ASTM E2610-08(2011)
(Test Method)Standard Test Method for Sensory Analysis—Duo-Trio Test
Standard Test Method for Sensory Analysis—Duo-Trio Test
SIGNIFICANCE AND USE
The test method is effective for the following test objectives:
To determine whether a perceivable difference results or a perceivable difference does not result, for example, when a change is made in ingredients, processing, packaging, handling or storage; or
To select, train and monitor assessors.
The test method itself does not change whether the purpose of the duo-trio test is to determine that two products are perceivably different versus that the products are not perceivably different. Only the selected values of pd, α, and β change. If the objective of the test is to determine if there is a perceivable difference between two products, then the value selected for α is typically smaller than the value selected for β. If the objective is to determine if the two products are sufficiently similar to be used interchangeably, then the value selected for β is typically smaller than the value selected for α and the value of pd is selected to define “sufficiently similar.”
The test method may change based on the test objective or the assessors’ familiarity with the product. The balanced-reference technique (see 9.1.1) typically is used when neither product is more familiar than the other. The constant-reference technique (see 9.1.2) frequently is used when one product is a control/current product or is familiar to the assessors.
SCOPE
1.1 This test method covers a procedure for determining whether a perceptible sensory difference exists between samples of two products.
1.2 This test method applies whether a difference may exist in a single sensory attribute or in several.
1.3 This test method is applicable when the nature of the difference between the samples is unknown. It does not determine the size or the direction of the difference. The attribute(s) responsible for the difference are not identified.
1.4 Compared to the triangle test, the duo-trio test is statistically less efficient, but easier to perform by the assessors. For details on how the duo-trio test compares to other three-sample tests, see Refs (1-4).
1.5 This test method is applicable only if the products are homogeneous. If two samples of the same product can often be distinguished, then another method, for example, descriptive analysis, may be more appropriate.
1.6 This test method is applicable only when the products do not cause excessive sensory fatigue, carryover or adaptation.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: E2610 − 08 (Reapproved 2011)
Standard Test Method for
Sensory Analysis—Duo-Trio Test
This standard is issued under the fixed designation E2610; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E456 Terminology Relating to Quality and Statistics
E1871 Guide for Serving Protocol for Sensory Evaluation of
1.1 This test method covers a procedure for determining
Foods and Beverages
whether a perceptible sensory difference exists between
E1885 Test Method for Sensory Analysis—Triangle Test
samples of two products.
2.2 ISO Standards:
1.2 This test method applies whether a difference may exist
ISO 4120 Sensory Analysis—Methodology—Triangle Test
in a single sensory attribute or in several.
ISO 10399 Sensory Analysis—Methodology—Duo-Trio
Test
1.3 This test method is applicable when the nature of the
difference between the samples is unknown. It does not
3. Terminology
determine the size or the direction of the difference. The
attribute(s) responsible for the difference are not identified. 3.1 Definitions—For definition of terms relating to sensory
analysis, see Terminology E253, and for terms relating to
1.4 Compared to the triangle test, the duo-trio test is
statistics, see Terminology E456.
statistically less efficient, but easier to perform by the asses-
sors. For details on how the duo-trio test compares to other 3.2 Definitions of Terms Specific to This Standard:
three-sample tests, see Refs (1-4). 3.2.1 α (alpha) risk—probability of concluding that a per-
ceptible difference exists when, in reality, one does not. (Also
1.5 This test method is applicable only if the products are
known as Type I Error or significance level.)
homogeneous. If two samples of the same product can often be
3.2.2 β (beta) risk—probability of concluding that no per-
distinguished, then another method, for example, descriptive
ceptible difference exists when, in reality, one does. (Also
analysis, may be more appropriate.
known as Type II Error.)
1.6 This test method is applicable only when the products
3.2.3 p —probability of a correct response.
do not cause excessive sensory fatigue, carryover or adapta- c
tion.
3.2.4 p (proportion of discriminators)—proportion of the
d
population represented by the assessors that can distinguish
1.7 This standard does not purport to address all of the
between the two products.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.2.5 product—material to be evaluated.
priate safety and health practices and determine the applica-
3.2.6 sample—unit of product prepared, presented, and
bility of regulatory limitations prior to use.
evaluated in the test.
3.2.7 sensitivity—general term used to summarize the per-
2. Referenced Documents
formance characteristics of the test. The sensitivity of the test
2.1 ASTM Standards:
is rigorously defined, in statistical terms, by the values selected
E253 Terminology Relating to Sensory Evaluation of Mate-
for α, β, and p .
d
rials and Products
3.2.8 triad—three samples given to an assessor in the
duo-trio test; one sample is labeled as a reference the other two
This test method is under the jurisdiction ofASTM Committee E18 on Sensory
samples are labeled with different codes. One of the coded
Evaluation and is the direct responsibility of Subcommittee E18.04 on Fundamen-
tals of Sensory. samples is the same product as the reference. The other coded
Current edition approved Nov. 15, 2011. Published March 2012. Originally
sample is different.
approved in 2008. Last previous edition approved in 2008 as E2610 – 08. DOI:
10.1520/E2610-08R11.
4. Summary of Test Method
The boldface numbers in parentheses refer to the list of references at the end of
this standard.
4.1 Clearly define the test objective in writing.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2610 − 08 (2011)
4.2 Choose the number of assessors based on the level of evaluation). Experience and familiarity with the product and
sensitivity desired for the test. The sensitivity of the test is, in testmethodmayincreasethesensitivityofanassessorandmay
part, a function of two competing risks: the risk of declaring therefore increase the likelihood of finding a significant differ-
the samples different when they are not (that is,α-risk) and the ence. Monitoring the performance of assessors over time may
risk of not declaring the samples different when they are (that be useful.
is,β-risk).Acceptable values ofα andβ vary depending on the
7.2 Choose assessors in accordance with test objectives. For
test objective and should be determined before the test (see for
example, to project results to a general consumer population,
example Appendix X1 and Appendix X2).
assessors with unknown sensitivity might be selected. To
4.3 Each assessor receives a triad where one sample is
increase protection of product quality, assessors with demon-
labeled as the reference and the other two samples are labeled strated acuity should be selected.
with different codes.The assessors are informed that one of the
7.3 Thedecisiontousetrainedoruntrainedassessorsshould
coded samples is the same as the reference and that one is
be addressed prior to testing. Training may include a prelimi-
different.Theassessorsreportwhichofthecodedsamplesthey
nary presentation on the nature of the samples and the problem
believe to be the same as (or different from) the reference.
concerned. If the test concerns the detection of a particular
4.4 Results are tallied and significance determined by ref-
taint, consider the inclusion of samples during training that
erence to a statistical table.
demonstrate its presence and absence. Such demonstration will
increase the panel’s acuity for the taint but may detract from
5. Significance and Use
other differences. See Ref (8) for details.Allow adequate time
5.1 The test method is effective for the following test
between the exposure to the training samples and the actual
objectives:
duo-trio test to avoid carryover.
5.1.1 To determine whether a perceivable difference results
7.4 During the test sessions, avoid giving information about
or a perceivable difference does not result, for example, when
product identity, expected treatment effects or individual per-
a change is made in ingredients, processing, packaging, han-
formance until all testing is complete.
dling or storage; or
5.1.2 To select, train and monitor assessors.
7.5 Avoid replicate evaluations by the same assessor when-
ever possible. However, if replications are needed to produce a
5.2 The test method itself does not change whether the
sufficient number of total evaluations, every effort should be
purpose of the duo-trio test is to determine that two products
made to have each assessor perform the same number of
are perceivably different versus that the products are not
replicate evaluations.
perceivably different. Only the selected values of p , α, and β
d
change. If the objective of the test is to determine if there is a
8. Number of Assessors
perceivable difference between two products, then the value
selected for α is typically smaller than the value selected for β.
8.1 Choose the number of assessors to yield the level of
If the objective is to determine if the two products are
sensitivity called for by the test objectives. The sensitivity of
sufficiently similar to be used interchangeably, then the value
the test is a function of three values: the α-risk, and the β-risk,
selected for β is typically smaller than the value selected for α
and the maximum allowable proportion of distinguishers, p .
d
and the value of p is selected to define “sufficiently similar.”
d
8.2 Priortoconductingthetest,selectvaluesforα,βand p .
d
5.3 The test method may change based on the test objective
The following can be considered as general guidelines.
or the assessors’ familiarity with the product. The balanced-
8.2.1 For α-risk—A statistically significant result at:
reference technique (see 9.1.1) typically is used when neither
10 to 5 % (0.10 to 0.05) indicates “slight” evidence
product is more familiar than the other. The constant-reference
that a difference was apparent
technique (see 9.1.2) frequently is used when one product is a
5 to 1 % (0.05 to 0.01) indicates “moderate” evidence
that a difference was apparent
control/current product or is familiar to the assessors.
1 to 0.1 % (0.01 to 0.001) indicates “strong” evidence
that a difference was apparent
6. Apparatus
Below 0.1 % (<0.001) indicates “very strong” evidence
that a difference was apparent
6.1 Carry out the test under conditions that prevent contact
between assessors until the evaluations have been completed,
8.2.2 For β-risk—The strength of the evidence that a differ-
for example, using booths that comply with Ref (5).
ence was not apparent is assessed using the same criteria as
above (substituting “was not apparent” for “was apparent”).
6.2 Sample preparation and serving sizes should comply
8.2.3 For p —The maximum allowable proportion of
with Guide E1871. See Refs (6) or (7).
d
distinguishers, p , falls into three ranges:
d
7. Assessors
7.1 All assessors must be familiar with the mechanics of the
duo-trio test (the format, the task, and the procedure of
In this test method, the probability of a correct response, p , is modeled as
c
p 51·p 1 1/2 · 12p , where p is the proportion of the entire population
~ ! ~ !
c d d d
Organizations differ in the instructions they give their assessors. Some of assessors who can distinguish between the two products. It is a strictly statistical
organizations instruct their assessors to select the sample that is most similar to the “guessing model” of the assessor’s behavior. It is not a psychometric model of the
reference. Others instruct their assessors to select the sample that is most different assessor’s decision process, such as the Thurstone-Ura model that could also be
from the reference. Either approach is acceptable. applied in discrimination testing.
E2610 − 08 (2011)
9.3 Instruct the assessors to evaluate the reference sample
p < 25 % represent small values
d
25%< p < 35 % represent medium sized values
d
first and then evaluate the two coded samples in the order in
p > 35 % represent large values
d
which they were presented. The assessor should then indicate
8.3 Having defined the required level of sensitivity for the
which of the two coded samples is the same as the reference.
test using 8.2, use Table A1.1 to determine the number of
9.4 Each scoresheet should provide for a single triad of
assessors necessary. Enter Table A1.1 in the section corre-
samples. If a different set of products is to be evaluated by an
sponding to the selected value of p and the column corre-
d
assessor in a single session, the completed scoresheet and any
sponding to the selected value of β. The minimum required
remaining product should be returned to the test administrator
number of assessors is found in the row corresponding to the
prior to receiving the subsequent triad. The assessor cannot go
selected value of α. Alternatively, Table A1.1 can be used to
back to any of the previous samples or change the verdict on
develop a set of values for p , α and β that provide acceptable
d
any previous test.
sensitivity while maintaining the number of assessors within
practical limits. The approach is presented in detail in Ref (9). 9.5 Do not ask questions about preference, acceptance, or
degreeofdifferenceaftertheinitialselectionofthesamplethat
8.4 Often in practice, the number of assessors is determined
matches the reference.The selection the assessor has just made
by material conditions (for example, duration of the
may bias the reply to any additional questions. Responses to
experiment, number of available assessors, quantity of prod-
such questions may be obtained through separate tests for
uct). However, increasing the number of assessors increases
preference, acceptance, degree of difference, etc. (see Ref
the likelihood of detecting small proportions of distinguishers.
(10)). A comment section asking why the choice was made
Thus, one should expect to use larger numbers of assessors
may be included for the assessor’s remarks.
when trying to demonstrate that products are similar compared
towhenoneistryingtoprovetheyaredifferent.Often20to36 9.6 The duo-trio test is a forced-choice procedure; assessors
assessors are used when testing for a difference. For compa-
are not allowed the option of reporting “no difference.” An
rable sensitivity when testing for similarity, 40 to 78 assessors assessor who detects no difference between the samples and
are needed.
requests to report “no difference” should be instructed to
randomly select one of the coded samples as being the same as
9. Procedure the reference. In such situations the assessor can indicate that
the selection was only a guess in the comments section of the
9.1 Ifneitherproductismorefamiliarthantheother,usethe
scoresheet.
balanced reference technique (9.1.1). If the product is familiar
to the assessors (for example, a control sample from the
10. Analysis and Interpretation of Results
production line), use the constant reference technique (9.1.2).
9.1.1 Balanced-Reference Technique—Prepare worksheets 10.1 Use Table A1.2 to analyze the data obtained from a
and scoresheets (see Appendix X1) in advance of the test so as duo-trio test. The actual number of assessors can be greater
to utilize an equal number of the four possible sequences of than the minimum value given in TableA1.1. If the number of
two products, A and B: correct responses is greater than or equal to the number given
in Table A1.2, conclude that a perceptible difference exists
A AB A BA
R R
B AB B BA
R R between the samples. If the number of correct answers is less
thanthenumbergiveninTableA1.2,concludethatthesamples
9.1.1.1 Distribute these at random among the assessors so
are sufficiently similar.Again, the conclusions are based on the
that serving order is balanced.
risksacceptedwhenthelevelofsensitivity(thatis, p ,α
...
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