A METHOD, A PACKAGE, AND A METHOD FOR MAKING A PACKAGE, FOR REMOVING OXALIC ACID FROM A BEVERAGE

TECHNICAL FIELD

The present invention relates to a method for removing oxalic acid from a beverage. Further, the invention relates to a package for removing oxalic acid from a beverage and a method for making said package.

BACKGROUND ART Oxalic acid is present in different kinds of food and drink, for instance in spinach, rhubarb, cocoa and tea. Ingesting this acid is generally undesired, since the negative side effects are numerous and include kidney stones and bone disorders in humans who are unable to properly metabolize oxalate. Oxalic acid also hinders the body's absorption of calcium and iron, which can lead to osteoporosis or anaemia. The former is particularly dangerous in the elderly, while the latter is common among women of a fertile age and especially among those who are pregnant.

A beverage such as tea is believed to have many positive effects and is generally recommended for human consumption. However, the presence of oxalic acid means that drinking any kind of beverage containing substances from the tea plant, such as black or green tea, for many can lead to the problems mentioned above, the most apparent being the unpleasant and often very painful kidney stones. If the oxalate/oxalic acid could be removed, more people could enjoy the taste and all the health benefits from tea.

Several methods of removing oxalate/oxalic acid are known in the field. US

2005/0232901 Al (Zaghmout) shows a material and method for treating or preventing oxalate-related disease, wherein bacteria or enzymes able to degrade oxalate are added in different types of food, for instance yoghurt, milk, chocolate or peanut butter, or are given as capsules. The substance used can then degrade the oxalate already present in the body. It would, however, be cumbersome for the consumer to continuously eat a particular oxalate-removing product in order to be able to have tea. It could also be that the dose necessary to remove all the ingested oxalic acid varies with the consumption of the products containing this acid and different doses would thus be required on different days, which makes it even harder for the consumer to be able to enjoy a cup of tea without having to plan ahead for the oxalate removal.

DE 19806132 Al (Todemann) shows another method for removing oxalic acid from vegetables, such as spinach or rhubarb. This method, however, requires a pH between 2 and 5, preferably in the range of 3 to 4, which is significantly lower than that of tea (which normally has a pH of around 5.4-5.7). The method also requires a temperature of 10-60 ⁰ C, which is significantly lower than freshly brewed tea, and would mean that the tea must be cooled off after brewing in order to remove the oxalic acid and then reheated before drinking. Such a process would be unnecessarily complicated for a regular consumer.

The Japanese patent JP3290151 (Tatsuyuki) shows a method where oxalic acid can be removed from tea at a high temperature before it is consumed. According to this method, a calcium compound, preferably calcium hydroxide, is added to the tea and binds the oxalic acid in the form of calcium oxalate. This will then have to be filtered away before the tea is drunk, which is a cumbersome process. The adding of a strong base such as calcium hydroxide would also mean increasing the pH of the beverage, which would considerably alter the taste.

Thus, the need is apparent for a method which can remove the oxalic acid from tea in an easy way, without the need for filtering or re-heating the beverage before drinking it.

DISCLOSURE OF THE INVENTION

The object of the present invention is to solve the problem described above. This, according to an aspect of the invention, can be achieved by a package for tea which comprises a substance which removes oxalic acid from the tea during brewing. Thereby, oxalic acid can be removed in an easy and convenient manner.

According to an aspect of the invention, said package can be a tea bag in which a portion of tea leaves is contained, and the substance for removing oxalic acid can be in the form of granules or powder placed inside the bag along with the tea leaves or added to the material of the tea bag. The package could alternatively be a package suitable for multiple portions of tea leaves, where said substance is either mixed with the tea leaves inside the package or provided in a separate compartment for mixing with said leaves just before brewing. By any of these arrangements, a product is achieved where said substance is in close proximity to the tea leaves used for brewing tea, and where these can be mixed in such a way that oxalic acid is removed from the tea being brewed in an easy and convenient manner, without the need for additional procedures for removing oxalic acid. To the user, the process is as easy as brewing conventional tea, and it would

even be possible to achieve tea free from oxalic acid without performing any additional procedures compared to this conventional way of brewing. Thereby, the reaction takes place while the tea leaves are immersed in the tea being made, and after the brewing, the tea leaves can be removed and the beverage is ready to drink.

According to another aspect of the invention, the substance is an enzyme, preferably belonging to the groups of oxalate decarboxylase (EC 4.1.1.2) or oxalate oxidase (EC 1.2.3.4). Thereby, the results from the degrading of the oxalic acid will be substances which are harmless for a human in the amounts that can be expected from the process. In the case of oxalate decarboxylase, the result of the degrading will be another acid, thus keeping the flavour of the beverage especially well.

According to yet another aspect of the invention, the substance reacts with the oxalic acid at a temperature of higher than 50 ⁰ C. Thereby, no re-heating or other additional preparations are needed after the reaction, and the tea can be drunk at once. This makes the device according to the invention especially easy and convenient to use.

According to an aspect of the invention, a method is presented for making a device for removing oxalic acid from a beverage, wherein the substance for removing oxalic acid is applied to a material suitable for use in tea bags, containers or filters. Thereby, the substance can be applied during the production of the material before the tea bags themselves are constructed from the material, which allows for a convenient and cost efficient production method.

According to another aspect of the invention, the substance is applied to the material as an aqueous solution. Thereby, application can take place simply through spraying the material with the active substance in a water solution, which allows for a very easy and cost efficient production method.

According to another aspect of the invention, the substance is bonded to the material by ionic bonds. Thereby, the substance can be bonded tighter to the material and will stay in place in the material throughout the brewing process.

According to yet another aspect of the invention, the substance is bonded to the material by covalent bonds. Thereby, the substance can be bonded even tighter to the material and will be able to stay adhering to the material throughout the brewing process.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be described in more detail with reference to preferred embodiments and the appended drawings, wherein:

Fig. 1 shows a schematic view of a package according to a preferred embodiment of the invention, Fig. 2 shows a schematic view of a process for producing a material for a package according to the invention,

Fig. 3 shows a schematic view of a second process for producing a material for a package according to the invention, and

Fig. 4 shows a schematic view of a third process for producing a package for a device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a preferred embodiment of a package according to a preferred embodiment of the invention. Here, a tea bag lfor containing one portion of tea leaves 2 is shown. A string 3 is fastened to the tea bag 1 by any suitable method such as stapling, and connected to a holder 4 which can be made of paper. The material 5 of the tea bag 1 is a porous paper which does not dissolve in hot water but is at the same time permeable to the water in such a way that the tea leaves 2 inside the bag 1 can be subjected to the water, and the flavour from the leaves be drawn out from the leaves 2 and pass out into the surrounding water while the leaves themselves stay behind.

When the tea bag 1 is used, it is inserted into a container, such as a cup 6, with hot water 7 and left there for a period of time, preferably about 3-5 minutes. The water can now pass through the material of the tea bag 1 and wet the tea leaves 2, which will begin to give off the substances that give the tea its flavour and other properties, including oxalic acid. The oxalic acid comes into contact with an active substance, preferably an enzyme from the groups of oxalate decarboxylase (EC 4.1.1.2) or oxalate oxidase (EC 1.2.3.4), for instance as it passes through the material 5 of the tea bag 1. After a degradation process, the oxalic acid is degraded into substances which are harmless to humans in the quantities which can be expected from the process, and after the brewing time only a small amount of oxalic acid is present in the finished tea, or indeed no oxalic acid at all!

The tea bag 1 can now be removed from the cup 6 by pulling the string 3, and the tea is ready for drinking.

If an oxalate oxidase is used, the oxalic acid is degraded into carbon dioxide and hydrogen peroxide, and if oxalate decarboxylase is used, the result is carbon dioxide and formic acid. Little or no difference in taste from the original tea will be perceived by the consumer, especially in the case of formic acid being produced, since this acid will taste the same as the now removed oxalic acid.

In another embodiment of the invention, the package for containing tea leaves is made for containing several portions of tea leaves, and the substance, preferably an enzyme from the groups described above, is mixed with the tea leaves, creating a tea leaf mixture inside this larger package. For brewing, the consumer would extract an amount of tea leaf mixture and insert into a suitable container for use with a cup or a teapot, or indeed directly into the cup or teapot itself. After hot water is added, the tea is being brewed and at the same time undergoes the process of removing oxalic acid. After a suitable time period, the tea leaves can be removed along with the enzyme, or the enzyme can be left in the newly brewed tea.

It would also be possible for a package according to another embodiment of the invention to contain a separate compartment for the active substance in such a way that a suitable amount of this substance is mixed with tea leaves before or during brewing.

In Fig. 2, a preferred method for producing a material for a tea bag according to the preferred embodiment of the invention described above is shown. A material such as a paper 5 suitable for tea bags is produced according to any suitable method, and passed continuously along a manufacturing line, where at the end stage of the production a spray nozzle 22 is placed to spray the paper 5 with a solution 31 containing the active substance chosen, preferably an enzyme from the groups of oxalate oxidase or oxalate decarboxylase. This solution can also contain water and a buffer to keep the pH of the solution at a stable level. After the paper 5 has been sprayed with the solution 31, it passes through a drying device 23 for drying the paper 5 and thus producing a material containing the active substance in a convenient manner. The paper 5 can be stored on a roll 24, from which tea bags are later made by any suitable method.

As the resulting tea bag is put into hot water in a manner shown in Fig. 1, the active substance can be dissolved in the water and flow freely in the cup, degrading oxalic acid

inside the tea bag as well as outside. In this case, the active substance remains in the cup and is drunk along with the tea, but remains harmless for human consumption in the concentrations which can be anticipated according to this method.

In Fig. 3, an alternative method for producing the material for the tea bag 1 is shown. Here, a paper material 5 is first sprayed with a solution 32 containing carboxymethyl cellulose (CMC) or another polysaccharide, for instance xylan, glucomannan or pectin, at a first spray nozzle 21 and subsequently dried in a drying device 23 A. Then, the paper 5 is sprayed by a second spray nozzle 22 with the solution 31 containing the active substance. Now, the charged groups of the CMC will bind the substance, which will give a stronger bond than an ordinary spraying, before the paper 5 is dried in the drying device 23B and rolled onto the roll 24. The ionic bond created between the active substance and the CMC is strong enough to hold even as the finished tea bag is immersed in hot water, making it possible for the oxalic acid in the tea leaves to be degraded during the passage through the material 5 of the tea bag 1 shown in Fig. 1.

Fig. 4 shows a third method for producing the material 5 for the tea bag 1. Here, the paper 5 is transported along a series of rollers 41 and during its path dipped into a bath 42 with a solution containing ethyl-3-(3-dimethylaminopropyl)-carbodiimide, which acts as a reagent and serves to activate the paper 5. Afterwards, the paper continues into a second bath 43 where the active substance, preferably an enzyme, is present. The inactive sections of the enzyme are now bonded to the material 5 and forms very strong covalent bonds. Afterwards, the paper passes through a drying device 23 where it is dried before being rolled onto the roll 24.

When the resulting tea bag filled with tea leaves is placed in hot water, the active substance will stay even more securely fastened to the material 5 of the tea bag 1 than is the case with an ionic bond as described above. The oxalic acid from the tea leaves 2 will be degraded as the acid passes through the material 5, and the amount of oxalic acid will be reduced to a level where the health effects are negligible. After brewing, the tea bag 1 is removed along with the active substance remaining in connection with the material 5 of said tea bag 1.

Test data on the degradation of oxalic acid in tea using oxalate oxidase is shown in Fig. 5. It can be seen from this figure that the degradation of most of the oxalic acid present in a cup of tea is degraded in a matter of minutes, corresponding to the recommended time of 3-5 minutes for keeping tea leaves immersed in hot water in order to brew tea.

Another way of adding the active substance to the tea bag 1 is to include said substance, for instance in the form of powder or granules, among the tea leaves inside the bag. The active substance would then begin the process of degrading oxalic acid as soon as the tea bag 1 including tea leaves 2 is inserted into the hot water 7 and would come into contact with said oxalic acid in an easy and convenient manner.

It is evident to the person skilled in the art that the method, the device, and the method for producing the device can be varied within the scope of the appended claims. For instance, the packages used can be of any kind of design and made from a number of different suitable materials. The method could also work well at lower temperatures and could be used for any beverage containing oxalic acid, for instance coffee or a beverage containing cocoa, spinach or rhubarb. For a cocoa package, for instance, the substance for removing oxalic acid could be placed in a separate compartment inside the package and be mixed with the cocoa before manufacturing of a beverage. The substance for removing the oxalic acid could also be another than those described herein.

It is thus possible to understand the invention more generally as relating to a package containing a substance for making a brewage and which package also contains a substance for removing oxalic acid from the brewage during brewing. It follows that the invention can also be understood generally in terms of a method for making such a package.