DETECTION AND INTERPRETATION OF VARIATION WITHIN AND BETWEEN ASSESSORS IN SENSORY PROFILING

In this paper we discuss methods that can be used to evaluate the performance of sensory panels. In particular we concentrate on detection of variation within and among panelists. A systematic presentation of some simple, graphically oriented tools will be given. Interpretation aspects of the tools will be emphasized. The methods will be illustrated by computations from a sensory experiment based on 4 sausage products. The example demonstrates how the tools can be used to evaluate the reproducibility of the assessors and also how they can be used to detect different types of individual differences among the assessors.     

SENSORY EVALUATION OF INDIAN-STYLE MARINATED CHICKEN BY MALAYSIAN AND EUROPEAN NAÏVE ASSESSORS

This study was carried out to determine the sensory acceptability of chicken breast fillets marinated with 13 different commercially available Indian-style marinades. Thirty-four naïve assessors (untrained panelists), 20 Malaysian and 14 European, were selected to assess the following sensory attributes: color, color uniformity, Tikka-Masala aroma, Tikka-Masala flavor, herblike flavor, hotness, authenticity, juiciness and overall acceptability. The color of the cooked samples and the pH, moisture and fat content of the marinades were analyzed instrumentally. Marinades were applied to the chicken fillets, which were then dry cooked at 170C for 15 min to an internal temperature of 73C. Sensory evaluation showed significant differences ( P <  0.05) in color uniformity, hotness and juiciness of the cooked marinated chicken perceived between groups. Samples marinated with marinades L and I received the highest score from the Malaysian panelists in terms of overall acceptability, whereas marinades A and F were chosen by the European group.

PRACTICAL APPLICATIONS

The findings from this research will benefit manufacturers of marinade and marinated chicken products in developing or optimizing their products for the local and international markets. The optimal characteristics of an ideal marinade were identified for each assessor group. These results are also of interest to individuals undertaking cross-cultural consumer studies, even though the results presented here used naïve assessors.     

SOME ISSUES IN THE DESIGN AND ANALYSIS OF SENSORY DATA: REVISITED

Sensory experimental data whether collected via the consumer or via the laboratory population have many characteristics in common. Among the more important characteristics are that they are relative, skewed, and difficult to replicate. These characteristics result from the use of human beings as instruments to measure multivariate stimuli as opposed to the use of a mechanical instrument. The use of human beings as instruments presents several problems in the design and analysis of sensory/consumer studies. In the clinical/medical applications of sensory evaluation, we have used people both as the experimental unit (panelists/subjects) and as the instrument (judges) to measure panelists’ responses. Thus it is my belief that sensory data are the most difficult scientific data to statistically analyze and interpret. Unfortunately, limited theoretical work has been done to tackle the resulting problems. These problems include the comparison of responses obtained from independent populations (monadic design), sample size estimation with special reference to time-dependent responses, analysis of degree of difference data, the invariance property of rating scales, effect of correlated errors in observations, and the use of laboratory panels to predict results from a consumer panel. Some solutions to these problems have been provided by experience. My purpose here is to discuss each of these problems in greater detail and offer some possible scientific solutions.     

COMPARISON OF DISCRIMINATION ABILITY BETWEEN A PANEL OF BLIND ASSESSORS AND A PANEL OF SIGHTED ASSESSORS

The objective of this work was to compare a panel of blind assessors with one of sighted assessors in the discrimination of food products. Each panel had 20 screened and trained assessors. Five commercial food products were used: crackers, liver paste, powdered orange juice mix, Reggiano cheese and yogurt. Slight flavor and/or texture modifications were introduced for adequate discrimination difficulty. Each pair of products was tested by both panels using the triangle test and a scaled difference from control test. Numbers of correct answers for the triangle test were similar for both panels. There were minor differences between the panels in the difference from control test, due to the sighted panel having more training in the use of the scale. Overall the panels of trained blind and sighted assessors were equivalent in their performance.     

COMPARISON OF DISCRIMINATION ABILITY BETWEEN TASTE PANEL ASSESSORS

Expanded tables are presented for the selection of assessorsfor taste panels. These tables may also be used for comparingthe assessors' discrimination ability, after the panel sessionshave been completed. ^*Contribution from the Agricultural Research Organization, TheVolcani Center, Bet Dagan, Israel. 1976 Series, No. 159-E.     

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.     

EFFECT OF ASSESSORS EXPERTISE LEVEL ON EFFICIENCY OF WARM-UP FOR TRIANGLE TESTS

The effect of warm-up on performance for repeated triangle tests is studied according to assessors' expertise level for both triangle test strategy and the pair of products to compare. Three experiments performed with orange flavored soft drinks show that the effect of warm-up depends on the assessors' expertise: (1) naive assessors do not increase their performance with warm-up; (2) assessors with a moderate practice of both triangle tests and the pair of products improve their performance with warm-up; (3) assessors with a moderate practice of triangle tests, but not familiar with the pair of products, improve their performance with warm-up too; and (4) assessors highly experienced for both triangle tests and products do not improve their performance with warm-up. These results support the idea that the positive effect of warm-up is due to an attentional process: Warm-up seems to help assessors focusing their attention on the dimension on which the two products are actually different and ignoring the other dimensions. Thus, results show that assessors are able to learn the difference between the two products and to learn to focus their attention on this difference at any time. They also suggest that prior knowledge of the triangle test scheme is required to benefit from warm-up.     

脑电图复杂度分析中的粗粒化问题II.量化对复杂度计算的影响

在对生物医学信号时间序列进行复杂度分析时,粗粒化预处理有可能会造成丢失原始信号中所蕴含的信息,甚至在某些情况下根本改变原信号的动力学性质。用计算机计算时的量化过程也是一种粗粒化,民有这类问题。通过对近似熵和我们所定义的Ｃ０复杂度这两种复杂度在不同量化精度下对一些典型时间序列复杂度分析的比较研究,发现一秀说来量化精度对复杂度分析的影响不是很大,仅当时原始信号进行二值比等极端情况下,才会显著改变原信号     

PERCEPTION OF TASTE MIXTURES BY EXPERIENCED AND NOVICE ASSESSORS1

The total intensity, sweetness, and acidity of sucrose/citric acid mixtures were judged by two types of taste panel: experienced assessors, most of whom had had many years of experience in sensory evaluation; and novice assessors, none of whom had previously taken part in a taste experiment. In other respects the experimental conditions remained almost constant. There was good correspondence between the two panels, particularly for judgments of total intensity, indicating that novice and experienced assessors evaluate taste mixtures in the same way. However, there was also an indication that experience on sensory panels may attenuate taste suppression, the suppression of acidity by sweetness being less pronounced for the experienced panel than for the novice panel. The implications for mixture perception are noted.