TIME-TEMPERATURE INDICATOR DEVICE Field of the invention

The present invention concerns a time-temperature indicator (TTI) system for monitoring the time and temperature exposure of foods, nutraceuticals,

pharmaceuticals, chemicals and similar products. More particularly, the present invention provides a time -temperature indicator device being activated by moisture.

Background of the invention

The quality of food products and other perishables are highly dependent on storage conditions such as the temperature and the storage time from production or packing until it finally reaches the end consumer. The deterioration processes are faster when the temperature is raised due to increasing biochemical, microbial or physical reaction rates, and therefore the quality of perishable goods declines more rapidly at high temperatures than at low temperatures.

Currently, date marking is the standard method applied for the insurance of storage quality. By date marking only, no information is given to the consumer or others about the storage conditions to which the product has been exposed; hence, the purchasers of the product are not able to determine whether the product has been stored under appropriate temperature conditions during the time of storage. Relying on date marking as a sole quality criterion presupposes that the perishable product has been stored under appropriate conditions throughout the entire storage period.

To be on the safe side, producers of perishable goods often use date marking with a wide safety margin and products, which are still suitable for consumption or use, are often discarded.

Therefore, there is a continuing interest in the monitoring of the time and

temperature to which storage sensitive products have been exposed in e.g. food, pharmaceutical and chemical distribution chains from factory to consumer. By supplying a perishable product with a time-temperature indicator (TTI) which follows the individual product from packing to sale, the producer, the grosser, the retailer and the consumer will have a better product control than they currently have.

The reliability of a TTI system depends to a large extent on the correlation of the TTI response with that of reactions leading to quality loss. Unless the change in the rate with temperature of the TTI system closely parallels the temperature

dependence of the rate of quality deterioration of the monitored product, the system will not be able to predict accurately the shelf life remaining for a variable temperature distribution. Further, as the temperature dependence on quality deterioration may be different in different temperature intervals, the temperature dependency of the TTI may in these cases advantageously be of a non-linear response.

Alternatively, the TTI system should be adjustable and controllable to certain agreed specifications in order to be used as general control indicators e.g. for use on pallets in the value chain.

Further, the response to time and temperature should be substantially irreversible to prevent the TTI from being reset. It is also preferred that the TTI is capable of indicating the time -temperature history within a wide temperature range. The indicator should also be conveniently activated so that pre-usage storage of the indicator is not a problem, and the response to time and temperature should be given in an easily interpretable manner, e.g. in the form of a detectable change, such as a visual change. In addition, the indicator should be stable upon long storage times at the requested conditions prior to activation and use. Finally, and importantly, it should be non-toxic and not pose any threat to human health. WO 2012/141594 (Keep-It Technologies) discloses a TTI system comprising two compartments initially being separated by suitable means for preventing contact between them. The system is activated by bringing said two compartments into contact and thereby allow a mutarotational reducing agent to migrate in a time- temperature dependent manner from one of the compartments into the other which contain an agent that changes visual appearance upon reduction. The mutarotational reducing agent will then reduce the agent, which changes visual appearance upon reduction in a time-temperature dependent manner. Thus, the time-temperature sensitivity of the system is the result of a combination of two time-temperature dependent processes. WO 2012/141593 (Keep-It Technologies) discloses a TTI system comprising two compartments initially being separated by suitable means for preventing contact between them. The system is activated by bringing said two compartments into contact and thereby allow a reactive agent to migrate in a time -temperature dependent manner from one of the compartments into the other. The time- temperature dependent migration is made even more sensitive to temperature by having a two-component temperature sensitive matrix system within the latter compartment.

A common feature of the above prior art TTI systems is the requirement of having two different compositions present in separate compartments of the TTI system. The TTI system is activated by bringing the two compartments into contact and thereby allow the two different compositions to interact which results in a visually detectable signal. The requirement of having two different compositions contained in separate compartments of the TTI systems entails that the manufacture and design of such systems, as well as their incorporation in a suitable product packaging, are somewhat complicated for certain applications and activation requires removal of the means for preventing contact between the two compartments.

While the above listed prior art documents teach TTI systems capable of

continuously indicating the time -temperature history within a wide temperature range, US2017/131 152 (Innorese AG) is focused on TTI systems which reliably displays breaks in the refrigeration chain, in particular for deep frozen products. By means of heating, the monitored product releases moisture which typically will migrate first into a delaying layer of the TTI system. When sufficient moisture has accumulated within the delaying layer, the moisture will typically migrate into an activator layer. There, an activator is mobilized and migrates together with the moisture into an indicator layer. By interaction of the indicator with the activator in the presence of moisture, a colour conversion occurs, which indicates exceedance of a critical temperature, i.e. a break in the refrigeration chain. However, the TTI system is neither able to indicate the time/temperature exposure before the critical temperature has been reached nor the length of the break in the refrigeration chain. Further, the TTI system will typically be non-responsive to time as long as the critical temperature has not been reached.

One object of the present invention is to provide an improved TTI system for a product packaging, which is simple and inexpensive to manufacture and at the same time is easy to activate.

The inventive TTI system features a threshold indicator or a time indicator, preferably a time -temperature indicator, which is activated by moisture. The source of the activating moisture may e.g. be moisture naturally present inside the package of a packaged material or optionally be moisture from a reservoir integrated as part of the TTI system.

Summary of the invention A first aspect of the present invention relates to a time -temperature indicator device, the indicator comprising a first layer, a second layer and a third layer, wherein the first layer is made in a material with a moisture permeability that is equal to or lower than the moisture permeability of the third layer; the second layer comprises a dry indicator composition comprising at least one active agent which provides a time -temperature dependent detectable change when activated by moisture; and the third layer is made in a moisture permeable material; the first, second and third layers being arranged such that moisture can pass via the third layer and/or first layer to contact and thereby activate the dry indicator composition. In one embodiment, the detectable change is a visual change and the resulting time- temperature dependent visual change may be observed through the first or third layer. In one embodiment according to the first aspect of the present invention, the first layer is made in a moisture impermeable material; and the first, second and third layers are arranged such that moisture can pass via the third layer to contact and thereby activate the dry indicator composition. In one embodiment according to the first aspect of the present invention, the first layer is made in a moisture impermeable material; and the first, second and third layers are arranged such that moisture can pass via the third layer to contact and thereby activate the dry indicator composition. In one embodiment according to the first aspect of the present invention, the first layer is made in a transparent material; and the resulting time-temperature dependent visual change may be observed through the first layer.

In one embodiment according to the first aspect of the present invention, the third layer is made in a transparent material; and the resulting time-temperature dependent visual change may be observed through the third layer.

In another embodiment according to the first aspect of the present invention, the indicator device is for monitoring time and temperature exposure of a packaged product. Non-limiting examples of packaged products is selected from the group consisting of foods, nutraceuticals, pharmaceuticals and chemicals.

In another embodiment according to the first aspect of the present invention, the third layer does not have different moisture permeabilities in different areas of the third layer.

In another embodiment according to the first aspect of the present invention, the first layer does not have different moisture permeabilities in different areas of the first layer.

In another embodiment according to the first aspect of the present invention, the one or more active agent(s) which provides the time-temperature dependent detectable change, such as a visual change, when activated by moisture is neither able to pass the third layer nor the first layer.

In another embodiment according to the first aspect of the present invention, the moisture is water vapor. In another embodiment according to the first aspect of the present invention, the third layer and optionally the first layer is a water vapor selective membrane.

The term "water vapor selective membrane" as used herein refers to a membrane which allows water vapor (g) to pass while water (1) is not allowed to pass the membrane; i.e. that water in gaseous state may freely pass through the membrane while water in liquid state cannot pass through the membrane.

In another embodiment according to the first aspect of the present invention, the time -temperature indicator device further comprises a fourth layer arranged on an opposite side of the third layer relative to the second layer, the fourth layer being made in a moisture permeable material having a higher moisture permeability than the third layer. In another embodiment according to the first aspect of the present invention, the fourth layer has uniform thickness.

In another embodiment according to the first aspect of the present invention, the fourth layer does not have different moisture permeabilities in different areas of the fourth layer.

In another embodiment according to the first aspect of the present invention, the time -temperature indicator device further comprises a fourth layer arranged on an opposite side of the third layer relative to the second layer, the fourth layer being made in a water vapor permeable but water impermeable material. The third layer preferably being made in a water vapor permeable material. By having this configuration, the third layer is never exposed to water in liquid form but only exposed to water in gas state (water vapor). In another embodiment according to the first aspect of the present invention, the time -temperature indicator device further comprises a layer arranged on an opposite side of the first layer relative to the second layer, the layer being made in a water vapor permeable but water impermeable material. By having this configuration, the first layer is never exposed to water in liquid form but only exposed to water in gas state (water vapor).

In another embodiment according to the first aspect of the present invention, the third layer and/or first layer is heat sealable. In another embodiment according to the first aspect of the present invention, the fourth layer is heat sealable. In another embodiment according to the first aspect of the present invention, the first, third and fourth layers are heat sealable. In another embodiment according to the first aspect of the present invention, the dry indicator composition comprises a first active agent and a second active agent, the first and the second active agent reacting with each other when moistened, e.g by coming into contact with water vapour, to provide the time-temperature dependent detectable change, such as a visual change.

In another embodiment according to the first aspect of the present invention, the second layer comprises at least a first and a second section; and

- the number of moles of the first active agent in said first section is different from the number of moles of the first active agent in said second section; or

- the first active agent: second active agent molar ratio of the first section is

different from the first active agent : second active agent molar ratio of the second section. Preferably both the first and the second section comprise the first active agent and the second active agent.

In another embodiment according to the first aspect of the present invention, the third layer and optionally the first layer has uniform thickness.

In another embodiment according to the first aspect of the present invention, the first layer and/or the third layer; or optionally the first and/or the fourth layer, may be perforated, e.g. laser perforated, with varying hole density and hole diameters. The third layer and optionally the first layer may be a mono-layer or a laminate composition and may comprise any moisture permeable plastics e.g. high moisture permeable plastics such as BOPET, BOPA, PU, or very thin layers lower moisture permeable plastics such as PE, e.g. LDPE, PP or PET; or layers comprising permeable or breathable plastics such as perforated layers of plastics such as PE or plastics comprising particles, such as PE plastics comprising CaC0 ₃ .

In one embodiment according to the present invention, one or more of the layers have been subjected to surface treatment in order to increase surface tension of the surface and thereby obtain improved printing characteristics. In a preferred embodiment, at least the first and/or third layer has been subjected to surface treatment in order to increase surface tension of the surface and thereby obtain improved printing characteristics. Representative examples of surface treatments being corona, flame or plasma treatment; chemically treated or SiOX treated. The fourth layer may be a mono-layer or a laminate composition and may comprise any plastics, thermoformable or non-thermoformable, e.g. plastic such as PE, PP or PTFE, BOPA, BOPET; PU or PET; or layers comprising permeable or breathable plastics such as perforated layers of plastics such as PE or plastics comprising particles, such as PE plastics comprising CaC03.

The layers of the invention may be laminated together using any conventional method, e.g. by using an adhesive tie layer or through a temperature sealing.

In another embodiment according to the first aspect of the present invention, the device comprises even further layers. In one embodiment according to the present invention, the first and or/third layers comprises a coating. The coating may be i) a solvent based coating, e.g. a coating comprising ethyl cellulose, PE wax and/or a polymeric resin; and/or ii) a water based coating, such as a water based dispersion such a Reflex 131 cheese laqeuor from Resino. The coating is preferably approved for food contact and has a sufficient permeability for moisture and is sufficiently impermeable for other components in the system, such as the active agents. The coatings may e.g. be biodegradable or non-biodegradable or from biobased or petroleum based sources. Preferably, the coating stops or hinders or sufficiently delays the at least one active agent from diffusing into product and is sufficiently permeable to moisture to allow activation of the TTI system.

In one embodiment according to the present invention, the third layer comprises a coating. In a preferred embodiment, the coating has been dried. In one embodiment, the third layer does not comprise further laminate compositions.

In one embodiment according to the present invention, the second layer further comprises a coating. In this embodiment the coating may additionally protect the at least on active agent from inadequate reaction. The coating may then be intimately mixed with the at least one active agent and may be dried.

In another embodiment according to the first aspect of the present invention the indicator composition is directly printed, coated or applied to the first or third layer. In another embodiment according to the first aspect of the present invention, the indicator composition is directly printed, coated or applied to an auxiliary structure, such as paper.

In another embodiment according to the first aspect of the present invention, the first, second, third and/or any further layers further comprises printed color to provide auxiliary contrast for the TTI-device.

In another embodiment according to the first aspect of the present invention, the dry indicator composition is moistened by moisture originating from the packaged product. The packaged product may be a product comprising a water activity sufficient to activate the indicator composition. The water activity may be in the range or 0,7-1 ; 0.8-1 ; 0,9-1 or 0,95-1 as measured at a temperature in the range 0-40 °C, preferably at 4 °C. The packaged product may be a food product such as, but not limited to, fruits, vegetables, meat, poultry, fish, or liquid foods or drinks such milk or juice. The food product may be sliced, cut, minced, filleted or processed and mixed with other food ingredients.

The packaged product may be a medical or pharmaceutical product such as vaccines, suspension, syrups or intravenous medicines. The pharmaceutical product may be in the form of a liquid, mist or a solid, such as a gel. The packaged product may be a biological product or sample such as blood or blood serum, a blood sample, a urine sample, a faeces sample or a sperm specimen sample. The packaged product may be a chemical product such as ultrapure water, buffers, suspensions or other solutions.

In one embodiment according to the first aspect of the present invention, the time- temperature indicator device does not contain a metal compound prior to activation. In another embodiment according to the first aspect of the present invention, the dry indicator composition does not contain a metal compound prior to activation. In another embodiment according to the first aspect of the present invention, the active agent(s) is/are not a metal compound prior to activation.

In one embodiment according to the present invention, the term "metal compound" refers to a non-ionic compound being composed of only one element, said element being a metal. Ag( _s ) being a typical example of a metal compound that is composed of only one element, said element being silver, and which is in non-ionic form. AgCl(s) is a compound containing two different elements of which only one of the elements is a metal. Thus, in this embodiment AgCl( _S ) is not to be considered as a metal compound. It is preferred that the metal compound is not soluble in water. It is also preferred that the metal compound is an electrical conductor.

In another embodiment according to the present invention, the term "metal compound" refers to a non-ionic compound being composed of two or more elements wherein each of said elements are metals. Bronze is an alloy consisting primarily of copper and a small amount of tin and often with the addition of other metals. Thus, in this embodiment bronze is to be considered a metal compound. It is preferred that the metal compound is not soluble in water. It is also preferred that the metal compound is an electrical conductor.

In another embodiment according to the present invention, the term "metal compound" refers to a non-ionic compound being composed of two or more elements wherein at least one of said elements is a metal. Thus, in this embodiment an alloy consisting of copper, tin and at least one non-metal is to be considered a metal compound. It is preferred that the metal compound is not soluble in water. It is also preferred that the metal compound is an electrical conductor.

In another embodiment according to the present invention, the term "metal compound" refers to a non-ionic compound being composed of one or more elements; wherein at least one of said elements is a metal. The metal compound being an electrical conductor. The term "electrical conductor" as used herein refers to a material which allows the flow of an electric charge.

A second aspect of the present invention relates to a product -packaging element, comprising the indicator device according to the first aspect of the present invention, the indicator device being arranged such that:

- the first layer is visible on an outer side of the product-packaging element; and the third layer is at an internal surface of the product-packaging element or in contact with an internal volume of the product-packaging element; or

- the third layer is visible on an outer side of the product-packaging element and the first layer is at an internal surface of the product-packaging element or in contact with an internal volume of the product-packaging element.

In one embodiment according to the second aspect of the present invention, the first layer is made in a transparent material; the resulting time-temperature dependent detectable change is a visual change and the visual change may be observed through the first layer; the indicator device being arranged such that the first layer is visible on an outer side of the product-packaging element; and the third layer is at an internal surface of the product-packaging element or in contact with an internal volume of the product-packaging element.

In another embodiment according to the second aspect of the present invention, the element is a screw cap, a carton, a container, a bag, a tray, a MAP (modified atmosphere) package, a skin-packed package, a blister pack or a polymer laminate film.

A third aspect of the present invention relates to a product packaging comprising the indicator according to the first aspect of the present invention or the product- packaging element according to the second aspect of the present invention. In one embodiment according to the third aspect of the present invention, comprising - the indicator according to the first aspect of the present invention wherein the first layer is made in a transparent material and the resulting time-temperature dependent detectable change, such as a visual change, may be observed through the first layer; or

- the product-packaging element according to the second aspect of the present invention wherein the first layer is made in a transparent material; the resulting time-temperature dependent detectable change, such as a visual change, may be observed through the first layer; and the indicator device being arranged such that the first layer is visible on an outer side of the product-packaging element; and the third layer is at an internal surface of the product -packaging element or in contact with an internal volume of the product-packaging element;

wherein the third layer is arranged such that moisture present within the packaging may activate the dry indicator composition. In one embodiment according to the third aspect of the present invention, the dry indicator composition is moistened upon packaging of the product or upon opening the product packaging for the first time after packaging.

Brief description of drawings The present invention is described in detail by reference to the following drawings:

Figure la and figure lb illustrate the effect of using two alternative moisture permeable materials (PU membrane and BOPA membrane respectively; see example 1) on the time-temperature dependent indicator response. The two figures also show how the indicator response changes with time at a temperature of 12 °C. Figure 2 illustrates one embodiment according to the present invention, where the TTI device takes the form of a cap. Left figure is a top side view of the cap, where the first layer (1) is made in a transparent moisture impermeable material, the second layer (2) comprises the dry indicator composition and the third layer (3) is made in a moisture permeable material. Right figure is a top view of the cap, where the numbers indicate the number of days until product should be discarded.

Figure 3 illustrates another embodiment according to the present invention, where the TTI device is attached to a carton, such as a fresh milk carton, and activated when the carton is filled with liquid. The TTI device has a first layer (1) that is made in a transparent moisture impermeable material, a second layer (2) which comprises a dry indicator composition and a third layer (3) which is made in a moisture permeable material.

Figure 4 illustrates another embodiment according to the present invention, where the TTI device has a first layer (1) that is made in a transparent moisture impermeable material, a second layer (2) which comprises a dry indicator composition and a third layer (3) which is made in a moisture permeable material interrupted by moisture impermeable blocks (4).

Figure 5 illustrates another embodiment according to the present invention, where the TTI device is an integrated part of a product packaging and is in direct contact with liquid, such as water. The TTI device has a first layer (1) that is made in a transparent moisture impermeable material, a second layer (2) which comprises a dry indicator composition, a third layer (3) which is made in a moisture permeable material and a fourth layer (5) which is made in a moisture permeable but liquid impermeable material. The fourth layer ensures that liquid is never in direct contact with the dry indicator composition.

Figure 6a illustrates another embodiment according to the present invention, where the TTI device is an integrated part of a product packaging. The TTI device has a first layer (1) that is made in a transparent moisture impermeable material, a first intermediate layer (6) comprising a dry design composition, a second intermediate layer (7) that is made in a transparent material; a second layer (2) which comprises a dry indicator composition, a third layer (3) which is made in a moisture permeable material and a fourth layer (5) which is made in a moisture permeable but liquid impermeable material. A representative example of a dry design composition is the numbers indicating the days remaining until product should be discarded as shown in figure 6b. The dry indicator composition will change visual appearance with time and temperature as illustrated in figure 6b (light grey).

Figure 7 and 8 illustrates the three-layer printing design where the ingredients of the dry composition has been printed in the reverse order.

Figure 9 illustrates the effect of using a PU moisture permeable membrane on the indicator performance on a sideways indicator reaction.

Detailed description of the invention

All embodiments of the present invention comprise a time -temperature dependent indicator based on an indicator composition, which is inactive when dry. In the below description, the time or time -temperature indicator is generally disclosed as comprising a dry indicator composition. The dry indicator composition provides a time-temperature dependent detectable change, such as a visual change, when brought in contact with moisture, such as water, in particular water vapor. The detectable change may e.g. be a visual change or another detectable change such as a change in conductivity, resistiity, or other electrical properties, magnetic field, strength or other magnetic properties; crystallinity or other crystal properies;

electromagetic spectra such as UV or IR-spectra, physical properties such as hardness or texture or fluid properties. A visual change is commonly a change in color or the fading of a color to reveal a graphical symbol and similar which may be directly detected by the human eye. A visual change may e.g. be the result of a redox reaction, where the products of the reaction has a different color than the reactants of the reaction. A detectable change such as a change in conductivity, resistiity, or other electrical properties, magnetic field, strength or other magnetic properties; crystallinity or other crystal properies; electromagetic spectra such as UV or IR-spectra, physical properties such as hardness or texture or fluid properties is not necessarily directly detectable by the human eye but may be indirectly detected by using an instrument designed to measure e.g. conductivity. A change in conductivity may be the result of a redox reaction, where silver ions are reduced to metallic silver. Metallic silver (Ag(s)) has higher conducting capacity than silver ions (Ag(i) ⁺ ). It is to be understood that some reactions, e.g. the reaction where silver ions are reduced to metallic silver, may be both directly detectable by the human eye (AgNCb is colorless while metallic silver has a shiny metallic expression) and indirectly detectable by using an instrument designed to measure conductivity.

As used herein the term "detectable change" refers to a change that is directly and/or indirectly detectably by the human eye. The term directly detectably by the human eye refers to a visual change such as a change in color. The term indirectly detectably by the human eye refers to a change which requires measurement of a physical parameter, e.g. conducting capacity, conductibility, in order to be detectable by the human eye. It is to be understood that a detectable change may be both indirectly detectably by the human eye and directly detectably by the human eye. One example of the latter being silver ions that are reduced to metallic silver in a time -temperature dependent manner when the TTI system is activated.

The term "dry indicator composition" in the context of the present invention refers to an indicator composition with a moisture content that is sufficiently low so that the at least one active agent does not provide a detectable change, such as a visual change, with time and temperature. In one embodiment, the dry indicator composition comprises a first active agent and a second active agent which is accommodated in a layer comprising at least a first and a second section. Preferably, the number of moles of the first active agent in said first section is different from the number of moles of the first active agent in said second section. The dry indicator composition provides a time-temperature dependent detectable change, such as a visual change, when brought in contact with moisture, such as water, in particular water vapor. The rate of the detectable change, such as a visual change, is dependent on the concentration(s) of active agent(s) and the multiple separate sections provides a time-temperature dependent detectable change, such as a visual change. The one or more active agent(s) which provides the time-temperature dependent detectable change, such as a visual change, when activated by moisture is preferably not able to pass the third layer and/or first layer. The term "not able to pass" means that only a very limited amount or no amount of material may pass during use of the indicator. One limitation may be the amounts approved to pass a functional barrier when used within food products.

In an alternative embodiment according to the present invention, the dry indicator composition comprises a first active agent and a second active agent which is accommodated in a layer comprising at least a first and a second section. The number of moles of the first and second active agent in said first section is equal to the number of moles of the first and second active agent in said second section. The dry indicator composition is separated from a source of activating moisture by a moisture permeable third and/or fourth layer through which moisture may diffuse over a time-period depending on the thickness/permeability of the third and optionally fourth layer. By having varying thickness/permeability of the third and optionally fourth layer in the various sections, the rate of detectable change, such as a visual change, is dependent on the thickness/permeability of the third and optionally fourth layer.

In an alternative embodiment according to the present invention, the dry indicator composition comprises a first active agent which is accommodated in a first section of a layer comprising multiple sections. The dry indicator composition provides a time-temperature dependent detectable change, such as a visual change, when brought in contact with moisture, such as water, in particular water vapor. The rate of detectable change, such as a visual change, is dependent on the diffusion of the active agent from the first section to the other section(s).

In an alternative embodiment according to the present invention, the dry indicator composition comprises a first active agent which is accommodated in a first section and a second active agent which is accommodated in a second section. The dry indicator composition provides a time-temperature dependent detectable change, such as a visual change, when brought in contact with moisture, such as water, in particular water vapor. The rate of detectable change, such as a visual change, is dependent on the diffusion of the first active agent from the first section to the second section.

The indicator of the current invention is additionally controlled by the amount of moisture that can be absorbed by the indicator.

The water activity (a _w ) levels in the indicators after activation is higher than prior to activation and may be in the range of 0,3-1 ; 0,5-1 ; 0,7-1 or 0,8-1. The source of activation moisture may have a water activity level (a _w ) in the range of 0,5-1 ; 0,7-1 ; 0,8-1 or 0,9-1.

In one embodiment, the amount of moisture that can be absorbed by the indicator device can be modified with the amount of hygroscopic material present in the indicator composition. At equilibrium conditions, this can be used to additionally control speed and temperature sensitivity of the indicator device.

The amount of moisture present in the indicator may be in equilibrium with the humidity of the environment to which the third layer is exposed. In one preferred embodiment according to the present invention, the third layer is in contact with an internal volume of a product-packaging. The vapour pressure within the product- packaging increases with increasing temperature resulting in an increased transport of moisture across the third layer at higher temperatures and thereby faster indicator response at higher temperatures than lower temperatures which provides additional control to temperature sensitivity. Once moisture arrives at the second layer, the at least one active agent starts to develop a detectable signal, i.e. a detectable change. In order to be able to provide a detectable change reflecting the cumulative time-temperature exposure after activation, it is essential that the detectable change is continuously developing in response to time and temperature after activation. The rate of the detectable change is dependent on temperature exposure. Thus, in one embodiment according to the present invention, the rate of the detectable change is dependent on temperature exposure also after the dry indicator composition has been activated.

In another embodiment according to the present invention, the detectable change starts to develop when the dry indicator composition has been activated by moisture and continues to develop further in a time -temperature dependent manner.

In yet another embodiment according to the present invention, the detectable change is responsive to time and temperature exposure after the dry indicator composition has been activated by moisture. In another embodiment according to the present invention, the rate of the detectable change is responsive to temperature exposure after the dry indicator composition has been activated by moisture.

It is acknowledged that the rate of most chemical reaction systems in principle may be considered to be dependent on temperature. However, there are chemical reaction systems that are more sensitive to temperature than others and there are chemical reaction systems that theoretically are very sensitive to temperature but where the reaction rate is very high even at lower temperatures. In order to suit the purpose of the invention, it is important that the rate of the detectable change, e.g. rate of reaction, is dependent on temperature within a wide temperature range, e.g. -30 to lOOC. It is preferred that the rate of the detectable change reflects detonation of the product to be monitored. If the rate of the detectable change is very high both at high and low temperatures, it will not be possible to determine whether the product has been stored at too high temperatures

The TTI device according to the present invention is preferably not a TTI device which only provides a detectable signal if the refrigeration chain has been interrupted. Even if a product is stored at recommended temperature, the product may not be suitable for use if stored for a very long time. Thus, in one embodiment according to the present invention, the detectable change is responsive to time at any temperature, in particular responsive to time at a temperature in the range -30 to lOOC. In another embodiment according to the present invention, the detectable change is responsive to time even at isothermal condition. In another embodiment according to the present invention, the detectable change is responsive to time and temperature after the dry indicator composition has been activated by moisture. In another embodiment according to the present invention, the detectable change reflects the time-temperature exposure before activation, at activation and after activation. In another embodiment according to the present invention, the time- temperature exposure until activation is detectable as the time until start of a first detectable change while time -temperature exposure after activation is detectable as a further development of the detectable change.

When the TTI device is exposed to moisture, the moisture will penetrate the first and/or third layer before reaching the second layer. When sufficient moisture has penetrated the second layer to allow the at least one active agent to provide a detectable change, the dry indicator composition is activated. In one embodiment according to the present invention, the dry indicator composition in active state (i.e. that the dry indicator composition is in fact no longer dry) still provides a detectable change in response to time and temperature, the rate of the detectable change preferably being dependent on temperature.

Moisture will continue to penetrate the second layer until the TTI device is in equilibrium with the origin of the moisture. At the time equilibrium has been established, there will be a close to zero net transport of moisture in and out of the TTI device, i.e. that the amount of moisture entering the TTI device is substantially equal to the amount of moisture leaving the TTI device. When the TTI device is in equilibrium with the origin of the moisture, the net moisture transport in the TTI device is close to 0, such as less than 5 mg/m2*d, less than 1 mg/m2*d, less than 0,5 mg/m2*d, preferably less than 0,1 mg/m2*d or most preferably less than 0,01 mg/m2*d. In one embodiment according to the present invention, the detectable change is responsive to time and temperature exposure when equilibrium condition with respect to moisture has been established. When the second layer is in equilibrium with the origin of the moisture, e.g. the environment within product packaging, the net moisture transport in the second layer is close to 0, such as less than 5 mg/m2*d, less than 1 mg/m2*d, less than 0,5 mg/m2*d, preferably less than 0, 1 mg/m2*d or most preferably less than 0,01 mg/m2*d. In one embodiment according to the present invention, the detectable change is responsive to time and temperature exposure when equilibrium condition with respect to moisture has been established in the second layer. The term "isothermal condition" refers to a condition where a product is stored at constant temperature, e.g. at recommended temperature.

In a preferred embodiment according to the present invention, the time-temperature indicator device provides a detectable cumulative response to time and temperature exposure after the dry indicator composition has been activated by moisture. It is preferred that the detectable cumulative response to time and temperature exposure reflects both the time -temperature exposure before and after activation of the dry indicator composition. Thus, in one embodiment the detectably change reflects the time-temperature exposure before the dry indicator composition has been activated and the time-temperature exposure after the dry indicator composition has been activated.

The third layer may be in contact with an internal volume of a product-packaging or optionally be in contact with either an external moisture reservoir or the

surroundings. In case of the latter, the rate of indicator response will depend on the vapour pressure of the surroundings.

In one embodiment, the moisture permeable third and/or fourth layer has a permeability coefficient so high that the indicator device essentially is in

equilibrium with the environment to which the third and/or fourth layer is exposed. After the moisture enters the indicator device, the water activity levels are high enough to give a suitable reaction environment. Thus, depending on the dry indicator composition, the indicator does not necessarily itself react immediately as the moisture comes into contact with the dry indicator composition.

Thus, the temperature sensitivity of the present system may be controlled by

A) temperature sensitivity of the chemical reaction between the active agents; B) temperature dependent diffusion rate of active agent(s);

C) the amount of hygroscopic material in the indicator composition; D) the temperature dependent partial pressure of moisture, e.g. inside a closed system or inside an external moisture reservoir; and/or

E) permeability and/or thickness of the third and optionally first and/or fourth layer. In one embodiment according to the present invention, the temperature sensitivity of the time-temperature indicator device is not controlled by having different moisture permeability and/or thickness in different areas of the third and optionally first and/or fourth layer.

In one embodiment according to the present invention, the reaction time of the time- temperature indicator device is not controlled by having different moisture permeability and/or thickness in different areas of the third and optionally first and/or fourth layer.

In one embodiment according to the present invention, the active agent(s) which provide the time-temperature dependent visual change when activated by moisture does not pass via the first and/or third layer to provide the time-temperature dependent detectable change, such as a visual change. Said in other words, all of the active agent(s) which provide the time-temperature dependent detectable change, such as a visual change, when activated by moisture constitutes the second layer which is sandwiched between the first and third layer. In one embodiment according to the present invention, the moisture is not one of the active agent(s) which provide the time-temperature dependent detectable change, such as a visual change.

In one embodiment according to the present invention, the dry indicator

composition comprises at least two active agents. In a preferred embodiment, one of the active agents is applied to the second layer and then a second active agent is applied to the same layer thereby forming a sandwich like structure. In another embodiment according to the present invention, there is a coating layer separating the first active agent from the second active agent. This may e.g. be achieved by applying the first active agent, then there is a coating layer which is applied on top of the first active agent and a second active agent that is applied on top of the coating layer. The coating may be a solvent or water based coating. In another embodiment according to the present invention, the active agents are blended into a coating or the coating comprises the active agent(s). In case of the latter, the coating may be in the form of a dry coating or barrier comprising at least one of the active agent(s) in dry state.

In one embodiment according to the present invention, the thickness of each of the layers is 1 -200 microns, 1-100 microns, 5-50 microns or 5-30 microns. The thickness of each layer will typically depend on the material of the layer. If the dry indicator composition comprises at least two active agents and these two active agents are applied on top of each other, this may be considered to represent a two layered structure each layer having a thickness in the range 1 -200 microns, 1-100 microns, 5-50 microns or 5-30 microns.

In a preferred embodiment, the dry indicator composition used in the second layer of the time-temperature indicator of the present invention comprises a first and a second agent. In dry conditions, the first and the second agent is inert, i.e. that the agents do not react with each other. However, when moisture is added to a mixture of the first and the second agent, a time-temperature dependent detectable change, such as a visual change, is achieved.

Thus, in one embodiment according to the present invention, the dry indicator composition comprises at least two active agents which provides a time -temperature dependent detectable change when activated by moisture. The at least two active agents may be in direct contact with each other in the absence of moisture, but more preferably they are partly in contact with each other or are not in direct contact with each other. The term "partly in contact with each other" as recited above, refers to the situation where one of the agents is applied on top of the other thereby forming a two-layered structure. At the interface between said two layers, the two active agents will be in contact with each other but agents not located at the interface will not be in contact with each other.

An advantageous indicator device featuring a dry indicator composition suitable for use in the present invention is disclosed in WO2017103206. The dry indicator composition is typically obtained by, for instance, sequentially printing a first liquid containing a first active agent onto a substrate (i.e. for instance printed as a second layer upon the first or the third layer of the indicator according to the present invention) followed by drying, and then printing a second liquid containing a second active agent onto the same substrate followed by drying. The dried composition comprising both the first and the second agent is not active, i.e. does not provide a time -temperature dependent visual change. The concentration of active agent(s) in the dried composition may be varied at different sections of the second layer. The different sections may be designed in any desired shape, such as numbers and any suitable graphical symbols. The disclosure of WO2017103206 is hereby incorporated by reference in its entirety. In particular, the disclosure of

WO2017103206 describing the method used to obtain a dried indicator composition comprising a first agent and a second agent, as well as the examples of suitable combinations of first agent and second agent (see for instance p. 17-25), is herein incorporated by reference. Dry indicator composition:

In a preferred embodiment, the dry indicator composition of the second layer comprises a first agent and a second agent. Commonly, the first and second agent is applied to at least a first and a second section of the second layer. The first agent and the second agent provides a detectable change, such as a visual change in appearance, e.g. a change in color or fading of a color, when brought in contact in the presence of moisture.

A non-exhaustive list of suitable combinations of agents are as follows: the first agent is a reducing agent, such as thiosulfate (e.g. sodium

thiosulfate); and the second agent is an agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon reduction, such as iodine-starch complex; the first agent is an oxidizing agent; and the second agent is an agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon oxidation; the first agent is a salt; and the second agent is an agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, when forming a complex with the salt; or the first agent is a salt; and the second agent is an agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, when forming a precipitate with the salt; or the first agent is a reducing agent, such as thiosulfate or a reducing sugar such as fructose; and the second agent is a salt where at least one element is a metal, such as AgN0 ₃ , which change conductivity when the ionic metal is reduced to metallic metal (Ag(i) ⁺ - Ag( _s )); or the first agent is an acid, base or any mixture thereof; and the second agent is an agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon a change in pH.

It is acknowledged that the rate of a chemical reaction between an acid and an agent which changes visual appearance or changes other measurable physical

characteristics, such as conductivity, upon a change in pH often is very high. If such a pair of active ingredients is to be used, and the TTI device is to be responsive to temperature after activation, there must be a parameter different from the chemical reaction rate that is temperature dependent. One example of such a parameter being temperature dependent diffusion rate of active agents (see above list for further parameters), i.e. that one of the active agents is allowed to diffuse through a matrix in a time-temperature dependent manner, where the other active ingredient is attached to the matrix.

For instance, one of said first and second agent may be a Fe ³⁺ or Cu ²⁺ salt and the other agent a FeCN ₆ ^4" salt, or one of said first and second agent may be Iodide and the other agent a Cu ²⁺ salt, or one of said first and second agent may be Sulphate, Carbonate or Phosphate and the other agent a Ca ²⁺ salt, or one of said first and second agent may be Glucose, Fructose or Thiosulfate (e.g. sodium thiosulfate) and the other agent may be Iodine, or one of said first and second agent may be a Fe ²⁺ salt and the other agent a FeCN ₆ ^3" salt, or one of said first and second agent may be a FeCN ₆ ^3" salt and the other agent a Fe ²⁺ salt, or one of said first and second agent may be Glucose, Fructose or Thiosulfate (e.g. sodium thiosulfate) and the other agent a Cu ²⁺ salt. agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon reduction, The term "agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon oxidation" or "agent which provides a visual change in appearance, such as a change in color or fading of a color, or provides changes in other measurable physical characteristics, such as conductivity, upon oxidation" refers to an agent which provides a detectable change, such as changes in visual appearance, e.g. a change in color and/or change in phase, upon oxidation.

The term "agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon reduction" or "agent which provides a visual change in appearance, such as a change in color, or provides changes in other measurable physical characteristics, such as conductivity, upon reduction" refers to an agent that which provides a detectable change, such as changes in visual appearance, e.g. a change in color and/or change in phase, upon reduction. One example of such an agent is starch-complexed iodine, which upon reduction changes color from dark blue to transparent/colorless. Another example of such an agent is a solution of Cu ²⁺ , which upon reduction may precipitate and change color to red Cu ₂ 0. Ferroin is an example of a pH

independent agent which upon reduction changes color from slightly blue to red and methylene blue is an example of a pH dependent agent which changes color from blue to colorless upon reduction. Other suitable agents which changes color upon reduction are 2,2'-Bipyridine (Ru or Fe complexes); Nitroferroin; 5 ,6— Dimethylferroin; Phenylanthranilic acid; Ethoxy chrysoidine; o-Dianisidine; Sodium diphenylamine sulfonate; Viologen;

Diphenylbenzidine; Diphenylamine; Sodium 2,6-Dibromophenol-indophenol; Sodium 2,6-Dichlorophenol-indophenol; Sodium o-Cresol indophenol; Thionine; Indigotetrasulfonic acid; Indigotrisulfonic acid; Indigo carmine; Indigomono sulfonic acid; Phenosafranin; Safranin; Neutral red; variamine blue; potassium permanganate; xylenol orange; and xylene cyanol.

The term "reducing agent" refers to an agent that is capable of donating an electron to another chemical species in a redox chemical reaction. In context of the present specification the reducing agent must be capable of donating an electron to the agent which changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon reduction. One example of a reducing agent is a mutarotational reducing agent. Other examples of reducing agents may be thiosulfate (e.g. sodium thiosulfate), such as sodium thiosulfate (e.g. sodium thiosulfate), or ascorbic acid.

The term "mutarotational reducing agent", refers to an agent which is able to undergo mutarotation and which also is able to donate an electron or electrons to another specie in a reduction-oxidation reaction. Examples of mutarotational reducing agents are a reducing sugar or a mixture of reducing sugars, a non- reducing sugar which can be converted to a reducing sugar by tautomerization or a mixture of non-reducing sugars which can be converted to reducing sugars by tautomerization . The term "tautomerization", refers to the chemical reaction where tautomers, isomers of organic compounds, readily interconvert. It is common that this reaction results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond. The concept of tautomerizations is called tautomerism. Said sugar is preferably selected from a monosaccharide, disaccharide,

trisaccharide, oligosaccharide, polysaccharide or any mixture thereof.

More preferably, the mutarotational reducing agent is a reducing sugar selected from the group consisting of glucose, fructose, glyceraldehyde, galactose, lactose and maltose, or any mixture thereof. In a preferred embodiment, the mutarotational reducing agent is fructose.

In order for the mutarotational reducing agent to be able to donate electrons to the agent that changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon reduction, the mutarotational reducing agent must have an open chain with an aldehyde or a ketone group. This is typically the case for the intermediate product of a mutarotation process.

The mutarotation process rate is both dependent on temperature and pH. By increasing the temperature and/or pH, more intermediate products (open chain with an aldehyde or a ketone group) are formed resulting in an increased redox reaction rate. Said intermediate products then donate electrons to the agent that changes visual appearance or changes other measurable physical characteristics, such as conductivity, upon reduction. Since the mutarotation process rate is dependent on pH, the pH may be adjusted to fine tune the time -temperature indicator device of the present invention.

According to the present invention, the dry indicator composition comprising at least one agent (preferably a first agent and a second agent) will provide a detectable change, such as a visual change in appearance, e.g. as a change in color, when brought in contact with moisture. In the absence of moisture, the first agent and the second agent will not react, thereby no detectable change, e.g. visual change in appearance. Thus, in the presence of moisture the time -temperature indicator device will be in an active state while it will be in an inactive state in the absence of moisture. It is noted that based on the present disclosure and the prior art represented by WO2017103206, the skilled person would know of numerous dry indicator compositions, including optional additives, suitable for use in the present invention.

A particularly advantageous additive in the dry indicator composition is a hygroscopic material, such as various hydrophilic polymers, crosslinked Na- polyacrylate, crosslinked CMC, crosslinked starches, Na-starch glycolate and crosslinked polyvinylpyrrolidone, salts such as CaCh, sugars or sugar alcohol or fillers such as fumed silica. The hygroscopic material may contribute to control the final dry matter content (DMC) of an indicator composition at a certain water vapor pressure. Thus, in one embodiment according to the present invention, the dry indicator composition further comprises a hygroscopic material, such as various hydrophilic polymers, crosslinked Na-polyacrylate, crosslinked CMC, crosslinked starches, Na-starch glycolate and crosslinked polyvinylpyrrolidone, salts such as CaCh, sugars or sugar alcohol or fillers such as fumed silica.

Other hygroscopic materials may be humectants or plasticizers, such as glycerin og Polyethylene glycols.

In another embodiment according to the present invention, the dry indicator composition further comprises at least one surface active agent, such as at least one surfactant, at least one emulsifier, at least one surface active polymer or any combination thereof. By having surface active agents present, the process of applying the indicator composition is improved, in particular if the indicator composition is applied to a material different from paper, such as plastic. The presence of surface active agent may also improve indicator functionality after the indicator device has been activated. Suitable surface-active agent(s) may be selected from the group consisting of non-ionic, anionic or cationic agents, such as Tweens, Spans, Lecthins, Sugar esters, Pluronics, CTAC and Docusate or polymeric surface active agents such as Gum Arabic or Propylene Glycol Alginate.

In one embodiment according to the present invention, the surface tension of the dry indicator composition after activation (i.e. that the dry indicator composition is no longer dry as it has been subjected to moisture) is in the range of 20-70, 20-50, 20- 40 or 30-40 mN/m.

One example of an embodiment according to the present invention is illustrated in figure 2. This TTI-device takes the form of a cap, where the first layer (1) is made in a transparent moisture impermeable material, the second layer (2) comprises the dry indicator composition and the third layer (3) is made in a moisture permeable material. During opening the cap may puncture a sealing which will result in that the TTI device is exposed to moisture which then will pass the moisture permeable third layer (3) and activate the dry indicator composition present in the second layer (2). The sealing is typically made of a water and moisture impermeable material to ensure that the dry indicator composition is not in contact with moisture until the sealing is broken. Once the sealing is broken, the dry indicator composition will come into contact with moisture which will activate the TTI device and thereby provide a time-temperature dependent visual change.

In the context of the present invention, the term "moisture impermeable material" refers to a material that is moisture impermeable in the sense that once activated the moisture will be retained within the indicator device in sufficient amount to ensure that the indicator device remains activated during the period of use.

The moisture permeability of plastic films, laminates or other materials may be defined as the Water vapour transmission rate (WVTR) as measured according to ASTM E-96. The WVTR can be measured in units g/m ² /24h. In one embodiment according to the present invention, the moisture impermeable material has a WVTR less than 5 g/m ² /24h, less than 2 g/m ² /24h or preferable less than 1 g/m ² /24h.

In one embodiment according to the present invention, a moisture permeable material has a WVTR higher than a moisture impermeable material. A moisture permeable material may have a WVTR higher than 5 g/m ² /24h, higher than 10 g/m ² /24h, higher than 50 g/m ² /24h or preferably higher than 100 g/m ² /24h. A moisture permeable material may be in the range of 5-10000 g/m ² /24h, 10-5000 g/m ² /24h, 50-5000 g/m ² /24h or preferable 100-5000 g/m ² /24h. Another example of an embodiment according to the present invention is illustrated in figure 3. This TTI-device is attached to a product packaging material, such as a carton, in particular a fresh milk carton, and activated once the product packaging is filled with liquid. The TTI device has a first layer (1) that is made in a transparent moisture impermeable material, a second layer (2) which comprises a dry indicator composition and a third layer (3) which is made in a moisture permeable material. The indicator may puncture the product packaging material upon attachment or may be put on top of an area of the product packaging material which is pre-punctured, e.g. by the use of a laser, resulting in the formation of holes. Said holes may have any shape or size. After filling the product packaging material with liquid, the moisture exits the holes and will pass the moisture permeable third layer (3) and activate the dry indicator composition present in the second layer (2). The first layer (1) ensures that no moisture escapes the TTI-device.

It is to be understood that the TTI-device may also be put on the inside of a product packaging material. In such as case the first layer may be attached to the packaging material with e.g. example glue or the first layer may be the packaging material per se. In one setup a carton for liquid foods such as milk or juice (see figure 3) may be precut with at least one hole and a TTI device may be attached to the inside on the carton to cover the at least one hole. Upon subsequent folding and filling of the carton element in a filling machine, the at least one hole will from the outside appear as a window where in the indicating element is visible. In one setup the indicating element may be combined with other elements on a liquid food carton, such as measuring window (see figure 5).

It is to be understood that the third layer may be a continuous layer, e.g. along the length and/or breadth of the TTI device, as illustrated in figure 2; or a discontinuous layer, e.g. along the length and/or breadth of the TTI device as illustrated in figure 4. In case of the latter, the moisture permeable third layer is interrupted by moisture impermeable blocks (4).

Another example of an embodiment according to the present invention is illustrated in figure 5. This TTI-device represents an integrated part of a product packaging and may be in direct contact with liquid, such as water or liquid foods such as milk. The TTI device has a first layer (1) that is made in a transparent moisture impermeable material, a second layer (2) which comprises a dry indicator composition, a third layer (3) which is made in a moisture permeable material and a fourth layer (5) which is made in a moisture permeable but liquid impermeable material. The purpose of the fourth layer is to ensure that liquid is never in direct contact with either the third layer or the dry indicator composition.

Another example of an embodiment according to the present invention is illustrated in figure 6. This TTI-device has a first layer (1) that is made in a transparent moisture impermeable material, a first intermediate layer (6) comprising a dry design composition, a second intermediate layer (7) that is made in a transparent material; a second layer (2) which comprises a dry indicator composition, a third layer (3) which is made in a moisture permeable material and a fourth layer (5) which is made in a moisture permeable but liquid impermeable material. The dry design composition represents a composition which per se does not change visual appearance with time nor temperature. A representative example of a dry design composition is the numbers indicating the days remaining until product should be discarded as shown in figure 6b. The purpose of the second intermediate layer (7) is to ensure that the dry indicator composition and the dry design composition never come into direct contact and will also ensure that the dry design composition will not diffuse into the product. The dry indicator composition may change visual appearance with time and temperature as illustrated in figure 6b (light grey).

Intermediate layer (7) may be beneficially omitted for the device if there is no negative interaction between the design composition and indicator composition and that the components of design composition will not diffuse through the moisture permeable membrane

The design composition may comprise the whole printed package design and not only numbers. It is preferred that the TTI is capable of indicating the time-temperature history within a wide temperature range. The temperature use range may be in the range -30 to lOOC; in the range of 0- 100 C; in the range of 0-40C or in the range on 0-20C. Alternatively a range from -20 to +20C may be beneficial. In one embodiment according to the present invention, the TTI device does not comprise a delaying layer, i.e. that the TTI device is designed to facilitate quick transport of moisture, even when the level of moisture to which the TTI device is exposed is low, through the first and/or third layer. When the moisture penetrates the second layer, the dry indicator composition is activated and the detectable change starts to form. Preferably, the rate of the detectable change is dependent on temperature. As the time passes by, the detectable change continues to develop. If the temperature is high, the detectable change develops faster and if the temperature is low the detectable change develops slower. The term "delaying layer" as used herein refers to a layer which regulates the conveyance of moisture to the second layer. In a preferred embodiment, the TTI device does not comprise a delaying layer and the layer which moisture will pass through is in direct contact with the source of the moisture. In another embodiment according to the present invention, the TTI device provides a continuous cumulative detectable change in response to temperature and time after the dry indicator composition has been activated by moisture. In another embodiment according to the present invention, the TTI device is not a threshold TTI device. The term "threshold TTI device" as used herein refers to a TTI device which requires heightened levels of moisture in order for the dry indicator composition to be activated. In a further embodiment according to the present invention, the detectable change continues to develop after the dry indicator composition has been activated by moisture, the rate of the detectable signal being dependent on temperature. The rate of the detectable change is dependent on temperature and the response provided by the detectable change being dependent on time and temperature.

In yet another embodiment according to the present invention, the TTI device does not stop providing a detectable change, such as a visual change, after the dry indicator composition has been activated. Instead of an immediate and final detectable change at the point of activation, the TTI device continues to provide a detectable change after the dry indicator composition has been activated thereby being able to indicate the time-temperature exposure also after the dry indicator composition has been activated.

The TTI device according to the present invention provides a time-temperature dependent detectable change for a prolonged period after activation, the prolonged period being adapted to the product that is monitored. In one embodiment according to the present invention, the TTI device according to the present invention provides a time -temperature dependent detectable change for a period of at least 1 hour after activation, more particularly more than 2 hours, more than 3 hours, more than 6 hours, more than 12 hours or more than 24 hours. In another embodiment, the TTI device according to the present invention provides a time-temperature dependent detectable change for a period in the range 1 hour to 120 days, 1 hour to 60 days, 6 hours to 45 days, 12 hours to 45 days, 24 hours to 40 days or 24 hours to 25 days after the dry indicator composition has been activated.

In another embodiment according to the present invention, the indicator

composition comprises the at least one active agent, the at least one active agent being dissolved in a water based matrix, a solvent based matrix or dissolved in a mixture of a water based matrix and a solvent based matrix. In case the indicator composition comprises at least two active agents, one of the active agents may be dissolved in a water based matrix or a mixture of a water based matrix and a solvent based matrix and the other active agent may be dissolved in a mixture of a water based matrix and a solvent based matrix or a solvent based matrix respectively. This may be particularly useful if the active agents are applied in a step wise printing process in order to avoid pre-activation of indicators and improve the stability of the dry indicator composition. It is to be understood that the indicator composition refers to the composition which is part of or constitutes the second layer of the TTI device during production and that the indicator composition is dried in order to obtain the claimed TTI device.

An alternative aspect of the present invention relates to a time-temperature indicator device, the indicator comprising a first layer (1), a second layer (2) and a third layer (3), wherein

- the first layer (1) is made in a material with a moisture permeability that is equal to or lower than the moisture permeability of the third layer (3);

- the second layer (2) comprises a dry indicator composition comprising at least one active agent which provides a time-temperature dependent detectable change after being activated by moisture; and

- the third layer (3) is made in a moisture permeable material;

the first, second and third layers being arranged such that moisture can pass via the third layer (3) and/or first layer (1) to contact and thereby activate the dry indicator composition and the resulting time -temperature dependent detectable change may be detected.

Each and all of the embodiments listed with respect to the first aspect of the present invention are also embodiments of the above alternative aspect of the present invention.

Examples

Example 1:

Preparation of a TTI device

Materials:

Solution A: 50 mM I ₂ , 14,3% (w/w) starch

Solution B: Fructose 32.5% (w/w) in a 0.75M Carbonate buffer

Substrate: Thin plastic coated white self-adhesive label

PU membrane: Norgesplaster, product 2021-1 1

BOP A membrane: (13 μιη)

Preparing TTI devices:

Solution A was applied to the substrate in 3 homogeneous layers (the same thickness) using Flexo printer. The substrate was dried for 5 seconds at room temperature. Solution B was applied to the substrate with varying thickness along the length of the substrate using flexo printer. The substrate was dried for 3 hours at room temperature.

A PU membrane was put on top of one substrate and a BOPA membrane was put on top of the other substrate, both substrates being prepared as described above. Both substrates were then exposed to moisture by incubating the substrates in an airtight box with close to 100% humidity (water) at 12 °C. The indicator response after 0, 1 , 4 and 10 days is illustrated in figure l a (PU membrane) and the indicator response after 0, 1 , 3 and 10 days is illustrated in figure lb (BOPA membrane) respectively.

Example 2:

Preparation of a TTI device

Materials:

Solution A: 50 mM I ₂ , 14,3% (w/w) starch

Solution B: Fructose 32.5% (w/w)

Solution C: 0.75M Carbonate buffer

Substrate: Thin plastic coated white self-adhesive label

BOPA membrane: (13 μιη)

Preparing TTI devices:

Solution A was applied to the substrate in 3 homogeneous layers (same thickness) using Flexo printer. The substrate was dried for 5 seconds at room temperature. Solution B was applied to the substrate in 3 homogeneous layers (the same thickness) using Flexo printer. The substrate was dried for 3 hours at room temperature. Solution C was applied to the substrate with varying thickness along the length of the substrate using Flexo printer.

A BOPA membrane was put on top of the substrate. Substrate was then exposed to moisture by incubating the substrates in an airtight box with close to 100% humidity (water) at 12 °C. The indicator responses after 0, 5, 12 and 16 days are illustrated in Figure 7.

Example 3:

Preparation of a TTI device

Materials:

Solution A: 50 mM I ₂ , 14,3% (w/w) starch

Solution B: 0.75M Carbonate buffer

Solution C: Fructose 32.5% (w/w)

Substrate: Thin plastic coated white self-adhesive label

BOPA membrane: (13 μιη) Preparing TTI devices:

Solution A was applied to the substrate in 3 homogeneous layers (the same thickness) using Flexo printer. The substrate was dried for 5 seconds at room temperature. Solution B was applied to the substrate in 3 homogeneous layers (the same thickness) using Flexo printer. Solution C was applied to the substrate with varying thickness along the length of the substrate using Flexo printer. The substrate was dried for 3 hours at room temperature.

A BOPA membrane was put on top of the substrate. Substrate was then exposed to moisture by incubating the substrates in an airtight box with close to 100% humidity (water) at 12 °C. The indicator response after 0, 5, 12 and 16 days is illustrated in Figure 8.

Example 4:

Preparation of a TTI device

Materials:

Solution A

Alginate: 5, 1 % (w/vol)

Na-Thiosulphate: 10,3 % (w/vol)

Glycerin 38,5 % (w/vol)

in water

Solution B

Alginate 2,2 % (w/vol)

12 18,4 mM

Starch 2,2 % (w/vol)

Glycerin 37,8 % (w/vol)

in water

Substrate: Paper sheet on top of Biaxer 1 15 laminate foil

PU-Membrane : Norgesplaster, prod 2021-1 1

Preparing TTI devices:

Solution A and B was applied to the substrate side by side using a 60 Microns coating bar from RK print, such that solution A and B was touching at the interface but not overlapping. Solution A and B was dried for 30 seconds in hot air using an air blower, resulting in inactive indicators with no visual reaction.

The paper sheet was cut in pieces of approximately 1cm x 5 cm, put on Biaxer 1 15, intersection marked with a pen and coated with the PU-membrane Substrate was then exposed to moisture by incubating the substrates in an airtight box with close to 100% humidity (water) at 4 and 12°C. The indicator responses after 0, 3 and 6 days at 4 and 12°C are illustrated in Figure 9. A summary of the findings is presented in table 1 below.

Table 1 :

Temp Membrane Start 3 days 6 days

(third

layer)

4C PU No 1-2 mm 3 mm

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12C PU No 4 mm 7 mm

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