METHOD FOR SELECTING TIME-TEMPERATURE INDICATORS

Abstract: A method for a distributor to market time-temperature indicators or integrators (TTIs) to customers. The distributor maintains an Internet web site having performance characteristic specifications for each TTI of its product line. The performance characteristic specifications can be visual graphs of the time/temperature relationships of the TTIs at a range of time-outs and temperatures. The customer, knowing at least one time/temperature point for a particular product, can review the TTI performance specifications on the web site and select one or more TTIs having performance specifications which match the known time/temperature point. The customer can then request samples of the selected TTIs. Products with the sample TTIs can be subjected to shelf-life degradation tests to evaluate the suitability of the TTIs.

Description: METHOD FOR SELECTING TIME-TEMPERATURE INDICATORS BACKGROUND The present invention relates generally to time-temperature indicators. In particular, the invention relates to a method for selecting time-temperature indicators including performance characteristics suitable for particular products. Food and other perishable products are often marked with expiration dates to indicate either the presumed end of their usable shelf life or the freeze-by date. These expiration dates are typically determined on the assumption that the product will be stored within a standard storage temperature range (e.g., refrigerated) for its entire life. However, since the shelf life of most perishable products is both time and temperature dependant, the product may degrade to an unsuitable quality state sooner than the marked expiration date if it is exposed to temperatures higher than those of the standard storage range. The product may also degrade to an unsuitable quality if it is stored in the standard storage range, but for a longer time than is desired. Time-temperature indicators and integrators, also known as TTIs, are sometimes attached to the packages of perishable products to supplement, or in some cases replace, the expiration dates. These devices monitor the combined time and temperature history of the product. When the product monitored by the TTI has been subjected to a time and temperature history (known as the activation energy) corresponding to the expiration of the product shelf life, the device "times-out" by changing color or some other characteristic. TTIs can be used to estimate the remaining shelf life of the product or to indicate the end of the product's usable shelf life. Devices of these types are commercially available from a number of manufacturers or other distributors including 3M of St. Paul, Minnesota. Different types of food products exhibit a wide range of shelf lives and degrade at very different rates. The performance characteristics of a TTI (i.e., the length of time the device must be subjected to a given temperature before it will time-out) for a given food product must therefore be matched to the shelf life and degradation characteristics of the product. To accommodate this need, TTI distributors generally offer a line or set of TTIs, each of which has different performance characteristics. The food processor or other TTI customer must therefore select a TTI having performance characteristics which best match or correspond to the shelf life and degradation characteristics of the product to which the device is to be attached. A TTI suitable for a given product can be selected in one of several ways. If the customer knows the shelf life of its product at two different temperatures (i.e., there are two known life time/temperature points), the TTI from the distributor's available set which has a time-out/temperature relationship which extends through or intersects (i.e., matches) both the known life time/temperature points can be used. However, making accurate determinations of the known life time/temperature points can be difficult and time consuming since it requires relatively costly constant-temperature chambers and test procedures that the customers may not have. More commonly, the customer will know the shelf life of the product at only the proper storage temperature, and be generally unaware of the life time/temperature point at a higher temperature. Sometimes the TTIs are described as having performance characteristics suitable for certain types of food products (e.g., chicken, ground beef, lettuce, milk). While these published descriptions can be used to effectively eliminate the suitability of some TTIs that might otherwise have been considered if they had characteristics that matched the known shelf life point, these descriptions are sometimes very inconsistent. In general, published descriptions of these types of TTIs are of relatively limited use. Approaches for selecting TTIs are also presented in ASTM Designation F 1416. SUMMARY OF THE INVENTION The present invention is an efficient and accurate method for selecting a time-temperature indicator or integrator (TTI) suitable for a particular product from a set of TTIs having different performance characteristics. Only one known life time/temperature point for the product is required to perform the method, although the method can also be used if more than one life time/temperature point is known. One embodiment of the invention includes providing a performance characteristic specification for each TTI of the set. The performance characteristic specifications include information describing the TTI time/temperature relationship at a range of time-outs and temperatures. One or more TTIs having performance characteristic specifications with time/temperature relationships which match the known life time/temperature point are selected. If several TTIs are selected, samples of the TTIs can be applied to the product and the product subjected to a degradation test. The suitability of the selected TTIs can then be evaluated to select the TTI that best matches a suitable shelf-life curve of the product. This method can be performed in any of a number of different approaches. One implementation of the invention includes providing an Internet web site with visual graphs of the time/temperature relationships for each TTI of a distributor's product line. Using the graphs available over the distributor's web site and the known life time/temperature point, a customer can identify one or more suitable TTIs. The customer can then obtain samples of the identified TTIs for testing. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of the time/temperature relationships of a number of TTIs having a room temperature time-out of 7 hours. Figure 2 is a graph of the time/temperature relationships of a number of TTIs having a room temperature time-out of 12 hours. Figure 3 is a graph of the time/temperature relationships of a number of TTIs having a room temperature time-out of 16 hours. Figure 4 is a graph of the time/temperature relationships of a number of TTIs having a room temperature time-out of 20 hours. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A manufacturer or other distributor of time-temperature indicators and integrators (individually and/or collectively referred to as TTIs herein) will generally have a product line including a set or group of TTIs. All the TTIs of the product line will typically have unique performance characteristics. The present invention is a method for selecting TTIs which have performance characteristics suitable for a particular food or other perishable product. The method involves the use of a set of TTI performance characteristic specifications. Each TTI of the set offered by the distributor will have an associated performance characteristic specification. The performance characteristic specifications include information which describes the time/temperature relationship of the associated TTI at a range of time and temperatures. Visual graphs (i.e., performance characteristic specifications) with information describing the time/temperature relationships of a number of TTIs are shown in Figures 1-4. Figures 1-4 each include graphs of the time/temperature relationships of a plurality of TTIs, with a range of temperatures plotted on the x-axis and the time-out of the TTI at the associated temperature plotted on the y-axis. The performance characteristic specifications shown in Figures 1-4 are grouped to include on a common set of graphs those associated with TTIs having a common time-out at a predetermined and relatively high temperature (e.g., a common time-out at 72°F, room temperature). Figure 1, for example, includes the time/temperature relationship for six TTIs 7ι-7 6 , all of which have a room temperature time-out of seven hours (i.e., TTIs 7 7 6 will all time out seven hours following exposure to a constant temperature of 72°F). The time/temperature relationships of six TTIs YΣ \ -Yl_, having a twelve hour room temperature time-out are shown in Figure 2. The time/temperature relationships of six TTIs lό lόβ, having a sixteen hour room temperature time-out are shown in Figure 3. The time/temperature relationship of six TTIs 20 1 -20 6 , having a twenty hour room temperature time-out is shown in Figure 4. The performance characteristic specifications shown in Figures 1-4 show the time-out of the associated TTI in terms of a range of time-outs at each temperature. This feature of the performance characteristic specifications reflects the fact that the time-outs of the associated TTIs vary somewhat. By way of example, TTI 7ι (Figure 1) will time-out at between about 260 hours and 400 hours when exposed to a constant temperature of 37°F. The method of the present invention also involves the use of at least one known time/temperature point for the particular product for which a TTI is being selected. For example, a food processor, distributor or other customer desiring to select an appropriate TTI from the family of TTI products offered by a distributor may know the shelf life of its product at 37°F. Other known time/temperature points can of course also be used with the method of the present invention. Generally, using the performance characteristic specifications and known time/temperature point, one or more TTIs which have performance characteristic specifications with time/temperature relationships which match the known life time/temperature point are selected. In other words, the known time/temperature point is compared to the set of performance characteristic specifications to determine which performance characteristic specifications intersect or extend through the known time/temperature point. Even if several TTIs have performance characteristic specifications which match the known time/temperature point, a relatively limited set of possibly suitable TTIs can be identified in this manner. By way of example, a customer having a product with a known time/temperature point of 500 hours at 37°F can select a TTI from the product line represented by the performance characteristic specifications shown in Figures 1-4. It is evident from Figures 1-4 that only TTIs 12χ (Figure 2), 16 2 (Figure 3) and 20 (Figure 4) have performance characteristic specifications suitable for this product. Of the twenty-four TTIs having performance characteristic specifications shown in Figures 1-4, the three described immediately above are identified as those that can be used for the product. Having identified a subset of the distributor's TTI product line that may be used for the particular product on the basis of the known time/temperature point, the customer can use empirical, qualitative or other approaches to determine which of the TTIs is the most suitable (i.e., the best) for the application. In one such approach the customer may know from a review of the associated performance characteristic specifications that one or more of the identified TTIs are unsuitable for the product based upon other known time/temperature information for the product. As a first example of this approach using the TTIs 12 ls 16 2 and 20 , if the customer knows that the product would have a maximum shelf life of about 800 hours at 32°F, TTIs 12ι, 16 2 would not be suitable since both have time-out ranges which are generally greater than 800 hours at 32°F. As a second example of this approach using the TTIs 12 1; 16 2 and 20 3 , if the customer knows that the product has a room temperature shelf life of no more than 12 hours, only TTI 12ι would be suitable since TTIs 16 2 and 20 3 have room temperature time-outs which are considerably greater than 12 hours. In another such approach the customer can test samples of the identified TTIs on a sample of the particular product. For example, the customer can obtain samples of the identified TTIs from the distributor, apply them to samples of the particular product, and subject the sample to one or more shelf-life degradation tests. By observing the degradation of the product in connection with the time-out of the TTIs, the customer can determine which TTI is best suited for the product. This approach to identifying the most suitable TTI can be performed without knowing the time/temperature characteristics of the product, and can be used separately from or in addition to the approach described above. Even if only one suitable TTI is identified using the selection process described above, this shelf-life degradation test method can be used to confirm the suitability of the selection. The method described generally above can be implemented in any of a number of different approaches. One approach involves the use of visual graphs of the TTI performance characteristic specifications (e.g., graphs of the type illustrated in Figures 1-4). These graphs can be printed in brochures which are distributed to customers, distributed electronically (e.g., presented on an Internet or other public or private network site of the distributor which can be accessed and viewed by the customer) or maintained by the customer (e.g., as confidential information). On the basis of the knowledge of the one known time/temperature point, the customer or distributor in possession of the TTI performance characteristic specification graphs can use the graphs in the manner described above to identify the one or more TTIs suitable for the product. Samples of the identified TTIs can then be obtained from the distributor and tested in the manner described above to select the best TTI or confirm the suitability of the selection. In one variation of this approach, the telephone and/or in-person discussions can be used to communicate the known time/temperature point from the customer to the distributor. Alternatively, the customer can communicate the known time/temperature point to the distributor electronically (e.g., by e-mail or over the Internet). In yet another variation, the customer may prefer to maintain the known time/temperature point for the product as a trade secret, and select the matching TTI performance characteristic specifications itself. In this variation the customer can communicate to the distributor the selected TTIs without having to disclose the known time/temperature point. A second approach involves maintaining a computer system with an electronically searchable database of the TTI performance characteristic specifications. The performance characteristic specifications are in effect maintained and provided electronically in this approach. For example, the time/temperature relationship can be described as a mathematical relationship or by a look-up table. The known time/temperature point can then be input into the database in electronic form, and the system operated to electronically or "automatically" select the TTIs having performance characteristic specifications which match the known time/temperature point. Samples of the TTIs identified using this approach can then be tested in the manner described above to select the best TTI or confirm the suitability of the selection. In one variation of this approach, the system and database are maintained by the distributor, with access being provided to the customer over the Internet or another network. In another variation the system is operated by the distributor on the basis of known time/temperature point information received from the customer. The present invention offers a number of important advantages. It enables the relatively quick and yet accurate identification of a TTI suitable for a product. The method can also be performed in a number of efficient approaches. Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention. In particular, although only one known time/temperature point is required, the method can be used if two or more known time/temperature points are available.

Claims: Claims: 1. A method for selecting a time-temperature indicator (TTI) having performance characteristics suitable for a product having at least one known time/temperature point from a set of TTIs having different performance characteristics, including: providing a performance characteristic specification for each TTI of the set, each performance characteristic specification including information describing the TTI time/temperature relationship at a range of time-outs and temperatures; and selecting one or more TTIs from the set which have performance characteristic specifications with time/temperature relationships which match the known time/temperature point. 2. The method of claim 1 wherein: providing the performance characteristic specifications includes providing a visual graph of the time/temperature relationship for each TTI of the set; and selecting the one or more TTIs includes visually identifying performance characteristic specifications having time/temperature relationships which match the known life time/temperature point. 3. A method for a distributor to market time-temperature indicators (TTIs) to customers, including: maintaining performance characteristic specifications for each TTI of an available set of TTIs, each performance characteristic specification including information describing the TTI time/temperature relationship at a range of time-outs and temperatures; receiving from the customer at least one known life time/temperature point for a product; selecting one or more TTIs from the set which have performance characteristic specifications with time/temperature relationships which match the known time/temperature point received from the customer. 4. The method of claim 3 wherein receiving the time/temperature point from the customer includes receiving digital information representative of the life time/temperature point electronically over a network of the type including the Internet. 5. A method for a distributor to market time-temperature indicators (TTIs) to customers, including: providing to customers performance characteristic specifications for each TTI of an available set of TTIs, each performance characteristic specification including information describing the TTI time/temperature relationship at a range of time-outs and temperatures; causing a customer with a product having at least one known time/temperature point to select one or more TTIs from the set which have performance characteristic specifications with time/temperature relationships which match the known time/temperature point. 6. Operating an on-line site for performing the method of claim 5.

Inventors: MATNER RICHARD R, SPEVACEK JOHN A, MATNER, RICHARD, R., SPEVACEK, JOHN, A.
Applicants: 3M INNOVATIVE PROPERTIES CO, 3M INNOVATIVE PROPERTIES COMPANY
Application year: 2001
Main classification: G01K3
IPC codes: G01K3, G01K11, G06Q30