Marjorie C. King

A proposed approach for evaluating expert wine judge performance using descriptive statistics

Descriptive statistics were used to evaluate the performance of five expert wine judges using a 20‐point quality scorecard in a wine competition environment. For each judge, frequency distributions were used to assess scorecard usage, and deviation font‐means were calculated as an index of consistency with the group. Differences in curve shapes were described using means, skewness and kurtosis values. Four of the five judges showed unimodal frequency distributions that were slightly skewed to lower scores. This information was believed to be useful for identifying expert judges whose use of a 20‐point quality scorecard and perspective of wine quality are consistent with the group.

Use of principal component analysis for the evaluation of judge performance at wine competitions

Abstract Principal component analysis (PCA) was used to evaluate the performance of five wine judges using a 20‐point quality scoring system. Data were collected for 97 wines as part of a wine competition. Principal component plots were used to (1) identify underlying mechanisms that judges used to differentiate wine quality, and (2) evaluate the relationships among the quality components. Judges’ ‘styles’ differed according to their use, or lack of use, of the individual quality components (appearance, aroma, flavour, acidity, finish, body, balance and overall character) in making a final quality assessment of the wines. In general, judges showed individual patterns of separating the wines according to the presence or absence of aroma and flavour and overall character. These component scores were highly correlated with each other and with the final wine quality score. A comparison of the PCA plots with eggshell plots, an established methodology, indicated that judges who used a systematic approach to qua...

The evaluation of judges at wine competitions: the application of Eggshell plots

Abstract Eggshell plots were used to evaluate wine judge performance at two annual wine competitions. Judge curves were examined on a daily basis to identify similarities and differences among the judges. These techniques are believed to be an important complement to existing techniques to examine judge performance and assist competition co‐ordinators in future judge selection.

Evaluation of R-indices for preference testing of apple juices

Abstract New hedonic consumer evaluations, based on signal-detection theory, were examined using three sensory panels [consumer ( n = 256), ‘experienced taster’ ( n = 36), ‘proprietary’ ( n = 36)] and four apple juices. For each panel, half the panellists rated and the other half ranked the apple juices. Scale and panel performance were evaluated by comparing Friedmans rank-sum preference scores and by calculating R-indices. For the consumer panel, results from the rated and ranked analyses were similar, with juices having the same relative order of preference. Although the children as a group ( n = 78), were non-discriminating, the adults ( n = 178) significantly differentiated the juices, disliking one juice from the others. Small panel size as well as proprietary bias markedly affected the stability of the R-index. Results from ‘experienced’ and ‘proprietary’ panels were not effective indicators of consumer response. Differences in juice preferences, between the consumer and other panels were attributed to proprietary bias, expectation error, and differences in sample size ( n ). R-indices and mean preference scores for the consumer panel were highly correlated ( r > 0.98), for both ranking and rating data, and were believed to monitor the same underlying variation. The R-index, however, provided alternate information to conventional preference methodologies and was believed to be an important complement to the existing sensory methodologies.

Effectiveness of the ‘Mouth-feel Wheel’ for the evaluation of astringent subqualities in British Columbia red wines

This research examined the effectiveness of the ‘mouth-feel wheel’ for the assessment of astringent subqualities in 25 commercial British Columbia (BC) red wines. Twelve judges discussed, adapted and practised the definitions and reference standards (fabrics) to characterise the astringent subqualities. The astringent qualities were organised into six categories (surface smoothness, drying, dynamic, weight, complex ripe/integrated, unripe/unintegrated), each consisting of specific descriptors or subqualities (3≤n≤7), as outlined in the literature. The wines were evaluated in duplicate using a strict tasting protocol. Judges rated the magnitude of astringency and aftertaste and identified the astringent subqualities using a check-off system. The subquality frequencies were weakly correlated (r=0.40) with the astringent and aftertaste intensities. Judge consistency and overall performance were examined using chi-square and principal component analysis (PCA); in general, judge consistency was poor, both within and between judges. The interrelationship of the astringent subqualities was explored using multidimensional scaling and PCA, employing distance and correlation matrices, respectively. Both techniques showed that the descriptors successfully identified different levels of astringency. However, the close location of some of the descriptors suggested that some judges may have been using different vocabularies to describe the same astringent subqualities. It was believed that the lexicon describing the astringent subqualities would need simplification and clarification before it could be used effectively to describe BC red wines.

Influence of Serving Temperature and Wine Type on Perception of Ethyl Acetate and 4-ethyl Phenol in Wine

This research explored the effect of temperature on the perception of two chemical compounds (ethyl acetate, 4-ethyl phenol) in four base wines (Gewurztraminer, Chardonnay, white blend, red blend). The perceived aroma intensity was evaluated at three serving temperatures (5°C, 10°C, 22°C) with wines which were spiked with 200 ppm ethyl acetate and 1000 ppm 4-ethyl phenol, using a panel of eight judges. Special attention was paid to the insulation of the wine glasses to maintain the temperature of the wine samples. The panel was required to wear wool scarves and gloves to eliminate cognitive and physical clues. The relationships between temperature and perceived intensity for fruit, ethyl acetate and 4-ethyl phenol were between 0.951 and 0.991, with all base wines. The perception of ethyl acetate was most noticeable in the neutral wines (white, red blends) and least noticeable in the highly aromatic Gewurztraminer and Chardonnay wines at 20°C. In contrast, 4-ethyl phenol was least noticeable at 20°C in the wines with greater phenolic constituents, Chardonnay and the red blend. The chemical 4-ethyl phenol appeared to suppress the perception of fruit in all base wines at all temperatures.