Sensory analysis — Methodology — "A" - "not A" test

ISO 8588:2017 specifies a procedure for determining whether a perceptible sensory difference exists between samples of two products. The method applies whether a difference exists in a single sensory attribute or in several.

The "A" ? "not A" test can be used in sensory analysis in the following ways:

a) as a difference test, particularly for evaluating samples having variations, for example, in appearance (making it difficult to obtain strictly identical repeat samples) or in aftertaste (making direct comparison difficult);

b) as a recognition test, particularly for determining whether an assessor or group of assessors identifies a new stimulus in relation to a known stimulus (for example, recognition of the quality of the sweet taste of a new sweetener);

c) as a perception test, to determine the ability of an assessor to discriminate stimuli.

The "A" ? "not A" test is not appropriate for assessing if two products are sufficiently similar to be used interchangeably (i.e. for similarity testing) because the "A" ? "not A" test inherently involves replicate evaluations of the same products by all assessors. These replicate evaluations violate the basic assumptions for similarity