Descriptive analysis utilizes human perceptions functioning as instrumental measures to quantify the sensory parameters of products. These perceptions reflect how the panelists respond to the products, including all sensations related to appearance, auditory, smell, touch, feeling, etc
4,7. Sensations are complex processes affected by many different factors and there are inherent differences in human subjects. As a result, individual panelists can perceive and interpret the same stimulus differently
5. This may result from panelists assigning different meanings to the same stimulus
1, differences in threshold sensitivity, ability/inability to detect small intensity differences
8, and different scoring behaviors. Individual scoring effects from scale and ranges are quite common in descriptive analysis. For example, if one panelist scores the products at a high intensity levels, but another one evaluates the same products at low intensity levels, a scale effect, or a magnitude interaction, is created. In the range effect, some panelists use a greater range of intensities on the scale to rate the products than others
2. As a result, one or more panelists may commit magnitude or crossover interaction; some also may fail to discriminate differences on specific attributes in the product array.
In practice, there is inherent variablity in perception and appropriate statistical software programs have been specifically designed to help understand the sources of variability. Variability can come from subjects, products, replications, and the experimenter. The analysis of variance can partition the sources of variability to allow the sensory scientist to gain a better understanding of the research experiment. Panel performance assessment and monitoring are important practices in quantitative descriptive analysis.
The performance panel and individual panelist can be evaluated by their reliability, reproducibility, and discrimination in sensory descriptive tests.
- Reliability is the ability to provide the same attribute scores to the same product; also referred to as “repeatability”
6;
- Reproducibility indicates how an individual agrees, on average, with the panel as a whole; for the panel; shows the homogeneity of the team6;
- Discrimination refers to the ability of a panel or panelist to differentiate between the products based on their attributes.
Among these requirements, discrimination among the products is critical since this is often the main goal of descriptive analysis.
References
1 Dijksterhuis G. 1995b. Multivariate data analysis in sensory and consumer science: an overview of development. Trends Food Sci. Techno 6: 206-11.
2 Dijksterhuis G. 1996. Procrustes analysis in sensory research. In Næs, T and Risvik, E, editors. Multivariate analysis of data in sensory science. Elsevier Science. Pp. 185-219.
3 Labbe D., Rytz A., Hugi A. 2004. Training is a critical step to obtain reliable product profiles in a real food industry context. Food Quality and Preference 15: 341-48.
4 Meilgaard MC, Civille GV, and Carr BT (2007). Sensory Evaluations Techniques, CRC Press, Boca Raton, FL
5 Næs T. 1990. Handling individual differences between assessors in sensory profiling. Food Quality and Preference 2: 187-99.
6 Rossi F. 2001. Assessing sensory panelist performance using repeatability and reproducibility measures. Food Quality and Preference 12:467-79.
7 Stone H., Bleibaum, R. N., and Thomas, H., 2012. Sensory Evaluation Practices. 4th edition. San Diego, CA: Elsevier Academic Press.
8 Schiffman S., Lockhead GR. 1983. Individual difference scaling of taste and smell. In: Martens, H and H.
9 Wilkinson C., Yuksel D. 1997. Modeling difference between panelists in use of measurement scales. J.Sensory Stud 12: 55-68.
