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J H Kroeze

Publications and source records attributed to J H Kroeze.

17 recordsLinked to original sources
PubMed2001

The influence of olfactory concept on the probability of detecting sub- and peri-threshold components in a mixture of odorants.

The headspace of apple juice was analysed to obtain an ecologically relevant stimulus model mixture of apple volatiles. Two sets of volatiles were made up: a set of eight supra-threshold volatiles (MIX) and a set of three sub-threshold volatiles. These sets were used to test the hypothesis that sub-threshold components can change the quality of a familiar smelling mixture of odorants when added to this mixture. In order to test this hypothesis, three successive dilutions of the sub-threshold volatiles were prepared in such a way that the strongest was at the threshold concentration and the two lower concentrations were below the threshold. The detection probabilities of the sub-threshold components in a blank stimulus were compared with the detectabilities in MIX. The sub- and peri-threshold volatiles were detected no better in MIX than in a blank. On the contrary, sub- and peri-threshold volatiles were better detected alone than when added to MIX. However, when the group of subjects was split into two sub-groups, employing either a rough or a detailed concept definition of the target stimulus, respectively, the subjects with highly refined concepts were better able to detect the presence of sub-threshold volatiles in MIX than those with poorly refined stimulus concepts. The effect of stimulus concept definition occurred independently of the proportions of correct detections of sub-threshold volatiles in a blank.

Adolescent↗
PubMed2000

Taste adaptation during the eating of sweetened yogurt.

Taste adaptation, a gradual decline of taste intensity with prolonged stimulation, is frequently observed in laboratory experiments. However, during normal eating the taste of food does not seem to decrease or disappear. During eating, the presence of saliva, the interactions between tastants and odorants, and mouth movements can influence the time course of taste intensity. Therefore, results from standard laboratory adaptation experiments about adaptation seem of limited relevance to the prediction of the time course of taste intensity when eating real foods. We studied whether taste adaptation occurs when subjects eat yogurt, sweetened with two concentrations of sucrose (3.75 and 7.5%). In addition, we examined whether this adaptation is related to taste adaptation measured with a filter paper method. During the eating of yogurt, sweetness intensity declined with time, whereas sourness intensity did not. As expected, taste adaptation in the "yogurt task" was only slightly correlated to adaptation measured with filter paper.

Adaptation, Physiological↗
PubMed2000

Testing taste sensitivity and aversion in very young children: development of a procedure.

Taste perception in 45 3- to 6-year-old children was tested using procedures specifically designed for this age group. Detection thresholds for sucrose and urea were measured by a staircase method and aversion to urea was assessed hedonically, using drawings of facial expressions. All children understood the task and could perform the necessary actions. A subgroup of 20 children participated in a second measurement after a mean interval of 9.5 days: there was a satisfactory degree of stability between the sessions. However, a third measurement, on a subgroup of 13 children after a somewhat longer interval, showed a marked drop in the stability of the urea thresholds. This drop was thought to arise from a decrease in the children's motivation, leading to increased distractibility. Mean threshold estimates were 31 mmol/l for sucrose detection, 59 mmol/l for urea detection and 134 mmol/l for urea aversion, but some children were extremely sensitive to the taste of urea. The findings show that it is possible to study taste perception in very young children if their age is taken into consideration in developing the test procedure. Valid data can be obtained if the procedures are short, easy to understand and intrinsically motivating.

Child↗
PubMed2000

Neohesperidin dihydrochalcone is not a taste enhancer in aqueous sucrose solutions.

Neohesperidin dihydrochalcone (NHDC) is an intensive sweetener, obtained by alkaline hydrogenation of neohesperidin. In this investigation a supposed taste enhancing effect of this substance was tested. A three-step procedure was used. In the first experiment, using a pool of 31 subjects, NHDC and sucrose detection thresholds were measured. In the second experiment, psychophysical functions for both tastants were determined. Then, 15 participants closest to the group threshold who, in addition, had produced monotonic psychophysical taste functions were selected to participate in the next two experiments. In the third experiment, taste enhancement was tested. Three psychophysical sucrose functions were constructed, one with a near-threshold amount of NHDC added to each of seven sucrose concentrations, one with a near-threshold amount of sucrose added (control 1) and one without any addition (control 2). No difference was found between the NHDC-enriched sucrose function and the sucrose-enriched sucrose function. Finally, in experiment 4, differential threshold functions were constructed with either NHDC or sucrose added. Neither the overall shape of the functions nor a comparison of the points of subjective equality showed enhancement. It was concluded that weak NHDC does not enhance the taste of aqueous sucrose solutions.

Adolescent↗
PubMed2000

Method of stimulation, mouth movements, concentration, and viscosity: effects on the degree of taste adaptation.

Although sensory adaptation, the gradual loss of sensation during prolonged stimulation, has been demonstrated in laboratory taste experiments, a comparable loss of taste intensity is not experienced in real-life eating situations. This discrepancy may be due to differences in the proximal stimuli or to differences in the ways the taste receptors are stimulated. In two experiments, the effects of four potentially relevant variables were investigated: stimulus intensity, stimulus viscosity, mouth movements, and presentation method. During the initial seconds of stimulation, adaptation to the weakest of the two solutions was faster. Although more viscous stimuli were less sweet, viscosity as such did not affect adaptation rate, nor did mouth movements. Among the three presentation methods, a sucrose-soaked filter paper on the tongue produced more adaptation than either sipping the solution or flowing it over the tongue. This suggests that even mouth movements far more subtle than those still present in the no-movement condition of a sip-and-spit experiment can disrupt the adaptation process.

Adolescent↗
PubMed1996

Mouth movements diminish taste adaptation, but rate of mouth movement does not affect adaptation.

The degree of adaptation to five concentrations of sucrose was measured. Solutions were kept in the mouth for 25 s; a sweetness judgement was given every 5 s. There were four conditions of mouth movements: no movement, slow, medium and fast mouth movements. It was found that when mouth movements are made there is less adaptation than when there is no mouth movement; however, the rate of movement does not appear to influence the degree of adaptation. Furthermore concentration was found to have an effect. In the no-movement condition, the degree of adaptation seems to rise with concentration, whereas in the movement conditions the opposite effect occurs, i.e. a decrease in the degree of adaptation occurs with increasing sucrose concentration. These phenomena might be explained by the stimulated tongue area, or by taste constancy.

Adaptation, Physiological↗
PubMed1995

The effect of sweeteners on perceived viscosity.

Two different sweeteners, sucrose and aspartame, were matched in perceived sweetness intensity. These solutions were thickened with carboxymethylcellulose to six different viscosity levels. Sucrose and aspartame appeared to decrease perceived viscosity of the solutions at a specific sweetener concentration, at all viscosity levels. However, in a second similar experiment with three viscosity levels and seven sucrose concentrations no effect of sucrose concentration on perceived viscosity was found. Reasons for these conflicting results are discussed. No definite conclusions about the effect of sweeteners on perceived viscosity can as yet be drawn.

Adult↗
PubMed1994

Ipsi- and bilateral interactions in taste.

In two experiments, the integration over spatial extent in taste was investigated for threshold sensitivity to NaCl and for suprathreshold intensity perception of saltiness. The area of stimulation was doubled by adding either an ipsilateral or a bilateral stimulus. The two stimuli could be of equal or unequal intensity. The data showed that at threshold level a probability summation model applied to all bilateral and most of the ipsilateral stimulus combinations. Probability summation failed to predict detection probability when two stimuli with different intensities were presented at the same tongue side. For suprathreshold stimuli, the magnitude of the saltiness sensation as estimated by a line-length method depended on the level of stimulation. The possible peripheral interaction mechanisms and central factors contributing to the taste response were discussed.

Adult↗
PubMed1987

Effects of adaptation and cross-adaptation to common ions on sourness intensity.

The effects of self and cross-adaptation of acetic acid and HCl solutions on the perception of sourness, were investigated using a filter paper method. In contrast to acetic acid and to pH-buffered acetic acid solutions, self-adaptation could not be obtained with HCl. In fact the sourness of the HCl test-stimulus after adaptation to HCl was increased compared to the sourness obtained with the unadapted tongue. Such a sourness potentiation was also observed with acetic acid and buffered acetic acid solutions after adaptation to distilled water. The results suggest that the reception process eliciting the sour taste of H+ ions and of undissociated acids are different and probably independent.

Acetates↗
PubMed1985

Bitterness suppression as revealed by split-tongue taste stimulation in humans.

QHCl-sucrose and QHCl-NaCl mixtures administered to the anterior part of the human tongue led to substantial bitterness suppression as determined by the method of magnitude estimation. In the QHCl-sucrose condition components separated by the tongue's midline and those spatially mixed produced equal amounts of bitterness suppression. However, the QHCl-NaCl mixture produced significantly more bitterness suppression with the spatially mixed than with the spatially separated stimulus components. It is concluded that bitterness suppression in mixtures with sucrose occurs centrally and in mixtures with NaCl both peripherally and centrally.

Brain↗
PubMed1985

Interindividual differences in acuity for odor and aroma.

To determine the olfactory acuity of 27 subjects a sensory test was presented which was divided into 4 subtests, 2 for nasal and 2 for oral stimulation. Each subtest contained 28 (4 substances X 7 concentrations) olfactory detection tasks (items). The substances used were lemon and rum aroma as well as ethyl butyrate and amyl acetate, the solvents tap water and sugared tap water. Analysis showed that the test provided a clear differentiation between subjects of low, medium, and high olfactory acuity. The intercorrelations among the test substances and the split-half reliabilities of the subtests proved relatively high, whereas only moderate to low intercorrelations among the subtests were found. This was considered an effect of intraindividual variations of olfactory sensitivity. Finally, some conclusions for the construction of acuity tests for odor and aroma are presented.

Adolescent↗
PubMed1983

Word matching and lexical decisions: a visual half-field study.

In unilateral Visual Half-Field tasks visuospatial and linguistic processing were compared. In a Word Matching task subjects judged the physical identity of simultaneously presented pairs of three-letter words or legal nonwords. No mainfield effects were found, but word pairs were recognized better and faster as "same" than nonword pairs. Latencies and errors in "different" pairs increased monotonically with position of letter change in the left but not in the right visual field (RVF), suggesting a serial, letter-by-letter way of processing for the right hemisphere and a whole word approach for the left. At this perceptual level the ability to store lexical information from the icon is stressed as a hemisphere-specific factor. In a Lexical Decision task the same subjects judged the same items on the word/nonword dimension. A RVF advantage associated with words as compared to nonwords occurred, as expected. Additional analysis suggests that order and difficulty of tasks may influence females' laterality, as compared to that of males.

Decision Making↗