ASTM E3261-21

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E3261 − 21
Standard Guide for
Odor Evaluation of Products and Materials Under Controlled
Conditions With Trained Panel
This standard is issued under the fixed designation E3261; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This guide provides guidelines for odor evaluation of 2.1 ASTM Standards:
products and materials under controlled conditions with a E253Terminology Relating to Sensory Evaluation of Mate-
trained panel. rials and Products
E544Practice for Referencing Suprathreshold Odor Inten-
1.2 This guide addresses odor, aroma, malodor and fra-
sity
grance (see Terminology E253).
E619Practice for Evaluating Foreign Odors and/or Flavors
1.3 This guide addresses assessor selection and training,
from Paper Packaging
sample preparation, and test procedures specific to odor evalu-
E1593Guide forAssessing the Efficacy of Consumer Prod-
ations.
ucts in Reducing the Perception of Malodor
1.4 This guide does not address odor of any specific E1885Test Method for Sensory Analysis—Triangle Test
E2139Test Method for Same-Different Test
category of products.
E2164Test Method for Directional Difference Test
1.5 This guide does not recommend a specific testing
E3000Guide for Measuring and Tracking Performance of
method. The user is responsible for identifying the most
Assessors on a Descriptive Sensory Panel
appropriate test design and analysis tools to address the
E3009Test Method for Sensory Analysis—Tetrad Test
research questions.
E3041Guide for Selecting and Using Scales for Sensory
1.6 Units—The values stated in SI units are to be regarded
Evaluation
asstandard.Nootherunitsofmeasurementareincludedinthis
3. Terminology
standard.
1.7 This standard does not purport to address all of the
3.1 See Terminology E253 for sensory evaluation terminol-
safety concerns, if any, associated with its use. It is the ogy.
responsibility of the user of this standard to establish appro-
4. Summary of Guide
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4.1 Odor testing has many unique requirements for sensory
1.8 This international standard was developed in accor-
assessment. This guide outlines proper assessor selection,
dance with internationally recognized principles on standard-
training, protocols for odor testing including sample collection
ization established in the Decision on Principles for the
and preparation, and presentation methods spanning assess-
Development of International Standards, Guides and Recom-
mentsfromsmalljarstolargechambersaswellasolfactometer
mendations issued by the World Trade Organization Technical
equipmentanddirectsniffing.Projectgoalsandobjectiveswill
Barriers to Trade (TBT) Committee.
dictate the evaluation method or methods. A complete report
will outline choices made in the final project protocol.
This guide is under the jurisdiction of ASTM Committee E18 on Sensory
Evaluation and is the direct responsibility of Subcommittee E18.07 on Personal For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Care and Household Evaluation. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Sept. 15, 2021. Published November 2021. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 2021. DOI: 10.1520/E3261-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3261 − 21
5. Significance and Use 7.1.3 Internal employees allow for assessors to be on site
and for control of proprietary information. However, this may
5.1 This guide provides general guidelines and recommen-
cause resource and schedule conflicts since evaluations may
dations for presenting product and material samples to asses-
not be the employees’primary job function.
sors for evaluation of odor attributes under controlled condi-
7.1.4 Care must be taken to ensure that employees with
tions. Specific situations may require variations to these
technicalknowledgeofaprojectareexcludedfromevaluations
guidelines.
to avoid significant biases.
5.2 This guide is designed for use in assessing odor of
7.1.5 Assessorsmustalsobewillingtoobserverulessuchas
productsandmaterialsforsuchapplicationsas,butnotlimited
not eating or chewing gum before a panel.
to, development, reformulation, complaint investigation, qual-
7.2 Recruitment and Screening:
ity control, and stability/shelf-life.
7.2.1 Initial screening of assessors should determine avail-
5.3 Elements of this guide may also be utilized for assessor
ability and interest.
training programs involving odor evaluation tasks.
7.2.2 Potential assessors should not have any health-related
problems that may interfere with their sense of smell, for
6. Facility Considerations
example, severe allergies, migraines, sinus issues, etc. They
6.1 The testing environment must be free of noise, non-test
must not have frequent aversions to odors or commonly
odors, and other distractions.
experience adverse symptoms from odors (for example,
headache,nausea,etc.).Theyshouldbecheckedforanosmiaor
6.2 All staff and assessors must be odor-free with consider-
hyperosmia to project related odors. Additionally, assessors
ations for wearing only odor-free, especially fragrance-free,
with overall low sensitivity to odors or specific anosmia
personal care products.
relevant to the study should be eliminated from consideration
6.3 Ventilation:
for the testing.
6.3.1 Ventilationmayrequireahigherairexchangeratethan
7.2.3 Potential assessors should be tested for their ability to
a typical laboratory space.
identify and discriminate odors, either generally or specific to
6.3.2 In sample preparation spaces and evaluation rooms,
the test samples. Some screening examples include odor
local exhaust ventilation (LEV) can be used to immediately
identification tests, odor threshold tests for standard odorants,
remove odors near the point of generation. It is best to remove
and difference tests for similar or related odors, or both.
odors from as close to the point of generation as possible.
Assessors might only be utilized for specific types of evalua-
6.3.3 Whenodorsaregeneratedmorebroadly,alargerspace
tion tests, so screening methods chosen should correspond to
may require exhaust with a wider capture area.
theevaluationmethodsforthesensorystudy.Variousscreening
6.3.4 Purge ventilation may be periodically necessary for
tests are commercially available, or samples can be prepared
short-term, high exhaust from laboratory spaces to remove
in-house (3, 4, 5).
odors generated during activities such as sample preparation.
7.2.4 Screening also may be conducted to test ability to
6.3.5 Exhaust ventilation typically is vented out of the
complete basic ranking or rating activities. For example,
building space. Ensure the exhaust is not adjacent to any
ranking three samples of a standard odorant (for example,
building air intakes. If exhaust requirements are excessive, it
butanol, isovaleric acid, phenyl ethyl alcohol) at multiple
may be necessary to utilize filtration systems (for example,
concentrations in air or liquid solution. Screening methods
carbon) to clean and then return air to the laboratory space.
should also be chosen that most directly match with project
6.3.6 Pressure differentials between areas of the laboratory
objectives.
should be considered. Odor-free areas tend to be designed at
7.2.5 A written program for assessor screening should be
positive pressure to keep odors out. Odorous areas tend to be
developed including clear criteria for acceptance and rejection
designed at negative pressure to keep odors contained.
of potential assessors for the training phase.
6.4 Work surfaces throughout the laboratory space should
7.3 Assessor Training:
beselectedforpropertiesoflowemissionsandodorabsorption
7.3.1 Training procedures will depend on the project objec-
as well as the ability to be easily and effectively cleaned.
tives. The level of training should match the level of the
6.5 Lighting and other laboratory features should also be
evaluation task to be completed. For example, descriptive
considered. Review ASTM MNL60-2ND (1) for detailed
analysis training on multiple attributes will require signifi-
facility design guidance.
cantly more training than ratings of overall odor intensity.
7.3.2 Specifictrainingprocedureswilldependonthechosen
7. Assessor Selection and Training
odor attribute(s) and the qualitative or quantitative method(s).
7.1 Assessor Selection:
7.3.3 Assessor training should be conducted by individuals
7.1.1 The assessor selection process should include the
having direct experience with appropriate sensory evaluation
principles embodied in ASTM STP758 (2).
training and testing techniques.
7.1.2 Assessors may be recruited from within the company
7.3.4 A written training program should be developed in-
or from the local community.
cluding clear criteria for acceptance and rejection of the
assessors as they progress through training.
7.3.5 The first step in training should be to orient assessors
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. togeneralconceptsofodorassessmentsandsensoryevaluation
E3261 − 21
testing procedures. This will include proper procedures for 8.2.3 Product variability must be considered when prepar-
confidential and objective assessments. ing samples for testing. For example, individual samples may
7.3.6 Assessors may be introduced to simple rating and be blended and then portioned for evaluation, for example,
ranking activities, with activity difficulty increasing as skills hand lotion.
are developed.
8.2.4 When testing is not representative of overall product
7.3.7 Group discussions, consensus activities and instant
variability, care should be used when generalizing results. For
feedback training methods, especially in early phases, may
example,resultsfromteststhatincludeonlyoneproductlotare
help an assessor during training.
generalizable to that product lot; other lots may or may not
7.3.8 Presentation of samples with large, small, and no
behave similarly.
differences are helpful during training activities.
8.3 Sample Preparation Tools:
7.3.9 Assessors may need to be trained to understand
8.3.1 All materials coming in contact with the test samples
conducting evaluations with background or substrate odors
during all preparation steps must be considered (for example,
also present. For example, assessors are presented with olfac-
scoop, tongs, knife, weigh bowl, etc.). Tests should be per-
tometer carbon filtered air or with control fabric swatches to
formed to determine if a chosen material, with the given
experience and understand baseline background odors.
contact time, imparts any taint or absorbs odorants from the
Additionally, assessors may need to be trained to rate mal-
samples to be presented. Any materials chosen for use in
odor(s) in the presence of a fragrance, as in consumer product
sample preparation should be clean, odor-free, and non-
evaluationsincluding,butnotlimitedto,laundry,haircare,and
reactive.
pet care products.
8.3.2 Consider the following when choosing containers and
7.4 Assessor and Panel Monitoring:
tools for sample preparation:
7.4.1 Individualassessorsshouldhavecontinualmonitoring
8.3.2.1 The need for lids to minimize off-gassing from the
to determine they do not have a shift in odor sensitivity and
samples;
continue to meet performance criteria.
8.3.2.2 Material interactions, for example, odor transfer
7.4.2 The panel, as a whole, should be monitored for
to/from sample container;
on-going performance.
8.3.2.3 Maintenance of sample characteristics, for example,
7.4.3 Control and reference samples can be presented dur-
dimensions, surface area, shape, serving temperature, moisture
ing training and as part of on-going test session sample sets.
level, combinations thereof, etc. The sample headspace must
This enables the evaluation of individual assessor ratings as
be consistent to provide the same dilution of odorants in the
well as the panel average ratings over time.
same air volume to be sniffed by the assessors;
7.4.4 Replicatesamplescanbeusedforassessingindividual
8.3.2.4 Amount of sample needed for the specific evalua-
and overall variability. This will provide information if asses-
tion; and
sors are (1) rating consistently higher or lower than the panel,
8.3.2.5 Ease of sample preparation and presentation to
and (2) if they are rating the same products consistently.
assessors.
7.4.5 See Guide E3000 for specific details in measurement
and tracking of assessors on a descriptive sensory panel.
8.4 Sample Presentation:
8.4.1 Samples may be evaluated with different presentation
8. Procedures
methods.Overall,theobjectiveofthepresentationmethodisto
8.1 Pretests:
provide a sample to assessors to sniff, with considerations to
8.1.1 A practice session may be conducted with a small
improve the evaluation by (1) reducing variability in
number of staff members or assessors to determine if the
presentation, (2)directingthesampletotheassessor’snose, (3)
selected procedures are appropriate for a specific test. Sample
concentrating the odorants in the headspace to increase
preparation method, presentation method, number of samples,
differentiation, and (4) providing a consistent method to
time between samples, number of attributes, etc. should be
execute in multiple testing sessions over the short and long
determined through pretesting and appropriately modified for
term.
the actual test.
8.4.2 The samples are prepared with the presentation
method in mind. Pretesting is needed to determine the best
8.2 Product Variability:
method for preparation including, but not limited to, container
8.2.1 Variability exists in all products. How product vari-
size, container material, holding temperature, holding time
ability is handled depends on the objective of the test, the size
beforefirstassessment,whetherasinglesampleisevaluatedby
oftheeffectoneisattemptingtodetect,andtheriskassociated
only one assessor or multiple assessors, and holding time
with the decision being made. Unless the test is designed to
between evaluations.
understandtheextentofvariability,appropriatestepsshouldbe
8.4.3 A procedure should be in place to confirm that any
taken to minimize variability.
sample containers or chambers used in testing are odor-free.
8.2.2 Sample variability considerations include, but are not
limited to, parameters such as product lot, age, packaging, 8.4.4 With any presentation method, it is important for
package size, and storage conditions. Test conditions and assessorstoplacetheirnosethesamedistancefromthesample
presentation procedures are determined by the test objective, headspace as much as possible. Moving closer or further away
testmethod,andtestdesign.Descriptivetestsordiscrimination from the material can change the perceived intensity and
tests may have different sample requirements. possibly other parameters of the sample.
E3261 − 21
8.4.5 Consider personal hygiene aspects of sample presen- 8.4.8 Open Small Containers:
tation methods.Assessors sniffing the same samples or sharing
8.4.8.1 Open small containers are the same as the closed
of equipment may require use of odor-free gloves or sanitizing
containersexceptthereisnolid.Anopensmallcontainerhelps
of sample containers, equipment, and workspaces between to concentrate the odorants from the product and material to
assessor evaluations. A wipe sanitizer provides more applica-
funnel the odors to the nose of the assessor.
tioncontrolthanaspraysanitizer.Ifasanitizerisused,careful
8.4.8.2 Opencontainerswillhavecontinuousodoremission
selectionshouldconsidertimeforproductodortodissipate,the
into the lab spaces. Care needs to be taken during sample
product should not leave a residual odor, and it should not
presentation to provide a separate chamber, storage area or
interact with the test samples.
adequate distance between samples to prevent cross contami-
8.4.6 Direct Sniffıng:
nation of the samples. The sample storage area must have
proper ventilation to prevent odors from contaminating the
8.4.6.1 Direct sniffing may involve the assessor sniffing the
product or material directly as they hold it, or a test adminis- assessor observation spaces. Time the samples are in the
assessor evaluation space should also be minimized. For these
tratormaymaintaincontrolofthesamplebyholdingitaseach
assessor makes their evaluation. reasons, open containers are more commonly used with lower
odor materials.
8.4.6.2 The test administrator may need to be wearing
odor-freeglovestoeliminateodorfromtheirhandsandprevent 8.4.9 Chambers:
interaction of the material with the test administrator’s skin. It 8.4.9.1 Chambers tend to refer to containers that are too big
isbestforthetestadministratortoholdthesampleandhavethe tobeheldinyourhands.Assessorscommonlyneedtomoveto
assessor bring their nose to it rather than having the test
the chambers in the laboratory space.
administrator attempt to put the material near the assessor’s
8.4.9.2 Annex3inGuideE1593describeschamberdesigns.
nose.
Chambers may be of different sizes and materials. Materials
8.4.6.3 Very low odor materials may not create a consistent should be selected to minimize adsorption or other interaction
headspace in a jar or chamber and evaluating the material with samples. Examples include non-porous materials and
directlybythenosemayproducethemostaccurateresult.This stainless-steel.
is an example of when low odor materials like textiles require
8.4.9.3 Assessors sniff from chambers either with a sniff
direct evaluation. port or a larger opening (hatch) to sniff inside the chamber.
8.4.6.4 A second example of direct evaluation is testing of
8.4.9.4 An advantage of chambers is that samples may be
large objects that cannot be placed in a jar or chamber. presented blind if the assessor sniffs from the chamber without
8.4.6.5 An advantage of direct sniffing is that many asses- seeing the samples.
sors can sniff the same sample without a change in the odor
8.4.9.5 Some chambers allow for assessors to walk into the
presentation.However,thesampleheldintheopenaircanalso chambertomakeafullyimmersiveobservation.Inthesecases,
create variability as odorants off-gas from the material.
assessorsmaywalkintothechamberwithacarbonfiltermask,
nose plug or another non-odorous filtering material to delay
8.4.7 Closed Small Containers:
observation until they have fully entered the chamber.
8.4.7.1 Theproductormaterialmaybeplacedinsideasmall
Additionally, an air-lock or barrier may be designed into the
containertocreateaheadspace.Typically,smallglassjarswith
chamber doorway to minimize transfer of air in or out while
lidsorothersmallhand-heldcontainersareused.Thisincludes
assessors enter and exit the chamber. Care should be taken to
very small vials (1 to 5 mL) to large jars (1 to 2 L).
be certain assessors do not introduce odors to the chambers
8.4.7.2 Lidmaterialmustbeasnon-reactiveaspossible,for
from their clothing or personal care products.
example, Polytetrafluoroethylene (PTFE) lined lids. Other
8.4.10 Pressurized Devices:
examples include a watch glass or aluminum foil placed over
the jar opening. 8.4.10.1 Pressurized devices, such as olfactometers, can
either be custom made or commercially purchased. In this
8.4.7.3 Consideration needs to be made for the time and
presentation method, the assessors receive the odorous air
ease of removing and replacing the lids.Awatch glass is easy
presented through a sniffing port (for example, cone/funnel,
to slide to the side to take a sniff and then return the cover.
tube, or mask).
Screw-down lids are more secure but require more time to
8.4.10.2 Pressurized devices are able to present the samples
close and have a higher chance of being dropped by assessors.
to assessors at controlled dilutions and at full-strength.
8.4.7.4 Removal of a lid allows the headspace to escape; so
multiple assessors sniffing from the same container may have 8.4.10.3 Olfactometers are able to present an odorous air
sample to assessors at defined dilution ratios. Multiple dilution
different olfactory experiences. Pre-testing is needed to check
if there is an appropriate hold time between evaluations if ratios allow for exploring how odor attributes of the sample
(odor intensity, characters) change with dilution (Power Law)
multiple assessors are sniffing the same samples, for example,
(6).
5 or 30min. Additionally, if there is a 5min hold between
evaluations, the jar should be opened initially 5min before the 8.4.10.4 Olfactometers usually require the sample container
test start, otherwise the first assessor may receive a very ordeliverypathtostayatambientpressurefortheolfactometer
different sensory experience. It is possible that no amount of to extract the odor at defined flow rate and dilution ratios.
hold time may be appropriate for recreating an equivalent Samplesarecommonlyplacedintosamplebagswhichareable
olfactory experience. In this case, all assessors must have their to remain at ambient pressure until pressurized to direct air
own container sample prepared. flow to the sniffing port. In other types of olfactometers, air or
E3261 − 21
nitrogen may flow across a sample in a jar or through a 8.5.2 Number of Samples—Consider assessor adaptation/
chamber before being directed to the sniffing port. desensitization and mental fatigue when determining the num-
ber of samples to be evaluated in a test session. The odor
8.4.10.5 Typically, the test odor samples are prepared by
placingproductormaterialsamplesintoasamplebag.Insome intensity and character of the samples, mode of presentation,
cases, odorous air can be withdrawn using a syringe and number of questions, and length of the test session should be
injectedintoabagorchamber.Analternativemethodologyfor takenintoaccountwhendeterminingthenumberofsamplesto
collecting odorous air samples into a sample bag is by passing be evaluated per testing session and for the total project.
air over the test material in a chamber or passing air through
8.5.3 Control Samples—Under certain circumstances, it
closed product packaging. This method can be helpful for
may be helpful to have control samples as part of a testing
collection of air from a package with limited headspace for
session. These controls could include, but are not exclusively,
assessment. For example, passing air through unopened medi-
materials with known desired and undesired attributes or
cal device packaging at a very slow rate to capture the odors
intensities of specific attributes, blank no-odor or substrate
experiencedwhileopeningthepackageandthenpresentingthe
only samples, or benchmark reference samples.These samples
captured air to assessors with controlled presentation through
should be presented blind to assessors.
an olfactometer.
8.5.4 Sample Manipulation—It may be appropriate to
8.4.10.6 Acceptable sample bag materials are polyvinyl
agitate, stir or otherwise manipulate a sample before assess-
fluoride (PVF), Polyethylene terephthalate (PET), and polytet-
ment. Examples include swirling liquid in a jar before
rafluoroethylene(PTFE).Othersmaybefoundtobeacceptable
assessment,shakingcatlitter,orrubbingfabricagainstitselfor
with validation testing.
withthehand.Detailedinstructionsanddemonstrationmustbe
8.4.10.7 An advantage of olfactometers is the active and
provided to assessors for consistency. For example, swirling a
controlled method of presenting the odor to the assessors.
jar on the table surface five times at a rate of two rotations per
Samples can be presented blind and configured with a defined
second. It is important for each assessor to be consistent with
volume and flow rate.This can provide a more cons
...