SIST ISO 8588:2018
Sensory analysis -- Methodology -- "A" - "not A" test
Sensory analysis -- Methodology -- "A" - "not A" test
This document 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.
Analyse sensorielle -- Méthodologie -- Essai "A" - "non A"
ISO 8588:2017 sp�cifie un mode op�ratoire visant � d�terminer s'il existe une diff�rence sensorielle perceptible entre les �chantillons de deux produits. La m�thode est applicable lorsqu'il existe une diff�rence probable pour une ou pour plusieurs propri�t�s sensorielles.
L'essai �A� ? �non A� peut �tre appliqu� en analyse sensorielle selon les mani�res suivantes:
a) comme essai de diff�renciation, notamment pour l'�valuation des �chantillons pr�sentant par exemple, des variations dans l'apparence (rendant difficile l'obtention d'�chantillons r�p�t�s strictement identiques) ou dans l'arri�re-go�t (rendant malais�e la comparaison directe);
b) comme essai de reconnaissance, notamment pour d�terminer si un sujet ou un groupe de sujets peut identifier un nouveau stimulus par rapport � un stimulus connu (par exemple, reconnaissance de la qualit� de la saveur sucr�e d'un nouvel �dulcorant);
c) comme essai de perception, pour d�terminer la sensibilit� d'un sujet � discriminer des stimuli.
L'essai �A� ? �non A� ne permet pas d'�valuer si deux produits sont suffisamment similaires pour pouvoir �tre interchangeables (par exemple, pour les essais de similarit�) car l'essai �A� ? �non A� implique des �valuations r�p�t�es de m�mes produits par tous les sujets. Ces �valuations r�p�t�es contreviennent aux hypoth�ses de base li�es � la validit� statistique des r�sultats.
Des exemples d'application sont donn�s en Annexe B.
NOTE Bi et Ennis[1] observent que l'estimation de la distance de discrimination d', comprise entre les �chantillons �A� et �non A� est la m�me ind�pendamment de la nature des �valuations r�p�t�es au cours de l'essai, mais que l'estimation de la variance de d' d�pend de la mani�re dont les �valuations r�p�t�es ont �t� r�alis�es. Par cons�quent, le pr�sent document ne contient aucune discussion d'ordre g�n�ral relative � une analyse thurstonienne de la m�thode �A� ? �non A� ou � la puissance de l'essai. Les lecteurs int�ress�s par ce sujet sont renvoy�s � la R�f�rence [1] pour une explication plus d�taill�e.
Senzorična analiza - Metodologija - Preskus "A" ali "ne A"
Ta dokument določa postopek za določanje tega, ali med vzorcema dveh proizvodov obstaja zaznavna senzorična razlika. Metoda se uporablja ne glede na to, ali razlika obstaja v enem ali več senzoričnih atributih.
Preskus »A« ali »ne A« je mogoče uporabiti v senzorični analizi na naslednje načine:
a) kot preskus razlike, zlasti za vrednotenje vzorcev z odstopanji, npr. v videzu (zaradi česar je pridobitev popolnoma enakih ponovnih vzorcev otežena) ali pookusu (zaradi česar je neposredna primerjava otežena);
b) kot preskus prepoznavanja, zlasti za določanje ali ocenjevalec ali skupina ocenjevalcev določi nov dražljaj, povezan z znanim dražljajem (npr. prepoznavanje kakovosti sladkega okusa novega sladila);
c) kot preskus zaznavanja za določanje tega, ali je ocenjevalec sposoben razlikovati dražljaje.
Preskus »A« ali »ne A« ni primeren za ocenjevanje, ali sta dva proizvoda dovolj podobna, da se lahko uporabljata drug namesto drugega (npr. pri preskušanju podobnosti), ker preskus »A« ali »ne A« vključuje ponovna vrednotenja vseh ocenjevalcev enakih proizvodov. Ta ponovna vrednotenja kršijo osnovne domneve preskusov podobnosti, zato niso statistično veljavni.
Primeri uporabe tega preskusa so podani v dodatku B.
OPOMBA: Avtorja Bi in Ennis[1] poudarjata, da je ocena razločevalne razdalje ‘d’ med vzorci »A« in »ni A« enaka, ne glede na naravo ponovnih vrednotenj, izvedenih pri preskusu, vendar je ocena razlike ‘d’ odvisna od izvedbe ponovnih vrednotenj. V tem dokumentu ni splošne obravnave Thurstonove analize metode »A« in »ni A« ter vpliva preskusa. Bralci, ki jih ta tema zanima, si lahko njeno podrobno obravnavo preberejo v sklicu [1].
General Information
Relations
Buy Standard
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 8588
Second edition
2017-07
Sensory analysis — Methodology —
“A” – “not A” test
Analyse sensorielle — Méthodologie — Essai “A” – “non A”
Reference number
ISO 8588:2017(E)
©
ISO 2017
---------------------- Page: 1 ----------------------
ISO 8588:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 8588:2017(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Sampling . 2
7 General test conditions . 2
8 Assessors . 3
8.1 Qualification, selection, arrangement . 3
8.2 Numbers of assessors and assessments . 3
9 Procedure. 3
10 Expression of results . 4
Annex A (informative) Examples of the application of the “A” – “not A” test .6
2
Annex B (informative) Extracts from χ and standard normal tables .10
Annex C (informative) Examples of answer forms for an “A” – “not A” test .11
Bibliography .13
© ISO 2017 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 8588:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 12,
Sensory analysis.
This second edition cancels and replaces the first edition (ISO 8588:1987), which has been technically
revised. The following changes have been made:
— more detailed explanations of all aspects of the test method have been added;
— the option of testing more than one “not A” sample in a single test has been added;
— statistical calculations are presented in detail for all examples;
— an alternative data analysis procedure that deals directly with the one-sided nature of the “A” – “not
A” test has been added.
iv © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 8588:2017(E)
Sensory analysis — Methodology — “A” – “not A” test
1 Scope
This document 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.
[1]
NOTE Bi and Ennis 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.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: General statistical terms and terms used in
probability
ISO 5492, Sensory analysis — Vocabulary
ISO 8586:2012, Sensory analysis — General guidelines for the selection, training and monitoring of selected
assessors and expert sensory assessors
ISO 8589, Sensory analysis — General guidance for the design of test rooms
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 5492, for terms concerning
sensory analysis, and ISO 3534-1, for statistical terms, apply.
© ISO 2017 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO 8588:2017(E)
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principle
An assessor is presented with a series of samples, some of which are composed of the “A” product while
others are composed of one or more “not A” products. For each sample, the assessor indicates whether
the sample is an “A” product or is a “not A” product. This test requires the assessor to be familiar with
product “A”, possibly through exposure to known samples of product “A”, prior to exposure to the test
samples.
5 Apparatus
The apparatus shall be selected by the test supervisor according to the nature of the product to be
analysed, the number of samples, etc. and shall in no way affect the test results.
If standard apparatus corresponds to the needs of the test, it shall be used.
6 Sampling
Refer to sampling standards for the sensory analysis of the product or products being tested.
In the absence of such standards, agreement shall be sought among the parties concerned.
7 General test conditions
7.1 Clearly define the test objective in writing.
7.2 Carry out each session of the test under conditions that prevent communication among assessors
until all evaluations have been completed.
7.3 The facilities in which the tests are conducted shall comply with ISO 8589.
7.4 Assessors shall not be able to identify the samples from the way in which they are presented.
For example, in a taste test, one should avoid any differences in temperature or appearance. Mask any
irrelevant colour differences using, for example, light filters, subdued lighting or opaque serving vessels.
7.5 Code the vessels that contain the test samples in a uniform manner, using 3-digit numbers chosen
at random for each sample. Each test sample in a set shall have a different code. The same two codes
(one for the “A“ sample and one for the “not A“ sample) can be used for all assessors within a test session
provided different codes are used from one session to another, if multiple sessions are required to
complete the test.
7.6 The quantity or volume of product served shall be identical for all test samples. In a taste test, the
quantity or volume to be placed in the mouth can be specified. If it is not, assessors shall be instructed to
evaluate the same quantity or volume of each test sample.
7.7 The temperatures of the test samples shall be identical, preferably at the temperature at which the
product is generally consumed.
2 © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 8588:2017(E)
7.8 Occupational safety of assessors shall be taken into account. The assessors shall be instructed as to
how they should assess the test samples. For example, the assessors shall be instructed whether or not
they are to swallow the test samples or whether they are free to do as they please. In the latter case, the
assessors shall be instructed to proceed in the same manner for all test samples.
7.9 During the test session, avoid giving information about product identity, expected treatment effects
or individual performance until after all testing is complete.
8 Assessors
8.1 Qualification, selection, arrangement
All assessors shall possess the same level of qualification, this being chosen on the basis of the test
objective in accordance with ISO 8586:2012. Depending on the objective of the test, assessors may
be completely naïve or highly trained. However, within a test, all assessors shall be equally qualified.
For example, if the test is being conducted because there is a suspicion that the “not A” product
may exhibit a particular taint, assessors with a history of being highly sensitive to the taint may be
selected. 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 “A” – “not A” test (the format, the task and the
procedure of evaluation).
8.2 Numbers of assessors and assessments
The number of assessors to be used depends on the objective of the test and on the required significance
level. Between 10 and 50 assessors who are familiar with the “A” product shall be used in the test.
The number of replicate evaluations performed by each assessor shall be determined based on how
fatiguing the product is. The total number of evaluations performed in an “A” – “not A” test typically
falls between 20 and 100 evaluations.
9 Procedure
To ensure familiarity with product “A”, assessors may be exposed to a known “A” sample prior to the
evaluations of the test samples. Depending on the objective of the test, assessors also may be exposed
to known “not A” samples prior to evaluations of the test samples. For example, if the researcher is
concerned that one or more of the “not A” products may exhibit a particular fruity note, the assessors
may be exposed to a sample that exhibits supra-threshold intensities of the fruity attribute. The
assessors shall not have access to any known samples once the evaluations of the test samples have
begun. In addition, in the series presented to the assessor, the respective number of “A” and “not A”
samples is unknown to the assessor.
Multiple “not A” products may be evaluated in the same test. The number of “not A” products included in
a single test shall be limited to avoid sensory fatigue.
The order of presentation of the “A” and “not A” samples shall be random and the order shall be different
for each assessor. All assessors shall be presented with the same number of “A” samples and the same
number of “not A” samples (these two numbers not necessarily being the same); see A.2. Similarly, if
multiple “not A” products are tested, the numbers of each “not A” product need not be the same; see A.3.
According to the nature of the samples and in order to avoid certain interfering effects of sensory
adaptation, the same time interval shall be observed between the presentations of any two successive
samples.
Specimen answer forms are reproduced in Annex C.
© ISO 2017 – All rights reserved 3
---------------------- Page: 7 ----------------------
ISO 8588:2017(E)
10 Expression of results
Separate analyses are carried out for each “not A” product in the test. For each “not A” product in the
test, the analyst obtains a table of three columns and three rows (see Table 1).
Table 1 — Observed numbers
Sample Sample
Assessor’s response presented presented Total
is “A” is “not A”
Assessor identifies the sample as “A” n n n
11 12 1.
Assessor identifies the sample as “
...
SLOVENSKI STANDARD
SIST ISO 8588:2018
01-oktober-2018
1DGRPHãþD
SIST ISO 8588:1997
6HQ]RULþQDDQDOL]D0HWRGRORJLMD3UHVNXV$DOLQH$
Sensory analysis -- Methodology -- "A" - "not A" test
Analyse sensorielle -- Méthodologie -- Essai "A" - "non A"
Ta slovenski standard je istoveten z: ISO 8588:2017
ICS:
67.240 6HQ]RULþQDDQDOL]D Sensory analysis
SIST ISO 8588:2018 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST ISO 8588:2018
---------------------- Page: 2 ----------------------
SIST ISO 8588:2018
INTERNATIONAL ISO
STANDARD 8588
Second edition
2017-07
Sensory analysis — Methodology —
“A” – “not A” test
Analyse sensorielle — Méthodologie — Essai “A” – “non A”
Reference number
ISO 8588:2017(E)
©
ISO 2017
---------------------- Page: 3 ----------------------
SIST ISO 8588:2018
ISO 8588:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 8588:2018
ISO 8588:2017(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Sampling . 2
7 General test conditions . 2
8 Assessors . 3
8.1 Qualification, selection, arrangement . 3
8.2 Numbers of assessors and assessments . 3
9 Procedure. 3
10 Expression of results . 4
Annex A (informative) Examples of the application of the “A” – “not A” test .6
2
Annex B (informative) Extracts from χ and standard normal tables .10
Annex C (informative) Examples of answer forms for an “A” – “not A” test .11
Bibliography .13
© ISO 2017 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 8588:2018
ISO 8588:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 12,
Sensory analysis.
This second edition cancels and replaces the first edition (ISO 8588:1987), which has been technically
revised. The following changes have been made:
— more detailed explanations of all aspects of the test method have been added;
— the option of testing more than one “not A” sample in a single test has been added;
— statistical calculations are presented in detail for all examples;
— an alternative data analysis procedure that deals directly with the one-sided nature of the “A” – “not
A” test has been added.
iv © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 8588:2018
INTERNATIONAL STANDARD ISO 8588:2017(E)
Sensory analysis — Methodology — “A” – “not A” test
1 Scope
This document 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.
[1]
NOTE Bi and Ennis 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.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: General statistical terms and terms used in
probability
ISO 5492, Sensory analysis — Vocabulary
ISO 8586:2012, Sensory analysis — General guidelines for the selection, training and monitoring of selected
assessors and expert sensory assessors
ISO 8589, Sensory analysis — General guidance for the design of test rooms
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 5492, for terms concerning
sensory analysis, and ISO 3534-1, for statistical terms, apply.
© ISO 2017 – All rights reserved 1
---------------------- Page: 7 ----------------------
SIST ISO 8588:2018
ISO 8588:2017(E)
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principle
An assessor is presented with a series of samples, some of which are composed of the “A” product while
others are composed of one or more “not A” products. For each sample, the assessor indicates whether
the sample is an “A” product or is a “not A” product. This test requires the assessor to be familiar with
product “A”, possibly through exposure to known samples of product “A”, prior to exposure to the test
samples.
5 Apparatus
The apparatus shall be selected by the test supervisor according to the nature of the product to be
analysed, the number of samples, etc. and shall in no way affect the test results.
If standard apparatus corresponds to the needs of the test, it shall be used.
6 Sampling
Refer to sampling standards for the sensory analysis of the product or products being tested.
In the absence of such standards, agreement shall be sought among the parties concerned.
7 General test conditions
7.1 Clearly define the test objective in writing.
7.2 Carry out each session of the test under conditions that prevent communication among assessors
until all evaluations have been completed.
7.3 The facilities in which the tests are conducted shall comply with ISO 8589.
7.4 Assessors shall not be able to identify the samples from the way in which they are presented.
For example, in a taste test, one should avoid any differences in temperature or appearance. Mask any
irrelevant colour differences using, for example, light filters, subdued lighting or opaque serving vessels.
7.5 Code the vessels that contain the test samples in a uniform manner, using 3-digit numbers chosen
at random for each sample. Each test sample in a set shall have a different code. The same two codes
(one for the “A“ sample and one for the “not A“ sample) can be used for all assessors within a test session
provided different codes are used from one session to another, if multiple sessions are required to
complete the test.
7.6 The quantity or volume of product served shall be identical for all test samples. In a taste test, the
quantity or volume to be placed in the mouth can be specified. If it is not, assessors shall be instructed to
evaluate the same quantity or volume of each test sample.
7.7 The temperatures of the test samples shall be identical, preferably at the temperature at which the
product is generally consumed.
2 © ISO 2017 – All rights reserved
---------------------- Page: 8 ----------------------
SIST ISO 8588:2018
ISO 8588:2017(E)
7.8 Occupational safety of assessors shall be taken into account. The assessors shall be instructed as to
how they should assess the test samples. For example, the assessors shall be instructed whether or not
they are to swallow the test samples or whether they are free to do as they please. In the latter case, the
assessors shall be instructed to proceed in the same manner for all test samples.
7.9 During the test session, avoid giving information about product identity, expected treatment effects
or individual performance until after all testing is complete.
8 Assessors
8.1 Qualification, selection, arrangement
All assessors shall possess the same level of qualification, this being chosen on the basis of the test
objective in accordance with ISO 8586:2012. Depending on the objective of the test, assessors may
be completely naïve or highly trained. However, within a test, all assessors shall be equally qualified.
For example, if the test is being conducted because there is a suspicion that the “not A” product
may exhibit a particular taint, assessors with a history of being highly sensitive to the taint may be
selected. 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 “A” – “not A” test (the format, the task and the
procedure of evaluation).
8.2 Numbers of assessors and assessments
The number of assessors to be used depends on the objective of the test and on the required significance
level. Between 10 and 50 assessors who are familiar with the “A” product shall be used in the test.
The number of replicate evaluations performed by each assessor shall be determined based on how
fatiguing the product is. The total number of evaluations performed in an “A” – “not A” test typically
falls between 20 and 100 evaluations.
9 Procedure
To ensure familiarity with product “A”, assessors may be exposed to a known “A” sample prior to the
evaluations of the test samples. Depending on the objective of the test, assessors also may be exposed
to known “not A” samples prior to evaluations of the test samples. For example, if the researcher is
concerned that one or more of the “not A” products may exhibit a particular fruity note, the assessors
may be exposed to a sample that exhibits supra-threshold intensities of the fruity attribute. The
assessors shall not have access to any known samples once the evaluations of the test samples have
begun. In addition, in the series presented to the assessor, the respective number of “A” and “not A”
samples is unknown to the assessor.
Multiple “not A” products may be evaluated in the same test. The number of “not A” products included in
a single test shall be limited to avoid sensory fatigue.
The order of presentation of the “A” and “not A” samples shall be random and the order shall be different
for each assessor. All assessors shall be presented with the same number of “A” samples and the same
number of “not A” samples (these two numbers not necessarily being the same); see A.2. Similarly, if
multiple “not A” products are tested, the numbers of each “not A” product need not be the same; see A.3.
According to the nature of the samples and in order to avoid certain interfering effects of sensory
adaptation, the same time interval shall be observed between the presentations of any two successive
samples.
Specimen answer forms are reproduced in Annex C.
© ISO 2017 – All rights reserved 3
---------------------- Page: 9 ----------------------
SIST ISO 8588:2018
ISO 8588:2017(E)
10 Expression of results
Separate
...
NORME ISO
INTERNATIONALE 8588
Deuxième édition
2017-07
Analyse sensorielle — Méthodologie
— Essai “A” – “non A”
Sensory analysis — Methodology — “A” – “not A” test
Numéro de référence
ISO 8588:2017(F)
©
ISO 2017
---------------------- Page: 1 ----------------------
ISO 8588:2017(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2017, Publié en Suisse
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni utilisée
sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie, l’affichage sur
l’internet ou sur un Intranet, sans autorisation écrite préalable. Les demandes d’autorisation peuvent être adressées à l’ISO à
l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – Tous droits réservés
---------------------- Page: 2 ----------------------
ISO 8588:2017(F)
Sommaire Page
Avant-propos .iv
1 Domaine d’application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Principe . 2
5 Appareillage . 2
6 Échantillonnage . 2
7 Conditions générales d’essai . 2
8 Sujets . 3
8.1 Qualification, sélection, disposition . 3
8.2 Nombre de sujets et évaluations . 3
9 Mode opératoire. 3
10 Expression des résultats. 4
Annexe A (informative) Exemples d’utilisation de l’essai «A» – «non A» .6
2
Annexe B (informative) Extraits de tableaux de distribution χ et de distribution normale
centrée réduite .10
Annexe C (informative) Exemples de formulaires de réponses pour un essai «A» – «non A» .11
Bibliographie .13
© ISO 2017 – Tous droits réservés iii
---------------------- Page: 3 ----------------------
ISO 8588:2017(F)
Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes
nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est
en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.
L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents
critères d’approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/ directives).
L’attention est appelée sur le fait que certains des éléments du présent document peuvent faire l’objet de
droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de
brevets reçues par l’ISO (voir www .iso .org/ brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion
de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir le lien suivant: w w w . i s o .org/ iso/ fr/ avant -propos .html
Le comité chargé de l’élaboration du présent document est l’ISO/TC 34, Produits alimentaires, sous-
comité SC 12, Analyse sensorielle.
Cette deuxième édition annule et remplace la première édition (ISO 8588:1987), qui a fait l’objet d’une
révision technique. Les modifications apportées sont les suivantes:
— ajout d’explications plus détaillées de tous les aspects de la méthode d’essai;
— ajout de la possibilité d’examiner plusieurs échantillons «non A» au cours d’un seul et même essai;
— présentation détaillée des calculs statistiques pour tous les exemples;
— ajout d’une méthode d’analyse des données permettant de traiter directement la nature unilatérale
de l’essai «A» – «non A».
iv © ISO 2017 – Tous droits réservés
---------------------- Page: 4 ----------------------
NORME INTERNATIONALE ISO 8588:2017(F)
Analyse sensorielle — Méthodologie — Essai «A» – «non A»
1 Domaine d’application
Le présent document spécifie un mode opératoire visant à déterminer s’il existe une différence
sensorielle perceptible entre les échantillons de deux produits. La méthode est applicable lorsqu’il
existe une différence probable pour une ou pour plusieurs propriétés sensorielles.
L’essai «A» – «non A» peut être appliqué en analyse sensorielle selon les manières suivantes:
a) comme essai de différenciation, notamment pour l’évaluation des échantillons présentant par
exemple, des variations dans l’apparence (rendant difficile l’obtention d’échantillons répétés
strictement identiques) ou dans l’arrière-goût (rendant malaisée la comparaison directe);
b) comme essai de reconnaissance, notamment pour déterminer si un sujet ou un groupe de sujets
peut identifier un nouveau stimulus par rapport à un stimulus connu (par exemple, reconnaissance
de la qualité de la saveur sucrée d’un nouvel édulcorant);
c) comme essai de perception, pour déterminer la sensibilité d’un sujet à discriminer des stimuli.
L’essai «A» – «non A» ne permet pas d’évaluer si deux produits sont suffisamment similaires pour
pouvoir être interchangeables (par exemple, pour les essais de similarité) car l’essai «A» – «non A»
implique des évaluations répétées de mêmes produits par tous les sujets. Ces évaluations répétées
contreviennent aux hypothèses de base liées à la validité statistique des résultats.
Des exemples d’application sont donnés en Annexe B.
[1]
NOTE Bi et Ennis observent que l’estimation de la distance de discrimination d’, comprise entre les
échantillons «A» et «non A» est la même indépendamment de la nature des évaluations répétées au cours de
l’essai, mais que l’estimation de la variance de d’ dépend de la manière dont les évaluations répétées ont été
réalisées. Par conséquent, le présent document ne contient aucune discussion d’ordre général relative à une
analyse thurstonienne de la méthode «A» – «non A» ou à la puissance de l’essai. Les lecteurs intéressés par ce
sujet sont renvoyés à la Référence [1] pour une explication plus détaillée.
2 Références normatives
Les documents suivants cités dans le texte constituent, pour tout ou partie de leur contenu, des
exigences du présent document. Pour les références datées, seule l’édition citée s’applique. Pour les
références non datées, la dernière édition du document de référence s’applique (y compris les éventuels
amendements).
ISO 3534-1, Statistique — Vocabulaire et symboles — Partie 1: Termes statistiques généraux et termes
utilisés en calcul des probabilités
ISO 5492, Analyse sensorielle — Vocabulaire
ISO 8586:2012, Analyse sensorielle — Lignes directrices générales pour la sélection, l’entraînement et le
contrôle des sujets qualifiés et sujets sensoriels experts
ISO 8589, Analyse sensorielle — Directives générales pour la conception de locaux destinés à l’analyse
3 Termes et définitions
Pour les besoins du présent document, les termes et définitions de l’ISO 5492, pour les termes relatifs à
l’analyse sensorielle, et de l’ISO 3534-1, pour les termes statistiques, s’appliquent.
© ISO 2017 – Tous droits réservés 1
---------------------- Page: 5 ----------------------
ISO 8588:2017(F)
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes:
— IEC Electropedia: disponible à l’adresse http:// www .electropedia .org/ .
— ISO Online browsing platform: disponible à l’adresse http:// www .iso .org/ obp.
4 Principe
Présentation à un sujet d’une série d’échantillons dont certains sont constitués du produit «A» alors que
d’autres sont constitués d’un ou de plusieurs produits «non A». Pour chaque échantillon, le sujet doit
indiquer si l’échantillon est un produit «A» ou «non A». Cet essai exige que le sujet connaisse le produit
«A», par exemple en le familiarisant avec des échantillons connus du produit «A» avant de lui présenter
les échantillons d’essai.
5 Appareillage
L’appareillage doit être choisi par l’organisateur des essais, selon la nature du produit devant être
analysé, le nombre d’échantillons, etc., et n’avoir aucune influence sur les résultats des essais.
Si des appareillages normalisés répondent aux besoins de l’essai, ils doivent être utilisés.
6 Échantillonnage
Se reporter aux normes relatives à l’échantillonnage pour l’analyse sensorielle du ou des produits à
examiner.
S’il n’en existe pas, un accord doit être recherché entre les parties concernées.
7 Conditions générales d’essai
7.1 Définir clairement les objectifs de l’essai par écrit.
7.2 Réaliser chaque session d’essai dans des conditions empêchant toute communication entre les
sujets jusqu’à la fin des évaluations.
7.3 Les locaux dans lesquels les essais sont conduits doivent être conformes à l’ISO 8589.
7.4 La manière dont les échantillons sont présentés ne doit pas permettre aux sujets de les identifier.
Par exemple, lors d’un essai gustatif, il convient d’éviter toute différence de température ou d’apparence.
Dissimuler toute éventuelle différence de couleur à l’aide, par exemple, d’un filtre lumineux, d’un
éclairage tamisé ou de récipients opaques.
7.5 Coder uniformément les récipients contenant les échantillons d’essai en utilisant des nombres
à 3 chiffres choisis au hasard pour chaque échantillon. Un code différent doit apparaître sur chaque
échantillon d’essai d’un ensemble. Il est possible d’utiliser les deux mêmes codes (un pour l’échantillon
«A» et l’autre pour le «non A») pour tous les sujets d’une même session d’essai; si plusieurs sessions sont
exigées à la réalisation de l’essai, des codes différents seront utilisés d’une session à l’autre.
7.6 La quantité ou le volume de produit servi doit être identique pour tous les échantillons d’essai.
Dans un essai gustatif, la quantité ou le volume à placer dans la bouche peut être spécifié. À défaut, les
sujets doivent disposer d’instructions leur permettant d’évaluer la même quantité ou le même volume de
chaque échantillon d’essai.
2 © ISO 2017 – Tous droits réservés
---------------------- Page: 6 ----------------------
ISO 8588:2017(F)
7.7 La température des échantillons d’essai doit être identique, de préférence la température à laquelle
le produit est généralement consommé.
7.8 La sécurité et la santé au travail des sujets doit être prise en compte. Les sujets doivent disposer
d’instructions relatives à la manière dont il convient d’évaluer les échantillons d’essai. Par exemple, les
sujets doivent savoir s’il faut avaler ou non les échantillons d’essai ou bien s’ils sont libres d’en décider.
Dans ce dernier cas, les sujets doivent disposer d’instructions les invitant à poursuivre de la même
manière pour tous les échantillons d’essai.
7.9 Durant la session d’essai, éviter de donner des informations sur l’identité du produit, les effets
prévus du traitement ou les performances individuelles avant la fin de tous les essais.
8 Sujets
8.1 Qualification, sélection, disposition
Tous les sujets doivent avoir le même niveau de qualification. Cette qualification doit être choisie en
fonction de l’objectif de l’essai conformément à l’ISO 8586:2012; les sujets peuvent être naïfs, soit
complètement inexpérimentés, ou experts, soit extrêmement entraînés. Toutefois, tous les sujets d’un
essai doivent avoir le même niveau de qualification. Par exemple, si le but de l’essai est de déterminer
la présence suspectée d’une saveur particulière dans un produit «non A», des sujets particulièrement
sensibles à cette saveur peuvent être sélectionnés. La performance d’un sujet peut être améliorée par
son expérience et sa connaissance du produit et par conséquent, la probabilité de trouver une différence
significative est également augmentée. La mesure des performances des sujets en fonction du temps
peut s’avérer être utile pour suivre l’augmentation de la sensibilité.
Tous les sujets doivent connaître la technique de l’essai «A» – «non A» (le format, la tâche et la procédure
d’évaluation).
8.2 Nombre de sujets et évaluations
Le nombre de sujets à retenir dépend de l’objectif de l’essai et du niveau de précision exigé. De 10 à 50
sujets qui connaissent le produit «A» doivent être retenus pour l’essai. Le nombre de répétitions réalisées
par chaque sujet doit être déterminé sur la base de la lassitude occasionnée par le produit. Le nombre
total d’évaluations réalisées dans un essai «A» – «non A» est généralement compris entre 20 et 100.
9 Mode opératoire
Pour garantir une reconnaissance suffisante du produit «A», il est admis de présenter aux sujets un
échantillon «A» connu avant le début des évaluations des échantillons d’essai. Selon l’objectif de
l’essai, il est également admis de présenter aux sujets des échantillons «non A» connus avant le début
des évaluations des échantillons d’essai. Par exemple, si le chercheur suspecte qu’un ou plusieurs des
produits «non A» possèdent une saveur fruitée particulière, il est admis de présenter aux sujets un
échantillon dont l’attribut fruité atteint l’intensité seuil. Dès le début et durant les évaluations des
échantillons d’essai, les sujets ne doivent avoir accès à aucun des échantillons connus. En outre, dans
les séries présentées au sujet, le nombre respectif d’échantillons «A» et d’échantillons «non A» leur est
inconnu.
Plusieurs produits «non A» peuvent être évalués au cours du même essai. Le nombre de produits
«non A» faisant partie d’un même essai doit être limité afin d’éviter la fatigue sensorielle.
L’ordre de présentation des produits «A» et «non A» doit être aléatoire et différent pour chaque sujet.
Le nombre d’échantillons «A» et le nombre d’échantillons «non A» présentés doivent être les mêmes
pour tous les sujets (ces deux nombres n’étant pas nécessairement identiques); voir A.2. De même, si
plusieurs produits «non A» sont soumis à essai, il n’est pas nécessaire que le nombre de chaque produit
«non A» soit le même; voir A.3.
© ISO 2017 – Tous droits réservés 3
---------------------- Page: 7 ----------------------
ISO 8588:2017(F)
Selon la nature des exemples et afin d’éviter tous biais dus à l’adaptation sensorielle, il est nécessaire de
maintenir le même intervalle de temps entre la présentation de deux échantillons successifs.
Les formulaires types de réponse figurent en Annexe C.
10 Expression des résultats
Des analyses distinctes sont effectuées pour chaque produit «non A» de l’essai. Pour chaque produit
«non A» de l’essai, l’analyste obti
...
SLOVENSKI STANDARD
oSIST ISO 8588:2018
01-september-2018
6HQ]RULþQDDQDOL]D0HWRGRORJLMD3UHVNXV$DOLQH$
Sensory analysis -- Methodology -- "A" - "not A" test
Analyse sensorielle -- Méthodologie -- Essai "A" - "non A"
Ta slovenski standard je istoveten z: ISO 8588:2017
ICS:
67.240 6HQ]RULþQDDQDOL]D Sensory analysis
oSIST ISO 8588:2018 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST ISO 8588:2018
---------------------- Page: 2 ----------------------
oSIST ISO 8588:2018
INTERNATIONAL ISO
STANDARD 8588
Second edition
2017-07
Sensory analysis — Methodology —
“A” – “not A” test
Analyse sensorielle — Méthodologie — Essai “A” – “non A”
Reference number
ISO 8588:2017(E)
©
ISO 2017
---------------------- Page: 3 ----------------------
oSIST ISO 8588:2018
ISO 8588:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST ISO 8588:2018
ISO 8588:2017(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Sampling . 2
7 General test conditions . 2
8 Assessors . 3
8.1 Qualification, selection, arrangement . 3
8.2 Numbers of assessors and assessments . 3
9 Procedure. 3
10 Expression of results . 4
Annex A (informative) Examples of the application of the “A” – “not A” test .6
2
Annex B (informative) Extracts from χ and standard normal tables .10
Annex C (informative) Examples of answer forms for an “A” – “not A” test .11
Bibliography .13
© ISO 2017 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST ISO 8588:2018
ISO 8588:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 12,
Sensory analysis.
This second edition cancels and replaces the first edition (ISO 8588:1987), which has been technically
revised. The following changes have been made:
— more detailed explanations of all aspects of the test method have been added;
— the option of testing more than one “not A” sample in a single test has been added;
— statistical calculations are presented in detail for all examples;
— an alternative data analysis procedure that deals directly with the one-sided nature of the “A” – “not
A” test has been added.
iv © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST ISO 8588:2018
INTERNATIONAL STANDARD ISO 8588:2017(E)
Sensory analysis — Methodology — “A” – “not A” test
1 Scope
This document 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.
[1]
NOTE Bi and Ennis 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.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: General statistical terms and terms used in
probability
ISO 5492, Sensory analysis — Vocabulary
ISO 8586:2012, Sensory analysis — General guidelines for the selection, training and monitoring of selected
assessors and expert sensory assessors
ISO 8589, Sensory analysis — General guidance for the design of test rooms
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 5492, for terms concerning
sensory analysis, and ISO 3534-1, for statistical terms, apply.
© ISO 2017 – All rights reserved 1
---------------------- Page: 7 ----------------------
oSIST ISO 8588:2018
ISO 8588:2017(E)
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principle
An assessor is presented with a series of samples, some of which are composed of the “A” product while
others are composed of one or more “not A” products. For each sample, the assessor indicates whether
the sample is an “A” product or is a “not A” product. This test requires the assessor to be familiar with
product “A”, possibly through exposure to known samples of product “A”, prior to exposure to the test
samples.
5 Apparatus
The apparatus shall be selected by the test supervisor according to the nature of the product to be
analysed, the number of samples, etc. and shall in no way affect the test results.
If standard apparatus corresponds to the needs of the test, it shall be used.
6 Sampling
Refer to sampling standards for the sensory analysis of the product or products being tested.
In the absence of such standards, agreement shall be sought among the parties concerned.
7 General test conditions
7.1 Clearly define the test objective in writing.
7.2 Carry out each session of the test under conditions that prevent communication among assessors
until all evaluations have been completed.
7.3 The facilities in which the tests are conducted shall comply with ISO 8589.
7.4 Assessors shall not be able to identify the samples from the way in which they are presented.
For example, in a taste test, one should avoid any differences in temperature or appearance. Mask any
irrelevant colour differences using, for example, light filters, subdued lighting or opaque serving vessels.
7.5 Code the vessels that contain the test samples in a uniform manner, using 3-digit numbers chosen
at random for each sample. Each test sample in a set shall have a different code. The same two codes
(one for the “A“ sample and one for the “not A“ sample) can be used for all assessors within a test session
provided different codes are used from one session to another, if multiple sessions are required to
complete the test.
7.6 The quantity or volume of product served shall be identical for all test samples. In a taste test, the
quantity or volume to be placed in the mouth can be specified. If it is not, assessors shall be instructed to
evaluate the same quantity or volume of each test sample.
7.7 The temperatures of the test samples shall be identical, preferably at the temperature at which the
product is generally consumed.
2 © ISO 2017 – All rights reserved
---------------------- Page: 8 ----------------------
oSIST ISO 8588:2018
ISO 8588:2017(E)
7.8 Occupational safety of assessors shall be taken into account. The assessors shall be instructed as to
how they should assess the test samples. For example, the assessors shall be instructed whether or not
they are to swallow the test samples or whether they are free to do as they please. In the latter case, the
assessors shall be instructed to proceed in the same manner for all test samples.
7.9 During the test session, avoid giving information about product identity, expected treatment effects
or individual performance until after all testing is complete.
8 Assessors
8.1 Qualification, selection, arrangement
All assessors shall possess the same level of qualification, this being chosen on the basis of the test
objective in accordance with ISO 8586:2012. Depending on the objective of the test, assessors may
be completely naïve or highly trained. However, within a test, all assessors shall be equally qualified.
For example, if the test is being conducted because there is a suspicion that the “not A” product
may exhibit a particular taint, assessors with a history of being highly sensitive to the taint may be
selected. 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 “A” – “not A” test (the format, the task and the
procedure of evaluation).
8.2 Numbers of assessors and assessments
The number of assessors to be used depends on the objective of the test and on the required significance
level. Between 10 and 50 assessors who are familiar with the “A” product shall be used in the test.
The number of replicate evaluations performed by each assessor shall be determined based on how
fatiguing the product is. The total number of evaluations performed in an “A” – “not A” test typically
falls between 20 and 100 evaluations.
9 Procedure
To ensure familiarity with product “A”, assessors may be exposed to a known “A” sample prior to the
evaluations of the test samples. Depending on the objective of the test, assessors also may be exposed
to known “not A” samples prior to evaluations of the test samples. For example, if the researcher is
concerned that one or more of the “not A” products may exhibit a particular fruity note, the assessors
may be exposed to a sample that exhibits supra-threshold intensities of the fruity attribute. The
assessors shall not have access to any known samples once the evaluations of the test samples have
begun. In addition, in the series presented to the assessor, the respective number of “A” and “not A”
samples is unknown to the assessor.
Multiple “not A” products may be evaluated in the same test. The number of “not A” products included in
a single test shall be limited to avoid sensory fatigue.
The order of presentation of the “A” and “not A” samples shall be random and the order shall be different
for each assessor. All assessors shall be presented with the same number of “A” samples and the same
number of “not A” samples (these two numbers not necessarily being the same); see A.2. Similarly, if
multiple “not A” products are tested, the numbers of each “not A” product need not be the same; see A.3.
According to the nature of the samples and in order to avoid certain interfering effects of sensory
adaptation, the same time interval shall be observed between the presentations of any two successive
samples.
Specimen answer forms are reproduced in Annex C.
© ISO 2017 – All rights reserved 3
---------------------- Page: 9 ----------------------
oSIST ISO 8588:2018
ISO 8588:2017(E)
10 Expression of results
Separate analyses ar
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.