AS 2542.2.6:2014 pdf – Sensory analysis Part 2.6: Methodology—Ranking.
6 Assessors
6.1 Qualification
The qualification of assessors depends on the aim of the test (see Annex A).
All assessors should preferably have the same level of qualificabon, this level being chosen according to the purpose of the test
a) selected assessors or experts, for
1) training assessors.
2) assessment on a descriptive criterion, for instance determining the influence of intensity levels of one or more parameters (e.g. order of dilution, influence of raw materials, of production, packaging or storage methods),
3) determInation of perception thresholds of individuals or groups; ti) untrained assessors or consumers. already trained on the method
1) for hedonic preference.
2) when pre-sorting samples (to select a few products from a large number, as a preliminary test)
For the conditions with w$iich assessors shall comply, see ISO 6658. ISO 8586-1 and ISO 8586-2. They shall all be specially trained on the ranking procedure and on the selected descriptors being used.
6.2 Number of assessors
The number of assessors depends on the aim of the test (see Annex A).
When testing assessors performance, training assessors or determining perception thresholds of individuals or groups, no minimum or maximum number is required.
For descriptive product assessment, the minimum number of assessors is determined by the levels of statistical risks accepted and shall comply with ISO 11035 or ISO 11036, ic. preferably around 12 to 15 selected assessors.
For determining the order of preference in a hedonic test, the minimum number of assessors is determined by the levels of statistical risks accepted e-g- a minimum of 60 assessors per group of consumer type.
For statistical analyses of the results, other things being equal (for example, test conditions, quatification of assessors), the larger the number of assessors, the greater the probability of revealing any systematic difference in rank among products
6.3 Preliminary discussion
The assessors shall be informed of the purpose of the test, i.e. ranking of test samples.
If necessary, a demonstration of a ranking procedure can be given, It is essential in this test to ensure common understanding by all assessors of the criterion under test- The preliminary discussion shell not influence assessors expectations,
7 Procedure
7.1 Presentation of the samples
The assessors shall not be able to draw conciusions about ins trom ins way in wnich iney are presented
Prepare samples out of sight of the assessors and in an identical manner same apparatus, vessels, same quantity of products, same temperature, same presentation All irrelevant differences in samples shall be masked to avoid influencing the ranking. It Is preferable to present the samples at the temperature at which the product Is generally consumed.
The vessels are identified by 3-digit numbers, chosen at raridoni. and different from one sample to another within one session (and preferably from one assessor to another).
The presentation takes into account the design chosen In a ‘tomplete block” design, each assessor ranks all the samples, It Is the preferred procedure. But, lithe number of samples or their nature makes it Impracticable to rank all the samples. a ‘balanced incomplete block design may be used. In either case, it is necessary to ensure that all assessors complete their part of the design and do not omit any assessment
For balanced incomplete block designs, each assessor is presented a specific subset of the samples in a randomized order (see Annex C for an example).
NOTE The use of a certain Balanced Incomplete Block is only possible when audi a block vanabon exists in re*ty. So it is necessary to look for a predefined block from literature. eg. Reference Ii in the Bibliography.
Each assessor is presented with k of the p samples (k