In sensory testing, consumers are employed to function as instruments to measure product differences, characteristics or preference levels. Since sensory skills vary among consumers and sensory performance is affected by numerous factors related or unrelated to the products, consumer qualifications to take part in sensory tests should be carefully diagnosed. Failure to meet these requirements may significantly damage the credibility of the results. Generally, there are approximately 30% of consumers who fail to detect some sensory attribute at some level1. So panel screening is an important practice in sensory testing.
Sensory testing refers mainly to discrimination, descriptive and affective tests. Discrimination and descriptive analysis are recognized as analytical tests to detect product differences or characteristics. In comparison, affective analysis is defined as a hedonic test, which explores consumer likings or preference levels of the products. Considering their mission in sensory evaluation, subject qualifications vary depending on the test. However, they still have some criteria in common, such as willingness to participate, availability and freedom from food allergies. Overall, subjects involved in sensory tests must be actual product users or potential consumers.
For analytical tests sensory acuity is critical. All the subjects participating in these tests are generally expected to be more sensitive to differences in tested products than normal consumers. Therefore, a set of screening exercises should be administered for panel selection. Often, these exercises include discrimination tests where the rate of correct answers for satisfactory subjects should be well above the chance probability for tests employed (e.g. p=1/3 for triangle tests or p=½ for duo-trio tests). In practice, the criteria to evaluate subjects sensory sensitivity varies depending on the difficulty of the screening test or the requirements of the project. Furthermore, those subjects who have prior technical knowledge of products or projects should not be invited to participate in analytical sensory testing in order to avoid possible bias in the results1. In addition to the requirements discussed above, panelist in descriptive tests are expected to have excellent verbal abilities, which are important for the consensus language development during training sessions.
The mission of affective tests is to differentiate the products based on consumer likings or preference levels. All subjects must be actual product users and likers, and able to express their acceptance levels for products differently in each category. For those subjects who rate all the products extremely liked or extremely disliked, their contributions are trivial for the project. These respondents can be potentially found and excused from actual product testing during screening sessions. To avoid negative influences from those who have been trained in analytical tests or have some knowledge about products or projects, they also should be excluded from the acceptance tests1.
1 Stone H., Sidel JL. 2004. Sensory Evaluation Practices. 3rd ed. San Diego, CA. Elsevier Academic Press.