PANEL PERFORMANCE AND NUMBER OF EVALUATIONS IN A DESCRIPTIVE SENSORY STUDY

The assessor performance is a key point in a sensory evaluation. In particular, at the end of a session, a decrease of the performance can be feared. We propose to analyze this performance with various criteria: usual ones as the main product effect or the error variance; a new one measuring the perceived products variability. The performance can then be studied all along the session from two points of view: in taking into account the only products tested at a given instant (named instantaneous); in taking into account all the products tested up to a given instant (named cumulative). In the presented example, in spite of the large number of products successively tested by each assessor, the instantaneous performance of the panel shows no significant deterioration. Furthermore, when the number of products tested by each assessor increases, more significant product effects can be obtained thanks to the accumulation of the amount of data. This shows that the number of products that can be reasonably studied by one assessor during one session is generally underestimated.     

SENSORY PROFILING AND POSITIONING OF COMMERCIAL SAMPLES OF MILK POWDER

Milk powders available commercially are of different qualities. The quality deviations may be due to inherent quality of the milk which in turn is dependent on various conditions like the fat content, the processing parameters, the storage time and the packaging materials used. The various brands of milk powders have been profiled sensorily for odor and flavor and also positioned using Canonical Discriminant Analysis (CDA). The study throws light on the relative qualities of the different brands, their positive and negative points and their relative position with respect to each other. The results indicate that the various types like whole milk powder, partially skimmed milk powder, skimmed milk powder and infant milk formula cluster together into the same group but the groups are separate from each other. The dominant quality attributes for the groups are different and are discussed in relation to the directional vectors.     

A COMPARISON OF METHODOLOGY APPLIED TO THE SELECTION OF A PANEL FOR SENSORY EVALUATION OF INSTANT COFFEE

Twenty judges performed a variety of chemosensory tasks in order to select the best scores to form a panel for coffee evaluation. An average of correct responses (P%), one-way analysis of variance (ANOVA) and principal components analysis (PCA) were compared. The tests involved: ability to recognize the four basic tastes, identification and matching of odors, taste intensity evaluation and perception of small differences in taste. P% accounted for 71.17 ± 4.34% and 10 of the judges had scores greater than the final average. ANOVA and PCA resulted in 2 different panels consisting of 9 and 12 judges, respectively. The panel was composed by the nine panelists selected by the three methods. The other three panelists that were doubtful could improve to the point of acceptance with additional training. These methods should be used simultaneously to have more security in the acceptance or rejection of panelists.     

CONSTRUCTION OF SENSORY VOCABULARIES FOR PROFILING FOOD

Sensory profiling laboratories rate products for sets of attributes. Order of tasting and carry-over effects from sample to sample are widely recognized. However, within samples, work investigating the possibility of effects due to the order of rating attributes and attribute to attribute carry-over has not been reported. Individual attributes were classified according to whether their presence in a product was perceived to be desirable or not. For both yoghurt and cheese, sample ratings for each attribute were compared when attributes perceived as desirable preceded those perceived as undesirable and vice-versa. In both stimuli, there was evidence that desirable attributes were biased to a lower value when preceded by undesirable ones. Similarly, negative attributes were biased downwards when preceded by desirable ones. For absolute scores, these effects, albeit small, make randomizing attribute ordering desirable. However, lack of evidence of interactions between samples and attribute ordering suggests comparative differences between samples are unaffected.     

CROSS VALIDATION OF A SENSORY LANGUAGE FOR CHEDDAR CHEESE

Communication and replication of sensory data from different sites are important to track progress on fundamental research issues and to ensure that research efforts are not duplicated. A uniform anchored Cheddar cheese sensory language has previously been identified and refined. The objective of this study was to demonstrate application of the defined sensory language for Cheddar cheese for communication between sensory panels at three different sites. The defined and referenced sensory language for Cheddar cheese was disseminated to panel leaders at the three sites and sensory panels (n ≤ 8) were trained for 40 to 80 h at each site. Ten forty-pound blocks of Cheddar cheese representing different ages were collected and evaluated by the panels. Cheeses were differentiated by the three panels by univariate and multivariate analysis (P<0.05). Cheeses were differentiated by the three panels in a similar manner. Results indicate that it is possible to calibrate panels using a standardized defined sensory language.     

INFLUENCE OF PANEL INCONSISTENCY ON THE OUTCOME OF SENSORY EVALUATIONS FROM DESCRIPTIVE PANELS

Different types of panelist by treatment interaction are explored to determine how they influence the outcomes of discrimination tests. The study compares the situations where panelists are considered as fixed or random effects over the range of most testing conditions for small panels (5–15 panelists) that replicate their judgements. Magnitude interaction and nonperceivers or nondiscriminators have minor effects on test outcomes. Cross-over interaction increases the chances for a type II error, especially when panelists are considered as random effects. False discrimination increases the chances for a type I error when panelists are considered as fixed effects. Applications of methods to reduce the chances for these errors in the testing for differences among treatments are discussed.