1、Designation: E1909 13 (Reapproved 2017)Standard Guide forTime-Intensity Evaluation of Sensory Attributes1This standard is issued under the fixed designation E1909; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. 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 guide covers procedures for conducting and ana-lyzing time-intensity (T-I) evaluations of products or othersensory stimu
3、li. Time-intensity is the measurement of theintensity of a single sensory sensation over time in response toa single exposure to a product or other sensory stimulus.Simultaneous evaluations of multiple sensory attributes arepossible, although are outside of the scope of this document.See Reference L
4、ist for more information.1.2 This guide utilizes a specially trained panel to measurethe intensity of a single continuous sensation during the timefrom initial exposure:1.2.1 To its extinction,1.2.2 To a specified intensity, or1.2.3 To a predetermined limit of time.1.3 Applications not covered in th
5、is guide include measur-ing:1.3.1 Multiple sensations,1.3.2 Multiple exposures within a single measurement, and1.3.3 Qualitative or hedonic changes in the perceived sen-sation.1.4 This guide includes protocols for the selection andtraining of judges, descriptions and use of physical datacollection d
6、evices, and methods of data handling,summarization, and statistical analysis. Illustration of twodifferent data handling and analysis approaches are included inthe appendixes.1.5 This guide is not applicable to measure product shelf lifeor stability that require evaluations over extended time.1.6 Th
7、is standard does not purport to 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, health and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 Th
8、is international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade
9、 (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E253 Terminology Relating to Sensory Evaluation of Mate-rials and Products3. Terminology3.1 Definitions of Terms Specific to This Standard: See Fig.1.3.1.1 area after Imaxpost-peak area under the curve.3.1.2 area before Imaxpre-peak area un
10、der the curve.3.1.3 AUCarea under the curve.3.1.4 Imaxor peak intensitymaximum observed intensityduring the time of measurement.3.1.5 perimetermeasured distance of perimeter of areadelineated by T-I curve.3.1.6 plateauduration of peak intensity.3.1.7 rate of increaserate of intensity increase before
11、 peakintensity (slope).3.1.8 rate of decreaserate of intensity decrease after peakintensity (slope).3.1.9 Tduror duration timetime from onset of sensationuntil it can no longer be perceived (TextTonset).3.1.10 Textor time to extinctiontime from initial exposureto the stimulus (Tinit) until it can no
12、 longer be perceived.3.1.11 Tinittime of initial exposure to the stimulus, typi-cally when the clock starts.3.1.12 Tmaxtime to reach maximum intensity of the sen-sation after exposure to the stimulus.3.1.13 Tonsettime point when the stimulus is first per-ceived after initial exposure to the stimulus
13、.1This guide is under the jurisdiction of ASTM Committee E18 on SensoryEvaluation and is the direct responsibility of Subcommittee E18.03 on SensoryTheory and Statistics.Current edition approved Aug. 1, 2017. Published August 2017. Originallyapproved in 1997. Last previous edition approved in 2013 a
14、s E1909 13. DOI:10.1520/E1909-13R17.2For referenced ASTM standards, visit the 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.Copyright ASTM Internatio
15、nal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guide
16、s and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.14 Ttrunor truncated timetime until a specified mini-mum intensity or until a pre-determined time point has beenreached.3.2 The graphical illustration of a typical time-intensitycurve is sho
17、wn in Fig. 1. The time increment may be seconds,minutes, hours, etc., depending upon the characteristic of theparticular material under study.4. Summary of Guide4.1 This guide describes procedures utilizing speciallytrained panelists to measure the intensity of a single sensorysensation as it change
18、s with time and the possible approachesto collect and analyze such data. Details on specific proceduresare given in Sections 69of this guide. Examples oftime-related evaluations are included in the appendixes.5. Significance and Use5.1 The purpose of time-intensity measurements is to estab-lish the
19、pattern of development and decline of a particularsensory characteristic under study. T-I evaluations are appli-cable when measurements at a single time point (an averagingprocess) are not sufficient to distinguish products that havevery different temporal characteristics. As pointed out by Leeand P
20、angborn (2)3, “This averaging process results in themasking or complete loss of important information such as rateof onset of stimulation, time and duration of maximumintensity, rate of decay of perceived intensity, time ofextinction, and total duration of the entire process.”5.2 Products rated simi
21、larly using traditional single pointtechniques of product profiling may provide very differenttemporal sensory experiences to the consumer.Acceptability ofthe product may be affected, and traditional descriptive meth-odology does not reflect the changes in an attributes intensityover time.5.3 T-I ha
22、s applications for a variety of products. Examplesinclude: food products, ranging from short-term sweetness in abeverage to long-term elasticity in chewing gum; personal careproducts, measuring the development and longevity of sham-poo lather and the residual skin feel of a skin cream; householdcare
23、 products, monitoring the intensity of scents over time;pharmaceuticals, monitoring skin cooling after application of atopical analgesic. Auditory signals or visual changes in prod-ucts can also be evaluated by the T-I technique.6. Time-Intensity Panel Selection and Training6.1 Screening and Selecti
24、on of Panelists6.1.1 Time-Intensity evaluation is a specialized type ofdescriptive analysis. Therefore, use of randomly selected,naive panelists is neither appropriate nor recommended. Pan-elists selected for Time-Intensity studies are screened asrecommended for other descriptive methods (see STP 75
25、8 (3).Use of panelists with previous descriptive training facilitatesthe T-I training because these panelists are competent in bothrecognizing and intensity scaling an attribute.6.1.2 The goal of the selection process is to identifypanelists who have the ability to:6.1.2.1 Continually focus on a sin
26、gle sensory attribute,6.1.2.2 Accurately identify and quantify a single sensoryattribute within a simple or complex sample,6.1.2.3 Accurately record changes in sensations as theyoccur,6.1.2.4 Perform consistently,6.1.2.5 Perform all test procedures with appropriate motorskills (for example, ability
27、to chew gum while manipulating theinput device to indicate the intensity of the mint flavor).6.1.3 Compared to other descriptive methods, T-I panelistsrequire more skills to complete the time-intensity task. Due tothe complexity of the method and techniques involved, finalselection of panelists may
28、not occur until after completion ofthe training.6.2 Time-Intensity Panel Training:6.2.1 The purpose of T-I training is to demonstrate how toperform the physical, mental and psychological tasks associ-ated with temporal profile method. Training begins with anorientation to the T-I method. Orientation
29、 to the methodinvolves explanation and demonstration of the temporal natureof sensory properties, utilizing products having diverse tempo-ral profiles. General time-intensity concepts may be illustratedby showing examples from alternate sensory modalities.Sound, light, odor, taste, touch/pressure or
30、 texture may alldisplay temporal properties.6.2.2 During training, panelists are thoroughly familiarizedwith all testing equipment and procedures.6.2.3 The purpose of training samples is to demonstratedifferent onset, plateau, or duration characteristics. These areoften best presented in contrasting
31、 pairs or sets. One exampleis a set of chewing gums, one with a fast flavor onset, anotherwith a slower onset. Another example is a series of margarineproducts that demonstrate different textural properties, such asrate of melt.6.2.4 References are samples that demonstrate an attributeat a given int
32、ensity. Use of references to calibrate intensity3The boldface numbers given in parentheses refer to a list of references at theend of the text.NOTE 1Based on a figure from Ref (1).FIG. 1 Representative Time-Intensity Curve with Selected Param-eters LabeledE1909 13 (2017)2ratings occurs prior to the
33、test. This is critical because in T-Ianalysis, attribute intensity is recorded without interruptionduring the test.6.3 Panel Performance Monitoring and Feedback6.3.1 Monitor panelist performance during the training andevaluation sessions. At the start of the study, determine anacceptable level of in
34、dividual and group performance. This caninclude deviation around a scale value at a specified time pointor similar indicator. STP 758 (3) provides statistical proceduressuitable for monitoring panelist performance.6.3.2 Panelists should be able to demonstrate consistency intheir evaluations. One app
35、roach is to measure reproducibilityin selected curve parameters, for example, Imax,Tmax,Text,oftheir individual T-I curves. However, consistency with otherpanelists is less likely than with general descriptive analysis, aseach panelist tends to produce distinctive curve shapes. In T-Ianalysis, withi
36、n-panelist consistency, particularly in their abil-ity to communicate relative differences among samples, ismore important than panelist-to-panelist agreement. See dis-cussion in Section 9.6.3.3 One parameter that should show some degree ofagreement among the panelists is Imax, particularly if refer
37、encestandards for intensity are being utilized. The Imaxvalue can beused to compare panelist performance with an appropriatemeans-separation test, percent standard deviation, or otheranalysis methods commonly used in monitoring descriptiveevaluations.7. Panel Protocol7.1 Specifics of the actual mana
38、gement of a time-intensitypanel are highly dependent upon study objectives. The follow-ing topics represent major steps or considerations in the designand execution of time-intensity panels. It is assumed that basicpanel training on the product of interest and selection of theappropriate data collec
39、tion device have been completed (seeSections 6 and 8, respectively).7.1.1 Design ConsiderationsBefore the panel isconducted, the following sample, experimental design, andset-up issues are resolved:7.1.1.1 The first consideration in designing a time-intensitypanel is to determine the length of time
40、for data collection. Itcan be relatively short, like the meltdown of a pat of butterwhen placed in the mouth, or relatively long, like the longevityof mint flavor in a chewing gum.7.1.1.2 Knowing the expected duration, and designing thestudy to cover critical changes in a product is prerequisite too
41、ther design considerations. The number of sampling pointsand the time interval between points is set to capture thechanges in an attribute at the time it occurs. Factors which mayaffect the duration of the attribute to be measured include:sample form (crystalline versus dilute solution of sugar),sam
42、ple size (larger amount of sample versus smaller amount ofsample), evaluation technique (dissolving versus chewing ahard candy), and other materials (water hardness for soaps andshampoos).7.1.2 The number of samples evaluated in a panel session isprimarily dependent upon the duration of the time-int
43、ensitysensation. If the evaluation of a chewing gum is designed tomeasure mint flavor intensity changes over a 20 min period,one to two samples may be the maximum number panelists canevaluate without excessive physical or mental fatigue.Conversely, 5 to 6 potato chips may be evaluated for durationof
44、 crisp/crunchy attributes before fatigue sets in.7.1.3 If the test is designed to measure the perception of anattribute to extinction, there is generally no need for lengthywaiting periods between samples. However, a longer waitingperiod is required when the perception of an attribute isaffected by
45、a preceding sample. Examples include: allowingmouth temperature to return to normal after ice creamevaluations, and recovery from numbing effects due to mentholor spices.7.1.4 Sample presentation order may be randomized, fixed,balanced, or presented as an incomplete block, depending onstudy objectiv
46、es. Typically, samples are presented in a bal-anced order to minimize position bias, context effects, etc. asrecommended for most sensory evaluations. During training,samples may be presented in fixed order (that is, all panelistssee the same samples in the same order of presentation), tofacilitate
47、discussion and learning.7.2 Data Collection ConsiderationsIn any time-intensityexperiment, regardless of the type of data collection deviceused, the rate at which information is collected must bedetermined. Data recording intervals are set to capturemaximum/critical change on a products profile, wit
48、h intensityratings collected at various time points depending on the studyobjective (see Sections 8 and 9).7.3 Sample PreparationAs with any sensory evaluation,sample preparation and presentation for T-I analysis need to becontrolled to eliminate extraneous effects. Recommendedguidelines are to be f
49、ollowed (Manual 26) (4).7.3.1 Reference SamplesIf appropriate in the test design,use of reference samples is recommended. References areevaluated prior to test samples, so that test sample evaluation isconducted without interruption. References are evaluated bythe same technique as the test samples and may be used tospecify an attributes intensity at a specific point in time.7.3.2 Conditioning SampleUse of a conditioning sample,presented prior to the actual test sample, can be used tocalibrate panelists to the same sensation, and to some extent, tocontrol f
