Biomedical subjects

J F Prinz

Publications and source records attributed to J F Prinz.

At least 19 recordsLinked to original sources

PubMed2006

Sensory correlation of glucose levels in a starch-based semi-solid model system before and after alpha-amylase breakdown.

In this study a diabetic glucose monitor was used to measure the glucose content of 40 model vanilla custard desserts, these were compared with sensory ratings from a trained quantitative descriptive analysis panel. Stimuli varied in starch type, concentration and homogenisation but had identical sugar, flavour and fat contents. Despite this, mean sensory ratings of sweetness varied from 21 to 43 on a 100-point scale. Glucose levels in the stimuli were measured, in vitro, before and after the addition of 0.1% whole human saliva to the product. In all cases glucose concentration increased after the addition of saliva as starch was converted to glucose. There were highly significant correlations of some odour, flavour, mouth feel and after-feel attributes with glucose concentration. The correlation of sweet flavour with glucose concentration was higher in unmodified stimuli than in stimuli with added saliva, suggesting that sweetness is perceived soon after ingestion. Additional glucose produced through starch breakdown appeared to have a relatively small impact on the sensory scores of the stimuli.

Adult↗

PubMed2006

Instrumental and sensory quantification of oral coatings retained after swallowing semi-solid foods.

After a mouthful of food has been swallowed, some food material is always retained in the mouth. With semi-solid foods this is in the form of a coating that adheres to the oral mucosa. The amount and location of this material may play an important role in food sensations. In this study two quantitative methods of describing the coatings, generated by a set of 16 model custards varying in degree of lubrication (fat content) and degree of viscosity (starch concentration) are investigated. In the first method, a trained quantitative descriptive analysis panel (N=8) was instructed to take single mouthfuls of semi-solid foods, swallow and then rinse twice for 5s with water and spit out. The turbidity of the rinse water was then measured. During the same session, sensory assessments of the products were obtained. In the second method the thickness of the coating on the anterior and middle one-thirds of the tongue was quantified using a pair of opto-electronic reflectance sensors mounted on a probe which was placed on the tongue, one sensor measuring the anterior part of the tongue the other the posterior (middle third) of the tongue. Turbidity of the first rinse related strongly to the food's viscosity, as well as to sensory attributes associated with the food's fat content and viscosity, such as perceived thickness, creaminess and fattiness. Turbidity of subsequent rinses related primarily to fat content. These results indicate that turbidity of rinse water is a useful tool in fundamental (e.g., food texture research) as well as applied research (e.g., product development and quality assurance in food industry). Reflectance varied primarily with fat content and did not relate well to sensory attributes.

Dairy Products↗

PubMed2005

Do tastants have a smell?

The stimuli used in taste research are usually considered to be odourless. This was tested in two experiments with aqueous solutions of two representative compounds for each of the five taste qualities including umami. In the first experiment elderly and young subjects rated the intensity and pleasantness of three concentrations of the stimuli, while wearing or not wearing a noseclip. Saliva production was also measured. Blocking olfaction only influenced salivation for umami. It reduced taste intensity ratings, but as in an earlier experiment with the same compounds in food products, this effect was stronger in the young, who also liked the stimuli better wearing the noseclip. In the second experiment, another group of young people tried to detect the odours of the tastants dissolved in demineralized, double-distilled or Evian water. A considerable number of subjects could regularly detect seven of the ten tastants by olfaction and the extent to which they did correlated significantly with the reduction in taste intensity ratings for the different tastants found in the first experiment. We suggest that most tastants can be smelled and that this smell contributes to taste intensity ratings.

Adolescent↗

PubMed2004

Abrasives in foods and their effect on intra-oral processing: a two-colour chewing gum study.

In this study we suggest that the presence of abrasives in food items lead to physiologic responses that reduce the amount of tooth loss because of abrasion. Subjects were presented with two pairs of two-colour chewing gum, one sample had 0.5 g of an abrasive powder added. Subjects were instructed to chew for 10 or 20 chewing strokes and then remove the gum. After removal the chewing gum was placed in a plastic bag and flattened. Each pair of gums was compared on the basis of the amount of mixing observed. In all cases the addition of the abrasive powder resulted in slower chewing and less mixing. Salivary flow rate increased from a resting value of 0.6 to 0.9 mL min(-1) when stimulated by the non-abrasive gum to 1.1 mL min(-1) with the abrasive gum. This difference was significant (P < 0.05). We conclude that when abrasive particles are detected in the mouth, less bolus manipulation is performed and more saliva is secreted. These responses would have the effect of reducing loss of tooth substance at the expense of reduced cominution of the food.

Adult↗

PubMed2002

The influence of density and material on oral perception of ball size with and without palatal coverage.

The size of a bolus determines how it will be manipulated in the mouth and swallowed. Ten healthy individuals assessed the size of ball bearings of five sizes (4-11 mm diameter) and four materials with different densities in order to investigate the effect of weight on oral size perception. To study the role of the tongue and palate, the experiment was performed with and without a custom-made plastic palate. The results revealed that size itself determines size perception, and that material and weight are negligible factors. An illusional effect in the direction of under-estimation was found for the ball bearings, especially for the small sizes up to 8 mm diameter. While wearing a plastic palate a significant improvement (P<0.05) occurred; the participants performed better and there was less under-estimation. An explanation for this could be that only a minor part of the total area of the ball bearing touches the palate and is hence detected, while the tongue alone is more compliant and thereby able to sense the ball's whole size.

Humans↗

PubMed2001

"The first bite of the cherry": Intra-oral manipulation prior to the first bite in humans.

The breakdown of food in the mouth during mastication can be described in terms of two parameters: a breakage function, which describes the fragmentation of food after a bite, and a selection function which defines the probability of particle fracture. The non-zero value of the selection function depends on the manipulation of food particles by the tongue. Little, however, is known about this. As a first step, this study investigated the manipulation of wax sheets of differing sizes and shapes by the tongue after ingestion. It was found that subjects tended to orientate rectangular and square wax wafers so that the long axis of the particle was parallel to the tooth row, independent of the initial orientation given when they were introduced into the mouth. Circular wafers were randomly oriented relative to initial orientation. If this could be extrapolated to the start of mastication, then it suggests that the tongue tends to align food particles so that the post-canines produce close to the greatest surface area possible by fragmenting them along their longest axis.

Eating↗

PubMed2000

Computer aided gnathosonic analysis: distinguishing between single and multiple tooth impact sounds.

Watt developed a classification of tooth contact sounds that distinguished between the short sharp, reproducible sounds heard when the teeth meet simultaneously and the dull prolonged, poorly reproducible sounds heard when tooth contacts are sequential. However, when a large occlusal prematurity, for instance a high restoration, is introduced, tooth contact sounds are also short sharp and highly reproducible. In this study, a method of distinguishing single from multiple tooth contact sounds is described, based on an analysis of the phase and amplitude of sounds detected by headphones placed over the ears.

Adult↗

PubMed2000

Bolus dimensions in normal chewing.

Samples of 17 different types of chewing gum weighing between 0.3 and 22 g were presented to eight subjects. After chewing the samples for between 20 and 100 strokes the boluses of gum were removed from the mouth and their length was measured. Bolus length increased with weight from 0.3 to 4 g, but remained constant between 4 and 18 g at which point it began to increase once more. The range of sizes associated with this plateau is similar to the range of sizes of natural bites with other foods.

Adult↗

PubMed2000

Saliva tannin interactions.

Many plant foods contain tannins, compounds that bind proteins, such as mammalian enzymes. Although described as tasteless, tannins can be detected orally by their astringency. However, the actual mechanism of oral detection and the effect of tannins on mastication and swallowing have been little investigated. Here, we show from in vitro tests that tannic acid, a common standard in tests used to detect tannins, significantly reduces the lubricating qualities of human saliva both by decreasing its viscosity and increasing friction, both factors lending support to the notion that astringency is a tactile phenomenon. From the literature, it is clear that this effect depends on the presence of salivary proline-rich proteins (PRP). In a mammalian context, ingestion of tannin-rich foods in a species with salivary PRP will be signalled by interference with bolus formation during mastication while the increase in friction may also be detectable and lead to increased tooth wear if the signal is ignored. In a human context, cross-cultural preferences for tannin-rich beverages such as tea, coffee and red wine at the end of meals may be explained by reduction in adhesion of food particles to the oral mucosa allowing their rapid oral clearance.

Adult↗

PubMed1999

Quantitative evaluation of the effect of bolus size and number of chewing strokes on the intra-oral mixing of a two-colour chewing gum.

One of the major aims of the dental profession is the maintenance of oral function, specifically chewing ability. However, there are no generally accepted measures of chewing ability or even general agreement as to what level of tooth loss is deemed to require clinical intervention. There is therefore a need for simple objective tests of oral function. In this study a modification of the two-colour chewing gum test devised by Liedberg & Owall (1991, 1995) is described. In this test chewing gum containing two contrasting colours is chewed. On removal from the mouth the bolus is placed in a transparent plastic bag, flattened and a digital image is taken. Several image processing techniques are described and evaluated as measures of the amount of mixing present in the chewed gum. Flattening the gum was found to increase the accuracy of subjective evaluation, which was similar to that achieved by the image processing techniques.

Chewing Gum↗

PubMed1998

Correlation of the characteristics of temporomandibular joint and tooth contact sounds.

In this study tooth contact sounds have been compared with temporomandibular joint (TMJ) sounds elicited during opening and closing movements. One hundred and eight subjects were instructed to open as far as possible and then close with sufficient force to produce a tooth contact sound. At least four cycles from each subject were recorded on tape, The first and last sounds in the recording were the tooth contact sounds, these were identified automatically. The mean duration and rise time of each tooth contact sound was calculated and their standard deviations for each subject were calculated to give a measure of the reproducibility. The number and mean amplitude of TMJ sounds occurring during tooth separation were also calculated for each cycle. Highly significant correlations were found between the number and amplitude of the TMJ sounds within a cycle and the duration and rise time, and particularly their standard deviations. Acoustic quiescence during the open-close cycle was associated with short, reproducible tooth contact sounds characterized by a short rise time. The longest and most variable tooth contact sounds were associated with TMJ sounds in all three phases of the open-close cycle. This supports previous clinical findings associating occlusal interferences with TMJ dysfunction.

Acoustics↗

PubMed1998

Validation of a recording protocol for assessing temporomandibular sounds and a method for assessing jaw position.

Sounds are often produced by the temporomandibular joint (TMJ) during movement in both symptomatic and asymptomatic subjects. However, subjective methods of describing these sounds have been shown to have poor inter- and intra-observer reliability. In this study, a low cost system in which TMJ sounds were detected using the loudspeakers of lightweight in-ear headphones as microphones is evaluated. The sounds were recorded on tape and then analysed using a computer. Sounds were elicited by asking subjects to bring their teeth together with sufficient force to produce a tooth contact sound, then open their mouths as far as possible and then close again. Placing the microphones in the ears attenuated ambient sounds by 58%, thus providing a degree of immunity from ambient noise. Sampling was performed on the left microphone only at 3.4 kHz and from the left and right microphones together at 1.7 kHz for 60 TMJ sounds and 60 tooth contact sounds. Spectral analysis of sounds recorded at the two sample rates revealed no significant differences. Therefore, a sample rate of 1.7 kHz is adequate to resolve the frequency components present in the TMJ sounds. Although simply recording TMJ sounds does not give a direct measurement of the position of the mandible, using this protocol allows the length of the open close cycle to be determined. If the envelope of movement is assumed to approximate a sinusoid, then the direction of mandibular movement can be assumed to reverse at the half way point in the cycle. The accuracy of this assumption was calculated by comparing the mid-point of the cycle to the point of maximum gape in 129 cycles from nine subjects. The mean difference expressed as percentage of cycle length was 1.3 +/- 0.9%.

Adolescent↗

PubMed1998

Autocorrelation of acoustic signals from the temporomandibular joint.

Although there have been many investigations of TMJ sounds in the time and frequency domains, no previous reports have been found of investigations of the autocorrelation spectra of these sounds. In the present study, TMJ sounds were digitized at 1.7 kHz and 300 ms samples containing either clicks (single short duration sounds), crepitus (long duration continuous sounds) or creaks (a series of two or more clicks) were selected. These samples were compared with sounds of known origin: tooth impact sounds, frictional sounds elicited by scratching the head, and bruxing sounds resulting from stick-slip friction as teeth were slid against one another under high pressure. There were clear qualitative and quantitative differences between the autocorrelation spectra of the three types of TMJ sounds. Clicks were similar to tooth impact contact sounds, creaks were similar to the bruxing sounds, and crepitus was similar to the scratching sounds. The repetition rate of creaks was 16 Hz (s.d. 9 Hz), this being similar to the resonance of the mandible about the condylar axis. It is suggested that the creaks are due to stick-slip friction in the lower joint compartment of the TMJ.

Acoustics↗

PubMed1998

Physical mechanisms involved in the genesis of temporomandibular joint sounds.

Several different mechanisms are potentially capable of generating sounds in the temporomandibular joint (TMJ). These include impact, sliding and stick-slip friction, fluid dynamic effects and the release of elastic strain energy. It is the aim of this paper to provide a framework with which to separate sounds resulting from the different underlying causes. Each mechanism is described and its relevance to TMJ sounds and clinical significance discussed. Since it is not possible to observe these mechanisms in vivo the arguments are based mainly on analogies which are used to make predictions of the characteristic acoustic signatures of the sounds produced by these different mechanisms. In particular the changes in the characteristics of the sounds as parameters such as mandibular speed and loading are stressed. It is suggested that single short duration sounds (clicks) are due to impact, multiple short duration sounds (creaks) to stick-slip friction and defects of form and long duration sounds (crepitus) to simple sliding friction. Several other mechanisms which have no obvious clinical significance but which are capable of producing similar sounds are also described and methods of distinguishing them from the sounds that do have clinical implications are discussed.

Acoustics↗

PubMed1998

Subjective assessment of temporomandibular joint sounds.

If it could be shown that the human ear was sufficiently sensitive to describe TMJ sounds, there would be no need to use sophisticated electronic equipment to analyse the sounds. To test this, the ability of normal listeners to distinguish the subtle changes in position, pitch, duration and latency present in TMJ sounds is measured using triangle tests to determine the just-noticeable differences. The results suggest that the human ear is a rather poor instrument for describing subtle differences in the position, duration and latency of TMJ sounds, but is capable of detecting small differences in frequency. It is therefore doubtful that the human ear can distinguish the reciprocal click associated with disc displacement with reduction from clicks due to defects of form on the basis of their relative position in the envelope of movement.

Computers↗

PubMed1998

Resonant characteristics of the human head in relation to temporomandibular joint sounds.

Frequency analysis of the sounds produced by the temporomandibular joint (TMJ) has been claimed to be of diagnostic value. In this study the resonant behaviour of the human skull has been characterized. Assuming that impact is one major mechanism generating the sound, it is shown that the frequencies seen in TMJ sounds relate to the resonant modes of the skull. Where the rise time of the impact is sufficiently short, higher resonant modes are excited.

Adolescent↗

PubMed1998

Techniques for rapid quantitative assessment of activity levels in small-group tutorials.

Two techniques for the rapid quantitative analysis of student participation in small-group teaching were investigated. In the first approach an observer, who also acted as a 'critical friend', recorded the length of individual contributions using a computer keyboard as a simple timing device. In the second approach, small-group sessions were recorded with a portable stereophonic audiotape recorder. The teacher was recorded on one channel, all students on the other. A computer program produced automated analysis of these small group interactions by computing relative amount of speech on each channel. Simple analysis produced automatically by the programs revealed the overall style of the tutorial--variably 'mini-lectures' by teachers with very little participation by the student body, rapid 'question and answer' sessions with about equal teacher/student body involvement or 'mini-presentations' by students with the teacher offering sparse comments in the manner of a facilitator. By presenting results in a graphic format, teachers can be given rapid objective feedback on their teaching style. Coupled with short verbal/non-verbal quizzes at the end of tutorials and information from other assessments, the value of using levels of participation as a measure of the efficiency of such small-group sessions can itself be assessed.

Computer-Assisted Instruction↗

PubMed1998

Food properties that influence neuromuscular activity during human mastication.

The rate of breakdown of food in mastication depends on the ratio of two mechanical properties of the food--the toughness and modulus of elasticity (Agrawal et al., 1997)--a result which can be predicted by an analysis of the energetics of fracture. The work input to produce food fragmentation is provided by the masticatory muscles, the activity levels of which depend on sensory feedback from the mouth. Here, we test the hypothesis that the activity of a representative of this musculature is modulated by the above combination of food properties. The surface electrical activity (EMG) of the anterior temporalis muscles of ten human subjects was recorded while subjects chewed standardized volumes of 15 food types. The integrated EMG in these muscles was highly significantly related to the square root of the ratio of the above two food properties. Significant correlations were found between this food property index and integrated EMG, both when data for all chews and all subjects were lumped together (r = -0.86; p < 0.0001) and when correlation coefficients between the index and EMG were plotted for each chew made by each subject. Except for two subjects in the first chew, these coefficients reached and maintained highly significant levels throughout the masticatory sequence. Thus, a clear relationship between the electrical activity of a jaw-closing muscle and the mechanical properties of food has been found for the first time.

Adult↗