ISO 8588:2017
Sensory analysis — Methodology — "A" - "not A" test
Sensory analysis — Methodology — "A" - "not A" test
- Статус документа:
- Действующий
- Формат:
- Электронный (PDF)
- Количество страниц:
- 17
- Дата публикации:
- 21 июля 2017 г.
- Издание:
- ISO IS 8588 edition 2 version 1
- ICS:
- 67.240
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 tests to be statistically valid. Examples of its application are given in Annex B. NOTE Bi and Ennis[1] point out that the estimate of the discriminal distance, d', between the "A" and "not A" samples is the same regardless of the nature of the replicated evaluations performed in the test but that the estimate of the variance of d' does depend on how the replicate evaluations were performed. As such, no general discussion of a Thurstonian analysis of the "A" ? "not A" method, nor of the power of the test is undertaken in this document. Interested readers are referred to Reference [1] for a detailed discussion of the topic.
Abstract
Overview
ISO 8588:2017 - Sensory analysis - Methodology - “A” – “not A” test specifies a controlled procedure to determine whether a perceptible sensory difference exists between samples of two products. The method applies when differences are in a single attribute or across several attributes. It defines how assessors classify each presented sample as either “A” (the reference product) or “not A” (one or more alternative products), and how results are organized and analysed.
Key topics and requirements
- Test principle: Present a randomized series of samples; assessors indicate for each sample whether it is “A” or “not A.” Assessors must be familiar with product A before testing.
- Uses: Difference test, recognition test, and perception/discrimination test (not suitable for similarity/interchangeability testing).
- Assessors: All assessors must have the same qualification level per the test objective (see ISO 8586:2012). Typical panel sizes are 10–50 assessors; total evaluations commonly fall between 20–100.
- Test conditions: Standardized facilities (ISO 8589), randomized coding, identical serving conditions (volume, temperature, presentation), and measures to prevent assessor communication or sample identification.
- Sampling & apparatus: Follow product-specific sampling standards or reach agreement among stakeholders; apparatus must not bias results.
- Data recording: Results aggregated into a 2×2 contingency table for each “not A” product (counts of correct/incorrect identifications).
- Statistical analysis: Two main approaches are provided. A common procedure uses a two-step method that first compares proportions of “not A” calls and, if appropriate, uses a chi-square test (1 degree of freedom) on the 2×2 table. Expected cell counts are computed from row/column totals; p-values or critical χ2 values determine significance. Annexes give worked examples, answer forms and distribution tables.
Applications and users
- Practical applications:
- Product development and formulation changes (detect perceptible differences).
- Evaluation of new ingredients (recognition of a new sweetener or taint).
- Assessing assessor discrimination ability in sensory panels.
- Quality control for detecting production shifts that produce detectable differences.
- Who uses it:
- Sensory scientists and panel leaders
- Food & beverage R&D teams
- Quality assurance laboratories and contract sensory testing providers
- Regulatory bodies and standardization professionals
Related standards
- ISO 8586:2012 - Selection, training and monitoring of assessors
- ISO 8589 - Design of test rooms for sensory analysis
- ISO 5492 - Sensory analysis vocabulary
- ISO 3534-1 - Statistics vocabulary and symbols
Keywords: ISO 8588:2017, sensory analysis, “A” – “not A” test, difference test, recognition test, perception test, assessors, chi-square, statistical analysis, sampling, ISO standards.
Технические детали
- Технический комитет
- ISO/TC 34/SC 12 - Sensory analysis
- SKU
- ISO 8588:2017
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