1、Designation: E1909 11E1909 13Standard 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 revision. A
2、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 analyzing time-intensity (T-I) evaluations of products or other sensorystimuli. Time-in
3、tensity is the measurement of the intensity of a single sensory sensation over time in response to a single exposureto a product or other sensory stimulus. Simultaneous evaluations of multiple sensory attributes are possible, although are outsideof the scope of this document. See bibliography Refere
4、nce List for more information.1.2 This guide utilizes a specially trained panel to measure the intensity of a single continuous sensation during the time frominitial 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
5、 in this guide include measuring:1.3.1 Multiple sensations,1.3.2 Multiple exposures within a single measurement, and1.3.3 Qualitative or hedonic changes in the perceived sensation.1.4 This guide includes protocols for the selection and training of judges, descriptions and use of physical data collec
6、tiondevices, and methods of data handling, summarization, and statistical analysis. Illustration of two different data handling andanalysis approaches are included in the appendixes.1.5 This guide is not applicable to measure product shelf life or stability that require evaluations at discrete time
7、intervals.overextended time.1.6 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 and health practices and determine the applicability of regulatorylimitations pr
8、ior to use.2. Referenced Documents2.1 ASTM Standards:2E253 Terminology Relating to Sensory Evaluation of Materials 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 under th
9、e curve.3.1.3 AUCarea under the curve.3.1.4 Imax or peak intensitymaximum observed intensity during the time of measurement.3.1.5 perimetermeasured distance of perimeter of area delineated by T-I curve.3.1.6 plateau timeplateauduration of peak intensity.1 This guide is under the jurisdiction of ASTM
10、 Committee E18 on Sensory Evaluation and is the direct responsibility of Subcommittee E18.03 on Sensory Theory andStatistics.Current edition approved April 1, 2011Oct. 1, 2013. Published May 2011October 2013. Originally approved in 1997. Last previous edition approved in 20032011 asE1909 97 (2003).E
11、1909 11. DOI: 10.1520/E1909-11.10.1520/E1909-13.2 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 Summary page on the ASTM website.This document
12、 is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been 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 appr
13、opriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.7 rate of increaserate of intensity increase before peak
14、intensity (slope).3.1.8 rate of decreaserate of intensity decrease after peak intensity (slope).3.1.9 Tdur or duration timetime from onset of sensation until it can no longer be perceived (Text Tonset).3.1.10 Text or time to extinctiontime from initial exposure to the stimulus (Tinit) until it can n
15、o longer be perceived.3.1.11 Tinittime of initial exposure to the stimulus, typically when the clock starts.3.1.12 Tmaxtime to reach maximum intensity of the sensation after exposure to the stimulus.3.1.13 Tonsettime point when the stimulus is first perceived after initial exposure to the stimulus.3
16、.1.14 Ttrun or truncated timetime until a specified minimum intensity or until a pre-determined time point has been reached.3.2 The graphical illustration of a typical time-intensity curve is shown in Fig. 1. The time increment may be seconds, minutes,hours, etc., depending upon the characteristic o
17、f the particular material under study.4. Summary of Guide4.1 This guide describes procedures utilizing specially trained panelists to measure the intensity of a single sensory sensationas it changes with time and the possible approaches to collect and analyze such data. Details on specific procedure
18、s are given inSections 6 9 of this guide. Examples of time-related evaluations are included in the Appendixes.appendixes.5. Significance and Use5.1 The purpose of time-intensity measurements is to establish the pattern of development and decline of a particular sensorycharacteristic under study. T-I
19、 evaluations are applicable when measurements at a single time point (an averaging process) are notsufficient to distinguish products that have very different temporal characteristics.As pointed out by Lee and Pangborn (2)3, “Thisaveraging process results in the masking or complete loss of important
20、 information such as rate of onset of stimulation, time andduration of maximum intensity, rate of decay of perceived intensity, time of extinction, and total duration of the entire process.”5.2 Products rated similarly using traditional single point techniques of product profiling may provide very d
21、ifferent temporalsensory experiences to the consumer. Acceptability of the product may be affected, and traditional descriptive methodology doesnot reflect the changes in an attributes intensity over time.5.3 T-I has applications for a variety of products. Examples include: food products, ranging fr
22、om short-term sweetness in abeverage to long-term elasticity in chewing gum; personal care products, measuring the development and longevity of shampoolather and the residual skin feel of a skin cream; household care products, monitoring the intensity of scents over time;pharmaceuticals, monitoring
23、skin cooling after application of a topical analgesic. Auditory signals or visual changes in productscan also be evaluated by the T-I technique.6. Time-Intensity Panel Selection and Training6.1 Screening and Selection of Panelists3 The boldface numbers given in parentheses refer to a list of referen
24、ces at the end of the text.NOTE 1Based on a figure from Ref (1).FIG. 1 Representative Time-Intensity Curve with Selected Parameters LabeledE1909 1326.1.1 Time-Intensity evaluation is a specialized type of descriptive analysis.Therefore, use of randomly selected, naive panelistsis neither appropriate
25、 nor recommended. Panelists selected for Time-Intensity studies are screened as recommended for otherdescriptive methods (see STP 758 (3). Use of panelists with previous descriptive training facilitates the T-I training because thesepanelists are competent in both recognizing and intensity scaling a
26、n attribute.6.1.2 The goal of the selection process is to identify panelists who have the ability to:6.1.2.1 Continually focus on a single sensory attribute,6.1.2.2 Accurately identify and quantify a single sensory attribute within a simple or complex sample,6.1.2.3 Accurately record changes in sens
27、ations as they occur,6.1.2.4 Perform consistently,6.1.2.5 Perform all test procedures with appropriate motor skills (for example, ability to chew gum while manipulating the inputdevice to indicate the intensity of the mint flavor).6.1.3 Compared to other descriptive methods, T-I panelists require mo
28、re skills to complete the time-intensity task. Due to thecomplexity of the method and techniques involved, final selection of panelists may not occur until after completion of the training.6.2 Time-Intensity Panel Training:6.2.1 The purpose of T-I training is to demonstrate how to perform the physic
29、al, mental and psychological tasks associated withtemporal profile method. Training begins with an orientation to the T-I method. Orientation to the method involves explanation anddemonstration of the temporal nature of sensory properties, utilizing products having diverse temporal profiles. General
30、time-intensity concepts may be illustrated by showing examples from alternate sensory modalities. Sound, light, odor, taste,touch/pressure or texture may all display temporal properties.6.2.2 During training, panelists are thoroughly familiarized with all testing equipment and procedures.6.2.3 The p
31、urpose of training samples is to demonstrate different onset, plateau, or duration characteristics. These are often bestpresented in contrasting pairs or sets. One example is a set of chewing gums, one with a fast flavor onset, another with a sloweronset. Another example is a series of margarine pro
32、ducts that demonstrate different textural properties, such as rate of melt.6.2.4 References are samples that demonstrate an attribute at a given intensity. Use of references to calibrate intensity ratingsoccurs prior to the test. This is critical because in T-I analysis, attribute intensity is recor
33、ded without interruption during the test.6.3 Panel Performance Monitoring and Feedback6.3.1 Monitor panelist performance during the training and evaluation sessions.At the start of the study, determine an acceptablelevel of individual and group performance. This can include deviation around a scale
34、value at a specified time point or similarindicator. STP 758 (3) provides statistical procedures suitable for monitoring panelist performance.6.3.2 Panelists should be able to demonstrate consistency in their evaluations. One approach is to measure reproducibility inselected curve parameters, for ex
35、ample, Imax, Tmax, Text, of their individual T-I curves. However, consistency with other panelistsis less likely than with general descriptive analysis, as each panelist tends to produce distinctive curve shapes. In T-I analysis,within-panelist consistency, particularly in their ability to communica
36、te relative differences among samples, is more important thanpanelist-to-panelist agreement. See discussion in Section 9.6.3.3 One parameter that should show some degree of agreement among the panelists is Imax, particularly if reference standardsfor intensity are being utilized. The Imax value can
37、be used to compare panelist performance with an appropriate means-separationtest, percent standard deviation, or other analysis methods commonly used in monitoring descriptive evaluations.7. Panel Protocol7.1 Specifics of the actual management of a time-intensity panel are highly dependent upon stud
38、y objectives. The followingtopics represent major steps or considerations in the design and execution of time-intensity panels. It is assumed that basic paneltraining on the product of interest and selection of the appropriate data collection device have been completed (see Sections 6 and8, respecti
39、vely).7.1.1 Design ConsiderationsBefore the panel is conducted, the following sample, experimental design, and set-up issues areresolved:7.1.1.1 The first consideration in designing a time-intensity panel is to determine the length of time for data collection. It canbe relatively short, like the mel
40、tdown of a pat of butter when placed in the mouth, or relatively long, like the longevity of mintflavor in a chewing gum.7.1.1.2 Knowing the expected duration, and designing the study to cover critical changes in a product is prerequisite to otherdesign considerations. The number of sampling points
41、and the time interval between points is set to capture the changes in anattribute at the time it occurs. Factors which may affect the duration of the attribute to be measured include: sample form(crystalline versus dilute solution of sugar), sample size (larger amount of sample versus smaller amount
42、 of sample), evaluationtechnique (dissolving versus chewing a hard candy), and other materials (water hardness for soaps and shampoos).7.1.2 The number of samples evaluated in a panel session is primarily dependent upon the duration of the time-intensitysensation. If the evaluation of a chewing gum
43、is designed to measure mint flavor intensity changes over a 20 min period, one totwo samples may be the maximum number panelists can evaluate without excessive physical or mental fatigue. Conversely, 5 to6 potato chips may be evaluated for duration of crisp/crunchy attributes before fatigue sets in.
44、E1909 1337.1.3 If the test is designed to measure the perception of an attribute to extinction, there is generally no need for lengthy waitingperiods between samples. However, a longer waiting period is required when the perception of an attribute is affected by apreceding sample. Examples include:
45、allowing mouth temperature to return to normal after ice cream evaluations, and recoveryfrom numbing effects due to menthol or spices.7.1.4 Sample presentation order may be randomized, fixed, balanced, or presented as an incomplete block, depending on studyobjectives. Typically, samples are presente
46、d in a balanced order to minimize position bias, context effects, etc. as recommendedfor most sensory evaluations. During training, samples may be presented in fixed order (that is, all panelists see the same samplesin the same order of presentation), to facilitate discussion and learning.7.2 Data C
47、ollection ConsiderationsIn any time-intensity experiment, regardless of the type of data collection device used, therate at which information is collected must be determined. Data recording intervals are set to capture maximum/critical change ona products profile, with intensity ratings collected at
48、 various time points depending on the study objective (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. Recommended guidelines are to be followed (Manual 26)(4).7.3.1
49、 Reference SamplesIf appropriate in the test design, use of reference samples is recommended. References are evaluatedprior to test samples, so that test sample evaluation is conducted without interruption. References are evaluated by the sametechnique as the test samples and may be used to specify 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 to calibratepanelists to the same sensation, and to some extent, to control first position b
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