ASTM F1416-96(2003)
(Guide)Standard Guide for Selection of Time-Temperature Indicators
Standard Guide for Selection of Time-Temperature Indicators
SCOPE
1.1 This guide covers information on the selection of commercially available time-temperature indicators (TTIs) for noninvasive external package use on perishable products, such as food and pharmaceuticals. When attached to the package of a perishable product, TTIs are used to measure the combined time and temperature history of the product in order to predict the remaining shelf life of the product or to signal the end of its usable shelf life. It is the responsibility of the processor of the perishable product to determine the shelf life of a product at the appropriate temperatures and to consult with the indicator manufacturer to select the available indicator which most closely matches the quality of the product as a function of time and temperature.
Note 1—Besides time-temperature indicator, TTI is also an abbreviation for time-temperature monitor and time-temperature integrator.
1.2 Time-temperature indicators may be integrated into a Hazard Analysis and Critical Control Point (HACCP) plan. Appropriate instructions should be established for handling products for which either the indicator has signaled the end of usable shelf life or the shelf life of the product at its normal storage temperature has been reached.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:F1416–96 (Reapproved 2003)
Standard Guide for
Selection of Time-Temperature Indicators
This standard is issued under the fixed designation F 1416; 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 (e) indicates an editorial change since the last revision or reapproval.
ln~LIFE /LIFE !
1. Scope
1 2
E 5 3 R (1)
a
1 1
1.1 This guide covers information on the selection of
T T
1 2
commercially available time-temperature indicators (TTIs) for
noninvasive external package use on perishable products, such where LIFE and LIFE = shelf lives at temperatures T and T .
1 2 1 2
as food and pharmaceuticals. When attached to the package of
2.1.2 all-temperature time-temperature indicator—a TTI
a perishable product, TTIs are used to measure the combined
that continues to change at some rate at all temperatures.
time and temperature history of the product in order to predict
2.1.3 Arrhenius plot—a plot of the logarithm of the shelf
the remaining shelf life of the product or to signal the end of its
life of a product versus the reciprocal of temperature (1\T).
usable shelf life. It is the responsibility of the processor of the
2.1.3.1 Discussion—If the shelf life of a product exhibits
perishableproducttodeterminetheshelflifeofaproductatthe
Arrhenius behavior, then anArrhenius plot of the shelf life will
appropriate temperatures and to consult with the indicator
be a straight line.The activation energy of the shelf life is equal
manufacturer to select the available indicator which most
to the slope of the line times R (see 2.1.1.1). It is more accurate
closely matches the quality of the product as a function of time
to use a regression analysis to determine the slope based on the
and temperature.
data from at least three temperatures than to use only two
points as in the previous equation. A blank Arrhenius plot is
NOTE 1—Besides time-temperature indicator, TTI is also an abbrevia-
shown in Fig. 1.The plot axes are the log of the shelf life and
tion for time-temperature monitor and time-temperature integrator.
the reciprocal of temperature. For ease of use, the Fahrenheit
1.2 Time-temperature indicators may be integrated into a
and Celsius temperatures are shown on the graph instead of the
Hazard Analysis and Critical Control Point (HACCP) plan.
inverse temperature.
Appropriate instructions should be established for handling
2.1.4 Arrhenius relationship—a relationship that describes
products for which either the indicator has signaled the end of
the dependence of the rate of a chemical reaction on tempera-
usable shelf life or the shelf life of the product at its normal
ture as follows:
storage temperature has been reached.
E
1.3 This standard does not purport to address all of the
a
k 5 A e 2 (2)
S D
RT
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
where:
priate safety and health practices and determine the applica-
k = rate constant,
bility of regulatory limitations prior to use.
A = constant with the same time units as k,
T = temperature, K (°C + 273), and
2. Terminology
R = universal gas constant.
2.1 Definitions:
When R = 0.001987 kcal/(mol · deg), the activation energy,
2.1.1 activation energy—the quantity commonly used to
E , is given in units of kcal/mol.
a
describe the dependence of the shelf life of a product (or the
When R = 0.00831 kJ/(mol · deg), the activation energy, E ,
a
rate of a reaction) on temperature, as given by the Arrhenius
is given in units of kJ/mol.
relationship.
2.1.4.1 Discussion—This relationship also describes the
2.1.1.1 Discussion—The higher the activation energy, the
dependence of the shelf life of many TTIs and perishable
more the shelf life of a product changes with temperature. If
products on the effective average temperature to which they are
the shelf life of a product is known at two temperatures, the
exposed. Since the shelf life is the time for the reaction to
activation energy is given by the following formula:
proceed to a specific extent, theArrhenius relationship for shelf
life is given by the following formula:
This guide is under the jurisdiction of ASTM Committee F02 on Flexible E
a
LIFE 5 Be (3)
S D
Barrier Materials and is the direct responsibility of Subcommittee F02.15 on
RT
Chemical/Safety Properties.
Current edition approved Feb. 10, 1996. Published April 1996. where B = constant with the same time units as LIFE.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1416–96 (2003)
2.1.9 threshold-temperature time-temperature indicator—a
TTI that only changes at temperatures above a specific thresh-
old.
2.1.10 time-temperature indicator (TTI)—a device that can
be affixed to the package of a perishable product and that
exhibits a change in a physically measurable or visually
measurable property as a combined function of both time and
temperature. For example, properties that change include color,
light reflectance, or a moving boundary between two colors.
2.1.11 time-temperature integrator—see time-temperature
indicator.
2.1.11.1 Discussion—This term emphasizes the fact that the
indicator’s response is an integration of the effects of both time
and temperature.
2.1.12 time-temperature monitor—see time-temperature in-
dicator.
2.2 Definitions of Terms Specific to This Standard:
2.2.1 activation method—the method by which an inactive
TTI is changed to an active state.
2.2.1.1 Discussion—This may include a physical activation
NOTE 1—This blank graph may be used to determine if the shelf life of
method, such as removing or breaking a barrier, or may require
a product exhibits standardArrhenius behavior.The plot axes are the log
of the shelf life and the reciprocal of temperature. Note that the X-axis of raising the temperature to the normal operating range of the
this plot is marked in Celsius degrees instead of inverse Kelvin degrees,
TTI.
so that the spacing between degrees is not uniform. For ease of use, the
2.2.2 inactive state—the state in which a TTI does not
Fahrenheit and Celsius temperatures are shown on the graph instead of the
respond to changes in temperature over time.
inverse temperature. To use, plot the shelf life of the product at
2.2.2.1 Discussion—Some types of indicators are active
temperatures for which it is known. If the shelf life follows theArrhenius
when manufactured and kept essentially inactive by storage at
relationship, the points can be connected with a straight line. The
activation energy may be calculated by the equation in 2.1.1.1. low temperatures.
FIG. 1 Blank Arrhenius Plot
2.2.3 slackened-out product—a product that is stored frozen
for an indeterminate time and then thawed (slackened out) for
the final part of its distribution and use.
2.1.5 dual function time-temperature indicator— a TTI that
3. Significance and Use
combines both all-temperature and threshold-temperature re-
sponses, overlaid in a single indicator in order to modify the
3.1 Expiration dates are often marked on the packages of
total time-temperature response.
perishable products to indicate the presumed end of their shelf
2.1.6 effective average temperature—the single constant
lives. Since the shelf lives of most perishable products are
temperature that would have the same effect on the shelf life of
temperature dependent, the expiration date is determined by
a product as the actual temperature profile has for the same
assuming the product will be kept within a prescribed tempera-
time period.
ture range for its entire life.Aproblem with this method is that
2.1.7 hazard analysis and critical control points
there is no way to determine if the shelf life of a product has
(HACCP)—a method to control food quality and safety by
been shortened by exposure to a higher temperature. A time-
identifying and controlling those processing and distribution
temperature indicator solves this problem when attached to the
steps where a food safety hazard may be prevented, eliminated,
package because it reaches its end point sooner when exposed
or reduced to acceptable levels.
to a higher temperature.
2.1.8 shelf life—the time required for various changes to a
3.2 In order to directly indicate the end of the shelf life, the
product to accumulate to the point where the product no longer
time-temperature indicator characteristics should be matched
meets predetermined criteria and is no longer considered
as closely as possible to the quality characteristics of the
suitable for its original purpose.
product. When kept at the standard storage temperature for the
2.1.8.1 Discussion—In some cases, such as where patho- product, the indicator should reach its end point at the same
genic microbial growth is involved, there may be a serious time as the product’s shelf life. In addition, to determine the
health risk in using a product past its shelf life. In such cases, accuracy of the match at other temperatures, the change of
the shelf life to be monitored should be conservative enough so shelf life with temperature should be known for both the
that its expiration is signaled well before a health concern product and the indicator. The Arrhenius relationship is a
develops. It may be desirable to indicate even short occur- common and convenient method of describing the change of
rences of undesirably high temperatures. Other changes may shelf life with temperature. In cases where it is not applicable,
also occur, such as in col
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