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K Hoppe

Publications and source records attributed to K Hoppe.

16 recordsLinked to original sources
PubMed1996

[The psychophysics of sweet taste. 8. Interindividual variability of differential findings].

Contribution to the psychophysics of sweet taste. Part 8. On the inter-individual variability of the difference sensitivity. The variability of sensitivity of volunteers is a considerable imponderability for the comparison of sensoric results. The paper deals with the quantitative determination of the different sensitivity of sweet taste of 132 persons, 38 men and 94 women at the age of 19 to 64 years, using a statistically defined method. The numbers of errors are estimated for each person by means of one test difference of two saccharose concentrations using 10 pairs of comparisons and 4 runs. The average number of error of 10 comparisons corresponds to the individual measure of sensitivity. The medium value of the total distribution is 1.54 and the standard deviation is 1.19 errors. The value is only less above the binomial calculated number. In random test women show in comparison to men a significant higher variance at the statistical identical mean. A variance analysis based on the cutting of the distribution edges in the range of 0.5 to 4.0 errors can detect high significantly the steady learning effect of the volunteers during the runs. The method is applicable to determine classified subjective characteristics. The calculations of necessary group numbers for such experiments on the base of binomial distribution are discussed.

Adult↗
PubMed1995

[The psychophysics of sweet taste. 6. Context effects by use of multiple stimuli sequences].

For the determination of differentiation probabilities in a multiple experimental design the range of stimuli is a significant source of disturbance. In order to determine their efficiency, sequences with 5 equidistant gradated concentrations of sucrose were used, which were compared with a basic concentration. The probability for each gradation was carried out with help of 2-AFC-technique (60 pairs each). 5 gradations at 3 basic concentrations with fixed, average balance were examined in a factorized experimental design. The frequency of the correct judgments is linearily dependent on the sequence of stimuli. In the experimental space the slope of this relationships decreases with increasing gradation hyperbolically (range-effects). The level of the basic stimuli is in this view without any greater importance. When determining the difference thresholds these context effects are to be considered.

Adult↗
PubMed1995

[The psychophysics of sweet taste. 7. New determination of sweet taste parameters of acesulfame, aspartame, cyclamate, saccharin, glucose and sorbitol].

By means of a new method (double staircase) concentration pairs of equal intensity for the sweet compounds acesulfame-K, aspartame, cyclamate-Na, saccharine-Na, dextrose and glucitol were determined with sucrose on 6 or 7 equidistant scaled levels, respectively, with 4 repetitions. The parameters maximal intensity Rm, the concentration coefficient b and the mean Rm/b, respectively, are calculated for each substance from the known parameters for sucrose using the exponential function R = Rm(1-e-bS/Rm), which describes the sweetness intensity R in dependence of the concentration S. For exact determination of the maximal intensity the upper concentration level was fixed at very high degree. Additionally, the relative sweetness of each concentration level of each substance is calculated. In all cases the exponential function is valid without limitation. The statistical parameters are homogenous and are laying within the applied staircase method. Systematical deviations could not be found.

Adult↗
PubMed1994

[The psychophysics of sweet taste. 5. The use of a sequential staircase method for the determination of equally intense concentration pairs].

The suitability of a sequential staircase-method for the determination of equal stimuli of the gustatory sense is experimentally investigated. The aim is the decrease of experimental expenditure when ruling sources of bias. In order to realize them sucrose solutions are used both for the constant stimulus and also for the sequence of stimuli. Possible factors are the gradation of the sequence of stimuli and its displacement towards the constant stimulus. These are factorized in a two-staged trial arrangement and are interpreted in a form of an analysis of variance. The gradation of sequence (grain) is the key factor. It defines both the occasional bias and also the efficiency of systematical sources of bias. Thus the subject-depending judgement errors, which occur in larger gradation, are avoidable with their adjustment on the half of the difference threshold. The errors, which are due to the direction, are counterbalanced through an up and down trial execution with a following meaning average. A remaining influence of the displacement of sequence is normally neglective. The standard deviation for the single determination lies--independently of the concentration level--dimensionally slightly above the half of the setting grain. The method of constant stimuli requires at least the twofold experimental expenditure for a similar result.

Adult↗
PubMed1992

Relationship between a long-term treatment of 2-mercaptoethanol and protein metabolism in the ageing rat.

Female RLEF1/Lati rats were chronically treated with 2-mercaptoethanol in a dose of 13 micrograms.100 g bw-1.day-1 dissolved in drinking water. During a 48-h experiment 15N-labelled glycine was given orally in a dose of 5 mg 15N.kg bw-1 and urine samples were collected and analysed by an emission spectrometric isotope method. Protein synthesis and nitrogen excretion rate constants were calculated according to the three-pool model, and 3-methylhistidine excretion rates were also determined. 2-Mercaptoethanol appears to influence protein metabolism; however, the slower rates of protein synthesis proved to be apparent in almost all groups of treated rats. Protein synthesis and nitrogen excretion rate constants have exceptionally high values in 2-year-old rats, possibly explained by the occurrence of hypercompensation mechanisms in old age. These were reflected by the excretion rates of 3-methylhistidine which were reduced as a result of sulphhydryl group interactions in age-dependent cellular metabolic changes.

Aging↗
PubMed1991

Prediction of total body lipid from total body water in rats. Part 1. Relations between directly measured major body components.

Aimed to the construction of a prediction equation for estimations of lipid content from animal water content body composition was determined by whole body analysis of male rats (1) given access, ad libitum, to a commercial standard diet (n = 144; ranging from 60 to 600 g in weight, and from the 4th to the 34th week of age), and (2) showing striking variations with regard to nutritional state, dietary history, enlarged fat deposition, genetic origin, intestinal microbial status, and advanced age (n = 75). It was shown that a unique coefficient of water content in lipid-free body mass does not exist. The results of statistical analysis for the grouped values of percentage body dry matter (x) and percentage body lipid (y) indicate that the latter can be estimated accurately from body water content directly determined by the use of the quadratic regression equation y = -0.2864 x +0.01615 x2 with a standard deviation of the procedure Sy = +/- 1.40. This prediction equation is valid for a wide developmental span even under highly different experimental states. Differences between the calculated body lipid contents vs. analytically determined values are smaller than by using a linear regression equation or coefficient(s) of hydration of lipid-free body mass.

Aging↗
PubMed1981

[Psychophysics of sweet taste. II. Statistical theory of the stimulus-response behavior of sweet taste receptors].

Considering various conditions of adaptation, the authors determined the Weber discrimination thresholds for the sweet taste of saccharose. When the adaptation to the basic stimulus is maintained and use is made of the differential coefficient behaviour, the discrimination threshold is an exponential function of the concentration. The discrimination threshold is by definition that amount of stimulant per unit of volume which will produce an effect of the magnitude of 1. Consequently, the numbers of moles being substituted, its reciprocal, the probability of obtaining a stimulus response, is greater than 1. A differential equation, namely (formula: see text), can be formulated as the basis of the stimulus-response behaviour of saccharose, the integration of which yields a discrimination characteristic expressed as (formula: see text). S = concentration of the solution as the stimulus intensity; R = stimulus response expressed in steps. The parameter b is the maximum probability of the stimulus response and can be termed substance-specific concentration coefficient. Rm is the maximum step number when the stimulus intensity tends to infinity; it is also substance-specific. As this characteristic involves both the proportional factors and the differential coefficients, it is called P-D characteristic. From this invariant relationship, the static P characteristic for a very slow increase in stimulus intensity can be derived. When the adaptation to the basic stimulus is abolished by mouth rinsing between tests in paired comparisons, the dependence of the discrimination threshold on the concentration is more than exponential. The stimulus-response characteristics obtained with different time-courses of stimulation are approximated by both the Weber-Fechner and the Stevens law.

Animals↗
PubMed1980

[Psychophysics of sweet taste. I. Goals and methods of investigation].

With a view to the solution of problems concerned with the consumer's acceptance of foods in which saccharose had been substituted, a discussion is opened on psychologic and physiologic aspects of the measurability of sensory stimulus-sensation relations. The classic method for measuring taste is the determination of the taste discrimination threshold which is also termed least discernible difference. In the lat years, the discrimination threshold has been determined and calculated mainly as the mean concentration (stimulus) difference resulting from the distribution of the tasters according to their efficiency (probit analysis). In contrast, the new method, which is described in detail, is based on the dependence of the probability of a perception of difference upon the intensity which is linear and represents the initial course of a stimulus-response curve. Differences in efficiency in the group of tasters, which is assumed to be homogeneous, are included in the variance of difference frequencies found. The control of the course of the test by sequential analysis and the binomial weighting of the probabilities obtained allow to perform calculations of the discrimination threshold which are largely free from systematic errors; this discrimination threshold is defined as the concentration difference that engenders the arbitrarily defined alternative probability of Pa = 0.75. To minimize the risk of overrating the measurement result, it is suggested to calculate in addition, on the basis of the binomial distribution, the confidence limits of the discrimination threshold. Furthermore, the constant stimulus method for determining the perception of two stimulus intensities of different sweetening agents is adapted, as to performance and calculation, to the new aspects in discrimination threshold determination.

Consumer Behavior↗
PubMed1979

[Sweetness potency of saccharin and cyclamate in hot drinks].

The sweetness potency of sweeteners depends on temperature. At 50 degrees C the 2.4-fold concentration of saccharin and the 1.3-fold of cyclamate respectively is needed to produce the same sweetness (as related to sucrose) as in solutions at 20 degrees C. As well as in water the sweetening power decreases in chinese tea with increasing temperature. Only in case of cyclamate solutions of high sweetness this effect is diminished. In the mathematical description of the relation between stimulus and perception the decrease of the relative sweetness observed can be expressed by a comformable decrease of the concentration coefficient. The effect of temperature on the perception of sweetness can be explained by the Arrhenius' conception. The critical increments are 23 kJ/mol for saccharin and 8 kJ/mol for both cyclamate and fructose.

Cyclamates↗
PubMed1979

[The effects on caries in animal experiments when reducing sugar in cola-drinks(author's transl)].

The effect of stepwise sugar reduction in cola drinks was tested in a programmed animal experiment using Wistar rats. In a parallel study the pH-decrease at different sucrose concentrations was measured in vitro using a plaque model system which involved s. mutans (strain OMZ 176). The reduction of sugar contents by 20%, 33% und 42% results in a lower acid production by s. mutans strain connected with a decrease of the experimental produced caries. For this reason the sugar restriction in cola drinks will be seen as a contribution towards an improvement of dental health.

Animals↗