1、Designation: F 1416 96 (Reapproved 2008)Standard Guide forSelection of Time-Temperature Indicators1This standard is issued under the fixed designation F 1416; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. 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 information on the selection ofcommercially available time-temperature indicators (TTIs) fornoninvasive external
3、 package use on perishable products, suchas food and pharmaceuticals. When attached to the package ofa perishable product, TTIs are used to measure the combinedtime and temperature history of the product in order to predictthe remaining shelf life of the product or to signal the end of itsusable she
4、lf life. It is the responsibility of the processor of theperishable product to determine the shelf life of a product at theappropriate temperatures and to consult with the indicatormanufacturer to select the available indicator which mostclosely matches the quality of the product as a function of ti
5、meand temperature.NOTE 1Besides time-temperature indicator, TTI is also an abbrevia-tion for time-temperature monitor and time-temperature integrator.1.2 Time-temperature indicators may be integrated into aHazard Analysis and Critical Control Point (HACCP) plan.Appropriate instructions should be est
6、ablished for handlingproducts for which either the indicator has signaled the end ofusable shelf life or the shelf life of the product at its normalstorage temperature has been reached.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is the
7、responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Definitions:2.1.1 activation energythe quantity commonly used todescribe the dependence of the shelf life of a p
8、roduct (or therate of a reaction) on temperature, as given by the Arrheniusrelationship.2.1.1.1 DiscussionThe higher the activation energy, themore the shelf life of a product changes with temperature. Ifthe shelf life of a product is known at two temperatures, theactivation energy is given by the f
9、ollowing formula:Ea5lnLIFE1/LIFE2!1T121T23 R (1)where LIFE1and LIFE2= shelf lives at temperatures T1and T2.2.1.2 all-temperature time-temperature indicatora TTIthat continues to change at some rate at all temperatures.2.1.3 Arrhenius plota plot of the logarithm of the shelflife of a product versus t
10、he reciprocal of temperature (1T).2.1.3.1 DiscussionIf the shelf life of a product exhibitsArrhenius behavior, then an Arrhenius plot of the shelf life willbe a straight line. The activation energy of the shelf life is equalto the slope of the line times R (see 2.1.1.1). It is more accurateto use a
11、regression analysis to determine the slope based on thedata from at least three temperatures than to use only twopoints as in the previous equation. A blank Arrhenius plot isshown in Fig. 1. The plot axes are the log10of the shelf life andthe reciprocal of temperature. For ease of use, the Fahrenhei
12、tand Celsius temperatures are shown on the graph instead of theinverse temperature.2.1.4 Arrhenius relationshipa relationship that describesthe dependence of the rate of a chemical reaction on tempera-ture as follows:k 5 A0e 2SEaRTD(2)where:k = rate constant,A0= constant with the same time units as
13、k,T = temperature, K (C + 273), andR = universal gas constant.When R = 0.001987 kcal/(mol deg), the activation energy,Ea, is given in units of kcal/mol.When R = 0.00831 kJ/(mol deg), the activation energy, Ea,is given in units of kJ/mol.2.1.4.1 DiscussionThis relationship also describes thedependenc
14、e of the shelf life of many TTIs and perishableproducts on the effective average temperature to which they areexposed. Since the shelf life is the time for the reaction toproceed to a specific extent, theArrhenius relationship for shelflife is given by the following formula:1This guide is under the
15、jurisdiction of ASTM Committee F02 on FlexibleBarrier Packaging and is the direct responsibility of Subcommittee F02.15 onChemical/Safety Properties.Current edition approved Oct. 1, 2008. Published November 2008. Originallyapproved in 1996. Last previous edition approved in 2003 as F 1416 96(2003).1
16、Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.LIFE 5 BeSEaRTD(3)where B = constant with the same time units as LIFE.2.1.5 dual function time-temperature indicator a TTI thatcombines both all-temperature and threshold-temperature re-
17、sponses, overlaid in a single indicator in order to modify thetotal time-temperature response.2.1.6 effective average temperaturethe single constanttemperature that would have the same effect on the shelf life ofa product as the actual temperature profile has for the sametime period.2.1.7 hazard ana
18、lysis and critical control points(HACCP)a method to control food quality and safety byidentifying and controlling those processing and distributionsteps where a food safety hazard may be prevented, eliminated,or reduced to acceptable levels.2.1.8 shelf lifethe time required for various changes to ap
19、roduct to accumulate to the point where the product no longermeets predetermined criteria and is no longer consideredsuitable for its original purpose.2.1.8.1 DiscussionIn some cases, such as where patho-genic microbial growth is involved, there may be a serioushealth risk in using a product past it
20、s shelf life. In such cases,the shelf life to be monitored should be conservative enough sothat its expiration is signaled well before a health concerndevelops. It may be desirable to indicate even short occur-rences of undesirably high temperatures. Other changes mayalso occur, such as in color, te
21、xture, or rancidity, which rendera product unacceptable for its original use. For most perishableproducts, the shelf life decreases with increasing temperature.2.1.9 threshold-temperature time-temperature indicatoraTTI that only changes at temperatures above a specific thresh-old.2.1.10 time-tempera
22、ture indicator (TTI)a device that canbe affixed to the package of a perishable product and thatexhibits a change in a physically measurable or visuallymeasurable property as a combined function of both time andtemperature. For example, properties that change include color,light reflectance, or a mov
23、ing boundary between two colors.2.1.11 time-temperature integratorsee time-temperatureindicator.2.1.11.1 DiscussionThis term emphasizes the fact that theindicators response is an integration of the effects of both timeand temperature.2.1.12 time-temperature monitorsee time-temperature in-dicator.2.2
24、 Definitions of Terms Specific to This Standard:2.2.1 activation methodthe method by which an inactiveTTI is changed to an active state.2.2.1.1 DiscussionThis may include a physical activationmethod, such as removing or breaking a barrier, or may requireraising the temperature to the normal operatin
25、g range of theTTI.2.2.2 inactive statethe state in which a TTI does notrespond to changes in temperature over time.2.2.2.1 DiscussionSome types of indicators are activewhen manufactured and kept essentially inactive by storage atlow temperatures.2.2.3 slackened-out producta product that is stored fr
26、ozenfor an indeterminate time and then thawed (slackened out) forthe final part of its distribution and use.3. Significance and Use3.1 Expiration dates are often marked on the packages ofperishable products to indicate the presumed end of their shelflives. Since the shelf lives of most perishable pr
27、oducts aretemperature dependent, the expiration date is determined byassuming the product will be kept within a prescribed tempera-ture range for its entire life. A problem with this method is thatthere is no way to determine if the shelf life of a product hasbeen shortened by exposure to a higher t
28、emperature. A time-temperature indicator solves this problem when attached to thepackage because it reaches its end point sooner when exposedto a higher temperature.3.2 In order to directly indicate the end of the shelf life, thetime-temperature indicator characteristics should be matchedas closely
29、as possible to the quality characteristics of theproduct. When kept at the standard storage temperature for theproduct, the indicator should reach its end point at the sametime as the products shelf life. In addition, to determine theaccuracy of the match at other temperatures, the change ofshelf li
30、fe with temperature should be known for both theproduct and the indicator. The Arrhenius relationship is acommon and convenient method of describing the change ofshelf life with temperature. In cases where it is not applicable,NOTE 1This blank graph may be used to determine if the shelf life ofa pro
31、duct exhibits standardArrhenius behavior. The plot axes are the log10of the shelf life and the reciprocal of temperature. Note that the X-axis ofthis plot is marked in Celsius degrees instead of inverse Kelvin degrees,so that the spacing between degrees is not uniform. For ease of use, theFahrenheit
32、 and Celsius temperatures are shown on the graph instead of theinverse temperature. To use, plot the shelf life of the product attemperatures for which it is known. If the shelf life follows the Arrheniusrelationship, the points can be connected with a straight line. Theactivation energy may be calc
33、ulated by the equation in 2.1.1.1.FIG. 1 Blank Arrhenius PlotF 1416 96 (2008)2individual time-temperature points for the product may beestablished and an approximate correlation with the TTIobtained.3.3 When attached to the package of a perishable product, atime-temperature indicator may supplement,
34、 or in some casesreplace, the expiration date code. The addition of a TTIprovides a greater level of confidence that the perishableproduct is within its shelf life because it responds to the actualtemperature conditions to which the product has been exposed.3.4 In the case of minimally processed ref
35、rigerated foods,the rapid growth of pathogenic bacteria at elevated tempera-tures may pose a serious health hazard even before thedeterioration of the quality of the product becomes apparent tothe consumer. In this case, an expiration date may be used forstorage at the standard temperature, while a
36、threshold-temperature TTI is used to indicate the exposure to tempera-tures at which growth becomes measurable. It is also possibleto use a dual-function TTI, in which case the standard TTIwould indicate the shelf life at the correct storage temperaturewhile the threshold-temperature part would indi
37、cate the expo-sure to higher temperatures.4. Methods of Classification4.1 Temperature Response:4.1.1 All Temperature Active at all temperatures. Theseindicators are most applicable for products that have anArrhenius shelf life versus temperature relationship, such asmany fresh and processed foods.4.
38、1.2 Threshold TemperatureActive at temperaturesabove a threshold. These indicators are most applicable forslackened-out products, in order to respond only during thetime when the product is not frozen. They are also useful forminimally processed refrigerated foods to indicate that aproduct has been
39、exposed to abusive temperatures.4.1.3 Dual Function A combination of the previous types.This type of indicator may be used to respond slowly when theproduct is in the frozen state and to jump to a much fasterresponse curve in the temperature range where the product isthawed. For minimally processed
40、refrigerated foods, this typeof indicator can be used to indicate the remaining shelf lifewhen the product has been kept at the proper storage tempera-ture and to signal the end of shelf life more rapidly at abusivetemperatures.4.2 Reading Method:4.2.1 Instrument ReadableIntended to be scanned instr
41、u-mentally. A computer (normally hand held) calculates theremaining shelf life of a product based on the state of theindicator. The shelf life history of the product may be main-tained in a database file in the computers memory.4.2.2 Visually ReadableIntended to be interpreted visu-ally. This type o
42、f indicator may be constructed either to showjust the end point of the shelf life or to show a few levels ofprogression to the end point.4.3 FormAll forms of TTIs should be produced with ameans of attaching to a perishable products package.4.3.1 Bar CodeInstrument readable TTI in which both theindic
43、ator and auxiliary information are printed in bar codedform. The remaining shelf life of the product is calculated bya hand-held computer.4.3.2 Bulls-EyeVisually readable TTI in which the end ofthe shelf life is indicated when the printed center dot is thesame color as an outer reference ring or in
44、which the state ofthe product is determined by comparing the indicator color tomultiple colors surrounding the center dot.4.3.3 Window-in-Pouch Visually readable TTI in whichthe state of the product is determined by comparing the colorof an indicator liquid behind a window to the reference color orc
45、olors on the plastic pouch containing the liquid.4.3.4 Sandwiched Rectangular WickVisually readableTTI in which the state of the product is determined by amoving color boundary. The boundary is viewed and measuredthrough multiple holes in the outer layer.4.3.5 Special Graphics Printable, visually re
46、adable TTIsproduced in alternate forms containing specific logos andgraphics.4.3.6 Other Forms TTIs that use a physical property otherthan color to indicate the status of the shelf life.5. Selection Criteria5.1 Product Shelf-Life CharacterizationIt is the responsi-bility of the processor of the peri
47、shable product to determinethe relevant time-temperature dependent characteristics of theproduct to be correlated with the indicator characteristics. Inorder to specify the appropriate time-temperature indicator fora product, information is needed on the shelf life of theproduct. Where a perishable
48、product may pose a health riskafter its shelf life has expired, the indicators shelf lifeprediction must be conservative enough to ensure that theindicator will predict the end point well before a risk develops.The following information is required:5.1.1 Product Storage ConditionsThe product may bef
49、rozen, refrigerated, stored at ambient temperature, orslackened-out.5.1.2 Standard Storage Time and TemperatureThe shelflife of the product at the temperature at which it is intended tobe stored and used.5.1.3 Additional Time and Temperature ParametersTheshelf life shall be known for at least one other temperature if itis to be treated as an Arrhenius response, and it is desirable toknow the shelf life for at least three temperatures to verify thatthe behavior is Arrhenius. It is also sufficient to specify onetemperature point and t
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