ASTM E1909-13(2017)
(Guide)Standard Guide for Time-Intensity Evaluation of Sensory Attributes
Standard Guide for Time-Intensity Evaluation of Sensory Attributes
SIGNIFICANCE AND USE
5.1 The purpose of time-intensity measurements is to establish the pattern of development and decline of a particular sensory characteristic under study. T-I evaluations are applicable when measurements at a single time point (an averaging process) are not sufficient to distinguish products that have very different temporal characteristics. As pointed out by Lee and Pangborn (2)3, “This averaging process results in the masking or complete loss of important information such as rate of onset of stimulation, time and duration 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 different temporal sensory experiences to the consumer. Acceptability of the product may be affected, and traditional descriptive methodology does not reflect the changes in an attribute's intensity over time.
5.3 T-I has applications for a variety of products. Examples include: food products, ranging from short-term sweetness in a beverage to long-term elasticity in chewing gum; personal care products, measuring the development and longevity of shampoo lather and the residual skin feel of a skin cream; household care products, monitoring the intensity of scents over time; pharmaceuticals, monitoring skin cooling after application of a topical analgesic. Auditory signals or visual changes in products can also be evaluated by the T-I technique.
SCOPE
1.1 This guide covers procedures for conducting and analyzing time-intensity (T-I) evaluations of products or other sensory stimuli. Time-intensity is the measurement of the intensity of a single sensory sensation over time in response to a single exposure to a product or other sensory stimulus. Simultaneous evaluations of multiple sensory attributes are possible, although are outside of the scope of this document. See Reference 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 from initial exposure:
1.2.1 To its extinction,
1.2.2 To a specified intensity, or
1.2.3 To a predetermined limit of time.
1.3 Applications not covered in this guide include measuring:
1.3.1 Multiple sensations,
1.3.2 Multiple exposures within a single measurement, and
1.3.3 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 collection devices, and methods of data handling, summarization, and statistical analysis. Illustration of two different data handling and analysis approaches are included in the appendixes.
1.5 This guide is not applicable to measure product shelf life or stability that require evaluations over extended time.
1.6 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, health and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1909 − 13 (Reapproved 2017)
Standard Guide for
Time-Intensity Evaluation of Sensory Attributes
This standard is issued under the fixed designation E1909; 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 ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This guide covers procedures for conducting and ana-
mendations issued by the World Trade Organization Technical
lyzing time-intensity (T-I) evaluations of products or other
Barriers to Trade (TBT) Committee.
sensory stimuli. Time-intensity is the measurement of the
intensity of a single sensory sensation over time in response to
2. Referenced Documents
a single exposure to a product or other sensory stimulus.
Simultaneous evaluations of multiple sensory attributes are 2.1 ASTM Standards:
possible, although are outside of the scope of this document. E253 Terminology Relating to Sensory Evaluation of Mate-
See Reference List for more information. rials and Products
1.2 This guide utilizes a specially trained panel to measure
3. Terminology
the intensity of a single continuous sensation during the time
from initial exposure: 3.1 Definitions of Terms Specific to This Standard: See Fig.
1.
1.2.1 To its extinction,
1.2.2 To a specified intensity, or 3.1.1 area after I —post-peak area under the curve.
max
1.2.3 To a predetermined limit of time.
3.1.2 area before I —pre-peak area under the curve.
max
1.3 Applications not covered in this guide include measur-
3.1.3 AUC—area under the curve.
ing:
3.1.4 I or peak intensity—maximum observed intensity
max
1.3.1 Multiple sensations,
during the time of measurement.
1.3.2 Multiple exposures within a single measurement, and
3.1.5 perimeter—measured distance of perimeter of area
1.3.3 Qualitative or hedonic changes in the perceived sen-
delineated by T-I curve.
sation.
3.1.6 plateau—duration of peak intensity.
1.4 This guide includes protocols for the selection and
3.1.7 rate of increase—rateofintensityincreasebeforepeak
training of judges, descriptions and use of physical data
intensity (slope).
collection devices, and methods of data handling,
summarization, and statistical analysis. Illustration of two
3.1.8 rate of decrease—rate of intensity decrease after peak
different data handling and analysis approaches are included in
intensity (slope).
the appendixes.
3.1.9 T or duration time—time from onset of sensation
dur
1.5 Thisguideisnotapplicabletomeasureproductshelflife until it can no longer be perceived (T –T ).
ext onset
or stability that require evaluations over extended time.
3.1.10 T or time to extinction—time from initial exposure
ext
1.6 This standard does not purport to address all of the to the stimulus (T ) until it can no longer be perceived.
init
safety concerns, if any, associated with its use. It is the
3.1.11 T —time of initial exposure to the stimulus, typi-
init
responsibility of the user of this standard to establish appro-
cally when the clock starts.
priate safety, health and environmental practices and deter-
3.1.12 T —time to reach maximum intensity of the sen-
max
mine the applicability of regulatory limitations prior to use.
sation after exposure to the stimulus.
1.7 This international standard was developed in accor-
3.1.13 T —time point when the stimulus is first per-
onset
dance with internationally recognized principles on standard-
ceived after initial exposure to the stimulus.
This guide is under the jurisdiction of ASTM Committee E18 on Sensory
Evaluation and is the direct responsibility of Subcommittee E18.03 on Sensory
Theory and Statistics. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2017. Published August 2017. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1997. Last previous edition approved in 2013 as E1909 – 13. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E1909-13R17. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1909 − 13 (2017)
5.3 T-I has applications for a variety of products. Examples
include: food products, ranging from short-term sweetness in a
beverage to long-term elasticity in chewing gum; personal care
products, measuring the development and longevity of sham-
poo lather and the residual skin feel of a skin cream; household
care products, monitoring the intensity of scents over time;
pharmaceuticals, monitoring skin cooling after application of a
topical analgesic. Auditory signals or visual changes in prod-
ucts can also be evaluated by the T-I technique.
6. Time-Intensity Panel Selection and Training
6.1 Screening and Selection of Panelists
6.1.1 Time-Intensity evaluation is a specialized type of
descriptive analysis. Therefore, use of randomly selected,
naive panelists is neither appropriate nor recommended. Pan-
elists selected for Time-Intensity studies are screened as
recommended for other descriptive methods (see STP758 (3)).
NOTE 1—Based on a figure from Ref (1).
Use of panelists with previous descriptive training facilitates
FIG. 1 Representative Time-Intensity Curve with Selected Param-
the T-I training because these panelists are competent in both
eters Labeled
recognizing and intensity scaling an attribute.
6.1.2 The goal of the selection process is to identify
3.1.14 T or truncated time—time until a specified mini-
trun
panelists who have the ability to:
mum intensity or until a pre-determined time point has been
6.1.2.1 Continually focus on a single sensory attribute,
reached.
6.1.2.2 Accurately identify and quantify a single sensory
3.2 The graphical illustration of a typical time-intensity
attribute within a simple or complex sample,
curve is shown in Fig. 1. The time increment may be seconds,
6.1.2.3 Accurately record changes in sensations as they
minutes, hours, etc., depending upon the characteristic of the
occur,
particular material under study.
6.1.2.4 Perform consistently,
6.1.2.5 Perform all test procedures with appropriate motor
4. Summary of Guide
skills(forexample,abilitytochewgumwhilemanipulatingthe
4.1 This guide describes procedures utilizing specially
input device to indicate the intensity of the mint flavor).
trained panelists to measure the intensity of a single sensory
6.1.3 Compared to other descriptive methods, T-I panelists
sensation as it changes with time and the possible approaches
require more skills to complete the time-intensity task. Due to
to collect and analyze such data. Details on specific procedures
the complexity of the method and techniques involved, final
are given in Sections 6–9 of this guide. Examples of
selection of panelists may not occur until after completion of
time-related evaluations are included in the appendixes.
the training.
6.2 Time-Intensity Panel Training:
5. Significance and Use
6.2.1 The purpose of T-I training is to demonstrate how to
5.1 The purpose of time-intensity measurements is to estab-
perform the physical, mental and psychological tasks associ-
lish the pattern of development and decline of a particular
ated with temporal profile method. Training begins with an
sensory characteristic under study. T-I evaluations are appli-
orientation to the T-I method. Orientation to the method
cable when measurements at a single time point (an averaging
involves explanation and demonstration of the temporal nature
process) are not sufficient to distinguish products that have
of sensory properties, utilizing products having diverse tempo-
very different temporal characteristics. As pointed out by Lee
ral profiles. General time-intensity concepts may be illustrated
and Pangborn (2) , “This averaging process results in the
by showing examples from alternate sensory modalities.
maskingorcompletelossofimportantinformationsuchasrate
Sound, light, odor, taste, touch/pressure or texture may all
of onset of stimulation, time and duration of maximum
display temporal properties.
intensity, rate of decay of perceived intensity, time of
6.2.2 During training, panelists are thoroughly familiarized
extinction, and total duration of the entire process.”
with all testing equipment and procedures.
5.2 Products rated similarly using traditional single point
6.2.3 The purpose of training samples is to demonstrate
techniques of product profiling may provide very different
different onset, plateau, or duration characteristics. These are
temporalsensoryexperiencestotheconsumer.Acceptabilityof
often best presented in contrasting pairs or sets. One example
the product may be affected, and traditional descriptive meth-
is a set of chewing gums, one with a fast flavor onset, another
odology does not reflect the changes in an attribute’s intensity
with a slower onset. Another example is a series of margarine
over time.
products that demonstrate different textural properties, such as
rate of melt.
6.2.4 References are samples that demonstrate an attribute
The boldface numbers given in parentheses refer to a list of references at the
end of the text. at a given intensity. Use of references to calibrate intensity
E1909 − 13 (2017)
ratings occurs prior to the test. This is critical because in T-I measure mint flavor intensity changes over a 20 min period,
analysis, attribute intensity is recorded without interruption onetotwosamplesmaybethemaximumnumberpanelistscan
during the test. evaluate without excessive physical or mental fatigue.
Conversely, 5 to 6 potato chips may be evaluated for duration
6.3 Panel Performance Monitoring and Feedback
of crisp/crunchy attributes before fatigue sets in.
6.3.1 Monitor panelist performance during the training and
7.1.3 If the test is designed to measure the perception of an
evaluation sessions. At the start of the study, determine an
attribute to extinction, there is generally no need for lengthy
acceptable level of individualandgroupperformance.Thiscan
waiting periods between samples. However, a longer waiting
include deviation around a scale value at a specified time point
period is required when the perception of an attribute is
orsimilarindicator.STP758 (3)providesstatisticalprocedures
affected by a preceding sample. Examples include: allowing
suitable for monitoring panelist performance.
mouth temperature to return to normal after ice cream
6.3.2 Panelists should be able to demonstrate consistency in
evaluations,andrecoveryfromnumbingeffectsduetomenthol
their evaluations. One approach is to measure reproducibility
or spices.
in selected curve parameters, for example, I ,T ,T ,of
max max ext
7.1.4 Sample presentation order may be randomized, fixed,
their individual T-I curves. However, consistency with other
balanced, or presented as an incomplete block, depending on
panelistsislesslikelythanwithgeneraldescriptiveanalysis,as
study objectives. Typically, samples are presented in a bal-
each panelist tends to produce distinctive curve shapes. In T-I
anced order to minimize position bias, context effects, etc. as
analysis, within-panelist consistency, particularly in their abil-
recommended for most sensory evaluations. During training,
ity to communicate relative differences among samples, is
samples may be presented in fixed order (that is, all panelists
more important than panelist-to-panelist agreement. See dis-
see the same samples in the same order of presentation), to
cussion in Section 9.
facilitate discussion and learning.
6.3.3 One parameter that should show some degree of
agreement among the panelists is I , particularly if reference
max 7.2 Data Collection Considerations—In any time-intensity
standards for intensity are being utilized.The I value can be
max experiment, regardless of the type of data collection device
used to compare panelist performance with an appropriate
used, the rate at which information is collected must be
means-separation test, percent standard deviation, or other
determined. Data recording intervals are set to capture
analysis methods commonly used in monitoring descriptive
maximum/critical change on a product’s profile, with intensity
evaluations.
ratings collected at various time points depending on the study
objective (see Sections 8 and 9).
7. Panel Protocol
7.3 Sample Preparation—As with any sensory evaluation,
7.1 Specifics of the actual management of a time-intensity
sample preparation and presentation forT-I analysis need to be
panel are highly dependent upon study objectives. The follow-
controlled to eliminate extraneous effects. Recommended
ing topics represent major steps or considerations in the design
guidelines are to be followed (Manual 26) (4).
and execution of time-intensity panels. It is assumed that basic
7.3.1 Reference Samples—If appropriate in the test design,
panel training on the product of interest and selection of the
use of reference samples is recommended. References are
appropriate data collection device have been completed (see
evaluatedpriortotestsamples,sothattestsampleevaluationis
Sections 6 and 8, respectively).
conducted without interruption. References are evaluated by
7.1.1 Design Considerations—Before the panel is
the same technique as the test samples and may be used to
conducted, the following sample, experimental design, and
specify an attribute’s intensity at a specific point in time.
set-up issues are resolved:
7.3.2 Conditioning Sample—Use of a conditioning sample,
7.1.1.1 The first consideration in designing a time-intensity
presented prior to the actual test sample, can be used to
panel is to determine the length of time for data collection. It
calibrate panelists to the same sensation, and to some extent, to
can be relatively short, like the meltdown of a pat of butter
control first position bias or context effects. Consideration
when placed in the mouth, or relatively long, like the longevity
should be given to adaptation, carryover, and fatigue in
of mint flavor in a chewing gum.
deciding whether or not to use a conditioning sample.
7.1.1.2 Knowing the expected duration, and designing the
7.3.3 Inter-Stimulus Procedures—Specify whether panelists
study to cover critical changes in a product is prerequisite to
are to rinse, re-taste reference standards, or use a palate
other design considerations. The number of sampling p
...
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