Salt taste detection: an R-index approach to signal-detection measurements

The 9-point hedonic scale: Using R-Index Preference Measurement to compute effect size and eliminate artifactual ties

214 consumers used the verbal 9-point hedonic scale to assess 4 types of flavor coated peanuts and 4 types of flavored teas. They used the traditional ANOVA/LSD analysis to provide mean values derived from the 9-point hedonic scale along with measures of significant difference. However, these data did not provide effect sizes. They did not give direct measures of the strength of preference between the various products, which was the main interest. Accordingly, effect sizes were computed. For this, each consumer had also ranked their preferences as they made their ratings on the 9-point hedonic scale. From these, R-Index values were computed to provide the percentages of consumers, who preferred each product to every other product. These direct measures of effect size completed the analysis begun by the ANOVA analysis of the set of mean scores. Also, the measures were nonparametric and avoided issues of the validity of a parametric statistical analysis. They also avoided the problem with the traditional analysis when products in the same scale category are attributed the same scores, when they are not equally liked. Experiment 2, using 207 consumers indicated that this problem was only serious enough to reduce the power of the traditional analysis, compared with the R-Index Preference Measurement, when the number of products being tested approached a dozen say, for product optimization.

Salt Taste Sensitivity and Stimulus Volume: Sips and Drops. Some Implications for the Henkin Taste Test

Various presentation procedures and stimulus volumes were compared in their effect on salt taste sensitivity. For sodium chloride (NaCl) stimuli pipetted onto the tongue, subjects had comparable measured sensitivity to 10 ml and 1 ml volumes but a reduced sensitivity to 0.1 ml volumes. The greatest sensitivity was achieved with 10 ml sipped volumes. Modification of the Henkin dropwise triangluar taste test, by increasing the stimulus volumes, increased subjects' sensitivity. Only the 1 ml pipette presentation increased the sensitivity of the Henkin procedure, albeit slightly, to the detection of changes in taste sensitivity, the purpose for which the procedure was actually designed. Such modification did not perturb salivary NaCl levels more than the regular Henkin procedure, so it would not be expected to introduce sensitivity drift.

Taste acuity in response to zinc supplementation in older Europeans

Taste acuity declines with age and may be dependent upon Zn status. The aim of the present double-blind, randomised controlled intervention trial has been to determine taste acuity in response to Zn supplementation (placebo, or 15 or 30 mg Zn/d). Healthy older European adults aged 70–87 years were recruited within Italy (Rome) (n 108) and France (Grenoble) (n 91) to the European Commission-funded Zenith project. A signal detection theory approach was adopted for taste assessment. The data were converted to R indices and analysed by repeated-measures ANOVA controlling for baseline taste acuity as well as serum and erythrocyte Zn. Serum Zn increased post-intervention, indicating compliance with the intervention. Results differed across geographical region. Salt taste acuity was greater in response to Zn (30 mg) than placebo post-intervention among those recruited in Grenoble. There was no apparent change in acuity for sweet, sour or bitter taste in response to Zn. Supplemented Zn may have potential to enhance salt taste acuity in those over the age of 70 years. Further research is required to determine if enhanced salt taste acuity is reflected in the eating experiences of older individuals.

Dietary zinc intake and sex differences in taste acuity in healthy young adults

BACKGROUND

Previous research suggests that adequate dietary zinc intake may be important in determining the sensory experience of food, appetite and consequently, dietary quality. The aim of this pilot study was to explore relationships between taste sensitivity and dietary zinc intake in healthy young adults (age 20-40 years: 24 male, mean age +/- SD = 27 +/- 4.86 years; 26 female, mean age +/- SD = 23 +/- 2.10).

METHOD

A signal detection method was used to assess taste acuity for the four basic tastes: sweet (glucose), sour (citric acid), salt (sodium chloride) and bitter (quinine). A 4-day food diary was used to determine dietary intakes of zinc (mg day(-1)) and salt.

RESULTS

Males reported a higher zinc intake than females (P=0.001). Higher dietary zinc intake was associated with better taste acuity for salt in females (P=0.017) but not in males. Acuity for bitter taste appeared to be related to zinc intake in males (P=0.007) but not females. Among those whose average daily zinc intake was below the RNI, males were less sensitive than females to sour (P=0.02) and bitter (P=0.014) taste.

CONCLUSION

These findings suggest that zinc is more important for taste acuity in males than females and indicate the importance of taking sex differences into account when studying taste acuity.

Zinc status and taste acuity in older Europeans: the ZENITH study

BACKGROUND

Age-related decline in taste acuity may be both a cause and an effect of depleted zinc and/or increased zinc requirement.

OBJECTIVE

The aim of this study was to explore associations between zinc status and taste acuity in healthy older European adults aged 55-90 y.

SAMPLE

Volunteers were recruited within Italy (n = 108 aged 70-90 y), the United Kingdom (UK) (n = 93 aged 55-70) and two regions of France (n = 186), Grenoble (aged 70-90 y) and Clermont-Ferrand (aged 55-70 y).

METHODS

A signal detection theory approach was adopted, employing a three-alternative, forced-choice procedure. The data were converted to R-indices and bivariate correlations were computed to explore relationships between serum zinc, erythrocyte zinc and taste acuity. ANOVA was undertaken to determine regional differences in zinc status.

RESULTS

Higher erythrocyte zinc status was associated with better acuity for salt (sodium chloride) taste in the sample as a whole (P = 0.012) (n = 385). Higher serum zinc levels were associated with greater sensitivity to sour taste (citric acid) (P = 0.015) only in the older groups (aged 70-90 y). There were no apparent associations between serum or erythrocyte zinc status and acuity for bitter (quinine) or sweet (sucrose) tastes irrespective of age.

CONCLUSION

These results agree with those previously suggesting that age-related detriment in sensitivity for salt taste may be associated with depleted zinc.

Fast and accurate measurement of taste and smell thresholds using a maximum-likelihood adaptive staircase procedure

This paper evaluates the use of a maximum-likelihood adaptive staircase psychophysical procedure (ML-PEST), originally developed in vision and audition, for measuring detection thresholds in gustation and olfaction. The basis for the psychophysical measurement of thresholds with the ML-PEST procedure is developed. Then, two experiments and four simulations are reported. In the first experiment, ML-PEST was compared with the Wetherill and Levitt up-down staircase method and with the Cain ascending method of limits in the measurement of butyl alcohol thresholds. The four Monte Carlo simulations compared the three psychophysical procedures. In the second experiment, the test-retest reliability of MLPEST for measuring NaCl and butyl alcohol thresholds was assessed. The results indicate that the ML-PEST method gives reliable and precise threshold measurements. Its ability to detect malingerers shows considerable promise. It is recommended for use in clinical testing.

Alternative explanations for procedural effects on magnitude-estimation exponents for taste, invoking adaptation, context, and volume effects

Taste adaptation to residual stimuli from prior tastings was considered along with context and volume effects. These factors are proposed as alternative or supplemental explanations for the differences in the magnitude-estimation exponent (slope of the log-log plot of taste intensity versus solute concentration) that have been obtained by various workers using different stimulus presentation procedures.

Salt taste sensitivity and stimulus volume: effect of stimulus residuals

Sodium chloride (NaCl) stimulus residuals were seen to be greater after a large-volume NaCl rinse than after a small-volume rinse. Predicted changes in sensitivity dependent on adapting concentrations determined by residual levels were confirmed by signal detection R-index measures of sensitivity. R-index values were seen to be independent of the volume of the test water and NaCl stimuli used in their determination.