The time indicator of the present invention is suitable to be connected to a storage device for food, pharmaceutical compositions etc., and indicates highly reliable the time since such storage device has been opened. The invention further refers to the use of such time indicator and a method of determining the time since a storage device has been opened.

BACKGROUND OF THE INVENTION

Every year hundreds of million tons of food, cosmetics and pharmaceutical waste is generated worldwide. This large scale waste production has not only significant economic consequences, but also an alarming environmental impact. Only in the United States, it is estimated that 34 million tons of food end up yearly in the garbage can [www.epa.gov/wastes/conserve/smm/foodrecovery]. Detailed studies conducted in the United Kingdom showed that the annual cost of buying the foods and drinks that become waste would be £12 billions [Household Food and Drink Waste in the UK (ISBN: 1844054306)]. According to the same study, 2.9 million tons of avoidable household food waste is produced yearly because it is not consumed within the best before date.

"Best before indicators" have been available to consumers of foodstuffs since the 1960s in the U.S.A. [R.A. LaBudde, Durability indication: United States, in J.R. Blanchfield Food Labelling (ISBN: 0849308526)], whereas in Brazil only since the 1980s [http://www.anvisa.gov.br/legis/resol/10_84.htm]. Best before indicators provide consumers with a simple but valuable tool to assess the quality and safety of foodstuffs, cosmetics and pharmaceuticals. Foodstuffs beyond this date will have, for example, lower nutritional, flavor, textural, and microbiobgical qualities.

Pharmaceuticals and medical products, more alarmingly, may not have the expected effect from the active ingredient(s) when used beyond the best before date. Whereas assessing the best before date is generally an easy task for consumers, simply requiring reading this information on the product package, one particular troublesome and common situation arises in products that have a "durable life" once their seal is open. Most aseptic processed foodstuffs have a long shelf life (months) while kept in their aseptic packages, but have to generally be refrigerated and consumed within a few days once the packages are open. Here, keeping track of the durable life (i.e., the time during which the product possesses its optimal qualities after the aseptic seal is broken) requires a more active attitude by the consumer, such as writing down the date the product was open. Another troublesome situation arises in pharmaceuticals or medical products that have a durable life once their seal is open or once individual components are mixed together. In the latter, the durable life may be of even a few months and use of products beyond this time could clearly result in the usage of a product with lower efficacy. In doubt, consumers often discard such products.

The problem is increased by the fact that numerous people have problems with the smelL According to a study of the NIH, roughly 1 to 2 % of the people in North America say that they have a smell disorder. Problems with smell increase as people get older, and smell problems are more common in men than in women, In one study, nearly one quarter of men in the age between 60 and 69 had a smell disorder, while about 11 % of women in that age range reported a problem

(http://www.nidcd.nih.gov/health/smelltest/pages/smelLasp x).

The availability of a low-cost, easy- to-read, and automatically activated time indicator would provide consumers with a convenient means to track the durable life of food, cosmetics, pharmaceutical and medical products, fostering their consumption or usage with optimal qualities and, at the same time, minimizing the chances they will become waste. A number of time indication devices is described in the state of the art (BR7702492U, BRPI0502889A, WO2005014404A2, US2008210152A1,

US2004013839A1, US5446705A, WO03007088, US4292916, US5633835, and US5053339). These devices employ processes/techniques together with a chemical (mostly a dyestuff) that either becomes visible at the device's external surface after a specific period of time, or appears as a migrating cobr strip through a transparent window, thus constituting some sort of "chemical timer". However, all the aforementioned devices possess intrinsic drawbacks which are remediated by the present invention. The main problems of what is described in the state of the art are the lack of an automatic mechanism to activate the device, a large temperature dependence of the indicator response time, and an associated high production cost.

It is still not described in the state of the art a mechanism that automatically couples the opening of a product package with the activation of the time indicator. The automatic activation of a time indicator would be of great value to help disseminate its widespread use and to albw general public acceptance as the activation cannot be forgotten anymore.

The methods/techniques for time indicators currently available show large variations of the measured time for different temperatures and, as such, these devices are not time indicators, but rather thermotime indicators: i.e., their response depends on both the elapsed time and the temperature to which the devices are subjected to. This type of response is commonly less valuable to consumers. For example, the food industry generally recommends that aseptic products, once open, be refrigerated between 1°C and 10°C and be consumed within a few days. In this case, the pertinent information to the consumer is the elapsed time after the package is open, no matter if the product was kept at 1°C or at 10°C. A large temperature dependence of the indicator response will result in the device recommending either the product consumption beyond its durable life, or to dispose it within its durable life.

The temperature dependence of currently existing time indicators happens because these devices are based on either chemical reactions or the chemical diffusion of dyestuffs. BRPI0502889A and WO2005014404A2, for example, claim the use of chemical reactions, whose colored products, upon accumulation in a visible reservoir, provide an indication of elapsed time when compared to a standardized scale. The influence of the temperature on the rate of chemical reactions, however, is generally described by the Arrhenius equation that shows an exponential relationship by the reaction rate and the temperature. Thus in such devices, the time response has a very large temperature dependence.

Most of the devices known in the art are based on the chemical diffusion of a cobred substance. These devices generally possess two compartments whose media are brought into (physical) contact upon the device activation, whereby a cobred substance from one reservoir starts to migrate/diffuse into a second reservoir with an opaque or transparent background (e.g., WO03007088A2, US2008210152A1, US5446705A, US5053339A and US2004013839A1). Over time, the progress of cobr change against a colorless background is visually perceived through a transparent window and the elapsed time is determined by comparing the color boundary against marked indicia on the device external surface. Devices based primarily on the chemical diffusion have nonetheless three intrinsic drawbacks. First, the diffusion in liquids takes place with an average speed of 0.05 cm/min, which would result in a progress of color change in the range of 72 cm/day. This length is clearly incompatible with a device to be attached to packages of foods, cosmetics, pharmaceuticals or medical products. To sbw down this process, the above mentioned patents make use of either capillaries to retard the diffusion speed by reducing the physical area through which the dyestuffs can diffuse (e.g.,

US2008210152A1), and/or high viscosity media that offer higher resistance to the diffusion of the colored substance(s) (e.g., US5053339A, WO03007088A2,

US5446705A and US2004013839A1). However, such approaches (especially the latter) aggravate a second intrinsic problem associated with chemical diffusion, i.e., the diffusivity (or the diffusion coefficient) increases rapidly with an increase in the temperature, especially in viscous media. Third, the boundary of the color change generally appears blurred, and the lack of a sharp boundary makes it difficult to read the progress of the cobr change against marked indicia. To remediate this cobr boundary issue, WO03007088A2, US2004013839A1 and US5053339A describe the used of pH indicators along with strong acids or bases, which can result in a sudden color change.

These problems are overcome by the present invention, wherein the indicator device is directly connected to an opening device of a storage device, and the indicator device is highly independent of the surrounding temperature. A further advantage of the present indicator device is the bw cost for production.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a time indication device comprising two compartments, the first of which contains a dyestuff (the dye reservoir) that diffuses abng the second compartment (the display compartment) once the device is activated.

Preferably, chemical diffusion is used abng with the adsorption of a dyestuff to an adsorbent. An adsorbent with high affinity to the dye is provided in the medium of the display compartment. Once the device is activated, the dye starts to diffuse abng the length of the display compartment and is simultaneously adsorbed to the adsorbent. The dye adsorption immobilizes it onto the adsorption surface, resulting in a sbw down of the diffusion rate and in a very sharp boundary of the cobr change.

In addition, optionally viscosity enhancers are added to the dye reservoir medium. The use of such viscosity enhancers results in a reduction of or avoids the temperature dependence of the time indication response of the device of the present invention.

In a further embodiment, the present invention is directed to the use of the indicator device for monitoring and/or determining the time period a storage device has been opened. In another embodiment, the present invention refers to a method for determining the time period a storage device has been opened using the indicator device of the present invention, wherein a trigger penetrates a film, that is sealing the open end of a dye reservoir, when a storage device is opened, and the dye of the dye reservoir enters a display compartment through a first cap 3 and diffuses abng a display compartment 4, which indicates the time period to be determined from the opening of storage device.

Brief Description of the Drawings

FIGS. 1 and 2 are exploded top perspective views of the top components of the device of the present invention.

FIG. 3 and 4 are top perspective views of the assembled top components before they are fitted together with the coupling base.

FIG. 5 is a bottom perspective view of the assembled top components.

FIG. 6 is a top perspective view of the complete device.

FIG. 7 is a detailed perspective view of the first cap.

FIG. 8 is a detailed perspective view of the dye reservoir .

FIG. 9 is a detailed perspective view of the trigger cap.

Detailed Description of the Invention

The device of the present invention is made up of two compartments: a first compartment is filled with a medium containing a dye (the dye reservoir 1), while a second compartment is filled with a medium containing an adsorbent (the display compartment 4). The display compartment 4 is preferably manufactured from a transparent material to allow easy monitoring of the progress of cobr change. Both media are initially sealed from each other by means of a film 2, preferably a polymeric film, whose rupture activates the indicator device (FIG. 1). The device further comprises or consists of the following components: a first cap 3, a second cap 5, a trigger cap 6, a trigger 7, and a coupling base 9.

In a preferred embodiment the indicator device of the present invention comprises a dye reservoir 1 and a display compartment 4, a first cap 3, a second cap 5, a trigger cap 6, and a trigger 7, wherein the dye reservoir comprises a medium including a dye and optionally a viscosity enhancer, and the display compartment comprises an adsorbent medium, and the dye reservoir and the first cap are separated by a film 2, and wherein the trigger is in contact with opening means of a storage device via a trigger sheath 14 of the trigger cap 6.

In this embodiment, preferably the first end of the dye reservoir 1 is cbsed, and the second end of the dye reservoir 1 is open and the open end is sealed with the film 2 that is stretched. Further preferred, the first end of the first cap 3 is located between the film sealed end of the dye reservoir 1 and the first end of the display compartment 4, the second end of the display compartment is connected to the second cap 5. Preferably, the first cap 3 comprises a vent 15, and the trigger 7 is incorporated into the vent, wherein the first end of the trigger is proximate to the bottom of the vent, and the second end of the trigger is next to the stretched film sealing the second end of the dye reservoir 1. The second end of the trigger 7 is for example bcated opposite a trigger base 16, which is bcated cbse to the second end of the dye reservoir 1, where to the trigger extends when the indicator device is activated, penetrating the stretched film.

Preferably, the diameter of the sealed end of the dye reservoir 1 is identical to the diameter of the first end of the first cap 3 or marginally smaller that the dye reservoir and the first end of cap 3 fit tightly.

In a further preferred embodiment, the first cap 3, the display compartment 4, and the second cap 5 are connected to a coupling base 9. The indicator device is for example attached to a storage device via the coupling base 9 next to the opening means of the storage device. Preferably the first cap 3 and the display compartment 4 are transparent, and the other components comprising the dye reservoir 1, the second cap 5, the trigger cap 6, the trigger 7, and the coupling base 9 are transparent or opaque.

In a preferred embodiment the indicator device functions as follows: the display compartment 4 is filled with an adsorbent medium, its front end (first end) is connected to the first cap 3 and its rear end (second end) is connected to the second cap 5. The dye reservoir 1 is filled with the dye medium, the film 2, e.g., a polymeric film, is first stretched and then positioned directly above the open end of the dye reservoir 1 (FIGS. 1 and 2). The dye reservoir 1 is preferably cup-shaped having a closed first end, which is preferably an integral part of the dye reservoir (Fig. 8). While keeping the film 2 stretched, the previously assembled combination of first cap 3 -display compartment 4-second cap 5, is fitted against the polymeric film 2 into the dye reservoir 1 (FIGS. 1-4). "Fitted" means here that the combination is in direct contact with the film 2, and thus, via the film in contact with the dye reservoir 1. The dye reservoir 1 and the first cap 3 have the same or almost the same dimensions, i.e., the first cap 3 has a slightly bigger dimension than the dye reservoir 1 that the cap 3 and the dye reservoir 1 are stably connected and that in consequence no dye from the dye reservoir 1 gets bst and enters all the first cap 3.

Next, the trigger 7 is inserted into the first cap's vent 15 (FIGS. 1, 2 and 7) until its front end (first end) rests against the bottom of the vent (15). The second end of the trigger is bcated opposite the trigger base 16 (FIG. 8) of the dye compartment, which is covered by the film (2), which is preferably stretched.

The trigger 7 is an ebngated piece made of any material, preferably metal, hard plastic, any stiff polymer etc. If the trigger is activated, e.g., by opening a storage device, it moves inward into the trigger base 16 and activates the indicator device of the present invention. The surface of the trigger base 16 at the open end of dye reservoir 1 lies directed against and parallel to the rim of dye reservoir 1. Thus, as the film 2 is positioned on top of dye reservoir 1, it will also be in direct contact with the above trigger base 16 surface. The trigger cap 6 is attached on top of the trigger 7 onto the first cap 3 (FIGS. 1 and 2), ensuring all media will be kept sealed from the outside of the device.

Ultimately, protrusions 12 on the backsides of the first cap 3 and second cap 5 (FIG. 5) are fitted into the coupling base recesses 10 (FIGS. 3 and 4). The coupling base 9 also possesses protrusions 11 on its backside (FIG. 6), which are used to attach the complete device to product packages.

The coupling base 9 serves not only for assembling the device's top components 8, comprising components 1-7 (FIGS. 3 and 4), thereon, but also to attach the indicator device on a storage device for which the opening time has to be indicated, for example a food, cosmetic or pharmaceutical storage device such as a product package. Thus, printing indicia indicative of elapsed time is located on the external surface of the storage device. Alternatively, components 8 might be directly affixed to the base of lids of re-cbsable storage devices, in which case the indicia could be directly printed onto the base external surface. Further, components 8 might also be directly affixed onto the storage devices' external surface next to the devices' opening.

The stretched film 2 is fixed in its aforementioned designated position by pressure, by ensuring that the internal transverse dimensions of the first cap 3 are a few micrometers smaller for example 1 to 10 micrometers, preferably 1 to 5 micrometers than the external transverse dimensions of the dye reservoir 1.

Referring to FIG. 7, the first cap's vent 15 serves two purposes: it is used to insert the trigger 7, as well as to vent air from the first cap 3 when the latter is attached to the dye reservoir 1. Venting air from cap 3 avoids air being trapped at the interface between dye reservoir 1 and display compartment 4, which could bbck or severely affect the diffusion of dye into display compartment 4.

Referring to FIG. 8, the trigger base 16 is incorporated into the dye reservoir 1 to provide a surface against which the tip of the trigger 7 will rub in the moment the device is activated. Additionally, the trigger base 16 also provides a resistance to the inward displacement of trigger 7, ensuring that moving trigger 7 against trigger base 16 requires the active input of the consumer, i.e., pressure has to be applied onto the trigger, which will not happen accidentally or incidentally.

Referring to FIG. 9, the trigger mechanism of the present invention preferably comprises, besides the trigger 7, a trigger cap 6 and its trigger sheath 14. The trigger cap 6 and its trigger sheath 14 tightly cover the trigger 7 and act as a seal to prevent the leakage of media after the device is activated. Because of the tight cover provided by the trigger cap 6, especially by its trigger sheath 14, combined with the elasticity of the material used to make the trigger cap 6 and/or the sheath 14, the external surface of the trigger sheath 14, particularly its second end, which is proximate to opening means of the storage device, can be used as some sort of a button to be pressed inwards from outside against the trigger base 16. The trigger cap 6 is preferably made of an elastomeric resin, such as silicone or polyurethane, preferably with a hardness bwer than 100 Shore A, preferably in the range of 1 to 99 Shore A, more preferably in the range of 10 to 50 Shore A.

In one embodiment, the trigger 7 is made of a harder plastic material, such as common thermoplastics, including, but not limited to, high-density polyethylene, polypropylene, acrybnitrile butadiene styrene (ABS) resin and polyurethane, preferably with a Shore D hardness greater than 40, preferably in a range of 40 to 80 Shore D, more preferably in a range of 40 to 50 Shore D.

The device is activated by pressing the second end, i.e., the tip of the trigger sheath 14 inwards, causing the trigger 7 to move against the trigger base 16. The surface of the trigger base 16 enhances the friction on the film 2 during the device activation, facilitating the film 2 puncture. As the film 2 is fixed in its position on the dye reservoir 1 while stretched, its puncture results in the film being torn across the open end of the dye reservoir 1 instantaneously, when the trigger 7 penetrates the film 2, and the dye enters the display compartment.

Components 1, 3, 4, 5, 6, 7, and 9 are manufactured for example of plastics, preferably thermoplastics, such as polyethylene, polypropylene or polyvinyl chbride. Among these components, the first cap 3 and the display compartment 4 must necessarily be made of transparent materials, whereas the others can be either transparent or opaque. Components 1, 3, 4, 5, 6, 7, and 9 are joined together by commonly used plastic welding or heat-sealing processes, or with the use of adhesives or glues.

The film 2 is preferably manufactured with bw elastic modulus (E) polymers, typically with E values bebw 0.1 GPa, e.g., 0.01 to 0.1 GPa, preferably 0,01 to 0.08 GPa, more preferred 0.01 to 0.05 GPa. For example thin films of latex, nitrile rubber, butyl rubber, or polyurethane are used, with thicknesses in 10 to 100 micrometers range. The stretching of the film 2 is essential for the proper activation of the device because it facilitates the film puncture, which results in a very rapid and wide removing of the film between the dye reservoir 1 and the first cap 3, and thus, results in a wide opening of the dye reservoir 1 against the first cap 3 and in consequence with the display compartment 4.

The indicator device is attached to product packages, i.e., storage devices, in juxtaposition to a part of the storage device for example a package lid. In order for the device to be activated automatically, the part such as the lid has opening means such as a bump which is in contact with a trigger sheath 14 comprising the trigger 7 and which activates the trigger when the consumer turns the opening device such as a lid to open the storage device.

An indicator device of the present invention is preferably used to monitor the time period a storage device is open. The storage device is for example for storing a product selected from the group consisting of food, animal food, dietary supplement, pesticide, fungicide, cosmetic, pharmaceutical compound and/or composition, personal care, paint and medical product and it indicates for example an open time period of the storage device of days, weeks or months.

Each media prepared for the indicator device is aqueous based. Optionally a gelling agent is added to the media of both compartments in order to ensure that the progress of color change occurs exclusively by diffusion and no liquid convection takes place. Any gelling agent commonly employed in the food industry may be used, such as agar, agarose, gellan gum, or pectin, as well as the carrageenan/potassium ion, polyvinyl alcohol/borax, or alginic acid/calcium ion systems. Typical useful concentrations range from 0.1 to 10 %, preferably from 0.5 to 5 % (wt./wt).

Many food grade, water soluble dyes may be used, such as all the so called FD&C food cobr additives, i.e. the FDA (Food and Drug Administration) certified cobr additives for use in foods in the United States. These are for example brilliant blue FCF (FD&C Blue No. 1), indigotine (FD&C Blue No. 2), fast green FCF (FD&C Green No. 3), erythrosine (FD&C Red No. 3), allura red AC (FD&C Red No. 40), tartrazine (FD&C Yelbw No. 5), sunset yellow FCF (FD&C Yellow No. 6), orange B and citrus red No.2. Additionally, the following food grade cobr additives whose use is permitted for example in the European Union may be used: ponceau 4R (E124), patent blue V (E131), and brilliant black BN (E151). Further, the natural food color betanin may be used. In addition, any combination between these food cobr additives may be used, and also between these and others with similar properties. Typical concentrations of a dye or dye combination range for example from 0.1 to 20 %, preferably from 0.1 to 10% (wt./wt.).

In a preferred embodiment, the adsorbent is an ion exchange resin. This type of adsorbent is preferred as numerous of the aforementioned food cobr additives are organic salts and, additionally, most of them bear multiple negative charges in aqueous media. Ion exchange resins are typically provided with a monovalent counterion, such as chloride or hydroxyl ions for anionic exchange resins. Since ion exchange resins have a much greater affinity for multivalent ions, the multivalent charged cobr additives are rapidly exchanged by the monovalent ions of the ion exchange resin during the dye diffusion abng the length of the display compartment.

Preferred ion exchange resins are for example, polymers bearing sulfonic acid groups (e.g., sodium polystyrene sulfonate or poly[2-acry]amido-2-methyl-l- propanesulfonic acid]), quaternary amino groups (e.g., poly[acrylamido-N- propyltrimethylammonium chloride]), carboxylic acids and primary, secondary, and/or ternary amino groups (e.g., polyethylenimine), such as Lewatit® MP62 WS, Lewatit® MonoPlus MP 600, Lewatit® MonoPlus M 600, Purofine® PFC100E, Purofine® PFC104, Purolite® A845DL, Purofine® PFA300, Dowex® Monosphere C 350, Dowex® Marathon® A LB, and Dowex® Marathon® MR-3. In order to improve consumer safety, natural and food grade ion exchanger are preferred such as alginic acid, chitosan, or carrageenan. In a further embodiment, any combination of these ion exchangers may be used.

A substantial reduction in the temperature dependence of the time response is achieved through the use of viscosity enhancers in the medium for the dye reservoir. Various food grade viscosity enhancers may be employed, such as polyvinylpyrrolidone, polyvinyl alcohol (in the absence of borax), polyethylene glycol, methyl cellulose, hydroxyethyl cellulose, lecithin, sucrose, glycerol, propylene glycol, fatty acid esters of polyoxyethylene sorbitan, sucrose esters, sorbitan esters, glycerol esters, polyglycerol esters of fatty acids, and propylene glycol esters of fatty acids. Typical concentrations range for example from 0.1 to 20 %, preferably from 0.5 to 10% (wt./wt.). Moreover, any combination between these enhancers may be used.

In a preferred embodiment, the present invention relates to a method for determining the time period a storage device has been opened using an indicator of the present invention, wherein the trigger 7 is activated by the opening means, when the storage device is opened, and penetrates the stretched film 2, that is sealing the open end of the dye reservoir 1, and the dye of the dye reservoir enters the display compartment 4 through the first cap 3, adsorbs to the adsorbent medium and moves abng the display compartment, which indicates the time period. In such method, a viscosity enhancer is for example added to the display

compartment 4 to reduce temperature sensitivity of the indicator device.

The folbwing factors have a direct influence on the speed of the progress of cobr change in the display compartment. To optimize the indicator device to its intended use, the following parameters are optionally controlled: - the shape and volume of each compartment of the device: for example, a very large cross-sectional transverse area between the two compartments results in very rapid diffusion of the dye into the display compartment, whereas the volumes abng with the compartment's shape affect the rate of color change abng the length of the display compartment;

- the dye concentration in the dye reservoir, i.e., increasing concentration of the dye increases diffusion;

- the viscosity enhancer concentration in the dye reservoir: for example, increasing concentration of the viscosity enhancer reduces diffusion;

- the adsorbent concentration in the display compartment, i.e., the higher the concentration of adsorbent, the sharper the boundary of the cobr change and the sbwer the dye diffusion;

- the media pH, as ion exchangers ionization depends strongly on the pH: for example, so-called strong ion-exchange resins can be operated within a pH range of 0-14, whereas so-called weak ion exchangers have narrower operating pH ranges such as 0-8;

- the purity of all substances used to prepare the media: for example, the presence of multivalent ions in the agar as impurities compete with the dye molecules for binding sites of the ion exchanger, affecting the rate of dye binding and thus the progress of color change;

- the valence of the cobr additive and the charge density of the adsorbent, i.e., the higher the charge density of the adsorbent, the sbwer the progress of cobr change, whereas higher valence cobr additive have higher affinity for the adsorbent;

- the media viscosity in each compartment, especially the viscosity before the media gelling: i.e., the medium viscosity is inversely related to the diffusivity in that medium, meaning increases in viscosity results in lower diffusivities, whereas gelling results in little change in diffusivity, even though it causes medium

thickening, because gelling agents cause an extremely high increase in viscosity, making the diffusivity to become independent of viscosity.

The key determining factors on the progress of cobr change are the dye concentration, the viscosity enhancer concentration, and the adsorbent concentration. These factors can be adjusted to achieve a progress of color change in the order of a few millimeters or of a couple of centimeters in the display compartment, which indicates the elapsed time of a few hours, days, weeks or months.

The folbwing examples will serve to more specifically illustrate the invention, which is, however, not limited to these examples.

Example 1

Tests were carried out in two 17.1 mm bng cylindrical tubes with identical diameters, each representing one of the compartments. Chitosan was solubilized in 0.5% (wt./vol) acetic acid to a final concentration of 0.25 (wt./wt.), 2% (wt./wt.) agar was added and this solution was heated to 80°C to solubilize the agar. While still hot, this medium was used to fill one of the cylindrical tubes, representing the display compartment.

Methyl cellulose at 2% (wt./voL) was dispersed in hot water (at 60°C) and was let to cool to allow its solubilization. Ponceau 4R (E124) was then added to this solution to the folbwing final concentrations: 0.25, 0.4, 0.7, 1.0, 1.5 and 2.0

(wt./wt). These solutions were used to fill the other cylindrical tube, representing the dye reservoir.

The tubes were coaxially joined together, ensuring no air was trapped between the media, all open ends were sealed, and then the test device was immersed in constant temperature water baths at 0 and 10°C. Data on the progress of cobr change are shown in Table 1.

Table 1: progress of cobr change for ponceau 4R (E124) and 0.25% (wt./wt.) chitosan (in millimeters)

E124

% wt./wt. 1 day 2 days 3 days

0°C 10°C 0°C 10°C 0°C 10°C

0.25 3.41 3.98 5.12 5.69 6.12 6.83

0.4 4.27 4.84 6.33 7.00 7.53 8.75

0.7 6.49 7.17 9.16 10.24 10.96 12.58

1.0 7.61 7.90 10.81 11.52 13.30 14.37

1.5 8.82 9.67 12.46 13.59 15.08 n.a.*

2.0 8.87 9.96 12.58 14.46 15.42 n.a.*

+: percentage difference for the 0 and 10°C data.

*: not applicable; progress of cobr change attained tube's total length before shown time.

Example 2

Tests are carried out as in example 1 except that devices are maintained in constant temperature water baths at 0, 10, 20 and 30°C and that dye reservoir media are prepared with the following color additives: brilliant blue FCF, indigotine, fast green FCF, erythrosine, allura red AC, tartrazine, sunset yellow FCF, orange B, citrus red No.2, patent blue V, brilliant black BN and betanin.

Example 3

Tests are carried out as in example 2 except that the dye reservoir media are prepared with the following viscosity enhancers: glycerol at 0, 20, 40 and 60% (wt./wt.); polyethylene glycol at 20, 40, 50 and 60% (wt./wt.); polyvinylpyrrolidone at 2, 4 and 6% (wt./wt.); polyvinyl alcohol at 2, 4, 6 and 8% (wt./wt.); methyl cellulose at 4 and 6% (wt./wt.); and hydroxyethyl cellulose at 2, 4, 6 % (wt./wt.). Example 4

Tests are carried out as in example 3 except that the display compartment media are prepared with the following adsorbent: an anion exchange resin containing quarternary ammonium groups at 0.25, 0.50, 0.75 and 1.00% (wt./voL); an anion exchange resin bearing secondary amino groups at 0.25, 0.50, 0.75 and 1.00% (wt./voL); and chitosan at 0.40, 0.50, 0.60, 0.70, 0.80, 0.90 and 1.00% ( wt./voL).

Example 5

Tests are carried out as in examples 4 except that the progress of cobr change is monitored daily for 6 months.