1、Designation: E 2610 08Standard Test Method forSensory AnalysisDuo-Trio Test1This standard is issued under the fixed designation E 2610; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthe
2、ses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for determiningwhether a perceptible sensory difference exists betweensamples of two products.1.2 This test method a
3、pplies whether a difference may existin a single sensory attribute or in several.1.3 This test method is applicable when the nature of thedifference between the samples is unknown. It does notdetermine the size or the direction of the difference. Theattribute(s) responsible for the difference are no
4、t identified.1.4 Compared to the triangle test, the duo-trio test isstatistically less efficient, but easier to perform by the asses-sors. For details on how the duo-trio test compares to otherthree-sample tests, see Refs (1-4).21.5 This test method is applicable only if the products arehomogeneous.
5、 If two samples of the same product can often bedistinguished, then another method, for example, descriptiveanalysis, may be more appropriate.1.6 This test method is applicable only when the productsdo not cause excessive sensory fatigue, carryover or adapta-tion.1.7 This standard does not purport t
6、o address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E 253 Te
7、rminology Relating to Sensory Evaluation of Ma-terials and ProductsE 456 Terminology Relating to Quality and StatisticsE 1871 Guide for Serving Protocol for Sensory Evaluationof Foods and BeveragesE 1885 Test Method for Sensory AnalysisTriangle Test2.2 ISO Standards:4ISO 4120 Sensory AnalysisMethodo
8、logyTriangle TestISO 10399 Sensory AnalysisMethodologyDuo-TrioTest3. Terminology3.1 DefinitionsFor definition of terms relating to sensoryanalysis, see Terminology E 253, and for terms relating tostatistics, see Terminology E 456.3.2 Definitions of Terms Specific to This Standard:3.2.1 a (alpha) ris
9、kprobability of concluding that a per-ceptible difference exists when, in reality, one does not. (Alsoknown as Type I Error or significance level.)3.2.2 b (beta) riskprobability of concluding that no per-ceptible difference exists when, in reality, one does. (Alsoknown as Type II Error.)3.2.3 pcprob
10、ability of a correct response.3.2.4 pd(proportion of discriminators)proportion of thepopulation represented by the assessors that can distinguishbetween the two products.3.2.5 productmaterial to be evaluated.3.2.6 sampleunit of product prepared, presented, andevaluated in the test.3.2.7 sensitivityg
11、eneral term used to summarize the per-formance characteristics of the test. The sensitivity of the testis rigorously defined, in statistical terms, by the values selectedfor a, b, and pd.3.2.8 triadthree samples given to an assessor in theduo-trio test; one sample is labeled as a reference the other
12、 twosamples are labeled with different codes. One of the codedsamples is the same product as the reference. The other codedsample is different.4. Summary of Test Method4.1 Clearly define the test objective in writing.4.2 Choose the number of assessors based on the level ofsensitivity desired for the
13、 test. The sensitivity of the test is, inpart, a function of two competing risks: the risk of declaringthe samples different when they are not (that is, a-risk) and therisk of not declaring the samples different when they are (that1This test method is under the jurisdiction of ASTM Committee E18 on
14、SensoryEvaluation and is the direct responsibility of Subcommittee E18.04 on Fundamen-tals of Sensory.Current edition approved April 15, 2008. Published May 2008.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards, visit the
15、ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10
16、036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.is, b-risk).Acceptable values of a and b vary depending on thetest objective and should be determined before the test (see forexample Appendix X1 and Appendix X2
17、).4.3 Each assessor receives a triad where one sample islabeled as the reference and the other two samples are labeledwith different codes. The assessors are informed that one of thecoded samples is the same as the reference and that one isdifferent. The assessors report which of the coded samples t
18、heybelieve to be the same as (or different from) the reference.54.4 Results are tallied and significance determined by ref-erence to a statistical table.5. Significance and Use5.1 The test method is effective for the following testobjectives:5.1.1 To determine whether a perceivable difference result
19、sor a perceivable difference does not result, for example, whena change is made in ingredients, processing, packaging, han-dling or storage; or5.1.2 To select, train and monitor assessors.5.2 The test method itself does not change whether thepurpose of the duo-trio test is to determine that two prod
20、uctsare perceivably different versus that the products are notperceivably different. Only the selected values of pd, a, and bchange. If the objective of the test is to determine if there is aperceivable difference between two products, then the valueselected for a is typically smaller than the value
21、 selected for b.If the objective is to determine if the two products aresufficiently similar to be used interchangeably, then the valueselected for b is typically smaller than the value selected for aand the value of pdis selected to define “sufficiently similar.”5.3 The test method may change based
22、 on the test objectiveor the assessors familiarity with the product. The balanced-reference technique (see 9.1.1) typically is used when neitherproduct is more familiar than the other. The constant-referencetechnique (see 9.1.2) frequently is used when one product is acontrol/current product or is f
23、amiliar to the assessors.6. Apparatus6.1 Carry out the test under conditions that prevent contactbetween assessors until the evaluations have been completed,for example, using booths that comply with Ref (5).6.2 Sample preparation and serving sizes should complywith Guide E 1871. See Refs (6) or (7)
24、.7. Assessors7.1 All assessors must be familiar with the mechanics of theduo-trio test (the format, the task, and the procedure ofevaluation). Experience and familiarity with the product andtest method may increase the sensitivity of an assessor and maytherefore increase the likelihood of finding a
25、significant differ-ence. Monitoring the performance of assessors over time maybe useful.7.2 Choose assessors in accordance with test objectives. Forexample, to project results to a general consumer population,assessors with unknown sensitivity might be selected. Toincrease protection of product qual
26、ity, assessors with demon-strated acuity should be selected.7.3 The decision to use trained or untrained assessors shouldbe addressed prior to testing. Training may include a prelimi-nary presentation on the nature of the samples and the problemconcerned. If the test concerns the detection of a part
27、iculartaint, consider the inclusion of samples during training thatdemonstrate its presence and absence. Such demonstration willincrease the panels acuity for the taint but may detract fromother differences. See Ref (8) for details. Allow adequate timebetween the exposure to the training samples and
28、 the actualduo-trio test to avoid carryover.7.4 During the test sessions, avoid giving information aboutproduct identity, expected treatment effects or individual per-formance until all testing is complete.7.5 Avoid replicate evaluations by the same assessor when-ever possible. However, if replicati
29、ons are needed to produce asufficient number of total evaluations, every effort should bemade to have each assessor perform the same number ofreplicate evaluations.8. Number of Assessors8.1 Choose the number of assessors to yield the level ofsensitivity called for by the test objectives. The sensiti
30、vity ofthe test is a function of three values: the a-risk, and the b-risk,and the maximum allowable proportion of distinguishers, pd.68.2 Prior to conducting the test, select values for a, b andpd. The following can be considered as general guidelines.8.2.1 For a-riskA statistically significant resu
31、lt at:10 to 5 % (0.10 to 0.05) indicates “slight” evidencethat a difference was apparent5 to 1 % (0.05 to 0.01) indicates “moderate” evidencethat a difference was apparent1 to 0.1 % (0.01 to 0.001) indicates “strong” evidencethat a difference was apparentBelow 0.1 % ( 35 % represent large values8.3
32、Having defined the required level of sensitivity for thetest using 8.2, use Table A1.1 to determine the number ofassessors necessary. Enter Table A1.1 in the section corre-sponding to the selected value of pdand the column corre-sponding to the selected value of b. The minimum required5Organizations
33、 differ in the instructions they give their assessors. Someorganizations instruct their assessors to select the sample that is most similar to thereference. Others instruct their assessors to select the sample that is most differentfrom the reference. Either approach is acceptable.6In this test meth
34、od, the probability of a correct response, pc, is modeled aspc5 1pd1 1/2! 1pd! , where pdis the proportion of the entire populationof assessors who can distinguish between the two products. It is a strictly statistical“guessing model” of the assessors behavior. It is not a psychometric model of thea
35、ssessors decision process, such as the Thurstone-Ura model that could also beapplied in discrimination testing.E2610082number of assessors is found in the row corresponding to theselected value of a. Alternatively, Table A1.1 can be used todevelop a set of values for pd, a and b that provide accepta
36、blesensitivity while maintaining the number of assessors withinpractical limits. The approach is presented in detail in Ref (9).8.4 Often in practice, the number of assessors is determinedby material conditions (for example, duration of the experi-ment, number of available assessors, quantity of pro
37、duct).However, increasing the number of assessors increases thelikelihood of detecting small proportions of distinguishers.Thus, one should expect to use larger numbers of assessorswhen trying to demonstrate that products are similar comparedto when one is trying to prove they are different. Often 2
38、0 to 36assessors are used when testing for a difference. For compa-rable sensitivity when testing for similarity, 40 to 78 assessorsare needed.9. Procedure9.1 If neither product is more familiar than the other, use thebalanced reference technique (9.1.1). If the product is familiarto the assessors (
39、for example, a control sample from theproduction line), use the constant reference technique (9.1.2).9.1.1 Balanced-Reference TechniquePrepare worksheetsand scoresheets (see Appendix X1) in advance of the test so asto utilize an equal number of the four possible sequences oftwo products, A and B:ARA
40、B ARBABRAB BRBA9.1.1.1 Distribute these at random among the assessors sothat serving order is balanced.9.1.2 Constant-Reference TechniquePrepare worksheetsand scoresheets (see Appendix X2) in advance of the test so asto utilize an equal number of the two possible sequences of twoproducts, A and B:AR
41、AB ARBA9.1.2.1 Distribute these at random among the assessors sothat serving order is balanced.9.2 Present each triad simultaneously if possible, followingthe same spatial arrangement for each assessor (on a line to besampled always from left to right, in a triangular array, etc.).Within the triad,
42、assessors are typically allowed to makerepeated evaluations of each sample as desired. If the condi-tions of the test require the prevention of repeat evaluations forexample, if samples are bulky, leave an aftertaste, or showslight differences in appearance that cannot be masked, presentthe samples
43、sequentially and do not allow repeated evaluations.In addition, if the samples change over time, for example,chewing gum or cereal with milk, samples should be testedsequentially.9.3 Instruct the assessors to evaluate the reference samplefirst and then evaluate the two coded samples in the order inw
44、hich they were presented. The assessor should then indicatewhich of the two coded samples is the same as the reference.9.4 Each scoresheet should provide for a single triad ofsamples. If a different set of products is to be evaluated by anassessor in a single session, the completed scoresheet and an
45、yremaining product should be returned to the test administratorprior to receiving the subsequent triad. The assessor cannot goback to any of the previous samples or change the verdict onany previous test.9.5 Do not ask questions about preference, acceptance, ordegree of difference after the initial
46、selection of the sample thatmatches the reference. The selection the assessor has just mademay bias the reply to any additional questions. Responses tosuch questions may be obtained through separate tests forpreference, acceptance, degree of difference, etc. (see Ref(10). A comment section asking wh
47、y the choice was mademay be included for the assessors remarks.9.6 The duo-trio test is a forced-choice procedure; assessorsare not allowed the option of reporting “no difference.” Anassessor who detects no difference between the samples andrequests to report “no difference” should be instructed tor
48、andomly select one of the coded samples as being the same asthe reference. In such situations the assessor can indicate thatthe selection was only a guess in the comments section of thescoresheet.10. Analysis and Interpretation of Results10.1 Use Table A1.2 to analyze the data obtained from aduo-tri
49、o test. The actual number of assessors can be greaterthan the minimum value given in Table A1.1. If the number ofcorrect responses is greater than or equal to the number givenin Table A1.2, conclude that a perceptible difference existsbetween the samples. If the number of correct answers is lessthan the number given in TableA1.2, conclude that the samplesare sufficiently similar. Again, the conclusions are based on therisks accepted when the level of sensitivity (that is, pd, a andb) was selected in determining the number of assessors (TableA1.1).10.2 If d
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