ASTM F1416-96(2008)
(Guide)Standard Guide for Selection of Time-Temperature Indicators
Standard Guide for Selection of Time-Temperature Indicators
SIGNIFICANCE AND USE
Expiration dates are often marked on the packages of perishable products to indicate the presumed end of their shelf lives. Since the shelf lives of most perishable products are temperature dependent, the expiration date is determined by assuming the product will be kept within a prescribed temperature range for its entire life. A problem with this method is that there is no way to determine if the shelf life of a product has been shortened by exposure to a higher temperature. A time-temperature indicator solves this problem when attached to the package because it reaches its end point sooner when exposed to a higher temperature.
In order to directly indicate the end of the shelf life, the time-temperature indicator characteristics should be matched as closely as possible to the quality characteristics of the product. When kept at the standard storage temperature for the product, the indicator should reach its end point at the same time as the product's shelf life. In addition, to determine the accuracy of the match at other temperatures, the change of shelf life with temperature should be known for both the product and the indicator. The Arrhenius relationship is a common and convenient method of describing the change of shelf life with temperature. In cases where it is not applicable, individual time-temperature points for the product may be established and an approximate correlation with the TTI obtained.
When attached to the package of a perishable product, a time-temperature indicator may supplement, or in some cases replace, the expiration date code. The addition of a TTI provides a greater level of confidence that the perishable product is within its shelf life because it responds to the actual temperature conditions to which the product has been exposed.
In the case of minimally processed refrigerated foods, the rapid growth of pathogenic bacteria at elevated temperatures may pose a serious health hazard even before the deterioration of the quality of ...
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.
General Information
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Standards Content (Sample)
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Designation: F1416 − 96(Reapproved 2008)
Standard Guide for
Selection of Time-Temperature Indicators
This standard is issued under the fixed designation F1416; 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 the shelf life of a product is known at two temperatures, the
activation energy is given by the following formula:
1.1 This guide covers information on the selection of
commercially available time-temperature indicators (TTIs) for ln LIFE /LIFE
~ !
1 2
E 5 3R (1)
a
noninvasive external package use on perishable products, such
1 1
as food and pharmaceuticals. When attached to the package of
T T
1 2
a perishable product, TTIs are used to measure the combined
where LIFE and LIFE = shelf lives at temperatures
1 2
time and temperature history of the product in order to predict
T and T .
1 2
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
2.1.2 all-temperature time-temperature indicator— a TTI
perishableproducttodeterminetheshelflifeofaproductatthe
that continues to change at some rate at all temperatures.
appropriate temperatures and to consult with the indicator
2.1.3 Arrhenius plot—aplotofthelogarithmoftheshelflife
manufacturer to select the available indicator which most
of a product versus the reciprocal of temperature (1\T).
closely matches the quality of the product as a function of time
2.1.3.1 Discussion—If the shelf life of a product exhibits
and temperature.
Arrhenius behavior, then anArrhenius plot of the shelf life will
NOTE 1—Besides time-temperature indicator, TTI is also an abbrevia-
beastraightline.Theactivationenergyoftheshelflifeisequal
tion for time-temperature monitor and time-temperature integrator.
to the slope of the line times R (see 2.1.1.1). It is more accurate
1.2 Time-temperature indicators may be integrated into a
to use a regression analysis to determine the slope based on the
Hazard Analysis and Critical Control Point (HACCP) plan.
data from at least three temperatures than to use only two
Appropriate instructions should be established for handling
points as in the previous equation. A blank Arrhenius plot is
products for which either the indicator has signaled the end of
shown in Fig. 1.The plot axes are the log of the shelf life and
usable shelf life or the shelf life of the product at its normal
the reciprocal of temperature. For ease of use, the Fahrenheit
storage temperature has been reached.
and Celsius temperatures are shown on the graph instead of the
1.3 This standard does not purport to address all of the
inverse temperature.
safety concerns, if any, associated with its use. It is the
2.1.4 Arrhenius relationship—a relationship that describes
responsibility of the user of this standard to establish appro-
the dependence of the rate of a chemical reaction on tempera-
priate safety and health practices and determine the applica-
ture as follows:
bility of regulatory limitations prior to use.
E
a
k 5 A e 2 (2)
S D
2. Terminology 0
RT
2.1 Definitions:
where:
2.1.1 activation energy—the quantity commonly used to
k = rate constant,
describe the dependence of the shelf life of a product (or the
A = constant with the same time units as k,
rate of a reaction) on temperature, as given by the Arrhenius
T = temperature, K (°C + 273), and
relationship.
R = universal gas constant.
2.1.1.1 Discussion—The higher the activation energy, the
When R = 0.001987 kcal/(mol · deg), the activation energy,
more the shelf life of a product changes with temperature. If
E , is given in units of kcal/mol.
a
When R = 0.00831 kJ/(mol · deg), the activation energy, E ,
a
is given in units of kJ/mol.
This guide is under the jurisdiction of ASTM Committee F02 on Flexible
Barrier Packaging and is the direct responsibility of Subcommittee F02.15 on
2.1.4.1 Discussion—This relationship also describes the de-
Chemical/Safety Properties.
pendence of the shelf life of many TTIs and perishable
Current edition approved Oct. 1, 2008. Published November 2008. Originally
productsontheeffectiveaveragetemperaturetowhichtheyare
approved in 1996. Last previous edition approved in 2003 as F1416 – 96(2003).
DOI: 10.1520/F1416-96R08. exposed. Since the shelf life is the time for the reaction to
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1416 − 96 (2008)
develops. It may be desirable to indicate even short occur-
rences of undesirably high temperatures. Other changes may
also occur, such as in color, texture, or rancidity, which render
a product unacceptable for its original use. For most perishable
products, the shelf life decreases with increasing temperature.
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.
NOTE 1—This blank graph may be used to determine if the shelf life of
a product exhibits standardArrhenius behavior.The plot axes are the log
10 2.1.12 time-temperature monitor—see time-temperature in-
of the shelf life and the reciprocal of temperature. Note that the X-axis of
dicator.
this plot is marked in Celsius degrees instead of inverse Kelvin degrees,
so that the spacing between degrees is not uniform. For ease of use, the
2.2 Definitions of Terms Specific to This Standard:
Fahrenheit and Celsius temperatures are shown on the graph instead of the
2.2.1 activation method—the method by which an inactive
inverse temperature. To use, plot the shelf life of the product at
TTI is changed to an active state.
temperatures for which it is known. If the shelf life follows theArrhenius
2.2.1.1 Discussion—This may include a physical activation
relationship, the points can be connected with a straight line. The
method, such as removing or breaking a barrier, or may require
activation energy may be calculated by the equation in 2.1.1.1.
FIG. 1 Blank Arrhenius Plot
raising the temperature to the normal operating range of the
TTI.
2.2.2 inactive state—the state in which a TTI does not
proceed to a specific extent, theArrhenius relationship for shelf
respond to changes in temperature over time.
life is given by the following formula:
2.2.2.1 Discussion—Some types of indicators are active
E
a
when manufactured and kept essentially inactive by storage at
LIFE 5 Be (3)
S D
RT
low temperatures.
where B = constant with the same time units as LIFE.
2.2.3 slackened-out product—a product that is stored frozen
2.1.5 dual function time-temperature indicator— a TTI that for an indeterminate time and then thawed (slackened out) for
combines both all-temperature and threshold-temperature re- the final part of its distribution and use.
sponses, overlaid in a single indicator in order to modify the
total time-temperature response. 3. Significance and Use
2.1.6 effective average temperature—the single constant
3.1 Expiration dates are often marked on the packages of
temperature that would have the same effect on the shelf life of
perishable products to indicate the presumed end of their shelf
a product as the actual temperature profile has for the same
lives. Since the shelf lives of most perishable products are
time period.
temperature dependent, the expiration date is determined by
assuming the product will be kept within a prescribed tempera-
2.1.7 hazard analysis and critical control points
ture range for its entire life.Aproblem with this method is that
(HACCP)—a method to control food quality and safety by
there is no way to determine if the shelf life of a product has
identifying and controlling those processing and distribution
been shortened by exposure to a higher temperature. A time-
steps where a food safety hazard may be prevented, eliminated,
temperature indicator solves this problem when attached to the
or reduced to acceptable levels.
package because it reaches its end point sooner when exposed
2.1.8 shelf life—the time required for various changes to a
to a higher temperature.
product to accumulate to the point where the product no longer
meets predetermined criteria and is no longer considered 3.2 In order to directly indicate the end of the shelf life, the
suitable for its original purpose. time-temperature indicator characteristics should be matched
2.1.8.1 Discussion—In some cases, such as where patho- as closely as possible to the quality characteristics of the
genic microbial growth is involved, there may be a serious product. When kept at the standard storage temperature for the
health risk in using a product past its shelf life. In such cases, product, the indicator should reach its end point at the same
the shelf life to be monitored should be conservative enough so time as the product’s shelf life. In addition, to determine the
that its expiration is signaled well before a health concern accuracy of the match at other temperatures, the change of
F1416 − 96 (2008)
shelf life
...
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