Duo Trio Research Articles

On repeated difference testing

If the number of assessors in a difference test is not large enough to ensure the desired power of the testing procedure, then it is often advised to use assessors repeatedly. That is, each assessor performs the testing not just once but several times. There is a discussion going on, how results of a repeated difference testing are to be analysed. The present paper (as was to be expected) supports the point of view expressed in Kunert, J., & Meyners, M. (1999) On the triangle test with replications. Food Quality and Preference, 10, 477–482. It also tries to generalise their approach such that we get confidence limits. While the exposition concentrates on the triangle test, the approach is also applicable for other difference testing procedures (e.g. pairwise difference test, duo–trio test).

Investigation of the effect of within-trial retasting and comparison of the dual-pair, same-different and triangle paradigms

The performance on three protocols (same–different, triangle, dual–pair) was compared under two conditions: with and without sample retasting permitted. Allowing sample retasting was investigated as a means of improving the discrimination power of sensory discrimination methods. This improvement is predicted by the sensory sampling model or SESAM [Juslin, P., & Olsson, H. (1997). Thurstonian and Brunswikian origins of uncertainty in judgment: a sampling model of confidence in sensory discrimination. Psychological Review, 104, 344–366.]. Sixteen judges took part in the experiment which involved non-carbonated orange flavored beverages. No significant difference was observed among the three protocols' d′ values in either the retasting and no retasting conditions but there was a trend for the same–different to be more sensitive than the other two procedures. Such a trend would depend on the effects of stimulus presentation order and memory. Yet, since the same–different test is statistically more powerful, it is a preferable choice over the triangle, duo–trio and dual–pair tests. Also, retasting brought significant improvement for all tests over the no retasting condition as predicted by SESAM. This was illustrated by significantly larger d′ values. A further analysis indicated that when subjects were allowed to, but chose not to retaste, they performed better than when they chose to retaste the samples. Data involving sureness judgments in the same-different test provided an explanation on such a ‘discrepancy’. Therefore, it appears that sample retasting, when possible, should be allowed, but not required, in order to improve sensory discrimination among products.

Effect of Hot Water Immersion on Sensory Properties of Non-Refrigerated Peanuts1

Abstract Sensory properties of Fla Early Bunch and NC 7 peanuts immersed in hot water at 79 C for 90 sec and subjected to non-refrigerated storage were evaluated. Sensory scores were lower for immersed peanuts than the non-immersed peanuts, however the attributes for the immersed peanuts were not scored lower than borderline throughout storage. Flavor scores for both cultivars ranged between 6 for slightly good and 7 for moderately good. Significant cultivar differences were observed for color at the initial month and flavor at 2, 5, and 8 mo. NC 7 peanuts had significantly higher flavor sensory scores than the Fla Early Bunch nuts. Duo trio tests showed that panelists detected significant differences between non-immersed and immersed peanuts at the eighth month of storage.

Hydroxycinnamates of Vitis vinifera: Sensory assessment in relation to bitterness in white wines

AbstractThe bitter and astringent taste properties of hydroxycinnamoyl tartaric acids have been responsible for incorrect speculation that these compounds influence the taste of wine. The sensory contribution of the major hydroxycinnamates found in wine was evaluated by duo—trio difference tests in model wine solutions and in white wine. The major hydroxycinnamate compound, trans‐caffeoyl tartaric acid, was not detectable when added at the highest level at which it has been found in wine, 150 mg litre−1. Similarly, no significant difference in taste was produced when caffeic acid and p‐coumaric acid were added at 120 mg litre−1 and 30 mg litre−1, respectively. Trans‐2‐S‐glutathionyl caffeoyl tartaric acid, a product of oxidase activity in must, was not detectable at 50 mg litre−1. It was concluded that the hydroxycinnamates do not play any direct role in the taste of wines.

Exemples d'interprétation de résultats de dégustation

<p style="text-align: justify;">De nombreux auteurs ont proposé des méthodes et des tables pour l'interprétation de résultats de dégustation, notamment ROESSLER et al. (1978) pour les tests de différence et KRAMER (1956, 1974) pour les tests de classement. Ces dernières ont été remises en question par JOANES (1985) et SMITH (1985) préconise le test de FRIEDMAN. Les méthodes d'analyses multidimensionnelles (AC.P. et A.F.C.) permettent l'interprétation de dégustations descriptives (notation ou appréciation d'un vin sur plusieurs paramètres). Des exemples sont donnés pour développer l'utilisation de ces méthodes en oenologie.</p><p style="text-align: justify;">+++</p><p style="text-align: justify;">Statistics seem to be essential in a sensory valuation, not only to interpret the results but also to define the experimental protocol, to distribute samples in a balanced way, to avoid the effect of sytematic mistakes (SAUVAGEOT 81).</p><p style="text-align: justify;">A lot of authors proposed methods of calculs and tables: KRAMER (1956), KRAMER et al. (1974), ROESSLER et al. (1978), LARMOND (1969), TOMASSONE et FLANZY (1977).</p><p style="text-align: justify;">A. JOANES (1985) has just called in question again validity of KRAMER's tables (very used in œnology) it was important for us to present with few examples, some methods of interpretation of difference and preference tests.</p><p style="text-align: justify;">We especially use « duo trio and triangle tests ». The last one, more difficult, must be done with a expert panel. ROESSLER and al. (1978) proposed tables giving critical values (number of correct answers) at different probability levels.</p><p style="text-align: justify;">So we advise the FRIEDMAN's test; it's a non parametric method, with which you can know if one wine is different or not. Two wines are different if the difference between their rank sums is rank above a value determined with the NEWMAN's test.</p><p style="text-align: justify;">The descriptive tasting (appreciation of a wine with several variables: colour, arome intensity, sourness, bitterness...) give more informations.</p><p style="text-align: justify;">Two methods of multidimensional analysis are proposed to take into account the entire information:</p><p style="text-align: justify;">- The principal components analysis if the results are presented as quantitative variables,</p><p style="text-align: justify;">- The correspondance analysis if the results are presented as qualitative variables.</p><p style="text-align: justify;">Examples of interpretations are proposed to develope the use of theses methods in œnology. That's easier with the introduction of the micro-computer.</p>