Oral processing assessed by M-mode ultrasound imaging varies with food attribute

Ultrasonographic analysis of the hyoid bone distance in individuals with neurogenic oropharyngeal dysphagia

To compare the ultrasound measurement of distance from the approximation of the hyoid bone during of the maximum deglutition peak between healthy individuals and neurogenic dysphagic individuals and to verify the effect of food consistencies on the displacement of the hyoid bone. Prospective, controlled clinical study. Ultrasound recordings of the oropharyngeal deglutition were conducted in 10 adults diagnosed with oropharyngeal dysphagia and in 10 healthy adults, matched by sex and age group. A portable ultrasound model Micro ultrasound system with a microconvex transducer 5-10 MHz, coupled to a computer as well as the head stabilizer were used. The ultrasound images were recorded using the AAA software (Articulate Assistant Advanced) at a rate of 120 frames/second. Food consistencies level 0 (free volume and 5 mL) and level 4 (5 mL) were used, based on the International Dysphagia Diet Standardisation Initiative (IDSSI). The calculation of the mean and standard deviation was used for the descriptive analysis, while the repeated measures ANOVA test was used for the inferential analysis. Results showed dysphagic individuals had lower elevation of the hyoid bone marked by a longer distance from the approximation of the hyoid bone during of the maximum deglutition peak when compared to healthy individuals, regardless of the food consistency offered. It was concluded that the ultrasound measurement of distance from the approximation of the hyoid bone during of the maximum deglutition peak showed less laryngeal elevation in individuals with neurogenic oropharyngeal dysphagia when compared to healthy individuals for all food consistencies offered.

The effect of taste on swallowing: A scoping and systematic review

Consuming foods and liquids for nutrition requires the coordination of several muscles. Swallowing is triggered and modified by sensory inputs from the aerodigestive tract. Taste has recently received attention as a potential modulator of swallowing physiology, function, and neural activation; additionally, taste impairment is a sequela of COVID-19. This review presents factors impacting taste and swallowing, systematically summarizes the existing literature, and assesses the quality of included studies. A search was conducted for original research including taste stimulation, deglutition-related measure(s), and human participants. Study design, independent and dependent variables, and participant characteristics were coded; included studies were assessed for quality and risk of bias. Forty-eight articles were included after abstract and full-text review. Synthesis was complicated by variable sensory components of stimuli (taste category and intensity, pure taste vs. flavor, chemesthesis, volume/amount, consistency, temperature), participant characteristics, confounding variables such as genetic taster status, and methods of measurement. Most studies had a high risk of at least one type of bias and were of fair or poor quality. Interpretation is limited by wide variability in methods, taste stimulation, confounding factors, and lower-quality evidence. Existing studies suggest that taste can modulate swallowing, but more rigorous and standardized research is needed.

Oral processing behaviours of liquid, solid and composite foods are primarily driven by texture, mechanical and lubrication properties rather than by taste intensity

The aim of this study was to understand the influence of saltiness and sweetness intensity on oral processing behaviours of liquid, solid and composite foods. As salty foods, tomato sauce (liquid), penne pasta (solid) and their combination (composite food) were used at two levels of saltiness intensity (low/high). As sweet foods, strawberry sauce (liquid), milk gels (solid) and their combination (composite foods) were used at two levels of sweetness intensity (low/high). Saltiness, sweetness, hardness, chewiness, and liking were quantified using generalized labelled magnitude scales (gLMS). Oral processing behaviours were determined using video recordings (n = 39, mean age 25 ± 3 years) in a home-use-test (HUT) providing fixed bite sizes for all foods. As expected, taste intensity differed significantly between samples within the same food category. No significant effects of taste intensity on oral processing behaviours were found for sweet and salty foods. As expected, consistency strongly affected the consumption time per bite, number of chews per bite, number of chews per gram and eating rate. Solid foods were masticated for the longest time with the highest number of chews per bite, followed by composite foods as the liquid added to the solid foods enhanced lubrication. Liquid foods were masticated for the shortest time. We conclude that large differences in saltiness and sweetness intensity of liquid, solid and composite foods cause no differences in oral processing behaviours. We suggest that oral processing behaviours are primarily driven by texture, mechanical and lubrication properties of foods rather than by their taste intensity.

Emerging Role of Ultrasound in Dysphagia Assessment and Intervention: A Narrative Review

Ultrasonography has gained increasing attention as a non-invasive and radiation-free instrument for the assessment of swallowing function. In the past decades, an extensive repertoire of ultrasonographic techniques, such as, B-mode dynamic scanning, pixel analysis, M-mode, Doppler, 3D reconstruction, and sonoelastography, has been applied in the evaluation of oropharyngeal structures and movement. Yet, a universal consensus on the examination protocols and clinical implications remains to be established. This review aimed to provide a brief introduction of the application of ultrasound in dysphagia assessment and intervention, encompassing the ultrasonography of swallowing-related muscles, tongue movement, and hyolaryngeal excursion, as well as ultrasound-guided interventions in the management of dysphagia. In addition to non-invasiveness, ultrasonography, a portable, easy to use, and low-cost technique, could compliment videofluoroscopic swallowing study as a first-line screening and follow-up tool for the evaluation of swallowing function, although further study is warranted to provide quantitative diagnostic and prognostic values. Finally, ultrasonography aids in the precisely targeted injection of botulinum toxin in patients exhibiting oropharyngeal muscle spasticity.

Texture contrast: Ultrasonic characterization of stacked gels' deformation during compression on a biomimicking tongue

When undergoing compression during oral processing, stacked gels display different mechanical properties that shape perceptions of texture contrasts (Santagiuliana et al., 2018). However, to date, characterizing the mechanical responses of individual gel layers has been impossible. In this study, an ultrasound (US) technique was developed, that allowed such deformation dynamics to be visualized in real time. Stacked gels were created using layers (height: 5 mm) of brittle agar and elastic gelatin in different combinations. In a series of experimental tests, different stacked gel combinations were placed on a rough, deformable artificial tongue model (ATM) made of polyvinyl alcohol; a texture analyzer was used to apply uniaxial force, and deformation was monitored by an US transducer (5 MHz) located under the ATM.

From the obtained results, it was observed that the deformation of ATM surface during compression was in accordance with the force recorded by the texture analyzer, suggesting a collaborative response of different layers under compression. Moreover, US imaging revealed that differences in Young's modulus values between layers led to heterogeneous strain distributions, which were more pronounced for the agar layers. Biopolymer elasticity was also a key factor. Regardless of combination type, the gelatin layers never fractured; such was not the case for the agar layers, especially those with lower Young's modulus values. The results of this US study have thus paved the way for a better understanding of the mechanical deformation that occurs in heterogeneous foods, a phenomenon that has been difficult to examine because of the limitations of conventional techniques.

•

Agar and gelatin bilayer gels were compressed on deformable artificial tongue models.

•

Compressions and relaxations were monitored with a non-invasive ultrasound method.

•

Deformations in artificial tongue and food layers were assessed with signal processing.

•

The method shows potential for understanding texture contrast perception.

Food Oral Processing-An Industry Perspective

We illustrate how scientific understanding of Food Oral Processing enables food product development with specific benefits for several target populations. in vivo, in vitro, and in silico approaches are discussed in the context of their ability to quantify oral processing from the molecular to the macroscopic scale. Based on this understanding, food structures with enhanced performance in terms of hedonic and nutritional properties as well as appropriateness for age and certain medical conditions can be developed. We also discuss current gaps and highlight development opportunities from an industry perspective.

Using ultrasound to characterize the tongue-food interface: An in vitro study examining the impact of surface roughness and lubrication

We measured the apparent reflection coefficient of a 1-MHz ultrasound compressional wave at the interface between rough and lubricated tongue mimicking surfaces and various food gels, composed of agar or gelatin. For the smoothest mimicking surface, when a lubricating layer was present, the apparent reflection coefficient was fairly similar for the different food gels (33.6% on average). The apparent reflection coefficient was significantly larger in the following situations: (i) tongue asperities were high and dense; (ii) lubrication levels were low; and (iii) gels were less rigid (range for the different gels-45.9-84.3%). The apparent reflection coefficient conveys the ability of food gels to mold themselves to surface asperities or to form a coupling film of liquid at the interface. This study demonstrates that ultrasound methods can and should be used to explore the physical phenomena that underlie the texture perceptions resulting from tongue-palate interactions.

Morphological and masticatory performance variation of mouth behavior groups

Food texture preference and product acceptance are hypothesized to be influenced by mouth behavior. Recent work identified four mouth behavior (MB) groups that describe most consumers in the United States: Chewers, Crunchers, Smooshers, and Suckers. While these behavioral preferences are thought to play a significant role in food selection and purchasing decisions, it is unknown how closely they relate to body and oral cavity measures as well as masticatory apparatus performance. Our objectives were twofold: to determine whether MB groups are related to (a) morphological variation in body, head, and oral cavity size and (b) masticatory apparatus performance (i.e., maximum jaw gape, maximum bite forces at the incisors and first molar). Measurements were collected following an online MB assessment (JBMB Mouth Behavior Typing Tool) where participants self-identified as one of the four types of consumers. As expected, univariate associations were observed between masticatory performance and overall body as well as oral cavity size. These relationships did not persist when assessed with multivariate methods. MB groups did not differ by body, head, or oral cavity measurements; maximum gape; or maximum bite force. Because of small sample sizes for Smooshers and Suckers-a reflection of their limited prevalence in the U.S. population-we interpret the results for these groups with caution. We can more confidently conclude based on our sample that Chewers and Crunchers do not differ in size, bite force, or maximum gape, suggesting other factors primarily drive food texture choice and preference in these individuals.

Consumer textural food perception over time based on Mouth Behavior

Food texture assessment is difficult because it is constantly being modified as a food is eaten. While texture has generally been statically assessed, methods aimed at measurement over time are becoming more common. However, even when texture is assessed over time, that assessment is based on averages across all individuals. This study shows that individuals with different Mouth Behaviors eat foods differently in an effort to develop a texture that suits their Mouth Behavior. Because of this, their texture assessments differ over the eating experience. Overall liking was driven by whether individuals were able to transform the product texture into one that aligned with their Mouth Behavior and how well they liked the dominant texture attribute.

Exacting Responses: Lack of Endocrine Cephalic Phase Responses Upon Oro-Sensory Exposure

Oro-sensory exposure (OSE) to food plays an important role in the regulation of food intake. One proposed underlying mechanism is the occurrence of cephalic phase responses (CPRs). CPRs include the pre-digestive endocrine responses induced by food-related sensory input. Yet, whether OSE duration or sweetness intensity affects CPRs is unknown. The objective of this study was to determine the independent and interactive effects of oro-sensory duration (chewing) and stimulation intensity (sweetness) on endocrine CPRs and satiation. Eighteen males (22 ± 2 years, BMI 22 ± 2 kg/m2) participated in a 2 × 2 randomized study with a control condition. Each session participants performed modified sham feeding (MSF) with one of the four gel-based model foods. During the control session no MSF was performed. Model foods differed in chewing duration (hard or soft texture) and sweetness (low or high intensity). During each session, eight blood samples were collected up till 25 min after MSF onset. Subsequently, food intake from an ad libitum lunch was measured. No typical CPR was found for insulin, pancreatic polypeptide (PP), and ghrelin. However, the overall PP response was 1.1 times greater for the hard sweet MSF condition compared to control (p = 0.02). Overall ghrelin responses were 1.1 times greater for the hard model food compared to the soft model food conditions (p = 0.003). These differences in endocrine response were not associated with differences in food intake at the subsequent meal. Exploratory sub-analysis of the responsive insulin curves showed that after 2.5 min of MSF the hard texture model foods insulin concentrations were 1.2 greater compared to the soft texture. These findings indicate that texture hardness and sweetness increase the overall PP response and that MSF on hard texture increases the overall ghrelin response compared to soft texture model foods. However, MSF on model foods does not lead to a typical CPR. This study, among others, shows that there are major dissimilarities in the endocrine responses to food stimulation between individuals. This emphasizes the importance of considering cephalic responders and non-responders. More research is needed to understand CPRs in relation to food texture and taste properties.

Comparison of oro-sensory exposure duration and intensity manipulations on satiation

Oro-sensory exposure (OSE) is an important factor in the regulation of food intake with increasing OSE leading to lower food intake. Oral processing time and taste intensity both play an important role in OSE but their individual contribution to satiation is unknown. We aimed to determine the independent and combined effects of oral processing time and taste intensity on satiation. Fifty eight participants (23±9y, BMI 22±2kg/m²) participated in a 2×2 factorial randomized crossover study in which they consumed one of four gel-based model foods until satiation during four sessions. Model foods were offered ad libitum and differed in texture (soft or hard texture, yielding shorter and longer oral processing time) and sweetness (low or high intensity). Model foods were isocaloric and were matched for flavor and palatability. Outcome measures were intake of the model food and the microstructure of eating behavior, such as number of chews and eating rate. There was an overall significant effect of texture (p<0.001) but not sweetness (p=0.33) on intake with a 29.2% higher intake of the soft model foods compared to the hard model foods. After correction for palatability the difference in intake between the soft and hard model foods was 21.5% (p<0.001). The number of chews was significantly lower for the soft (10.1±6.2) than for the hard (26.9±6.2) model foods (p<0.001), which resulted in a significantly lower eating rate (soft, 26.3±10.2 and hard, 15.3±7.1g/min, p<0.001). These results show that increasing texture hardness of gel model foods decreases food intake independent of sweet taste intensity. The higher number of chews and faster eating rate may cause this effect. In conclusion, oro-sensory exposure duration rather than taste intensity appears to be the main determinant of food intake.

Análise ultrassonográfica qualitativa e quantitativa da deglutição orofaríngea

RESUMO Objetivo: Analisar a influência do efeito da consistência do alimento e da idade sobre os parâmetros qualitativos e/ou quantitativas no exame ultrassonográfico (USG) da deglutição. Métodos: Foram realizadas avaliações ultrassonográficas da deglutição em 100 indivíduos sadios (divididos em quatro grupos com idades entre 20 e 60 anos) nas consistências líquida e purê. Para análise qualitativa, considerou-se a presença de cinco etapas durante a deglutição orofaríngea. Para a análise quantitativa, foram observados os parâmetros: duração da propulsão da língua durante a deglutição e a distância do deslocamento máximo do osso hióide durante a deglutição. Resultados: Na análise ultrassonográfica qualitativa, todos os indivíduos, independente da faixa etária, apresentaram o mesmo padrão de posição de língua para a recepção e apreensão do alimento e repouso (fases 1, 2 e 5) e houve grande variabilidade inter-sujeitos do movimento ondulatório da língua na fase 3. Na fase 4, o pico máximo do deslocamento do osso hióide aumentou em função da consistência de alimento. Na análise quantitativa, observou-se efeito da idade (p=0,03) e consistência (p=0,00), bem como para a interação entre idade*consistência (p=0,03) nos parâmetros USG analisados. De forma geral, o grupo de indivíduos entre 20 e 30 anos (G1) diferenciou-se dos demais grupos e a consistência purê aumentou os valores de duração e deslocamento. Conclusão: A ultrassonografia do movimento de língua mostrou-se um instrumento viável para avaliar alguns dos parâmetros da deglutição orofaríngea. Idade e consistência alimentar modificam as imagens USG do movimento de língua em indivíduos normais e devem ser consideradas conjuntamente na avaliação ultrassonográfica da deglutição.

Ultrasound Imaging for Analyzing Lateral Tongue Movements during Mastication in Adults with Cerebral Palsy Compared with Adults without Oral Motor Disabilities

Described here is an ultrasound technique used to study tongue movements, particularly lateral tongue movements, during mastication. A method to analyze spatial and temporal tongue movements was developed, and the feasibility of using this method was evaluated. Biplane ultrasound images of tongue movements of four adults without oral motor disability and two adults with oral motor disability as a result of cerebral palsy, were acquired. Tongue movements were analyzed in the coronal and sagittal planes using B-mode and M-mode ultrasonography. Inter-rater and intra-rater agreement for manual tracing of tongue contours was good (ICC = 0.81 and 0.84, respectively). There were significant differences between the two adult groups in movement frequency in the horizontal direction in both coronal and sagittal planes. In the coronal plane, differences in movement frequency and range of vertical movement were detected. Data obtained from sagittal images, with the exception of vertical frequency, indicated no differences between the groups. The protocol developed in this study (using B-mode and M-mode) proved to be valid and reliable. By using this protocol with individuals with and without oral motor disability, we were able to illustrate the clinical application of our protocol to evaluation of differences in tongue movements during mastication.

Model for understanding consumer textural food choice

The current paradigm for developing products that will match the marketing messaging is flawed because the drivers of product choice and satisfaction based on texture are misunderstood. Qualitative research across 10 years has led to the thesis explored in this research that individuals have a preferred way to manipulate food in their mouths (i.e., mouth behavior) and that this behavior is a major driver of food choice, satisfaction, and the desire to repurchase. Texture, which is currently thought to be a major driver of product choice, is a secondary factor, and is important only in that it supports the primary driver-mouth behavior. A model for mouth behavior is proposed and the qualitative research supporting the identification of different mouth behaviors is presented. The development of a trademarked typing tool for characterizing mouth behavior is described along with quantitative substantiation of the tool's ability to group individuals by mouth behavior. The use of these four groups to understand textural preferences and the implications for a variety of areas including product design and weight management are explored.

Selecting food. The contribution of memory, liking, and action

The goal of the present experiment was twofold: identifying similarities and differences between flavour memory and visual memory mechanisms and investigating whether kinematics could serve as an implicit measure for food selection. To test flavour and visual memory an 'implicit' paradigm to represent real-life situations in a controlled lab setting was implemented. A target, i.e., a piece of cake shaped like either an orange or a tangerine, covered with either orange- or a tangerine-flavoured icing, was provided to participants on Day 1. On Day 2, without prior notice, participants were requested to recognize the target amongst a set of distractors, characterized by various flavours (orange vs. tangerine) and/or sizes (orange-like vs. tangerine-like). Similarly, targets and distractors consisting of 2D figures varying in shape and size were used to assess visual memory. Reach-to-grasp kinematics towards the targets were recorded and analysed by means of digitalization techniques. Correlations between kinematic parameters, memory and liking for each food item were also calculated. Results concerned with memory recollection indices provided evidence of different key mechanisms which could be based either on novelty of flavour memory or visual memory, respectively. To a moderate extent, kinematics may serve as an implicit index of food selection processes.

Designing food structures for nutrition and health benefits

In addition to providing specific sensory properties (e.g., flavor or textures), there is a need to produce foods that also provide functionality within the gastrointestinal (GI) tract, over and above simple nutrition. As such, there is a need to understand the physical and chemical processes occurring in the mouth, stomach, small intestine, and large intestine, in addition to the food structure-physiology interactions. In vivo techniques and in vitro models have allowed us to study and simulate these processes, which aids us in the design of food microstructures that can provide functionality within the human body. Furthermore, it is important to be aware of the health or nutritional needs of different groups of consumers when designing food structures, to provide targeted functionality. Examples of three groups of consumers (elderly, obese, and athletes) are given to demonstrate their differing nutritional requirements and the formulation engineering approaches that can be utilized to improve the health of these individuals. Eating is a pleasurable process, but foods of the future will be required to provide much more in terms of functionality for health and nutrition.

Vibromyography of oral processing varies with type of semi-solid food and with sensory judgements

Vibromyography was used to quantify oral activity during the processing of well-characterized semi-solid model foods whilst subjects assessed the intensity of the sensory attributes to thick, creamy, melting, fatty, rough and liking. A series of eleven starch-based vanilla custard desserts was prepared with five different viscosities, three different fat levels, and three different particle sizes. Over 5 sessions, subjects (N=10) took 5 ml spoonfuls of each of the stimuli for 5 s before they rated the strength of the various attributes. The results demonstrated that oral movements varied significantly with the type of semi-solid food and with the type of attribute. Individual subjects displayed a highly idiosyncratic behaviour. Oral movements were significantly related to sensory ratings of liking, creaminess and roughness.

The effects of food viscosity on bite size, bite effort and food intake

Two studies investigated the effect of a food's viscosity on bite size, bite effort and food intake using a standardized protocol in which subjects sipped through a straw every 20 s for a period of 15 min from one of two products, a chocolate-flavored dairy drink and a chocolate-flavored dairy semi-solid, matched for energy density. In the first study, subjects consumed 47% more from the liquid than from the semi-solid to reach the same degree of satiation, with larger bite sizes for the liquid throughout the 15 minute period (8.7+/-0.45 g) compared to the semi-solid (5.8+/-0.3 g, p<0.01). In the second study bite effort was eliminated by using a peristaltic pump to present the products every 20 s. Oral processing time before swallowing was set at 5 s (both products) or 8 s (semi-solid). With the elimination of bite effort and a standardized oral processing time, subjects consumed as much from the semi-solid as from the liquid to reach the same degree of satiation. Bite size for liquids started relatively small and grew gradually over successive bites, whereas the bite size for the semi-solid food started relatively large and became gradually smaller. The latter effect was even more pronounced when the oral processing time was increased from 5 to 8 s. In conclusion, semi-solids resulted in smaller bite sizes and lower intake than liquids, but these differences disappeared when differences in bite effort were eliminated.

Sensory and instrumental analysis for slipperiness and compliance of food during swallowing

In spite of its importance, there have been few attempts to evaluate the sensory attributes of the food bolus during swallowing. In the current study, the slipperiness, the degree of slide for the food bolus through the mucosal surface of the oro-pharynx, and the compliance, how easily the shape of a food bolus can be transformed for automatic and comfortable swallowing, were derived among several sensory attributes related to the swallowing. Therefore, the study aims were twofold: (1) to develop the methods of sensory and instrumental analyses for determining the slipperiness and compliance of the food bolus during swallowing and (2) to examine the appropriateness of the newly designed devices by correlating the data between the sensory and instrumental analyses. Six commercial food products were evaluated by 10 trained panelists for each attribute. The devices for assessing each attribute were developed in consideration of the oro-pharyngeal movements. The sensory and instrumental analyses showed high correlation and regression coefficients as well as intensity differences of the 6 samples for each attribute. In conclusion, the slipperiness and the compliance were suitable for acquiring a better understanding of the sensory attributes of the food bolus during swallowing, and the newly developed devices showed a high potential for determining those attributes.

Modulation of biting procedures induced by the sensory evaluation of cheese hardness with different definitions

This study seeks to clarify the bite process in individuals who assess cheese hardness to confirm the relationships among hardness definitions, their causative bite procedures, targeted intra-oral mechanical events, and judgment. Subjects were required to bite and evaluate samples using two different definitions of hardness. We measured an intra-oral bite time-force profile using a tactile pressure-measurement system with a sheet sensor unobtrusively inserted into the subject's mouth along with a sample. The first bite profile was an exploratory procedure adjusted to optimize perception of the designated textural attribute. From the temporal modification of the bite profile, we could estimate the bite parameter that was targeted as the sensory information for a particular texture attribute. We examined inter-definition and inter-subject variations in the relationship between hardness judgment and its sensory source estimated from the bite procedure. We demonstrated that the bite measurement could elucidate both the bite procedures and sensory information for hardness evaluation. Different definitions induced different bite procedures that resulted in a change in the sensory signal. The definition also affected inter-subject variability in bite procedures and sensory-judgment correspondence.

First bite for hardness judgment as haptic exploratory procedure

This study examines whether the modulation of biting behavior while subjects are engaged in food texture judgment can be explained as an intra-oral exploratory procedure optimized for recognizing a specified sensory attribute. Subjects were asked to compare two cheese samples for "the force required to penetrate the sample with the molar teeth" (the definition for "hardness" used in this study). Based on this definition, we hypothesize that the subjects targeted the first peak of the bite time-force profile (i.e. the intra-oral phenomenon of the initial fracture) as an essential property for judgment. We observed significant elongation of the first peak in the judgmental biting, compared to the biting without judgment, for all subjects. Shortening of the second peak (teeth-to-teeth contact) duration and decrease of the second peak force were also observed for all subjects. These active biting modulations suggested that the first peak was targeted for judgment, whereas the second peak was not targeted. The sample with greater maximum force or time-integral of the bite force at the first peak was also judged as requiring greater force; these agreements were statistically significant. This result confirmed that the parameters related to the first peak were targeted as judgmental cues. We concluded that the biting behavior in hardness judgment functions as the exploratory procedure and was optimized for encoding the target sensory properties.

Effect of bolus size on chewing, swallowing, oral soft tissue and tongue movement

Simultaneous 3D articulograph and ultrasonograph techniques were used to monitor the chewing, swallowing, oral soft tissue and tongue movements of six subjects whilst consuming varying numbers (1, 2 and 4) of a confectionery product. Modifying the number of confectionery units had a variable effect on chewing, swallowing and oral soft tissue movements during the start of the chewing sequence. The distance, range and velocity of chin movement were significantly lower when 1 confectionery unit was consumed compared with 2 and 4 during the middle stage of the chewing sequence. Significant differences in modioli movement were observed during the initial stages of chewing allowing the identification of a working and non-working side, whilst no differences in thyroid cartilage movement were noted over the whole chewing sequence. Increasing the number of confectionery units caused a significant increase in the index of tongue movement during the end of the eating sequence, although the mean index of tongue movement over the total chewing sequence remained constant. Jaw movement correlated with tongue movement, where for all samples, gape decreased linearly as the chewing sequence progressed, reflected in a similar decline in the index of tongue movement. The lack of differences in the index of tongue movement observed over the start and middle of the chewing sequence as a consequence of the number of confectionery units consumed suggested that the change in the physical properties of the bolus had a greater effect on the index of tongue movement than the change in bolus size.

Interactive relationship between the mechanical properties of food and the human response during the first bite

Biting is an action that results from interplay between food properties and the masticatory system. The mechanical factors of food that cause biting adaptation and the recursive effects of modified biting on the mechanical phenomena of food are largely unknown. We examined the complex interaction between the bite system and the mechanical properties. Nine subjects were each given a cheese sample and instructed to bite it once with their molar teeth. An intra-oral bite force-time profile was measured using a tactile pressure-measurement system with a sheet sensor inserted between the molars. Time, force, and impulse for the first peak were specified as intra-oral parameters of the sample fracture. Mechanical properties of the samples were also examined using a universal testing machine at various test speeds. Besides fracture parameters, initial slope was also determined as a mechanical property possibly sensed shortly after bite onset. The bite profile was then examined based on the mechanical parameters. Sample-specific bite velocities were identified as characteristic responses of a human bite. A negative correlation was found between bite velocity and initial slope of the sample, suggesting that the initial slope is the mechanical factor that modifies the consequent bite velocity. The sample-specific bite velocity had recursive effects on the following fracture event, such that a slow velocity induced a low bite force and high impulse for the intra-oral fracture event. We demonstrated that examination of the physiological and mechanical factors during the first bite can provide valuable information about the food-oral interaction.