Sensory analysis — Methodology — General guidance

ISO 6658:2017 gives general guidance on the use of sensory analysis. It describes tests for the examination of foods and other products by sensory analysis, and includes some general information on the techniques to be used if statistical analysis of the results is required. Generally these tests are intended only for objective sensory analysis. However, if a test can be used for determining preference in hedonic test, this is indicated. A hedonic test aims to determine the acceptability of the products and/or to determine preferences among two or more products by the specified consumer population. The methods are effective for determining whether a perceptible preference exists (difference in degree of liking), or whether no perceptible preference exists (paired similarity test). General guidance for hedonic tests is given in ISO 11136.

Analyse sensorielle — Méthodologie — Lignes directrices générales

ISO 6658:2017 fournit des lignes directrices générales sur la méthodologie de l'analyse sensorielle. Il décrit des essais destinés à l'examen des produits alimentaires et d'autres produits par analyse sensorielle et donne des informations générales relatives aux techniques à utiliser si une analyse statistique des résultats est requise. En général, ces essais sont uniquement destinés à une analyse sensorielle objective. Toutefois, s'il est possible d'utiliser un essai pour déterminer la préférence au cours d'un essai hédonique, cela est précisé. Un essai hédonique vise à déterminer l'acceptabilité des produits et/ou à déterminer les préférences d'une population de consommateurs spécifique entre deux produits ou plus. Les méthodes sont efficaces pour déterminer s'il existe une préférence perceptible (différence dans le degré d'appréciation), ou s'il n'existe aucune préférence perceptible (essai de similitude par paires). Les lignes directrices générales pour les essais hédoniques sont données dans l'ISO 11136.

Senzorična analiza - Metodologija - Splošne smernice (ISO 6658:2017)

Ta dokument podaja splošne smernice za uporabo senzorične analize. Opisuje preskuse za pregledovanje živil in drugih proizvodov z uporabo senzorične analize ter vključuje nekaj splošnih informacij o tehnikah, ki se uporabljajo, če je treba izvesti statistično analizo rezultatov.
Ti preskusi so v splošnem namenjeni samo za objektivno senzorično analizo. Vendar če je preskus mogoče uporabiti za določevanje prednostnih izbir v hedoničnem preskusu, je to navedeno.
Namen hedoničnega preskusa je določiti sprejemljivost proizvodov in/ali prednostne izbire
med dvema ali več proizvodi s pomočjo določene skupine potrošnikov. Metode so učinkovite pri
določevanju, ali zaznavna prednostna izbira obstaja (razlika v stopnji všečnosti) ali
zaznavna prednostna izbira ne obstaja (preskus parne podobnosti). Splošno navodilo za hedonične preskuse je podano v
standardu ISO 11136.

General Information

Status
Published
Publication Date
17-Jul-2017
Current Stage
9020 - International Standard under periodical review
Due Date
15-Jul-2022
Completion Date
15-Jul-2022

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INTERNATIONAL ISO
STANDARD 6658
Third edition
2017-07
Sensory analysis — Methodology —
General guidance
Analyse sensorielle — Méthodologie — Lignes directrices générales
Reference number
ISO 6658:2017(E)
ISO 2017
---------------------- Page: 1 ----------------------
ISO 6658:2017(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 6658:2017(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 General requirements ..................................................................................................................................................................................... 1

4.1 Basic information .................................................................................................................................................................................. 1

4.2 Statement of objectives .................................................................................................................................................................... 2

4.3 Choice of test ............................................................................................................................................................................................. 2

4.4 Choosing and training assessors ............................................................................................................................................. 3

4.5 Material to be tested ......... .................................................................................................................................................................. 3

4.6 Test room ..................................................................................................................................................................................................... 4

4.7 Planning and conduct of the test ............................................................................................................................................. 4

5 Test methods ............................................................................................................................................................................................................. 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Discrimination tests ........................................................................................................................................................................... 6

5.2.1 General...................................................................................................................................................................................... 6

5.2.2 Paired comparison test............................................................................................................................................... 6

5.2.3 Triangle test ......................................................................................................................................................................... 7

5.2.4 Duo-trio test ......................................................................................................................................................................... 8

5.2.5 Two-out-of-five test ....................................................................................................................................................... 8

5.2.6 “A — not A” test ................................................................................................................................................................ 9

5.2.7 Tetrad test .............................................................................................................................................................................. 9

5.3 Use of scales and categories .....................................................................................................................................................10

5.3.1 General considerations ............................................................................................................................................10

5.3.2 Interpretation of results .........................................................................................................................................10

5.3.3 Classification ....................................................................................................................................................................11

5.3.4 Grading ..................................................................................................................................................................................11

5.3.5 Ranking .................................................................................................................................................................................11

5.3.6 Rating and scoring .......................................................................................................................................................12

5.4 Descriptive tests..................................................................................................................................................................................12

5.4.1 General...................................................................................................................................................................................12

5.4.2 Qualitative sensory profile ...................................................................................................................................13

5.4.3 Quantitative descriptive profile .......................................................................................................................13

5.4.4 Consensus profile .........................................................................................................................................................15

5.4.5 Free-choice profile.......................................................................................................................................................15

5.4.6 Flash profile ......................................................................................................................................................................16

5.4.7 Deviation from reference profile.....................................................................................................................16

5.4.8 Temporal dominance of sensations (TDS)..............................................................................................17

6 Analysis of results.............................................................................................................................................................................................17

6.1 General ........................................................................................................................................................................................................17

6.2 Discrimination tests ........................................................................................................................................................................17

6.2.1 General...................................................................................................................................................................................17

6.2.2 Paired comparison test (see ISO 5495) .....................................................................................................18

6.2.3 Triangle test (see ISO 4120) ...............................................................................................................................19

6.2.4 Duo-trio test (see ISO 10399) ............................................................................................................................19

6.2.5 Two-out-of-five test ....................................................................................................................................................19

6.2.6 “A — not A” test (see ISO 8588) ......................................................................................................................19

6.2.7 Tetrad test ...........................................................................................................................................................................19

6.2.8 Treatment of “no difference” responses in discrimination tests .........................................19

6.2.9 Systematic effects .........................................................................................................................................................20

6.2.10 Sequential approach (see ISO 16820) ........................................................................................................20

© ISO 2017 – All rights reserved iii
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ISO 6658:2017(E)

6.3 Tests using scales and categories .........................................................................................................................................20

6.3.1 General...................................................................................................................................................................................20

6.3.2 Classification ....................................................................................................................................................................20

6.3.3 Grading (see ISO 4121) ...........................................................................................................................................20

6.3.4 Ranking (see ISO 8587) ..........................................................................................................................................20

6.3.5 Rating ......................................................................................................................................................................................21

6.3.6 Scoring ...................................................................................................................................................................................21

6.4 Analytical or descriptive tests .................................................................................................................................................21

7 Test report ................................................................................................................................................................................................................21

Annex A (informative) Statistical terms .........................................................................................................................................................23

Bibliography .............................................................................................................................................................................................................................25

iv © ISO 2017 – All rights reserved
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ISO 6658:2017(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 third edition cancels and replaces the second edition (ISO 6658:2005), which has been technically

revised. The following changes have been made:
— the definition of “sensory analysis” was updated;
— a tetrad test was added to the discrimination tests as 5.2.7;
— the descriptive test in 5.4 was expanded by new methods;
— Clause 6 was updated;
— Table A.1 was deleted from Annex A;
— the Bibliography was updated and expanded.
© ISO 2017 – All rights reserved v
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ISO 6658:2017(E)
Introduction

This document constitutes a general introduction to the methodology of sensory analysis and should be

read before undertaking the more detailed test procedures described in other International Standards.

It covers the general area of methodology and is intended to fulfil the following functions:

— to provide a brief background of the essential features of methods of sensory analysis for the user

of specific tests;

— to provide details of general requirements, procedures and interpretation of results common to all

or most tests;

— to provide sufficient guidance on requirements, procedures and interpretation of results for

the different specific tests to allow choice of the most appropriate procedure(s) for solution of a

particular problem.
It comprises three main aspects, covered in Clauses 4, 5 and 6.

It is essential that Clause 4 “General requirements” be read first. Clause 5 “Methods of test” describes,

in a general manner, all the main tests. Clause 6 is concerned with some general principles of data

collection and analysis of sensory data and also briefly covers general principles of statistical treatment

of the results.
vi © ISO 2017 – All rights reserved
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INTERNATIONAL STANDARD ISO 6658:2017(E)
Sensory analysis — Methodology — General guidance

WARNING — This document does not purport to address all of the safety problems, if any,

associated with its use. It is the responsibility of the user to establish appropriate safety and

health practices and to ensure compliance with any national regulatory conditions.

1 Scope

This document gives general guidance on the use of sensory analysis. It describes tests for the

examination of foods and other products by sensory analysis, and includes some general information

on the techniques to be used if statistical analysis of the results is required.

Generally these tests are intended only for objective sensory analysis. However, if a test can be used for

determining preference in hedonic test, this is indicated.

A hedonic test aims to determine the acceptability of the products and/or to determine preferences

among two or more products by the specified consumer population. The methods are effective for

determining whether a perceptible preference exists (difference in degree of liking), or whether no

perceptible preference exists (paired similarity test). General guidance for hedonic tests is given in

ISO 11136.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 5492, Sensory analysis — Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 5492 and the following apply.

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
3.1
sensory analysis

science involved with the assessment of the organoleptic attributes of a product by the senses

4 General requirements
4.1 Basic information

This clause covers the general requirements common to all situations encountered in sensory analysis.

The information basic to these requirements is as follows.

a) The human response to one stimulus cannot be isolated from previous experiences or from other

sensory stimuli received from the environment. Nevertheless, influences arising from these two

sources can be controlled and the effect standardized.
© ISO 2017 – All rights reserved 1
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ISO 6658:2017(E)

b) Variability in sensory response is inherent in any group of people used for testing and is

unavoidable; this can arise from inconsistencies within an individual, and through physiological

and psychological differences between individuals. However, with training, such a group can show

highly consistent individual responses. Recognition of these factors is important in the analysis of

results.

c) Systematic biases in sensory experiments involving human response can result in misleading

data and incorrect interpretation that can be difficult to identify. The factors that can result in

bias should be identified and controlled as far as possible by appropriate experimental design and

conduct of the tests.

d) The validity of the conclusions drawn from the results is dependent upon the test used and the way

it is conducted, including the questions that have been asked.
4.2 Statement of objectives
There are three main types of objective, as follows:

a) those in which the aim of the test is to categorize, rank or describe the product(s);

b) those in which the aim is to distinguish between two or more products; here it is important to

distinguish between the need to know
i) if there is a difference at all,
ii) how great is the magnitude of the difference,
iii) the direction (or quality) of that difference,
iv) the influence of that difference, e.g. with regard to preference, or
v) if all or only part of a population is detecting a difference;

c) those in which reassurance is sought that products are sufficiently similar to be used

interchangeably.

In sensory analysis, a given problem frequently requires appreciable discussion or thought before an

appropriate test is selected. This is because the initial concept of the problem may require clarification.

4.3 Choice of test

The choice of appropriate test depends largely on the nature of the test objective, but also needs to take

account of factors associated with the product, the assessors, the test environment, and the desired

level of analytical precision and statistical confidence in the conclusions. The action that would occur

based on the outcome of the test should be determined in advance.

For each test, an attempt is made in Clause 5 to give guidance as to its relevance. Preliminary tests may

be necessary to confirm the applicability of a given test.

Because of sensory fatigue and the effects of adaptation, only a limited number of samples can be

assessed during a session, depending on the nature of the test and the type of product. Some of these

effects can be moderated by appropriate rinse procedures and recovery between samples.

While the use of control samples is essential in most cases, their use naturally limits the number of

samples that can be assessed during any given session.

The statistical plan should always be determined before starting the tests. This is especially

recommended if the number of samples to be evaluated requires more than one session. Details of

statistical plans should be selected from specialized texts. Whatever test method is used, the sequential

testing approach described in ISO 16820 should be considered whenever it is desirable to keep the

number of samples or the number of assessors to a minimum.
2 © ISO 2017 – All rights reserved
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ISO 6658:2017(E)
4.4 Choosing and training assessors

A sensory analysis panel constitutes a true “measuring instrument”, and consequently the results of

the analyses conducted depend on its members. The recruitment of persons willing to participate in a

panel, therefore, needs to be carried out with care and should be considered as a real investment, both

in time and financially. Management support in the organization is necessary if it is to be effective.

Sensory assessment may be made by three types of assessor: “sensory assessors”, “selected assessors”

or “expert sensory assessors”. Assessors can be “naive assessors” who do not have to meet any precise

criterion of selection or training, or people who have already taken part in some sensory tests (“initiated

assessors”). “Selected assessors” are assessors who have been selected and trained for the particular

sensory test. “Expert sensory assessors” are selected assessors who have been selected and trained

for a variety of sensory analysis methods and who are able to make consistent and repeatable sensory

assessments of products in one or several categories.

The selection and training methods to be employed depend on the tasks and methods that it is intended

to give to the “selected assessors”. Procedures for training assessors for descriptive tests are different

from those for training assessors in discrimination tests.

Detailed procedures and methods for selection and training of assessors are given in ISO 8586. It

should be noted that these methods sometimes only constitute a way of choosing the better candidates

amongst those who are available, rather than to satisfy predetermined criteria. Also, the selection

of assessors for their ability to discriminate and describe foods and other products is quite different

from that used for preference tests. The former tasks require selection and training, whereas the latter

requires only that the panel be representative of a specified sector of the population, for example, a

group of consumers.

If a selection procedure is to be carried out, some important criteria for choosing assessors are as

follows:
a) general ability to perform the specific sensory task;
b) availability with respect to normal employment;
c) motivation (willingness and interest);

d) good health (including the absence of specific allergies or treatment with medications) and good

dental and general hygienic condition.

The performance of “selected assessors” and “expert sensory assessors” should be monitored regularly

to ensure that the criteria by which they were initially selected continue to be met (see ISO 11132).

4.5 Material to be tested

The nature of the product to be tested determines the experimental protocol of the test, and may

also have an influence on the type of test that is required to satisfy the test objectives. For example,

a protocol in which foods are to be consumed hot will need to take into account the cooling rate of

the product and the likely effect on sensory attributes, and the changes in sensory attributes that may

occur in keeping the product hot prior to testing.

Methods of preparation and presentation of samples should be appropriate for the product and to the

problem concerned.

EXAMPLE 1 A product that is normally consumed hot is prepared in the usual manner and tested hot; however,

elevated temperatures can be used in some circumstances to increase the ease with which some flavours can be

evaluated.

EXAMPLE 2 A product that is normally consumed in discrete pieces is not homogenized in order to retain

textural characteristics. Care is needed, however, to ensure maximum uniformity between sub-samples for each

assessor; this includes similar portion size and uniformity of composition.
© ISO 2017 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO 6658:2017(E)

General principles for product sampling (in accordance with International Standards relating to

the product under test) should be applied for test samples. In all cases, documentation of sample

identification codes or lot numbers is necessary. Valid conclusions can be drawn for a product as a

whole only if the samples tested are representative.

Carriers may sometimes be used for tests relating to the evaluation of products for which direct tasting

is not feasible (see ISO 5497), for example food ingredients.

Lighting conditions should be specified when appearance is being assessed. When the test concerns

only differences in flavour, the effect of colour differences may be partially masked by the use of lighting

conditions that minimize the colour difference.

Containers should be chosen so as not to affect the test or the product. These may include washable

ceramic or glass containers, or disposable plastic or paper containers, but shall not transfer chemical

materials that could result in taint. In particular, washable containers should be washed only in odour-

and taint-free detergents and rinsed in water, and polymeric and paper containers, including insulated

containers used for hot or cold samples, should be odour- and taint-free.

Palate cleansers may be used by the assessors between samples and between sessions, but care should

be taken to ensure that they do not influence the flavour of products to be assessed. Still and carbonated

water and bland foods (for example, unsalted crackers) may be used between samples and between

sessions. Checks on the water supply are desirable to ensure that it is bland and safe to consume. For

particular purposes, deionized water, glass-distilled water, low mineral content spring water, carbon-

filtered water or boiled tap water may be used, but it shall be noted that they are likely to have different

flavours.
4.6 Test room

Sensory analysis shall be conducted in a dedicated test room (see ISO 8589 for guidance). The aim shall

be to create for each assessor a separate environment with minimum distraction, so that each assessor

can quickly adjust to the nature of the new task(s). Extraneous activities, including preparation of the

samples, should not be allowed during the tests, as these can lead to biased results. The room should be

at a comfortable temperature and should be ventilated with odour-free air; limited airflow is desirable

to avoid excessive temperature fluctuations. Persistent odours, such as tobacco or cosmetics, shall not

be allowed to contaminate the environment of the test room.

Sound should be restricted. A low background noise is usually more tolerable than a fluctuating level

of noise. Conversation is more distracting than background noise. Interruptions cause the greatest

distraction.

It is usually helpful to have control over both the colour and the intensity of the lighting, although

coloured lights rarely succeed in completely masking differences in appearance.
Surfaces shall be non-absorbent and designed to facilitate a high standard
...

SLOVENSKI STANDARD
SIST ISO 6658:2018
01-oktober-2018
1DGRPHãþD
SIST ISO 6658:2011
6HQ]RULþQDDQDOL]D0HWRGRORJLMD6SORãQHVPHUQLFH ,62
Sensory analysis -- Methodology -- General guidance
Analyse sensorielle -- Méthodologie -- Lignes directrices générales
Ta slovenski standard je istoveten z: ISO 6658:2017
ICS:
67.240 6HQ]RULþQDDQDOL]D Sensory analysis
SIST ISO 6658:2018 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 6658:2018
---------------------- Page: 2 ----------------------
SIST ISO 6658:2018
INTERNATIONAL ISO
STANDARD 6658
Third edition
2017-07
Sensory analysis — Methodology —
General guidance
Analyse sensorielle — Méthodologie — Lignes directrices générales
Reference number
ISO 6658:2017(E)
ISO 2017
---------------------- Page: 3 ----------------------
SIST ISO 6658:2018
ISO 6658:2017(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 6658:2018
ISO 6658:2017(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 General requirements ..................................................................................................................................................................................... 1

4.1 Basic information .................................................................................................................................................................................. 1

4.2 Statement of objectives .................................................................................................................................................................... 2

4.3 Choice of test ............................................................................................................................................................................................. 2

4.4 Choosing and training assessors ............................................................................................................................................. 3

4.5 Material to be tested ......... .................................................................................................................................................................. 3

4.6 Test room ..................................................................................................................................................................................................... 4

4.7 Planning and conduct of the test ............................................................................................................................................. 4

5 Test methods ............................................................................................................................................................................................................. 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Discrimination tests ........................................................................................................................................................................... 6

5.2.1 General...................................................................................................................................................................................... 6

5.2.2 Paired comparison test............................................................................................................................................... 6

5.2.3 Triangle test ......................................................................................................................................................................... 7

5.2.4 Duo-trio test ......................................................................................................................................................................... 8

5.2.5 Two-out-of-five test ....................................................................................................................................................... 8

5.2.6 “A — not A” test ................................................................................................................................................................ 9

5.2.7 Tetrad test .............................................................................................................................................................................. 9

5.3 Use of scales and categories .....................................................................................................................................................10

5.3.1 General considerations ............................................................................................................................................10

5.3.2 Interpretation of results .........................................................................................................................................10

5.3.3 Classification ....................................................................................................................................................................11

5.3.4 Grading ..................................................................................................................................................................................11

5.3.5 Ranking .................................................................................................................................................................................11

5.3.6 Rating and scoring .......................................................................................................................................................12

5.4 Descriptive tests..................................................................................................................................................................................12

5.4.1 General...................................................................................................................................................................................12

5.4.2 Qualitative sensory profile ...................................................................................................................................13

5.4.3 Quantitative descriptive profile .......................................................................................................................13

5.4.4 Consensus profile .........................................................................................................................................................15

5.4.5 Free-choice profile.......................................................................................................................................................15

5.4.6 Flash profile ......................................................................................................................................................................16

5.4.7 Deviation from reference profile.....................................................................................................................16

5.4.8 Temporal dominance of sensations (TDS)..............................................................................................17

6 Analysis of results.............................................................................................................................................................................................17

6.1 General ........................................................................................................................................................................................................17

6.2 Discrimination tests ........................................................................................................................................................................17

6.2.1 General...................................................................................................................................................................................17

6.2.2 Paired comparison test (see ISO 5495) .....................................................................................................18

6.2.3 Triangle test (see ISO 4120) ...............................................................................................................................19

6.2.4 Duo-trio test (see ISO 10399) ............................................................................................................................19

6.2.5 Two-out-of-five test ....................................................................................................................................................19

6.2.6 “A — not A” test (see ISO 8588) ......................................................................................................................19

6.2.7 Tetrad test ...........................................................................................................................................................................19

6.2.8 Treatment of “no difference” responses in discrimination tests .........................................19

6.2.9 Systematic effects .........................................................................................................................................................20

6.2.10 Sequential approach (see ISO 16820) ........................................................................................................20

© ISO 2017 – All rights reserved iii
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SIST ISO 6658:2018
ISO 6658:2017(E)

6.3 Tests using scales and categories .........................................................................................................................................20

6.3.1 General...................................................................................................................................................................................20

6.3.2 Classification ....................................................................................................................................................................20

6.3.3 Grading (see ISO 4121) ...........................................................................................................................................20

6.3.4 Ranking (see ISO 8587) ..........................................................................................................................................20

6.3.5 Rating ......................................................................................................................................................................................21

6.3.6 Scoring ...................................................................................................................................................................................21

6.4 Analytical or descriptive tests .................................................................................................................................................21

7 Test report ................................................................................................................................................................................................................21

Annex A (informative) Statistical terms .........................................................................................................................................................23

Bibliography .............................................................................................................................................................................................................................25

iv © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 6658:2018
ISO 6658:2017(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 third edition cancels and replaces the second edition (ISO 6658:2005), which has been technically

revised. The following changes have been made:
— the definition of “sensory analysis” was updated;
— a tetrad test was added to the discrimination tests as 5.2.7;
— the descriptive test in 5.4 was expanded by new methods;
— Clause 6 was updated;
— Table A.1 was deleted from Annex A;
— the Bibliography was updated and expanded.
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SIST ISO 6658:2018
ISO 6658:2017(E)
Introduction

This document constitutes a general introduction to the methodology of sensory analysis and should be

read before undertaking the more detailed test procedures described in other International Standards.

It covers the general area of methodology and is intended to fulfil the following functions:

— to provide a brief background of the essential features of methods of sensory analysis for the user

of specific tests;

— to provide details of general requirements, procedures and interpretation of results common to all

or most tests;

— to provide sufficient guidance on requirements, procedures and interpretation of results for

the different specific tests to allow choice of the most appropriate procedure(s) for solution of a

particular problem.
It comprises three main aspects, covered in Clauses 4, 5 and 6.

It is essential that Clause 4 “General requirements” be read first. Clause 5 “Methods of test” describes,

in a general manner, all the main tests. Clause 6 is concerned with some general principles of data

collection and analysis of sensory data and also briefly covers general principles of statistical treatment

of the results.
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SIST ISO 6658:2018
INTERNATIONAL STANDARD ISO 6658:2017(E)
Sensory analysis — Methodology — General guidance

WARNING — This document does not purport to address all of the safety problems, if any,

associated with its use. It is the responsibility of the user to establish appropriate safety and

health practices and to ensure compliance with any national regulatory conditions.

1 Scope

This document gives general guidance on the use of sensory analysis. It describes tests for the

examination of foods and other products by sensory analysis, and includes some general information

on the techniques to be used if statistical analysis of the results is required.

Generally these tests are intended only for objective sensory analysis. However, if a test can be used for

determining preference in hedonic test, this is indicated.

A hedonic test aims to determine the acceptability of the products and/or to determine preferences

among two or more products by the specified consumer population. The methods are effective for

determining whether a perceptible preference exists (difference in degree of liking), or whether no

perceptible preference exists (paired similarity test). General guidance for hedonic tests is given in

ISO 11136.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 5492, Sensory analysis — Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 5492 and the following apply.

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
3.1
sensory analysis

science involved with the assessment of the organoleptic attributes of a product by the senses

4 General requirements
4.1 Basic information

This clause covers the general requirements common to all situations encountered in sensory analysis.

The information basic to these requirements is as follows.

a) The human response to one stimulus cannot be isolated from previous experiences or from other

sensory stimuli received from the environment. Nevertheless, influences arising from these two

sources can be controlled and the effect standardized.
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SIST ISO 6658:2018
ISO 6658:2017(E)

b) Variability in sensory response is inherent in any group of people used for testing and is

unavoidable; this can arise from inconsistencies within an individual, and through physiological

and psychological differences between individuals. However, with training, such a group can show

highly consistent individual responses. Recognition of these factors is important in the analysis of

results.

c) Systematic biases in sensory experiments involving human response can result in misleading

data and incorrect interpretation that can be difficult to identify. The factors that can result in

bias should be identified and controlled as far as possible by appropriate experimental design and

conduct of the tests.

d) The validity of the conclusions drawn from the results is dependent upon the test used and the way

it is conducted, including the questions that have been asked.
4.2 Statement of objectives
There are three main types of objective, as follows:

a) those in which the aim of the test is to categorize, rank or describe the product(s);

b) those in which the aim is to distinguish between two or more products; here it is important to

distinguish between the need to know
i) if there is a difference at all,
ii) how great is the magnitude of the difference,
iii) the direction (or quality) of that difference,
iv) the influence of that difference, e.g. with regard to preference, or
v) if all or only part of a population is detecting a difference;

c) those in which reassurance is sought that products are sufficiently similar to be used

interchangeably.

In sensory analysis, a given problem frequently requires appreciable discussion or thought before an

appropriate test is selected. This is because the initial concept of the problem may require clarification.

4.3 Choice of test

The choice of appropriate test depends largely on the nature of the test objective, but also needs to take

account of factors associated with the product, the assessors, the test environment, and the desired

level of analytical precision and statistical confidence in the conclusions. The action that would occur

based on the outcome of the test should be determined in advance.

For each test, an attempt is made in Clause 5 to give guidance as to its relevance. Preliminary tests may

be necessary to confirm the applicability of a given test.

Because of sensory fatigue and the effects of adaptation, only a limited number of samples can be

assessed during a session, depending on the nature of the test and the type of product. Some of these

effects can be moderated by appropriate rinse procedures and recovery between samples.

While the use of control samples is essential in most cases, their use naturally limits the number of

samples that can be assessed during any given session.

The statistical plan should always be determined before starting the tests. This is especially

recommended if the number of samples to be evaluated requires more than one session. Details of

statistical plans should be selected from specialized texts. Whatever test method is used, the sequential

testing approach described in ISO 16820 should be considered whenever it is desirable to keep the

number of samples or the number of assessors to a minimum.
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SIST ISO 6658:2018
ISO 6658:2017(E)
4.4 Choosing and training assessors

A sensory analysis panel constitutes a true “measuring instrument”, and consequently the results of

the analyses conducted depend on its members. The recruitment of persons willing to participate in a

panel, therefore, needs to be carried out with care and should be considered as a real investment, both

in time and financially. Management support in the organization is necessary if it is to be effective.

Sensory assessment may be made by three types of assessor: “sensory assessors”, “selected assessors”

or “expert sensory assessors”. Assessors can be “naive assessors” who do not have to meet any precise

criterion of selection or training, or people who have already taken part in some sensory tests (“initiated

assessors”). “Selected assessors” are assessors who have been selected and trained for the particular

sensory test. “Expert sensory assessors” are selected assessors who have been selected and trained

for a variety of sensory analysis methods and who are able to make consistent and repeatable sensory

assessments of products in one or several categories.

The selection and training methods to be employed depend on the tasks and methods that it is intended

to give to the “selected assessors”. Procedures for training assessors for descriptive tests are different

from those for training assessors in discrimination tests.

Detailed procedures and methods for selection and training of assessors are given in ISO 8586. It

should be noted that these methods sometimes only constitute a way of choosing the better candidates

amongst those who are available, rather than to satisfy predetermined criteria. Also, the selection

of assessors for their ability to discriminate and describe foods and other products is quite different

from that used for preference tests. The former tasks require selection and training, whereas the latter

requires only that the panel be representative of a specified sector of the population, for example, a

group of consumers.

If a selection procedure is to be carried out, some important criteria for choosing assessors are as

follows:
a) general ability to perform the specific sensory task;
b) availability with respect to normal employment;
c) motivation (willingness and interest);

d) good health (including the absence of specific allergies or treatment with medications) and good

dental and general hygienic condition.

The performance of “selected assessors” and “expert sensory assessors” should be monitored regularly

to ensure that the criteria by which they were initially selected continue to be met (see ISO 11132).

4.5 Material to be tested

The nature of the product to be tested determines the experimental protocol of the test, and may

also have an influence on the type of test that is required to satisfy the test objectives. For example,

a protocol in which foods are to be consumed hot will need to take into account the cooling rate of

the product and the likely effect on sensory attributes, and the changes in sensory attributes that may

occur in keeping the product hot prior to testing.

Methods of preparation and presentation of samples should be appropriate for the product and to the

problem concerned.

EXAMPLE 1 A product that is normally consumed hot is prepared in the usual manner and tested hot; however,

elevated temperatures can be used in some circumstances to increase the ease with which some flavours can be

evaluated.

EXAMPLE 2 A product that is normally consumed in discrete pieces is not homogenized in order to retain

textural characteristics. Care is needed, however, to ensure maximum uniformity between sub-samples for each

assessor; this includes similar portion size and uniformity of composition.
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General principles for product sampling (in accordance with International Standards relating to

the product under test) should be applied for test samples. In all cases, documentation of sample

identification codes or lot numbers is necessary. Valid conclusions can be drawn for a product as a

whole only if the samples tested are representative.

Carriers may sometimes be used for tests relating to the evaluation of products for which direct tasting

is not feasible (see ISO 5497), for example food ingredients.

Lighting conditions should be specified when appearance is being assessed. When the test concerns

only differences in flavour, the effect of colour differences may be partially masked by the use of lighting

conditions that minimize the colour difference.

Containers should be chosen so as not to affect the test or the product. These may include washable

ceramic or glass containers, or disposable plastic or paper containers, but shall not transfer chemical

materials that could result in taint. In particular, washable containers should be washed only in odour-

and taint-free detergents and rinsed in water, and polymeric and paper containers, including insulated

containers used for hot or cold samples, should be odour- and taint-free.

Palate cleansers may be used by the assessors between samples and between sessions, but care should

be taken to ensure that they do not influence the flavour of products to be assessed. Still and carbonated

water and bland foods (for example, unsalted crackers) may be used between samples and between

sessions. Checks on the water supply are desirable to ensure that it is bland and safe to consume. For

particular purposes, deionized water, glass-distilled water, low mineral content spring water, carbon-

filtered water or boiled tap water may be used, but it shall be noted that they are likely to have different

flavours.
4.6 Test room

Sensory analysis shall be conducted in a dedicated test room (see ISO 8589 for guidance). The aim shall

be to create for each assessor a separate environment with minimum distraction, so that each assessor

can quickly adjust to the nature of the new task(s). Extraneous activities, including preparation of the

...

NORME ISO
INTERNATIONALE 6658
Troisième édition
2017-07
Analyse sensorielle — Méthodologie
— Lignes directrices générales
Sensory analysis — Methodology — General guidance
Numéro de référence
ISO 6658:2017(F)
ISO 2017
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ISO 6658:2017(F)
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ISO 6658:2017(F)
Sommaire Page

Avant-propos ................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 1

3 Termes et définitions ....................................................................................................................................................................................... 1

4 Exigences générales .......................................................................................................................................................................................... 2

4.1 Informations de base ......................................................................................................................................................................... 2

4.2 Objectifs ........................................................................................................................................................................................................ 2

4.3 Choix de l’essai ........................................................................................................................................................................................ 2

4.4 Choix et entraînement des sujets ............................................................................................................................................ 3

4.5 Produit à soumettre à l’essai ....................................................................................................................................................... 4

4.6 Local d’essai ............................................................................................................................................................................................... 4

4.7 Planification et conduite de l’essai ........................................................................................................................................ 5

5 Méthodes d’essai .................................................................................................................................................................................................. 6

5.1 Généralités .................................................................................................................................................................................................. 6

5.2 Essais de discrimination ................................................................................................................................................................. 6

5.2.1 Généralités ............................................................................................................................................................................ 6

5.2.2 Essai de comparaison par paires ....................................................................................................................... 7

5.2.3 Essai triangulaire ............................................................................................................................................................. 7

5.2.4 Essai duo-trio ...................................................................................................................................................................... 8

5.2.5 Essai 2 sur 5 ......................................................................................................................................................................... 9

5.2.6 Essai «A» ou «non A».................................................................................................................................................... 9

5.2.7 Essai tétrade .....................................................................................................................................................................10

5.3 Essais utilisant des échelles et des catégories ..........................................................................................................10

5.3.1 Aspects généraux à prendre en compte ....................................................................................................10

5.3.2 Interprétation des résultats ................................................................................................................................11

5.3.3 Catégorisation .................................................................................................................................................................12

5.3.4 Classification ....................................................................................................................................................................12

5.3.5 Classement par rang ..................................................................................................................................................12

5.3.6 Cotation ou notation ..................................................................................................................................................13

5.4 Essais descriptifs ................................................................................................................................................................................13

5.4.1 Généralités .........................................................................................................................................................................13

5.4.2 Profil sensoriel qualitatif .......................................................................................................................................14

5.4.3 Profil sensoriel quantitatif....................................................................................................................................14

5.4.4 Profil par consensus...................................................................................................................................................16

5.4.5 Profil libre choix ............................................................................................................................................................16

5.4.6 Profil flash ...........................................................................................................................................................................17

5.4.7 Profil par rapport à une référence .................................................................................................................17

5.4.8 Dominance temporelle des sensations (DTS) ......................................................................................18

6 Analyse des résultats ....................................................................................................................................................................................18

6.1 Généralités ...............................................................................................................................................................................................18

6.2 Essais de discrimination ..............................................................................................................................................................19

6.2.1 Généralités .........................................................................................................................................................................19

6.2.2 Essai de comparaison par paires (voir l’ISO 5495) .........................................................................19

6.2.3 Essai triangulaire (voir l’ISO 4120) ..............................................................................................................20

6.2.4 Essai duo-trio (voir l’ISO 10399) ....................................................................................................................20

6.2.5 Essai 2 sur 5 ......................................................................................................................................................................20

6.2.6 Essai «A» ou «non A» (voir l’ISO 8588) .....................................................................................................20

6.2.7 Essai tétrade .....................................................................................................................................................................21

6.2.8 Traitement des réponses «aucune différence» dans les essais

de discrimination .........................................................................................................................................................21

6.2.9 Effets systématiques ..................................................................................................................................................21

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ISO 6658:2017(F)

6.2.10 Approche séquentielle (voir l’ISO 16820) ..............................................................................................21

6.3 Essais utilisant des échelles et des catégories ..........................................................................................................21

6.3.1 Généralités .........................................................................................................................................................................21

6.3.2 Catégorisation .................................................................................................................................................................21

6.3.3 Classification (voir l’ISO 4121) .........................................................................................................................22

6.3.4 Classement par rangs (voir l’ISO 8587) ....................................................................................................22

6.3.5 Essai de cotation ...........................................................................................................................................................22

6.3.6 Essai de notation ...........................................................................................................................................................22

6.4 Essais analytiques ou descriptifs .........................................................................................................................................22

7 Rapport d’essai ....................................................................................................................................................................................................22

Annexe A (informative) Termes statistiques .............................................................................................................................................24

Bibliographie ...........................................................................................................................................................................................................................26

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ISO 6658:2017(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 présent document a été élaboré par le Comité Technique ISO/TC 34, Produits alimentaires, sous-

comité SC 12, Analyse sensorielle.

Cette troisième édition annule et remplace la deuxième édition (ISO 6658:2005), qui a fait l’objet d’une

révision technique. Les modifications suivantes ont été apportées:
— la définition de «l’analyse sensorielle» a été révisée;
— un essai tétrade a été ajouté aux essais de discrimination, au 5.2.7;
— de nouvelles méthodes d’essai descriptif ont été ajoutées en 5.4;
— l’Article 6 a été révisé;
— le Tableau A.1 a été supprimé de l’Annexe A;
— la Bibliographie a été mise à jour et étendue.
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ISO 6658:2017(F)
Introduction

Le présent document constitue une introduction générale à la méthodologie de l’analyse sensorielle et il

convient de la lire avant d’appliquer les méthodes d’essai plus détaillées décrites dans d’autres Normes

internationales. Il traite du domaine général de la méthodologie et il est destiné à remplir les fonctions

suivantes:

— fournir à l’utilisateur d’essais spécifiques un bref exposé général sur les caractéristiques essentielles

des méthodes d’analyse sensorielle;

— fournir des détails sur les exigences générales, les modes opératoires et l’interprétation des résultats

communs à tous les essais ou à la plupart d’entre eux;

— constituer un guide suffisant relatif aux exigences, aux modes opératoires et à l’interprétation des

résultats des différents essais spécifiques, afin de permettre de choisir le ou les modes opératoires

les plus appropriés à la résolution d’un problème particulier.
Il comprend trois parties principales, faisant l’objet des Articles 4, 5 et 6.

Il est indispensable de lire en premier l’Article 4 («Exigences générales»). L’Article 5 («Méthodes d’essai»)

décrit les principaux essais d’une manière générale. L’Article 6 traite de certains principes généraux

relatifs à la collecte et à l’analyse de données sensorielles et aborde aussi brièvement les principes

généraux du traitement statistique des résultats.
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NORME INTERNATIONALE ISO 6658:2017(F)
Analyse sensorielle — Méthodologie — Lignes directrices
générales

AVERTISSEMENT — Le présent document n’a pas pour but de traiter les problèmes de sécurité

qui peuvent être liés à son utilisation. Il est de la responsabilité de l’utilisateur d’établir des

pratiques appropriées de sécurité, de protection de la santé et de garantir la conformité vis-à-

vis des réglementations nationales en vigueur.
1 Domaine d’application

Le présent document fournit des lignes directrices générales sur la méthodologie de l’analyse

sensorielle. Il décrit des essais destinés à l’examen des produits alimentaires et d’autres produits

par analyse sensorielle et donne des informations générales relatives aux techniques à utiliser si une

analyse statistique des résultats est requise.

En général, ces essais sont uniquement destinés à une analyse sensorielle objective. Toutefois, s’il est

possible d’utiliser un essai pour déterminer la préférence au cours d’un essai hédonique, cela est précisé.

Un essai hédonique vise à déterminer l’acceptabilité des produits et/ou à déterminer les préférences

d’une population de consommateurs spécifique entre deux produits ou plus. Les méthodes sont efficaces

pour déterminer s’il existe une préférence perceptible (différence dans le degré d’appréciation), ou s’il

n’existe aucune préférence perceptible (essai de similitude par paires). Les lignes directrices générales

pour les essais hédoniques sont données dans l’ISO 11136.
2 Références normatives

Les documents ci-après, dans leur intégralité ou non, sont des références normatives indispensables à

l’application 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 5492, Analyse sensorielle — Vocabulaire
3 Termes et définitions

Pour les besoins du présent document, les termes et définitions donnés dans l’ISO 5492 ainsi que les

suivants s’appliquent.

L’ISO et l’IEC mettent à jour les bases de données terminologiques utilisées en normalisation aux

adresses suivantes:
— IEC Electropedia: accessible sur http:// www .electropedia .org/
— ISO Online browsing platform: accessible sur http:// www .iso .org/ obp
3.1
analyse sensorielle

science relative à l’examen des propriétés organoleptiques d’un produit par les organes des sens

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ISO 6658:2017(F)
4 Exigences générales
4.1 Informations de base

Le présent article traite des exigences générales communes à toutes les situations rencontrées lors

d’analyses sensorielles et dont les principes de base sont les suivants.

a) La réponse humaine à un stimulus ne peut être isolée d’expériences précédentes ou des autres

stimuli sensoriels provenant de l’environnement. Néanmoins, l’influence de ces deux facteurs peut

être contrôlée et ses effets pris en compte.

b) La variabilité de la réponse sensorielle est inhérente à tout groupe de personnes utilisé pour les

essais et elle est inévitable; elle peut provenir d’incohérences propres à un individu et de différences

physiologiques et psychologiques entre les individus. Toutefois, avec de l’entraînement, un tel

groupe de sujets peut donner des réponses individuelles très homogènes. L’identification de ces

facteurs est importante lors de l’analyse des résultats.

c) Des biais systématiques lors d’expériences sensorielles impliquant une réponse humaine peuvent

aboutir à des données fausses et à une interprétation incorrecte qu’il peut être difficile d’identifier.

Il convient d’identifier les facteurs susceptibles d’aboutir à des biais et de les contrôler, dans toute

la mesure du possible, en concevant et en conduisant les essais de manière appropriée.

d) La validité des conclusions tirées des résultats dépend de l’essai utilisé et de la façon dont il a été

conduit, y compris le choix des questions posées.
4.2 Objectifs
Trois principaux types d’objectifs sont exposés:

a) ceux pour lesquels le but de l’essai est de classer par catégorie ou par rang, ou de décrire le(s)

produit(s);

b) ceux dont le but est de différencier deux produits ou plus; il est important ici de faire la distinction

entre la nécessité de savoir:
i) s’il existe bien une différence;
ii) quelle est l’ampleur de la différence;
iii) quel est le sens (ou la nature) de la différence;
iv) quelle est l’influence de cette différence (par exemple sur la préférence);

v) si la totalité ou seulement une partie de la population détecte une différence;

c) ceux dont le but est de vérifier que les produits sont suffisamment similaires pour être utilisés de

façon interchangeable.

En analyse sensorielle, le problème donné nécessite fréquemment une discussion ou une réflexion

sérieuse avant de choisir un essai approprié. Cela est dû au fait que le concept initial du problème peut

nécessiter d’être clarifié.
4.3 Choix de l’essai

Le choix d’un essai approprié dépend en grande partie de l’objectif de l’essai, mais nécessite également

la prise en compte de facteurs liés au produit, aux sujets, à l’environnement d’essai ainsi qu’au niveau

recherché de précision analytique et de confiance statistique des conclusions. Il convient que l’action

pouvant découler des résultats des essais soit déterminée à l’avance.

Pour chaque essai, l’Article 5 s’efforce de donner des lignes directrices pour son domaine d’application.

Des essais préliminaires peuvent s’avérer nécessaires pour confirmer la faisabilité d’un essai donné.

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Du fait de la fatigue sensorielle et de phénomènes d’adaptation, il n’est possible d’évaluer qu’un nombre

limité d’échantillons au cours d’une session, nombre variable selon la nature de l’essai et le type de

produit. Certains de ces effets peuvent être atténués par des modes opératoires appropriés de rinçage

et de repos entre échantillons.

Bien que des échantillons témoins soient nécessaires dans la plupart des cas, leur utilisation limite

naturellement le nombre d’échantillons qu’il est possible d’évaluer au cours d’une session donnée.

Il convient de toujours déterminer le plan d’expériences avant de commencer les essais. Cette

recommandation prévaut notamment si le nombre d’échantillons à évaluer nécessite plus d’une session.

Il convient de sélectionner les détails des plans d’expérience dans des ouvrages spécialisés. Quelle que

soit la méthode d’essai utilisée, chaque fois qu’il est souhaitable de minimiser le nombre d’échantillons

ou de sujets, il convient d’envisager l’approche séquentielle décrite dans l’ISO 16820.

4.4 Choix et entraînement des sujets

Un jury d’analyse sensorielle constitue un véritable «instrument de mesure» et, par conséquent, les

résultats des analyses effectuées dépendent de ses membres. Le recrutement de personnes désireuses

de faire partie d’un jury nécessite donc d’être effectué avec soin et il convient de le considérer comme

un réel investissement, à la fois en termes de temps et de coût. L’appui de la hiérarchie dans l’entreprise

est nécessaire pour qu’il soit accompli.

L’évaluation sensorielle peut être effectuée par trois types de personnes, à savoir des «sujets», des

«sujets qualifiés» ou des «sujets experts». Les sujets peuvent être des «sujets naïfs», n’ayant pas à

remplir de critère de sélection ou d’entraînement précis, ou encore des personnes ayant déjà pris

part à quelques essais sensoriels («sujets initiés»). Les «sujets qualifiés» sont des sujets qui ont été

sélectionnés et entraînés pour un essai sensoriel particulier. Les «sujets experts» sont des sujets

qualifiés qui ont été sélectionnés et entraînés pour différentes méthodes d’analyse sensorielle et qui

sont capables de réaliser des évaluations sensorielles homogènes et répétables de produits d’une ou

plusieurs catégories.

Les méthodes de sélection et d’entraînement à employer dépendent des tâches et des méthodes

destinées aux «sujets qualifiés». Les modes opératoires utilisés pour entraîner les sujets aux essais

descriptifs sont différents de ceux utilisés pour entraîner les sujets aux essais de discrimination.

Les modes opératoires et les méthodes de sélection et d’entraînement des sujets sont détaillés dans

l’ISO 8586. Il convient de noter que, parfois, ces méthodes ne font que constituer un moyen de choisir

les meilleurs candidats parmi ceux disponibles, plutôt que de satisfaire à des critères préétablis. Il

convient également de noter que la sélection de sujets pour leur aptitude à discriminer et à décrire les

produits alimentaires et d’autres produits est tout à fait différente de celle utilisée pour des essais de

préférence. Dans le premier cas, il est nécessaire d’effectuer une sélection et un entraînement alors que,

dans le second cas, il est uniquement demandé au jury d’être représentatif d’une certaine partie de la

population, par exemple un groupe de consommateurs ciblés.

Si un mode opératoire de sélection doit être mis en œuvre, plusieurs critères s’avèrent importants pour

le choix des sujets:
a) capacité générale à réaliser certaines tâches sensorielles spécifiques;
b) disponibilité par rapport au travail habituel;
c) motivation (volonté et intérêt);

d) bonne santé (y compris l’absence d’allergies particulières ou de traitement médicamenteux

particuliers) et bonnes conditions dentaires et d’hygiène générale.

Pour s’assurer que les «sujets qualifiés» et «sujets sensoriels experts» continuent de remplir les critères

sur lesquels ils ont été sélectionnés, il convient de contrôler régulièrement leurs performances (voir

ISO 11132).
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4.5 Produit à soumettre à l’essai

La nature du produit à soumettre à essai détermine le protocole expérimental de l’essai et peut

également avoir une incidence sur le type d’essai requis pour répondre aux objectifs. Par exemple, un

protocole dans lequel les produits alimentaires doivent être consommés chauds nécessite de prendre

en compte la vitesse de refroidissement du produit et son effet probable sur les propriétés sensorielles,

ainsi que les changements des propriétés sensorielles qui peuvent se produire lorsque le produit est

maintenu chaud avant l’essai.

Il convient que les méthodes de préparation et de présentation des échantillons soient adaptées au

produit et au problème posé.

EXEMPLE 1 Un produit qui est normalement consommé chaud est préparé selon la technique habituelle et

dégusté chaud; toutefois, dans certaines circonstances, il est permis d’utiliser des températures élevées afin

d’augmenter la facilité avec laquelle certains goûts peuvent être évalués.

EXEMPLE 2 Il convient de ne pas homogénéiser un produit normalement consommé en morceaux distincts

afin de conserver les caractéristiques de sa texture. Il est cependant nécessaire de s’assurer qu’il y a une

uniformité maximale entre les sous-échantillons destinés à chacun des sujets, ce qui inclut des tailles de portions

similaires et une composition uniforme.

Il convient d’appliquer aux échantillons pour essai les principes généraux d’échantillonnage de produit

(conformément aux Normes internationales portant sur le produit soumis à l’essai). Dans tous les cas,

il est nécessaire d’indiquer les codes d’identification des échantillons ou les numéros de lots. Il n’est

possible de tirer des conclusions valables pour un produit dans son ensemble que si les échantillons

soumis à essai sont représentatifs.

Des supports peuvent parfois être utilisés dans les essais portant sur des produits pour lesquels

l’analyse directe n’est pas possible (voir l’ISO 5497), par exemple des ingrédients alimentaires.

Dans le cas de l’évaluation de l’aspect du produit, il convient de spécifier les conditions d’éclairage.

Lorsque l’essai porte uniquement sur les différences de goût, l’effet des différences de couleur peut être

partiellement masqué en utilisant des conditions d’éclairage qui réduisent au minimum la différence de

couleur.

Il convient de choisir les récipients de manière qu’ils n’affectent pas l’essai ou les produits. Il peut s’agir

de récipients en verre ou en céramique lavables ou de récipients en papier ou en plastique jetab

...

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