ISO 4120:2021 Sensory analysis — Methodology — Triangle test.
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 just 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 ISO 6658 for guidance.) A comment section asking why the choice was made may he included for the assessor’s remarks.ISO 4120 pdf download.