1、Designation: E1885 04 (Reapproved 2011)E1885 18Standard Test Method forSensory AnalysisTriangle Test1This standard is issued under the fixed designation E1885; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for determining whether a perceptible sensory difference exists between samples of twoproduct
3、s.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 thesize or the direction of the difference. The attribute(s) responsibl
4、e for the difference are not identified.1.4 Compared to the duo-trio test, the triangle test can achieve an equivalent level of statistical significance with fewer assessors.For details on how the triangle test compares to other three-sample tests, see Refs (1),(2),(3) and (4).21.5 This test method
5、is applicable only if the products are homogeneous. If two samples of the same product can often bedistinguished, 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, carryove
6、r 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 responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulato
7、ry limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organizat
8、ion Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3E253 Terminology Relating to Sensory Evaluation of Materials and ProductsE456 Terminology Relating to Quality and StatisticsE1871 Guide for Serving Protocol for Sensory Evaluation of Foods and BeveragesE2262 P
9、ractice for Estimating Thurstonian Discriminal Distances2.2 ISO Standard:ISO 4120 Sensory Analysis Methodology Triangular Test43. Terminology3.1 DefinitionsFor definition of terms relating to sensory analysis, see Terminology E253, and for terms relating to statistics,see Terminology E456.3.2 Defini
10、tions of Terms Specific to This Standard:3.2.1 (alpha) riskprobability of concluding that a perceptible difference exists when, in reality, one does not. (Also knownas Type I Error or significance level.)1 This test method is under the jurisdiction of ASTM Committee E18 on Sensory Evaluation and is
11、the direct responsibility of Subcommittee E18.04 on Fundamentalsof Sensory.Current edition approved Aug. 1, 2011Aug. 15, 2018. Published August 2011August 2018. Originally approved in 1997. Last previous edition approved in 20042011 asE1885 04. 04 (2011). DOI: 10.1520/E1885-04R11.10.1520/E1885-18.2
12、The boldface numbers given in parentheses refer to a list of references at the end of the text.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document
13、 Summary page on the ASTM website.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have bee
14、n made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document
15、.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 (beta) riskprobability of concluding that no perceptible difference exists when, in reality, one does. (Also known asType II Error.)3.2.3 pcprobability of a correct response.3.2.4
16、 pd (proportion of discriminators)proportion of the population represented by the assessors that can distinguish betweenthe two products.3.2.5 productmaterial to be evaluated.3.2.6 sampleunit of product prepared, presented, and evaluated in the test.3.2.7 sensitivitygeneral term used to summarize th
17、e performance characteristics of the test. The sensitivity of the test isrigorously defined, in statistical terms, by the values selected for , , and pd.3.2.8 Thurstonian measure of sensory difference (effect size) relative to perceptual noise (standard deviation) (see PracticeE2262).3.2.9 triadthre
18、e uniquely coded samples given to an assessor in the triangle test; two samples are alike (that is, of one product)and one is different (that is, of the other product).3.3 triadthree uniquely coded samples given to an assessor in the triangle test; two samples are alike (that is, of one product)and
19、one is different (that is, of the other product).4. Summary of Test Method4.1 Clearly define the test objective in writing.4.2 Choose the number of assessors based on the level of sensitivity desired for the test. The sensitivity of the test is, in part,a function of two competing risks: the risk of
20、 declaring the samples different when they are not (that is, -risk) and the risk of notdeclaring the samples different when they are (that is, -risk). Acceptable values of and vary depending on the test objectiveand should be determined before the test (see Appendix X3).4.3 Assessors receive a triad
21、 and are informed that two of the samples are alike and that one is different. The assessors reportwhich they believe to be the different, or “odd,” sample, even if the selection is based only on a guess.4.4 Results are tallied and significance determined by reference to a statistical table.5. Signi
22、ficance and Use5.1 This test method is effective for the following test objectives:5.1.1 To determine whether a perceivable difference results or a perceivable difference does not result, for example, when achange is made in ingredients, processing, packaging, handling or storage; or5.1.2 To select,
23、 train and monitor assessors.5.2 This test method itself does not change whether the purpose of the triangle test is to determine that two products areperceivably different versus that the products are not perceivably different. Only the selected values of pd, , and change. If theobjective of the te
24、st is to determine if there is a perceivable difference between two products, then the value selected for istypically smaller than the value selected for . If the objective is to determine if the two products are sufficiently similar to be usedinterchangeably, then the value selected for is typicall
25、y smaller than the value selected for and the value of pd is selected todefine “sufficiently similar.”6. Apparatus6.1 Carry out the test under conditions that prevent contact between assessors until the evaluations have been completed forexample, booths that comply with STP 913 (5).6.2 Sample prepar
26、ation and serving sizes should comply with Practice E1871. See Refs (6) or (7).7. Assessors7.1 All assessors must be familiar with the mechanics of the triangle test (the format, the task, and the procedure of evaluation).Experience and familiarity with the product and test method may increase the s
27、ensitivity of an assessor and may therefore increasethe likelihood of finding a significant difference. Monitoring the performance of assessors over time may be useful for increasedsensitivity.7.2 Choose assessors in accordance with test objectives. For example, to project results to a general consu
28、mer population,assessors with unknown sensitivity might be selected.To increase protection of product quality, assessors with demonstrated acuityshould be selected.7.3 The decision to use trained or untrained assessors should be addressed prior to testing. Training may include a preliminarypresentat
29、ion on the nature of the samples and the problem concerned. If the test concerns the detection of particular taint, considerthe inclusion of samples during training that demonstrate its presence and absence. Such demonstration will increase the panelsE1885 182acuity for the taint but may detract fro
30、m other differences. See STP 758 for details (8).Allow adequate time between the exposureto the training samples and the actual triangle test to avoid carryover.7.4 During the test sessions, avoid giving information about product identity, expected treatment effects, or individualperformance until a
31、ll testing is complete.7.5 Pooling multiple evaluations by the same assessor is not recommended because results are less representative of thepopulation and the risk of incorrect conclusion is greater.8. Number of Assessors8.1 Choose the number of assessors to yield the level of sensitivity called f
32、or by the test objectives. The sensitivity of the testis a function of three values: the -risk, and the -risk, and the maximum allowable proportion of distinguishers, pd.58.2 Prior to conducting the test, select values for , and pd. The following can be considered as general guidelines.8.2.1 For -ri
33、sk: A statistically significant result at:8.2.1.1 10 to 5 % (0.10 to 0.05) indicates “slight” evidence that a difference was apparent;8.2.1.2 5 to 1 % (0.05 to 0.01) indicates “moderate” evidence that a difference was apparent;8.2.1.3 1 to 0.1 % (0.01 to 0.001) indicates “strong” evidence that a dif
34、ference was apparent; and8.2.1.4 Below 0.1 % ( 35 % represent large values.8.3 Having defined the required level of sensitivity for the test using 8.2, use TableTable A1.1 A1.1 to determine the numberof assessors necessary. Enter TableTable A1.1 A1.1 in the section corresponding to the selected valu
35、e of pd and the columncorresponding to the selected value of . The minimum required number of assessors is found in the row corresponding to theselected value of . Alternatively, TableTable A1.1 A1.1 can be used to develop a set of values for pd, and that provideacceptable sensitivity while maintain
36、ing the number of assessors within practical limits. The approach is presented in detail in Ref(9).8.4 If one wishes to use Thurstonian as a measure of sensory effect size, use TablesA2.1 and A2.2 to convert between pd and. See Ref (10) for further discussion on the relationship between Thurstonian
37、and pd.8.5 Often in practice, the number of assessors is determined by material conditions (for example, duration of the experiment,number of available assessors, quantity of product). However, increasing the number of assessors increases the likelihood ofdetecting small proportions of distinguisher
38、s. Thus, one should expect to use larger numbers of assessors when trying todemonstrate that products are similar compared to when one is trying to prove they are different. Often 18 to 36 assessors are usedwhen testing for a difference. For comparable sensitivity when testing for similarity, 42 to
39、78 assessors are needed.9. Procedure9.1 Prepare worksheets and scoresheets (see Appendix X1 Appendix X3) in advance of the test so as to utilize an equalnumber of the six possible sequences of two products, A and B. Distribute these at random in groups of six among the panelists.The six sequences ar
40、e:ABB AAB ABABAA BBA BAB9.2 Sometimes the final number of assessors does not end up as a multiple of six. For example, if a test was planned for 36assessors and only 34 actually participated, there would be five complete series of the six sequences and one incomplete set of fourin which two of the s
41、ix triads were randomly dropped.9.3 It is critical to the validity of the test that assessors cannot identify the samples from the way in which they are presented.For example, in a test evaluating flavor differences, one should avoid any subtle differences in temperature or appearance causedby facto
42、rs such as the time sequence of preparation. It may be possible to mask color differences using light filters, subduedillumination, or colored serving containers. Code the serving containers containing the samples in a uniform manner, preferablyusing three-digit numbers, chosen at random for each te
43、st. Prepare samples out of sight and in an identical manner: same apparatus,same serving containers, and same quantities of products (see ASTM Serving Protocols).5 In this test method, the probability of a correct response, pd is modeled as pc = 1/ pd + (1/3)/ (1-pd), where pd is the proportion of t
44、he entire population of assessorswho can distinguish between the two products. It is a strictly statistical “guessing model” of the assessors behavior. It is not a psychometric model of the assessors decisionprocess, such as the Thurstone-Ura model that could also be applied in discrimination testin
45、g.E1885 1839.4 Present each triad simultaneously if possible, following the same spatial arrangement for each assessor (on a line to besampled always from left to right, in a triangular array, etc.) Within the triad, assessors are typically allowed to make repeatedevaluations of each sample as desir
46、ed. If the conditions of the test require the prevention of repeat evaluations for example, ifsamples are bulky, leave an aftertaste, or show slight differences in appearance that cannot be masked, present the samplessequentially and do not allow repeated evaluations.9.5 Each scoresheet should provi
47、de for a single triad of samples. If a different set of products is to be evaluated by an assessorin a single session, the completed scoresheet and any remaining product should be returned to the test administrator prior toreceiving the subsequent triad. The assessor cannot go back to any of the pre
48、vious samples or change the verdict on any previoustest.9.6 Do not ask questions about preference, acceptance, or degree of difference after the initial selection of the odd sample. Theselection the assessor has just made may bias the reply to any additional questions. Responses to such questions ma
49、y be obtainedthrough separate tests for preference, acceptance, degree of difference, etc. (see Manual 26) (1011).Acomment section asking whythe choice was made may be included for the assessors remarks.9.7 The triangle test is a forced-choice procedure; assessors are not allowed the option of reporting “no difference.”An assessorwho detects no difference between the samples should be instructed to randomly select one of the samples as being the odd oneand can indicate that the selection was only a guess in the c
