BS EN ISO 4120:2021 pdf free.Sensory analysis – Methodology – Triangle test.
5.3 Prepare the samples out of sight of the assessors and in an identical manner (e.g. same apparatus. same vessels, same quantities of product).
5.4 Assessors shall not be able to identify the samples from the way in which they are presented. For example, in a taste test, avoid any differences in appearance. Mask any irrelevant colour differences using light filters and/or subdued illumination.
5.5 Code the test samples in a uniform manner, preferably using threedigit numbers, chosen at random for each test. Each triad is composed of three samples, each with a different code. Preferably. different codes should be used for each assessor during a session, However, the same three codes may be used for all assessors within a test, provided that each code is used only once per assessor during a test session (e.g. if several triangle tests on different products are being conducted in the same session).
5.6 It is preferable to present the samples under the conditions at which the product is generally used (e.g. in a taste test, present the samples at the temperature at which the product is generally consumed). The serving conditions of the three samples in each triad shall be identical (e.g. In a taste test, the three samples shall be served at the same temperature), just as that of all the other samples in a series of tests on a given type of product.
5.7 The size, quantity or volume presented shall be identical for the three samples in each triad, just as that of all the other samples in a series of tests on a given type of product. The size, quantity or volume to be evaluated may be imposed. If it is not, the assessors should be told to take sizes, quantities or volumes that are always similar whatever the sample.
5.8 In a taste test, the assessors shall be told whether or not they are to swallow the samples or whether they are free to do as they please. In this latter case, they shall be requested to proceed in the same manner for all the samples.
5.9 During the test sessions, avoid giving information about product identity expected treatment effects, or individual performance until all testing is completed. The only necessary information for the assessor is the nature of the product to be tested and the task to be performed.
All assessors should possess the same level of qualification, this level being chosen on the basis of the test objective (see ISO 8586 for guidance). Experience and familiarity with the product may improve the performance of an assessor and, therefore, may increase the likelihood of finding a significant difference. Monitoring the performance of assessors over time may be useful for increased sensitivity.
All assessors shall be familiar with the mechanics of the triangle test (i.e. format, task and evaluation procedure).
6.2 Number of assessors
Choose the number of assessors so as to obtain the sensitivity required [or the test (see the discussion in A.3). Using large numbers of assessors increases the likelihood of detecting small differences between the products. However, in practice, the number of assessors is often determined by material conditions (e.g. duration of the experiment, number of available assessors, quantity of product). When testing for a difference, typical numbers of assessors are between 24 and 30. When testing for no meaningful difference (i.e. similarity), twice as many assessors (i.e. approximately 60) are needed for equivalent sensitivity.
Avoid replicate evaluations by the same assessor whenever possible. However, if replicate evaluations are needed to produce a sufficient number of total evaluations, every effort should be made to have each assessor perform the same number of replicate evaluations. For example, if only 10 assessors are available, have each assessor evaluate 3 triads to obtain a total of 30 evaluations.
NOTE Treating three evaluations performed by 10 assessors as 30 independent evaluations is not valid when testing for similarity using Table A.2. However, the test for difference using Table A.1 is valid even when replicate evaluations are performed (see References [SI and 191)- References 141. 151 and 161 on replicated discrimination tests suggest alternative approaches for analysing replicated evaluations in discrimination tests.
7.1 l’repare worksheets and scoresheets (see iLl and JLZ) in advance of the test so as to utilize an equal number of the six possible sequences of two products, A and B:
ABB AAB ABA
BAA BBA BAB
Distribute these at random in groups of six among the assessors (i.e. use each sequence once among the first group of six assessors; use each sequence once again among the next group of six assessors, etc.). This will minimize the imbalance that results lithe total number of assessors is not a multiple of six.
NOTE The worksheets also can be prepared digitally and made available for the evaluations.
7.2 Present the three samples of each triad simultaneously if possible, following the same spatial arrangement for each assessor (e.g. on a line to be sampled always from left to right, in a triangular array). Within the triad, assessors are generally allowed to make repeated evaluations of each sample as desired (if, of course, the nature of the product allows for repeated evaluations).
7.3 Instruct the assessors to evaluate the samples in the order in which they were presented. Inform the assessors that two of the samples are the same and that one is different. Each assessor shall then indicate which one of the three samples is different from the other two.
7.4 The triangle test is a forced-choice procedure. Assessors are not allowed the option of reporting ‘no difference” An assessor who detects no difference between the samples should be instructed to randomly select one of the samples and to indicate that the selection was only a guess in the comments section of the scoresheet. The assessor has one chance out of three of giving the correct answer randomly.
7.5 The assessor shall not go back to any samples from previous triads or change the verdict on any previous test. If an assessor is to carry out more than one test in a session, it is imperative that the assessor shall not be able to change their response once given. For example, collect the completed scoresheet and unused samples prior to serving the subsequent triad or do not allow the assessor to return to an earlier answer screen once a response is confirmed.
7.6 Do not ask questions about preference, acceptance or degree of difference after the initial selection of the odd sample. The selection the assessor has )ust made may bias the reply to any additional questions. Responses to such questions may be obtained through separate tests for preference, acceptance, degree of difference, etc. (See ISQ 6658 for guidance.) A comment section asking why the choice was made may be included for the assessor’s remarks.BS EN ISO 4120 pdf download.Sensory analysis