Relationship between maximal isometric tongue pressure and limit of fracture force of gels in tongue squeezing.

BACKGROUND: There is no clear objective indicator for selecting soft foods that are required for food bolus formation in older people with impaired oral function. OBJECTIVE: This study aimed to investigate the relationship between maximal isometric tongue pressure (MITP) and the mechanical properties of gels that can be crushed by the tongue. METHODS: This study included 65 healthy participants aged 22-96 (young group; 15 males, 15 females; older dentate group; 7 males, 8 females; older edentulous group; 10 males, 10 females). MITP was measured by the balloon-probe device. Agar gel with 10 different kinds of fracture force from 10N to 100N was used. The limit of fracture force of gels (LFFG) that were crushed by the tongue was measured by the up-and-down method. In the older edentulous group, two items were measured with and without dentures. Spearman's rank correlation coefficient was used to evaluate the relationship between MITP and LFFG in each group (p < .05). RESULTS: There were positive correlations between MITP and LFFG in all groups (overall groups: rs = .66, young group: rs = .46, older dentate group: rs = .61, older edentulous group with dentures: rs = .60, older edentulous group without dentures: rs = .47). CONCLUSION: MITP and LFFG were positively correlated in young, older dentate and older edentulous groups, suggesting that MITP has the potential to be an objective indicator of the range of mechanical properties of soft food that can be crushed by the tongue.

Characteristics of O/W emulsion gels stabilized by soy protein-xanthan gum complex for plant-based processed meat products.

The aim of the present study is to characterize the mechanical properties of O/W emulsion gels stabilized through soy protein isolate (SPI)-xanthan gum (XG) complex and to elucidate their practical usefulness in plant-based processed meat products. O/W emulsions prepared by mixing aqueous solutions of SPI-XG complexes, which was formed via electrostatic interactions under acidic conditions (pH 4.0), with plant oil were gelled in the presence of several hydrocolloids. Effects of hydrocolloid composition, oil type and load, and oil droplet size on the mechanical properties of the emulsion gels were investigated by dynamic viscoelasticity measurements, and fluorescence microscopy was performed for observation of the oil droplet dispersion. Results indicated that methylcellulose should be required to provide the gels with heat resistance and that the type of oil used should affect dynamic storage modulus (G') of the gels particularly at lower temperatures. It was also found that increased oil load should decrease the gel's resistance to deformation, making the gel structure brittle, and that oil drop size should affect G' and dynamic loss modulus (G") at lower strains. Food application tests indicated that the emulsion gels used had a great impact on the mechanical properties of plant-based meat patties. These findings would contribute to the utilization of the emulsion gels as a lipid portion in plant-based processed meat products, leading to the progress of industrial practice.

Subjective-Physiological Coherence during Food Consumption in Older Adults.

BACKGROUND: Subjective-physiological emotional coherence is thought to be associated with enhanced well-being, and a relationship between subjective-physiological emotional coherence and superior nutritional status has been suggested in older populations. However, no study has examined subjective-physiological emotional coherence among older adults while tasting food. Accordingly, the present study compared subjective-physiological emotional coherence during food consumption among older and younger adults. METHODS: Participants consumed bite-sized gel-type foods with different flavors and provided their subjective ratings of the foods while their physiological responses (facial electromyography (EMG) of the corrugator supercilia, masseter, and suprahyoid, and other autonomic nervous system signals) were simultaneously measured. RESULTS: Our primary findings were that (1) the ratings of liking, wanting, and valence were negatively correlated with corrugator EMG activity in older and young adult participants; (2) the positive association between masseter EMG activity and ratings of wanting/valence was weaker in the older than in the young adult group; and (3) arousal ratings were negatively correlated with corrugator EMG activity in the older group only. CONCLUSIONS: These results demonstrate commonalities and differences in subjective-physiological emotional coherence during food intake between older and young adults.

Correlation of human perception in swallowing with extension rheological and tribological characteristics in comparison with shear rheology.

Correlation was investigated between instrumental characteristics obtained by extension rheological or tribological measurements and human perception while swallowing using aqueous solutions of xanthan gum and locust bean gum. Extension viscosity and the friction coefficient were measured using a capillary breakup rheometer and a rotation tribometer, respectively, as in our previous study. Results were compared with shear viscosity to clarify novelty and advantage of these mechanical parameters. It was indicated that perceived cohesiveness correlated the highest with the maximum extension viscosity immediately after the onset of extensional flow, perceived spinnability correlated with extension viscosity in high Hencky strain region, and perceived sliminess correlated with the friction coefficient at the critical point between the boundary lubrication and the mixed lubrication. These correlations were discussed and tried to validate considering biomechanics of human swallowing and food-human interactions.

Brow and Masticatory Muscle Activity Senses Subjective Hedonic Experiences during Food Consumption.

Sensing subjective hedonic or emotional experiences during eating using physiological activity is practically and theoretically important. A recent psychophysiological study has reported that facial electromyography (EMG) measured from the corrugator supercilii muscles was negatively associated with hedonic ratings, including liking, wanting, and valence, during the consumption of solid foods. However, the study protocol prevented participants from natural mastication (crushing of food between the teeth) during physiological data acquisition, which could hide associations between hedonic experiences and masticatory muscle activity during natural eating. We investigated this issue by assessing participants' subjective ratings (liking, wanting, valence, and arousal) and recording physiological measures, including EMG of the corrugator supercilii, zygomatic major, masseter, and suprahyoid muscles while they consumed gel-type solid foods (water-based gellan gum jellies) of diverse flavors. Ratings of liking, wanting, and valence were negatively correlated with corrugator supercilii EMG and positively correlated with masseter and suprahyoid EMG. These findings imply that subjective hedonic experiences during food consumption can be sensed using EMG signals from the brow and masticatory muscles.

Instrumental characteristics from extensional rheology and tribology of polysaccharide solutions.

Instrumental characteristics from extensional rheology and tribology for aqueous xanthan gum (XG) and locust bean gum (LBG) solutions were studied in the presence or absence of simulated saliva. Extensional viscosity was calculated from the filament shrinkage behavior using a capillary breakup extensional rheometer, whereas the friction coefficient was measured using a set-up consisting of polydimethylsiloxane substrate and a glass ball bearing on a rotational rheometer. Increase in extensional viscosity was detected immediately after initiation of extensional flow, particularly XG, and also immediately before the filament rupture, particularly LBG. Extensional viscosity tended to decrease with increased addition of simulated saliva for XG, while to increase for LBG. In both cases, effect of cations in the saliva was greater than that of mucin. From the shape of the Stribeck curve (i.e., dependence of the friction coefficient on the entrainment speed) and comparison of the friction coefficient itself, lubricity of XG was greater than that of LBG. Simulated saliva added decreased the friction coefficient for each polysaccharide through functions of cations rather than mucin. Extensional viscosity and tribological measurements revealed mechanical properties of polysaccharide solutions which cannot be determined or quantified by shear viscosity alone.

Effect of fracture properties of gels on tongue pressure during different phases of squeezing and swallowing.

To provide appropriate foods for elderly people with eating difficulties, it is necessary to take account of the ability of compensatory mastication such as tongue squeezing. However, the biomechanics of tongue squeezing is still unclear. The aim of present study is to investigate the effect of the initial mechanical properties of gels on the change in tongue pressure production during squeezing and swallowing. As test sample, nine kinds of gels with three fracture force and three fracture strain were prepared. Tongue pressure during squeezing and swallowing gels was measured by using an ultra-thin tongue pressure sensor with five measuring points attached on the hard palate in seven healthy participants, and analyzed at four phases; Initial squeeze, Middle squeeze, Last squeeze, and Swallowing. The maximal magnitude of tongue pressure was increased for gels with higher fracture force at most measuring points and was decreased for gels with higher fracture strain at some measuring points on the median line during Initial and Middle squeezing. However, no influence by fracture force and strain was found in magnitude during Last squeezing and Swallowing. The duration of tongue pressure increased for gels with higher force at most measuring points during Middle squeezing, although no influence by strain was found during each phase. The results clearly show how the initial fracture properties of gels influence on tongue pressure production during each phase of food oral processing, which clarified one aspect of squeezing with tongue, as the compensatory mastication.

Facial EMG Correlates of Subjective Hedonic Responses During Food Consumption.

An exploration of physiological correlates of subjective hedonic responses while eating food has practical and theoretical significance. Previous psychophysiological studies have suggested that some physiological measures, including facial electromyography (EMG), may correspond to hedonic responses while viewing food images or drinking liquids. However, whether consuming solid food could produce such subjective-physiological concordance remains untested. To investigate this issue, we assessed participants' subjective ratings of liking, wanting, valence, and arousal while they consumed gel-type food stimuli of various flavors and textures. We additionally measured their physiological signals, including facial EMG from the corrugator supercilii. The results showed that liking, wanting, and valence ratings were negatively correlated with corrugator supercilii EMG activity. Only the liking rating maintained a negative association with corrugator supercilii activity when the other ratings were partialed out. These data suggest that the subjective hedonic experience, specifically the liking state, during food consumption can be objectively assessed using facial EMG signals and may be influenced by such somatic signals.

Coordination of tongue pressure production, hyoid movement, and suprahyoid muscle activity during squeezing of gels.

OBJECTIVE: The aim of this study was to evaluate tongue movement and its biomechanical effects during squeezing, one of the oral strategies for processing soft foods, by tongue pressure sensors, videofluorography, and surface electromyography. DESIGN: Fifteen healthy men (mean age, 31.0 ± 4.1 years) without dysphagia were recruited. A 0.1-mm-thick pressure sensor sheet with five measuring points, videofluorography, and surface electromyography were used for synchronous measurements of tongue pressure, hyoid movement, and suprahyoid muscles activity, respectively, while squeezing 5 mL of gels. Amplitude, duration, area, and their sequential order during initial squeezing were analyzed. Differences in hyoid position at the onset, peak, and offset of hyoid movement were also analyzed. RESULTS: At the beginning of initial squeezing, tongue pressure at the middle area of the hard palate, hyoid movement, and suprahyoid muscle activity appeared simultaneously, followed by tongue pressure at the anterior area and then at the posterior area. When the hyoid was in an elevated position, the amplitude of suprahyoid muscle activity and tongue pressure peaked. At the end of initial squeezing, the hyoid position at the offset of hyoid excursion was superior to that at the onset. All evaluation items of tongue pressure, hyoid movement, and suprahyoid muscle activity were modulated according to the texture of gels. CONCLUSIONS: During initial squeezing, tongue pressure, hyoid movement, and suprahyoid muscle activity were coordinated while being modulated by the food texture. At the end of initial squeezing, the hyoid was maintained in an elevated position, which might be beneficial for subsequent squeezing.

Compression Test of Soft Food Gels Using a Soft Machine with an Artificial Tongue.

Care food is increasingly required in the advanced-aged society. Mechanical properties of such foods must be modified such that the foods are easily broken by the tongue without chewing. When foods are compressed between the tongue and the hard palate, the tongue deforms considerably, and only soft foods are broken. To simulate tongue compression of soft foods, artificial tongues with stiffness similar to that of the human tongue were created using clear soft materials. Model soft gels were prepared using gellan gums. A piece of gel on an artificial tongue was compressed using a texture analyzer. The deformation profile during the compression test was obtained using a video capture system. The soft machine equipped a soft artificial tongue sometimes fractured food gels unlike hard machine, which always fracture gels. The fracture properties measured using the soft machine were better than those obtained from a conventional test between hard plates to mimic natural oral processing in humans. The fracture force on foods measured using this soft machine may prove useful for the evaluation of food texture that can be mashed using the tongue.

Modulation of calcium-induced gelation of pectin by oligoguluronate as compared to alginate.

Previous studies have demonstrated that oligoguluronate (guluronate block extracted from alginate, GB) was an efficient modulator of the gelation and gelling properties of macromolecular alginate in the presence of calcium. Here we report totally different modulatory effects of the oligomer when used to modify the gelation of low methoxyl pectin (LMP). GB was found to promote the gelation of LMP in the range of R ([Ca]/[guluronate + galacturonate]) < 0.25 and could make non-gelling systems gellable. This is significantly different from the case of alginate where no gelation could be induced at all. In the range of 0.25 < R < 0.60, the addition of GB was found to inhibit the gelation of LMP, whereas it had a negligible effect on the gelation of alginate as long as a fixed R was considered. In the range of R > 0.60, GB was found to promote the gelation of LMP again, which is similar to the case of alginate. The results were in consistence with microstructural observations by AFM. The different modulatory effects of GB were thought to arise from the different gelation mechanisms of LMP and alginate, that is, a progressive dotting growth of LMP dimers vs. a critical zippering growth of alginate dimers during Ca-induced crosslinking. The mechanism of GB modulating the gelation of LMP was proposed and compared to that for alginate.

In vivo measurement of swallowing by monitoring thyroid cartilage movement in healthy subjects using thickened liquid samples and its comparison with sensory evaluation.

This research aimed to investigate the relationship between in vivo measurement of swallowing and sensory evaluation using thickened liquids as model foods. Healthy subjects (8 male and average 29.6-year old) participated in both tests, in which the subjects were asked to swallow the whole amount of sample (10 ml) at one time. In vivo measurement monitored thyroid cartilage movement during swallowing using a bendable pressure sensor synchronously with suprahyoid electromyography, whereas sensory evaluation measured perceived cohesiveness and adhesiveness on a visual analogue scale. Two variables from the pressure sensor analysis; activity of the thyroid cartilage and the maximum displacement of the thyroid cartilage were correlated negatively (p < .01) to perceived cohesiveness with high correlation coefficient (|r|> .9). Advantages of in vivo measurement over conventional shear rheology in assessing texture attributes perceived during swallowing were identified. PRACTICAL APPLICATIONS: This research provides food manufactures with knowledge on a novel objective method for texture measurement of fluid foods and beverages based on human physiology during swallowing. Variable from this method can work as a measure for texture design of food products to meet consumers' preference, particularly foods for dysphagia patients whose demand is increasing in this aged society although subjects of study should be expanded to these people in the future.

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.

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.

Influences of food hardness on the particle size distribution of food boluses.

OBJECTIVES: Bolus swallowing or deglutition is a vital oral action which transports orally processed food from the oral cavity to the stomach for further digestion. Swallowing is routine to most health individuals, but it could be highly hazardous to many elderly and dysphagia patients. In order to provide proper food for safe consumption by these disadvantaged populations, a fundamental understanding of how bolus swallowing is triggered and is based on what criteria is urgently needed. Main objective of this work was to understand the physical properties of food boluses, in particular the bolus particle size distribution in relation to the hardness of the food. METHODS: Food samples were chewed in free style by subjects and boluses were expectorated when subjects felt they were ready to be swallowed. Altogether seven different types of food were used and 10 health subjects participated in this study. Bolus particles were carefully washed and spread out on a flat surface. Images of bolus particles were taken using a digital camera and analysed using Image Pro Plus software for particle size quantification. Food hardness was measured using a Texture Analyser by a puncture test. RESULTS: It was observed that bolus particle size decreased with the increase of food hardness. The correlation between the two properties can be described by a power-law relationship. This relationship was also found applicable to literature results reported by Peyron et al. and Jalabert-Malbos et al. CONCLUSIONS: Food hardness has a direct influence on its bolus particle size. The harder the food, the smaller the bolus particle size.

Effects of Time and Temperature of Annealing on Rheological and Thermal Properties of Rice Starch Suspensions during Gelatinization.

Effects of annealing time, t a , and annealing temperature on the rheological and thermal properties of rice starch suspensions during the gelatinization were studied by dynamic viscoelasticity, steady shear viscosity, η, and differential scanning calorimetry measurements. When t a increased, for the sample which was annealed at almost the same temperature as the gelatinization temperature (= T gel ; 62C), 58 or 62C, the onset temperatures at which the storage and loss moduli, G' and G″, started to increase shifted to higher temperatures, and G' and G″ decreased in the temperature range from 65 to about 75C. Further, G' and G″ of the sample annealed at higher T than T gel , 65C, increased in the temperature range from 50 to 75C. The amorphous and thermally unstable portion in the starch decreased with increasing t a . Effects of annealing on the temperature dependence of η were found to be almost the same as those of G' and G″. The annealing tended to prevent starch sample from shear thinning. PRACTICAL APPLICATIONS: This article shows the effects of annealing time, t a , and annealing temperature on the rheological and thermal properties of rice starch suspensions. When t a increased, the storage and loss moduli, G' and G″, of rice starch decreased in the temperature range from 65 to about 75C and the gelatinization temperature increased due to the increase of the amount of leached-out amylose. For the sample annealed at 62C for 15 min, it was observed that the annealing tended to prevent starch sample from shear thinning. These findings are helpful to control rheological and thermal properties during cooking of starch-based foods.

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.

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.

Multiple steps and critical behaviors of the binding of calcium to alginate.

Previous research on the binding and gelation of calcium/alginate in aqueous solution were mostly conducted in the (semi-)concentrated regime, and it did not provide details of the binding process and the formation of egg-box junctions. In the present investigation, the binding of calcium to alginate, of low and high molecular weight and different guluronate/mannuronate ratios, was investigated in dilute solutions using isothermal titration calorimetry (ITC), Ca2+-selective potentiometry, and viscometry techniques. The results reveal three distinct and successive steps in the binding of calcium to alginate with increased concentration of Ca ions. They were assigned to (i) interaction of Ca2+ with a single guluronate unit forming monocomplexes; (ii) propagation and formation of egg-box dimers via pairing of these monocomplexes; and (iii) lateral association of the egg-box dimers, generating multimers. The third step has different association modes depending on the molecular weight of alginate. The boundaries between these steps are reasonably critical, and they closely correlate with the Ca/guluronate stoichiometry expected for egg-box dimers and multimers with 2/1 helical chains. The formation of egg-box dimers and their subsequent association are thermodynamically equivalent processes and can be fitted by a model of independent binding sites. The binding of Ca to alginates of different guluronate contents is controlled by a balance between enthalpy and entropy.