Simply stated, sensory evaluation is divided into two methods, subjective and objective testing. Subjective tests involve objective panelists, while objective testing employs the use of lab instruments with no involvement of the senses. Both tests are essential in sensory evaluation and necessary in a variety of conditions (Meilgaard et al., 1991).
One such subjective test is the use of the Hedonic scale method. This rating scale method measures the level of the liking of foods, or any other product where an affective tone is necessary. This test relies on peoples ability to communicate their feelings of like or dislike. Hedonic testing is popular because it may be used with untrained people as well as with experienced panel members. A minimum amount of verbal ability is necessary for reliable results (OMahony, 1986).
In Hedonic testing, samples are presented in succession and the subject is told to decide how much he likes or dislikes the product and to mark the scales accordingly. The nature of this test is its relative simplicity. The instructions to the panelist are restricted to procedures, and no attempt is made at direct response. The subject is allowed, however to make his own inferences about the meaning of the scale categories and determine for himself how he will apply them to the samples. A separate scale is provided for each sample in a test session. The scales may be grouped together on a page, or be on separate pages (ASTM, 1968).
The Hedonic scale is anchored verbally with nine different categories ranging from like extremely to dislike extremely. These phrases are placed on a line-graphic scale either horizontally or vertically. Many different forms of the scale may be used with success, however variations in the scale form is likely to cause marked changes in the distribution of responses and ultimately in statistical parameters such as means and variances (ASTM, 1968). Hedonic ratings are converted to scores and treated by rank analysis or analysis of variance. As mentioned earlier, hedonic scales are used with both experts and untrained consumers, with the best results obtained with an untrained panel (Amerine, et al., 1965). The ratings labels obtained on an hedonic scale may be affected by many factors other than the quality of the test samples. Characteristics of the subjects, the test situation, attitudes or expectations of the subjects can all have a profound affect on results. A researcher needs to be cautious about making inferences on the bases of comparison of average ratings obtained in different experiments (ATSM, 1968).
Many other tests, besides hedonic scales are used in the sensory evaluation of a food product. Determining the type of research that is being done, and the type of evaluation that is needed is crucial in obtaining accurate results from a sensory project.
2. ASTM, 1968. Manual on Sensory Testing Methods, no. 434. American Society for Testing and Materials, Philadelphia, Pa.
3. Meilgaard, D., Civille, G.V., Carr, B.T.: Sensory Evaluation Techniques. Boca Raton CRC Press: 1991.
4. OMahony, M.: Sensory Evaluation of Food. New York Marcel Dekker, Inc.: 1986.
