imitation tongue. Finally, we develop the texture evaluation system that estimates the values of human sensory evaluation of the texture. We show that the texture can be accurately estimated with the appropriate elasticity of the imitation tongue.