(Gatchalian , 1975)
Difference - The easiest to conduct and analyze. The method involves the presentation of a set of samples one at a time, in equally spaced intervals. Only one stimulus is being evaluated at any one time. A single sample is presented at a time but evaluation is passed on several samples which are successfully presented. Evaluation is based largely on pre-established "memory standards".(Pangborn, 1967) The first sample to be evaluated, coded "A" is the standard. The preceding samples will be identified whether it is same as sample coded "A" or "Not A" while memory is relied upon acquaintance with the "standard" would reduce the wide time elapsed needed for recall. This method can be used by expert tasters or consumers for product acceptance tests. This test is utilized in conditions where products of heterogeneous properties are to be compared for one homogeneous quality, e.g. products are different in all aspects except flaws. This test is used for product development, product comparison and storage stability.
Paired or Two-Sample Test Method - Two samples are presented at any one point for evaluation. Samples in pairs presented successively for evaluation. The panelists are asked if they find a "difference" or "no difference" between the pair of samples presented. Analysis of the results will establish if a difference exists between samples. If there is a difference, further tests could be done to establish the extent of the difference. This test can be used in the panel selection and in regular monitoring of the panel sensitivity. This test is used for product development and evaluation and product comparison. This test can also be used in the determination of the threshold difference.
Duo-Trio Test - This method is a modification of the two sample and triangle tests, or a combination of single sample and paired comparison tests. Three samples are used, two of which are alike as in the triangle test. However, in this test, the control/reference sample is made known to the panelist and he is then asked to pick the sample similar to the control/reference. This test is used for difference tests needed in quality control to determine variations between batches of production; stored and fresh products and for product improvement and development studies.
The Triangle Test - This method utilizes three samples at any one time with two of the samples being identical and the third different. The latter is the unknown. This test is used mainly for product development and improvement and quality control. This is used in storage studies and product improvement activities. This test can also be used for panel selection and training purposes and in instrument correlation.
Category or Descriptive Sensory Test Hedonic Scale method is a measure of acceptability gauged from consumer reaction in terms of their degree of like or dislike for a given product under a given set of conditions. The evaluators' reactions are indicated by descriptive words on a scale. This test is used to detect small differences in the degree of liking for similar foods and to detect gross differences even when time, subject and test conditions are allowed to vary. (Amerine, et. al., 1965)
Ranking for Preference or Consumer-Type Test - In this method, different samples are usually presented for preference judgment to untrained panels. This test is used