EVALUATION OF PANELIST PERFORMANCE IN DESCRIPTIVE PROFILING OF RANCID SAUSAGES: A MULTIVARIATE STUDY

This paper illustrates an application of principal component analysis (PCA), partial least squares regression (PLS) and generalized procrustes analysis (GPA) to evaluate the ability of a trained group of assessors to perceive rancidity in foods. PCA and regression PLS were utilized to determine to which extent sensory attributes capture the information perceived by a trained sensory panel, and if this can be developed into a predictive model for rancidity in sausages. The data were submitted to a GPA to obtain a map of the products for each subject as compared with a consensus products map. Assessors plots for the sensory attributes were also obtained to reveal the dissimilarities between panelists and to explore clustering.     

COMPARISON OF SENSORY PROFILES DONE BY TRAINED AND UNTRAINED JURIES: METHODOLOGY AND RESULTS

We compare the sensory profiles of six dark chocolates done by two types of juries: some trained juries and an untrained jury. Six laboratories, each one made up of 10 to 15 judges, are regarded as trained juries since the assessors were well trained before the evaluation of the products. The second type of jury is composed of only one panel of 29 untrained assessors and this jury is named the untrained jury. Fourteen attributes were evaluated and analyses of variance have been carried out by attribute to compare the sensory profiles of the six chocolates done by the trained juries and by the untrained jury. These analyses of variance show that the two types of juries give similar sensory profiles and that the few differences are mainly due to different ways of using the scale.     

THE RELATIONSHIP BETWEEN CONSUMER PREFERENCES AND TRAINED PANEL RESPONSES

Eight samples of dried tomato soups were profiled by a trained panel, who also provided ratings of overall liking and liking for particular attributes on relative-to-ideal rating scales. A consumer panel tested a subset of four of the soups in home trials, assessing them for overall liking and for particular attributes on either hedonic or relative-to-ideal rating scales. The pattern of overall preferences differed between the trained and untrained panelists, demonstrating the inappropriateness of using trained panelists to provide measures of preference or acceptance. The conclusions regarding consumer preferences would differ depending on which rating scale was used; these differences disappeared when the relative-to-ideal ratings were converted into values of the same form as the hedonic ratings. The overall liking was best predicted by flavor rather than color or thickness. A principal components analysis (PCA) of the profile data compared well with a plot based on the trained panel preference data using MDPREF. The preference data were also fitted to the PCA dimensions using the PREMAP vector model, which gave a good fit for only six of the 15 trained panelists; the PREMAP ideal point model failed to show a better fit. In order to test these models adequately more than eight samples would need to be tested.     

TASTE GROUP THRESHOLDS AND SENSORY EVALUATION OF SPANISH WINE VINEGARS

Wine vinegar is a product obtained from wine acidification which contains at least 5% by wt. of acetic acid, in general without any additives or colorings.
Aspects studied in this work include: the determination of the taste group thresholds (geometric mean of the individual best-estimate thresholds "BET") of two different acids (citric and acetic acids) in aqueous solution and spanish vinegars produced from table and sherry wines. The results obtained suggest that wine vinegar can be considered something more than just an acidulant agent.
In order to evaluate differences among wine vinegars, discriminant tests for twenty-five spanish vinegars (sherry, table and flavored vinegars) were applied. Six of the twelve attributes freely chosen by assessors allowed grouping of the spanish wine vinegars according to their sensory aspects.     

PREFERENCE MAPPING OF TEXTURE OF DULCE DE LECHE

The texture of 12 commercial samples of dulce de leche was characterized by means of texture profile analysis. Two sensory manual texture attributes (hardness and ropiness) were evaluated by a panel of 11 trained assessors. A panel of 50 consumers evaluated the texture acceptability of the samples using a 9‐point structured scale. Consumers showed highly significant different degrees of liking for the texture of the evaluated samples of dulce de leche. Clusters identified with Pearson's correlation coefficient showed opposite preference patterns and provided more useful information regarding market segmentation than clusters identified with Euclidean distances. External preference mapping and partial least squares regression showed that hardness was a driver of liking for one segment of consumers, whereas for the other one it was a driver of disliking. When all the consumers were considered, external preference mapping indicated that the ideal texture of dulce de leche would be intermediate, showing the importance of identifying preference patterns and suggesting that data averaging in consumer preferences might affect information recovery, and may lead to wrong conclusions. Different preference mapping techniques were compared; it was found out that when the relationship between acceptability and texture attributes was not linear, external preference mapping showed the best results.     

STUDY ON SENSORY AND COMPOSITION CHANGES IN ITALIAN AMARONE VALPOLICELLA RED WINE DURING AGING

Amarone is a red wine produced with a technique already known to the ancient Romans, based on withered grapes and a slow fermentation. Amarone is now considered to be one of the great Italian wines and it is exported all over the world. Sensory and compositional analyses were carried out to describe the profile of the Amarone over four vintages (1998–2001) at different stages of aging. All wines were analyzed for titratable and volatile acidity, pH, alcohol content, residual sugars, t‐resveratrol, antioxidant power, color, tonality, total polyphenols and anthocyans. Twelve trained people evaluated aroma and flavor attributes of all the wines in triplicate in a sensory session. Principal component analysis (PCA) of chemical, physical and sensory data for Amarone wine allowed us to highlight the differences between the wines. In general, the 1998 and 1999 vintages had higher aroma and flavor of Wood and Alcohol than the 2000 vintage, which, on the other hand, had higher aroma and flavor of Liquor and Cherry in alcohol. In contrast, the younger wine (2001 vintage) was the more Astringent and had many polyphenols and anthocyans, distinctive features for a red wine that has been in the cask for a short time.     

SELECTION AND SCREENING OF A DESCRIPTIVE PANEL FOR EWES MILK CHEESE SENSORY PROFILING

The aim of this work was to select a competent sensory panel considering its ability to describe ewes milk cheese sensory properties. The panelists evaluated the sensory characteristics of several ewes milk cheeses in terms of odor, flavor and texture. The performance of judges was assessed taking into account the following aspects: (1) individual discriminatory ability and reproducibility for each sensory attribute; (2) group discriminatory ability and reproducibility and agreement between judges for each attribute; (3) panel homogeneity; (4) panel consonance; and (5) overall panel discriminatory ability. The panel performance was checked with a set of statistical procedures. The results obtained by the selected group were better than the initial panel from the point of view of discriminant power, reproducibility and agreement. The suggested method can be easily applied in routine control of assessors performance and to discover deviant behavior or differences in individual perception of the samples.     

TRAINING, VALIDATION AND MAINTENANCE OF A PANEL TO EVALUATE THE TEXTURE OF DRY BEANS (PHASEOLUS VULGARIS L.)

The inclusion of dry beans in diets has clear health benefits. However, consumers in developed countries mainly choose beans for their sensory qualities, especially for their texture. This article describes the constitution, training and validation of a panel of judges to evaluate the texture of dry beans. The judges were trained in the perception of different textures, analyzed a wide range of beans and selected seed-coat roughness, seed-coat perceptibility and creaminess/mealiness of the cotyledon as the main attributes to be scored. After training, the panel was capable of discriminating between different varieties of beans and even between beans of the same variety grown at different locations. The analysis of the behavior of the panel in a standard tasting session 2 years after its formation showed that periodic inclusion of samples from the extremes of the scales for the attributes during tasting sessions was sufficient to keep the panel trained.

PRACTICAL APPLICATIONS

This article could serve as a guide for the training of sensory panels to evaluate the texture of dry beans. It describes the selection of the attributes on which the analysis is based, references for the extreme values of the attributes and how to train the panel. It also provides a practical example of the analysis of the behavior of the panel some time after training.     

FLAVOR PROPERTIES OF PLAIN SOYMILK*

A trained sensory panel was used to (1) establish terminology for describing flavor attributes of a wide range of “fresh” and processed soymilks (SMs); and (2) test the lexicon and describe the flavor properties of a wide range (n = 32) of plain SM samples. Twenty‐eight attributes were identified in the SMs studied. However, findings indicate that the main differences are a consequence largely of the presence of certain attributes that are either infrequently present or unique to a specific product. Thus, sensory evaluation of SM needs to include a review of samples to ensure that all attributes are documented prior to evaluation, or use a method that allows the addition of attributes during testing.