USE OF THE RECEIVER OPERATING CHARACTERISTIC IN THE STUDY OF TASTE PERCEPTION

Studies of the Receiver Operating Characteristic (ROC) for taste are reviewed and new data on its shape are presented. What evidence there is suggests that ROCs for taste conform to the normal-normal equal variance model of signal detection theory. Few ROCs for taste have been reported, probably because the large number of trials required by detection theory makes the task arduous for subjects in taste experiments. However, pooling ratings from several subjects and estimating the parameters of the pooled ROC by jackknife techniques circumvents that problem to some extent. Because experiments on taste are often based on a small number of trials, it is especially useful to determine the standard errors of ROC parameters. Methods for estimating these standard errors, including that of the area measure, p(A), are therefore presented.     

ADJUSTING ROASTED PEANUT ATTRIBUTE SCORES FOR FRUITY ATTRIBUTE AND NONOPTIMUM CIELAB L* VALUES1

Developing peanut breeding strategies for roasted peanut flavor improvement requires that roasting be to an optimum and effects of negative environmental exposure be to a minimum. In practice it is difficult to achieve these conditions. However, statistical adjustments are possible. To ascertain the proper adjustments, surface response equations were determined relating roast color and fruity attribute scores to roasted peanut attribute score. Fruity attribute had a depressing effect on roasted peanut attribute score. Similarly, underroasting as well as overroasting led to reduced roasted peanut attribute scores. Adjusting for genotype and location had nonsignificant effects on mean optimal roast color or linear equation slope values of the fruity-roasted peanut relationship. With these findings a method for maximization of roasted peanut values was developed using a modified SAS routine. Although the capability to estimate the roasted peanut flavor of a sample with optimal roasting and environmental effects has several potential applications, our specific application is to evaluate parentage contribution to flavor enhancement or flavor reduction.     

TASTE THRESHOLDS, TASTE SENSITIVITY AND THE EFFECTS OF ADRENALECTOMY IN RATS

A number of behavioral experiments have attempted to measurethe absolute taste thresholds in the rat. Certain aspects ofthe procedures and methods of data analysis used in these experimentsare reviewed with the suggestions that: (1) Although comparisonshave commonly been made between the taste threshold values reportedin different experiments, these are not valid because of theabsence of a common definition of threshold. (2) The high thresholdmodel on which these experiments are based may be inappropriate.(3) It is possible to measure taste sensitivity rather thantaste thresholds, and (4) Had these points been considered inprevious experiments different conclusions might have resultedregarding the effects of adrenalectomy on NaCl sensitivity.     

A NEW APPROACH TO CATEGORY SCALES OF INTENSITY II: USE OF d'VALUES

Using a Rank-Rating method, d'values were obtained for stimuli from a model system using 15-point, 9-point, 7-point and 5-point category scales. For an apple/grape juice system, d'values were compared for 9-point and 7-point scales. There was general agreement on d'values among the scales, except where stimuli had their scores 'bunched'into one category: this tended to occur for the strongest and weakest stimuli for Rank-Rating and for the scales with fewer points. Bunching altered distribution variances and distorted the calculated d'values. Further study gave d'values for the discrimination of confusable stimuli, using paired-comparison and rating data, thus providing numerical measures of their relative sensitivity.     

ON CENTRAL MECHANISMS OF TASTE IN FISHES

The comparison of medullar units and facial nerve fibres activityin response to stimulation of skin chemoreceptors around themouth with solutions of hydrochloric and citric acid and sodiumchloride was carried out by means of extracellular recordingin immobilized carps. The afferent information concerning thechemical stimulus was found to be modified during synaptic processingin the primary brain centre. By means of an across neuron patternmodel some aspects of neural coding of chemical stimulus qualityand intensity in fishes were elucidated. It was disclosed inparticular that the qualitative peculiarities of the stimulus,but not the level of pH play the main role in coding of acidicstimuli (for the range of low concentration solutions).     

THE NUMBER OF ASSESSORS REQUIRED FOR TASTE PANELS

Consideration of the difference in taste between two samplesas a variable leads to estimates of variance. Any minimum differencein taste scores can be detected if a large enough number ofassessors is used. ^* Contribution from the Agricultural Research Organization,The Volcani Center, Bet Dagan, Israel. 1976 Series, No. 271-E.     

USE OF PCR ANALYSIS FOR STERILITY TESTING IN PHARMACEUTICAL ENVIRONMENTS

To determine the sterility of pharmaceutical samples, highly conserved bacterial ribosomal DNA sequences were used in a PCR-based assay. Finished products, raw materials, growth media, and diluents were artificially contaminated with different types of microorganisms. Samples were incubated for 24 h. After incubation, microbial DNA was extracted from enrichment broths using a Tris-EDTA-Tween 20 buffer containing proteinase K. Extracted DNA was added to Ready-To-Go PCR beads and eubacterial primers. Contaminated samples were found to contain the conserved 1.5 kilobase (kb) DNA fragment of the bacterial genome by using the PCR assay. None of the uninoculated samples was found to show the presence of the 1.5 kb fragment. PCR test results were compared with standard conventional methods. There was a 100% correlation between standard conventional methods and the PCR assay. However, the PCR-based assay was completed within 27 h while conventional methods required 4–5 days. Rapid PCR analysis using a simple sample preparation reduced the time for sterility testing of pharmaceutical samples allowing optimization of risk assessment and implementation of corrective actions.     

USE OF THE SUTURE LOCK PLATE FOR STERNAL APPROXIMATION IN CHILDREN

Sternal closure after median sternotomy in the pediatric age group may be accomplished with non-resorbable sutures or stainless steel wire. The former has the disadvantages of chronic sinus formation and the latter may either break or cause pressure on the skin. The Pill-Wolvek Suture Lock Plate was used as an alternative method in 26 patients aged from seven days to six years. It has the advantage of greater strength and avoids the problem of prominent twisted wire ends. Healing has been excellent and there have been no complications attributed to the wires.