FILTER BAG

The object of the invention relates to a filled filter bag, which comprises a liquid-permeable filter wall delimiting a closed internal space and suitable for retaining a filling in the internal space.

The object of the invention also relates to a method for the production of such filter bags.

Filter bags have been used for many years with fillings such as teas, medicinal herbs, or herbs and spices. Patent documents numbered WO201 1 /047836, US2005/0051478, or EP1946652, for example, present such filter bags. The essence of the filter bag is that the filter wall permits liquid to flow through it, however it retains the filling located inside the filter within the filter. Filter bag is usually dipped into a hot liquid, usually hot water, which dissolves the active substance from the filling stored in the filter bag. The advantages of filter bag teas include cleanliness, easy control, disposability, and quick and simple use, as after preparation of the beverage the filling may be easily removed from the liquid along with the filter bag. The material of the filter bag may be, for example hemp, paper, silk, nylon or plastic.

In order to facilitate quick preparation of the beverage, the filling in the filter bag must react with the liquid it comes into contact with quickly, therefore the filling must have a large surface area. However, this involves the disadvantage that the filling packaged in the filter bag is subjected to contact with the air over a larger surface area, which means it loses its aroma sooner.

In the solutions according to the state of the art, the filling is placed in the filter bag in a raw (fresh), dried or frozen condition.

Among the listed possibilities, filler in a raw state provides the best quality, however, due to its limited shelf life, this solution is rarely used. Drying process ensures a long shelf life, however, the organoleptic properties (taste, smell, consistency, colour, etc.) are less intense as compared to untreated, raw filling. Freezing processing for preserving various kinds of foodstuff and for conserving nutritional value has been used for a very long time. The reason for its widespread use is this method best ensures the preservation of the nutritional value, advantageous characteristics, taste, smell, vitamin and enzyme content of the original raw materials and processed foodstuffs. The disadvantage of the method is that the product must be kept in frozen condition up until final use, as products may not be refrozen after defrosting. This mainly represents a problem when transporting frozen products home.

It was recognised that the organoleptic characteristics of the dried fillings frequently used in filter bags fall far short of those of raw or frozen fillings.

It was also recognised that as the filling of the filter bags has a very low weight, their heat capacity is also low. Fillings frozen on their own quickly start to melt at room temperature when cooling is stopped, which makes transportation difficult.

It was also recognised that fillings frozen on their own are much more susceptible to freezer burn than frozen products consisting of larger pieces, which has an unfavourable influence on the shelf life and enjoyment value of the product.

An apparent solution to the above problem may be if the filling is embedded in a frozen block of liquid (block of ice). Patent document number GR940100402, for example, presents such a frozen filling embedded in a frozen block of liquid (in ice), where the ice cubes contain fruit juice in them, or are mixed with herb extract and cooled to under freezing point. According to the specification, the ice cubes are placed in plastic packaging.

Filling frozen in a block of ice retains its original (when in the raw state) organoleptic characteristics for a long time, and the frozen liquid block prevents the filling from melting quickly, and reduces the filling's susceptibility to freezer burn. A further advantage of this solution is that the ice protects the plant content against sublimation, thereby increasing shelf life. In addition to the advantages mentioned, however, the solution has numerous disadvantageous characteristics. The block of ice placed in hot liquid melts only slowly. Therefore, it takes a long time before the filling within the ice block starts to dissolve. It also happens on many occasions that by the time the outer layers have melted, the liquid cools down so much, just as a result of environmental heat loss, that the active substance content of the filling is unable to or only slightly able to dissolve. This, on the one part, desires the use of a - - wastefully large amount of filling, and, on the other part, generates quality problems in that the filling sections within the various (internal-external) layers of the ice block are subjected to significantly different degrees of heat shock. Due to the large heat capacity of the solid block of ice, the temperature of the ready beverage is significantly lowered, and so its enjoyment value is damaged.

The objective of the invention is to provide a filled filter bag containing a liquid-permeable filter wall delimiting a closed internal space and suitable for retaining a filling in the internal space which is free of the disadvantages of the solutions according to the state of the art, especially to provide a filling that melts more quickly and evenly and that retains the original value of the content.

The objective of the invention is also to provide a method for the production of such filter bags.

The invention is based on the recognition that melting can be accelerated and made more even by using an open-cell and/or closed cell porous frozen filler medium instead of a frozen block of liquid, due to which an infusion may be made that has a greater content and is of a better quality. The invention is also based on the recognition that the porous frozen filler medium has less heat capacity for one unit of volume as compared to the frozen block of liquid, due to this its cooling effect on the liquid used to melt it is less and the melting process itself takes less time, at the same time its volume is sufficiently large to lessen the susceptibility of the frozen filling to freezer burn. The invention is also based on the recognition that the porous frozen filler medium may also function as a carrier for active components, and that aesthetic bag shapes may be formed by shaping the frozen filler medium.

In accordance with the invention the task was solved with the filled filter bag according to claim 1 and with the method according to claim 14.

Certain preferable embodiments of the invention are specified in the subclaims.

Further details of the invention will be presented in connection with embodiments, with reference to figures. Wherein

Figure 1 a illustrates a schematic perspective image of a preferable embodiment of the filled filter bag according to the invention containing closed cell porous frozen filler medium and a frozen filling embedded in it, - -

Figure 1 b illustrates a schematic perspective image of a preferable embodiment of the filled filter bag according to the invention containing open cell porous frozen filler medium and frozen filling embedded in it,

Figure 2a illustrates a schematic side-cutaway image of a preferable embodiment of a template and pressing tool serving for the production of the shaped filter wall according to the invention,

Figure 2b is a schematic side-cutaway image of a preferable embodiment of a filter wall shaped using the template and pressing tool shown in figure 2a,

Figure 3a is an overview flowchart of a preferable embodiment of the method aimed at the production of the filled filter bag according to the invention,

Figure 3b is an overview flowchart of another preferable embodiment of the method aimed at the production of the filled filter bag according to the invention.

Figure 1 a illustrates a schematic perspective image of a preferable embodiment of the filled filter bag 10 according to the invention. The filled filter bag 10 contains a closed cell porous frozen filler medium 22 and frozen filling 24 embedded in it, which together form the frozen mixture 30. In the context of the present invention porous means a structure that contains closed or open cavities filled with gas. The porous structure may be open cell or closed cell, or a combination of these. The cavities of an open cell porous structure permit the flow of fluids (liquids, gases) between the cavities, while the cavities of a closed cell structure are separated from each other by walls, which prevent the flow of fluids from one cavity to the other.

In the case of the embodiment illustrated in Figure 1 a the frozen filler medium 22 is produced during freezing by being mixed with a non-toxic gas or gas mixture resulting in a closed cell porous medium. The non-toxic gas or gas mixture is present in the frozen filler medium 22 as closed or, optionally, open gas bubbles of various sizes. The gas or gas mixture preferably contains a protective gas, carbon dioxide and/or nitrogen, but, naturally, the use of other inert gases is also conceivable, as is obvious for a person skilled in the art.

In the case of an especially preferable embodiment the closed internal space 12 of the filter bag 10 contains one or more space-increasing elements embedded in the frozen filler medium 22. The space-increasing element may be, for example, a - - plant part or other spatial element that does not damage consumption enjoyment, such as a plastic grid, which is suitable for ensuring faster dissolving of the filling 24.

In the case of the embodiment in Figure 1 b the frozen filler medium 22 is made as an open cell porous medium, which contains several substantially spherical ice pellets made using a quick-freeze process. The concept of substantially spherical also includes sphere-like shapes (e.g. droplet shape). In the case of a preferable embodiment the average diameter of the sphere-like ice pellets is between 0.15 - 7 mm, preferably 2 - 5 mm, and even more preferably 2.5 - 3.5 mm. The average diameter of the ice pellets is most preferably approximately 3 mm. An average diameter of approximately 3 mm means that the average diameter of at least 80% of the ice pellets falls between 2 and 5 mm so that the maximum of distribution is at 3 mm.

Optionally, an embodiment is also conceivable in the case of which the surface of the ice pellets is coated with a coating regulating the speed of melting, one or more sugar layers for example.

In the case of the embodiment shown in Figure 1 a the filter bag 10 contains a liquid-permeable filter wall 14 delimiting the closed internal space 12 retaining the filling 24 in the internal space 12. With respect to its material the filter wall 14 is preferably heat-softening plastic mesh, the grid size of which is preferably between 25 - 500 microns, preferably between 100 - 200 microns, more preferably approximately 150 microns. Grid size, in the context of the present invention, means the distance between two neighbouring cross members of the plastic mesh. Naturally, the filter wall 14 may be made from other liquid-permeable materials, such as paper, hemp, woven silk, etc., as is obvious for a person skilled in the art. In the case of the embodiment presented in Figures 1 a and 1 b, the filter bag 10 contains an elongated filter tab 18 fixed to the filter wall 14 in a permanent way, which may be, for example, an element comprising a thread 18a and a gripper sheet 18b fixed at its end. The material of the filter tab 18 may be, for example, heat-softening plastic, paper, fabric, thread, etc. It should also be noted that the filter tab 18 may optionally be made from the material of the filter wall 14. During use the filled filter bag 10 is immersed in steeping liquid, such as hot water, which gets into the internal space 12 through the liquid-permeable filter wall 14 and comes into contact with the frozen filler - - medium 22 and the frozen filling 24 embedded in it. The filter bag 10 may be easily grasped by the filter tab 18 and then removed from the steeping liquid.

In the case of an especially preferable embodiment the filter wall 14, the frozen filler medium 22 inserted in the internal space 12 and the frozen filling 24 embedded in it are established as a flattened spatial form with a high surface/volume ratio (such as a leaf, heart, star, etc.), therefore, in addition to an aesthetic appearance the frozen filler medium 22 and the filling 24 embedded in it of the filter bag 10 immersed in the steeping liquid are able to come into contact with the steeping liquid over a large area. The role of this will be explained below.

In the case of the embodiment illustrated in Figures 1 a and 1 b the filter bag

10 is placed in a freezing shape 16 suitable for storing it and, optionally, for establishing the frozen filler medium 22 and the frozen filling 24 embedded in it, into which the filter bag 10 preferably substantially fits. The freezing shape 16 may be made from materials such as plastic, rubber, silicon, or other, preferably flexible materials, from which the filter bag 10 may be removed when used at a later time. In the case of this embodiment the frozen filler medium 22 and the frozen filling 24 embedded in it are established to fit in the closed internal space 12 delimited by the filter wall 14, in other words the frozen filler medium 22 and the frozen filling 24 embedded in it completely fill the internal space 12 and conform to its shape. Naturally an embodiment may be conceived in which the frozen filler medium 22 and the frozen filling 24 embedded in it only partially fill the internal space 12.

The frozen filler medium 22 and/or the frozen filling 24 embedded in it contain at least one type of soluble active component, which continuously dissolves through the filter wall 14 in the steeping liquid getting into the internal space 12. In the context of the present invention active component means a substance that changes the colour and/or taste of the steeping liquid getting into the internal space 12, and/or exerts a physiological and/or organoleptic effect during consumption. Such active components may include natural colourings, artificial colourings used in the food industry, spices, cocoa powder, flavourings, aromas, sweeteners, coffee, tea leaves, herbs, herbal extract, fruit, other plant parts, minerals, vitamins, medicines, medicine excipients, nutrition supplements, energy supplements, proteins and similar. The sweeteners may be natural sweeteners, such as honey, beet sugar, fructose, cane sugar, malt syrup, glucose syrup, xilit, stevia, etc., or artificial sweeteners used in the food industry, such as saccharine, aspartame, Na-cyclamate, acesulfame-K, etc.

In the following an especially preferable embodiment of the production of the filter bag 10 according to the invention is presented with reference to Figures 2a, 2b and 3a. During the method a frozen mixture 30 containing porous frozen filler medium 22 and frozen filling 24 is provided in the internal space 12 of the filter bag 10, which is created by producing a porous frozen filler medium 22 by freezing a liquid medium containing one or more liquids, and the frozen filling 24 is embedded into the frozen filler medium 22 while it is being made or subsequently. With the embedding the surface of the filling 24 that comes into contact with the air can be significantly reduced, in this way reducing the susceptibility of the filling 24 to freezer burn, in other words preventing sublimation and oxidation processes starting as a result of the air. Due to this the frozen filler medium 22 provides sufficient protection for the essential oils and valuable active substances found in the filling 24.

In the case of a preferable embodiment the liquid medium is water, but apart from this the use of any other edible liquid, optionally containing an active component, such as milk, glucose syrup, liquid colouring, liquid sweetener (such as honey), liquid aromas, etc. is also conceivable, as is obvious for a person skilled in the art. Naturally an embodiment is also possible where the liquid medium is made from a mixture of more than one liquid.

In the case of a preferable embodiment the filling 24 contains aromatic plant material, which may be e.g. a medicinal plant, herb, tealeaves, fruit, etc. The filling 24, however, may also contain any other edible material, or material that although not edible does not dissolve to produce hazardous materials in the drink used during consumption, therefore, fillings 24 may include decorative flower petals, other parts of plants or other objects, such as beads, small children's toys, etc.

Optionally, the filling 24 is subjected to pre-treatment before being mixed with the liquid medium. Such pre-treatment may include processes widely used in the food industry, such as drying and/or blanching and/or damaging, the purpose of which includes enhancing the flavours, blocking enzyme activity (preventing discolouration, oxidation), transforming the cell structure, reducing the bacterial count, accelerating the release of active substances, etc. as is known to a person - - skilled in the art. Optionally, a pre-treatment process is also conceivable the purpose of which is to actually retain the enzymes.

During drying the initial moisture content of the filling 24 is significantly reduced using a chemical or physical process. Blanching (pre-cooking) may take place in a continuous or intermittent operation device, usually in water, more rarely in steam. The pre-cooking temperature is usually 50-100 °C, its duration 1 -10 minutes. The heat treatment is followed by intermittent or fast cooling. With the targeted damaging (e.g. chopping, making incisions, etc.) of the filling 24 before freezing, channels that promote the dissolving of the active substances of the filling 24 open, which on melting open a path for the essential oils in the filling 24, thereby increasing the efficiency of infusion. The freezing of the filling 24 seals the channels formed due to the damaging, which will only again be passable after the filling 24 has melted. In the case of a preferable embodiment the damaged filling 24 is immediately placed in liquid medium, so the active substances flowing due to the damage filling 24 do not evaporate, instead they are retained in the frozen filler medium 22.

In the case of a preferable embodiment of the method according to the invention a closed cell frozen mixture 30 is provided so that in the first step the filling 24 is mixed with the liquid medium, thereby making a liquid mixture. The liquid mixture is preferably cooled using a fast freezing method in such a way that the liquid mixture is mixed with a non-toxic gas or gas mixture during freezing. Mixing here means having a gas or gas mixture flow through the liquid mixture, in other words during the freezing process a non-toxic gas or gas mixture is made to flow through the liquid mixture in the form of tiny bubbles, or, optionally, a liquid gas-forming material subliming at a temperature under the freezing point of the liquid mixture, such as liquid nitrogen is injected into the liquid mixture thereby producing the gas bubbles.

The liquid mixture is frozen suddenly using a fast freezing method, for example, due to this the frozen mixture 30 will have a porous structure, inside which closed or open cavities conforming to the gas bubbles flowing through the liquid mixture are created.

Preferably carbon dioxide or nitrogen is used as the non-toxic gas, but, optionally, the use of other non-toxic gases or gas mixtures is also conceivable, as is obvious for a person skilled in the art. In the context of the present invention, a non- - - toxic gas or gas mixture means an edible gas or gas mixture the consumption of which does not have a health-damaging effect on the human body.

The advantage of the porous frozen mixture 30 is that due to the cavities within it, it contains less liquid medium per unit volume than a frozen mixture 30 made without being mixed with gas. Due to the bad heat transmission ability of the gas or gas mixture filling the cavities of the porous frozen mixture 30 as compared to liquids, it does not melt substantially faster in air than the frozen mixture 30 made without being mixed with gas, therefore the advantages mentioned in connection with the transportation of the filter bags 10 continue to exist. The advantage of the porous frozen mixture 30 is that as it contains less liquid medium than the frozen mixture 30 created without being mixed with gas, therefore its heat capacity per unit volume is less, and so it cools the steeping liquid down less.

The essence of the fast freezing method is that the liquid mixture is frozen in the shortest time possible (preferably within a few minutes), almost in a shock-like manner. As a consequence of this the water in the filling 24 of the liquid mixture freezes in the form of tiny ice crystals, therefore when the filling 24 melts its cell walls are not damaged, which is unavoidable if the filling 24 were to be cooled slowly, creating large ice crystals. As a result of the fast freezing method, the filling 24 retains its original shape, colour, useful materials, smell, etc. A further advantage of the fast freezing method is that it makes it easier to create the cavities filled with gas in the frozen mixture 30, as less gas is able to evaporate from the liquid mixture as a result of the acceleration of freezing.

In the case of an especially preferable embodiment the liquid mixture is cooled in a sealed space preventing the evaporation of the non-toxic gas or gas mixture, preferably in a capsule to the temperature of the freezing point of the liquid medium, or below. The form of the capsule is preferably the same as the shape of the open supporting part 13 of the filter wall part 14a, so a frozen mixture 30 can be made that precisely fits in the filter bag 10.

Optionally, the liquid mixture is intermittently or continually moved, preferably shaken while being frozen, with this the distribution of the liquid mixture may be improved, the melting surface increased and the degree of liquid transmission improved within the frozen mixture 30. A further preferable effect of the moving is that it increases the number of bubbles within the frozen mixture 30, which has a - - preferable effect on melting ability and on the evenness of active substance dissolution.

In the case of an especially preferable embodiment of the method according to the invention the filter wall 14 is made using the template 40 and pressing tool 42 presented in Figure 2a using so-called heat shaping in such a way that in the first step a filter material sheet 15 is placed on the template 40 preferably made from a heat-resistant material, such as metal or silicon. The filter material sheet 15 is preferably a heat-softening plastic mesh, such as PET, which may be easily shaped when heated, and which maintains its formed shape when cooled. In the second step of the method the pressing tool 42 matching the template 40 is heated to operation temperature. Operation temperature is the temperature sufficient for the pressing tool 42 to heat up the filter material sheet 15 to shapable temperature, without overheating it or damaging it. The filter material sheet 15 is pressed against the template 40 with the heated pressing tool 42, due to this the filter material sheet 15 between the template 40 and the pressing tool 42 heats up to shapable temperature and takes on the shape of the template. After the temperature has been reduced and the pressing tool 42 removed, the shaped filter material sheet 15 retains the shape of the template 40, through this a filter wall part 14a with an open supporting part 13 is created (see Figure 2b).

The open supporting part 13 of the filter wall part 14a is sealed with sealing filter material 14b, in this way producing a filter wall 14 delimiting a closed internal space 12. The sealing filter material 14b is preferably heat-softening plastic, the same as that used for the filter material sheet 15, such as PET, but naturally the use of other materials is also conceivable. In the case of a preferable embodiment, while sealing the open supporting part 13 of the filter wall part 14a the sealing filter material 14b is fixed to the filter wall part 14a by ultrasound welding. During the ultrasound welding process due to the absorption of vibration energy and its reflection from the other part, and as a result of the friction heat occurring, the vicinity of the welding point gets hot. As a result of the vertical vibrations the material locally melts, and an irreversible bond is created in a very short period of time. Naturally, in addition to ultrasound welding, the sealing filter material 14b may be fixed to the filter wall part 14a in other ways as well (such as by gluing, spot welding, thermal welding, laser welding, etc.), as is obvious for a person skilled in the art. - -

Figure 3a illustrates an overview flow chart of a preferable embodiment of the method according to the invention, during which the frozen mixture 30 comprising the frozen filler medium 22 in the closed internal space 12 of the filter bag 10 and the frozen filling 24 embedded in it is provided in the following way.

In the initial step 100 of the method the filling 24 is mixed with the liquid medium in a freezing shape 16 with an internal surface (wall) 16' substantially the same as the shape of the open supporting part 13 of the filter wall part 14a, by this creating a liquid mixture. During step 102 the liquid mixture is cooled in the freezing shape 16 to a temperature equal to the freezing point of the liquid medium or below in such a way that during the freezing process the liquid mixture is mixed with a nontoxic gas or gas mixture. As a result of the cooling the liquid mixture freezes, and is transformed into a porous frozen mixture 30, which contains the cavities made by the gas or gas mixture made to flow through the liquid mixture. As the liquid mixture takes on the shape of the internal surface 16' of the freezing shape 16 and as the liquid mixture substantially retains its shape during freezing, the shape of the frozen mixture 30 will be substantially the same as the shape of the internal surface 16' of the freezing shape 16.

During step 104 the frozen mixture 30 is filled into the open supporting part 13 of the filter wall part 14a, then in step 106 the open supporting part 13 is sealed, with the ultrasound welding process mentioned above, for example, using the sealing filter material 14b. Following this the filled filter bag 10 may be replaced in the freezing shape 16 and packaged together with it, using film wrap, for example. An embodiment is also conceivable in which the frozen mixture 30 is not produced in the freezing shape 16 later serving as storage, instead in another similarly formed shape serving for this purpose.

Figure 3b illustrates an overview flow chart of another preferable embodiment of the method for producing the filled filter bag 10 according to the invention , which differs from the embodiment presented in Figure 3a in that the open supporting part 13 is sealed before the frozen mixture 30 is created. In this embodiment in the first step 100' of the method the filling 24 is arranged in the open supporting part 13 of the filter wall part 14a, then in step 102' the open supporting part 13 is sealed with sealing filter material 14b. Liquid mixture is created in step 104' by mixing the liquid medium with the filling 24 located in the closed internal space 12 through the filter - - wall 14. This may take place by placing the filter wall 14 containing filling 24 in a freezing shape 16 with an internal surface 16' substantially the same as the shape of the filter wall part 14a, then following this or in advance the liquid medium is filled into the freezing shape 16. Passing through the liquid-permeable filter wall 14, the liquid medium penetrates into the closed internal space 12 and mixes with the filling 24 located there. In this way liquid medium and liquid mixture containing the filling 24 are provided in the closed internal space 12. In step 106' of the method the liquid mixture is cooled in the freezing shape 16 to the temperature equal to is freezing point, or below it in such a way as to mix the liquid mixture during freezing with a non-toxic gas or gas mixture. In the case of this embodiment the gas or gas mixture, similarly to the liquid medium, gets into the liquid mixture through the filter wall 14.

The filling 24 and the liquid medium may be mixed together before sealing the filter wall part 14a. In this case, during mixing, the filling 24 is in the open supporting part 13, which is only sealed with sealing filter material 14b after the creation of the liquid mixture or only after the creation of the porous frozen mixture 30.

In the case of an exemplary embodiment in a frozen mixture 30 containing closed cell porous frozen filler medium 22 the total volume of the cavities filled with the gas or gas mixture is 5-30% of the total volume of the frozen mixture 30, optionally an embodiment is also conceivable where this ratio is greater than 30%, 30-60% for example, or between 60-80%.

In the case of another especially preferable embodiment of the method according to the invention an open cell porous frozen mixture 30 is provided so that a plurality of substantially spherical ice pellets are made preferably using fast freezing, in a way known to a person skilled in the art, from the liquid medium, then the frozen filling 24 is embedded among the ice pellets. Optionally, the ice pellets of the frozen mixture 30 may be stuck to one another after the embedding of the filling 24, for example by the addition of edible adhesive materials, or heat shock (fast heating, then cooling). Naturally an embodiment may be conceived in which the ice pellets are not stuck to one another, instead the filter wall 14 keeps them together.

An important characteristic of the ice pellets is that it is not absolutely essential to create them together with the frozen mixture 30, which may be preferable from the point of view of production technology. Using many small-sized pellets an - - open cell porous frozen mixture 30 can be created that has even liquid transmission characteristics. With this, the melting characteristics of the frozen mixture 30 improve significantly while the negative effects originating from the melting together of the ice pellets remain at an acceptable level. A further advantage of the use of ice pellets is that the liquid medium serving as the basic material may be separated per component, varied per material, and the aesthetic properties of the final product may be improved (blackberry-coloured ice pellets, combined with raspberry coloured ice pellets, etc.).

In the case of an especially preferable embodiment the surface of the ice pellets is provided with a coating influencing the melting of the ice pellets, such as sugar coating, with which melting orders may even be determined when using ice pellets with differing content.

In the case of a preferable embodiment the filter bag 10 is packaged in the freezing shape 16 in such a way that the filter bag 10 is placed in the freezing shape 16 and the freezing shape 16 is sealed in some way, with plastic film, for example. In this way then, the filled filter bag 10 may be sold together with the freezing shape 16. With the filter bag 10 stored in the freezing shape 16 the frozen mixture is less fragile, it does not get broken during transportation and storage and does not puncture the filter wall 14, which would have a negative influence on or possibly even exclude use by the consumer.

During an exemplary use of the filter bag 10 the sealing element is removed, the filter bag 10 containing the frozen mixture 30 is taken out from the freezing shape 16, then while holding it by the filter tab 18 it is placed in hot liquid, such as hot water. The hot liquid gets into the internal space 12 through the filter wall 14, where it gets into thermal contact with the frozen filler medium 22 located there and with the frozen filling 24 embedded in it, and passes heat energy on to them. As a result of the heat energy passed on the frozen filler medium 22 and the frozen filling 24 embedded in it start to melt, the frozen filler medium 22 gradually turns into a liquid medium, while the frozen filling 24 melts. During the melting process and/or following it the active components dissolve into the steeping liquid.

The previously presented flattened structure of the frozen filler medium 22 and the frozen filling 24 embedded in it involves numerous advantages as long as it is to be employed in the filled filter bag 10 according to the invention. The surface - - increased in size due to the flatness further increases the dissolving of the active components from the internal space 12 of the filter bag 10 into the steeping liquid.

Before using the filter bag 10 it is preferable to store it in a household deep freezer, which keeps the filter bag 10 typically at a temperature of between -10 and - 18 °C. The weight of the porous frozen mixture 30 filled into filter bag 10 should be selected so that at the aforementioned temperature is does not significantly cool down the steeping liquid while melting, it should still be able to be drunk as a hot beverage, such as tea. In the case of a filter bag 10 destined for 1 cup (approx. 100- 300 ml hot liquid), the weight of the porous frozen mixture 30 is preferably between 5 and 25 grams, in the case of filter bags 10 destined for larger vessels, such as jugs, the weight of the porous frozen mixture 30 may also, naturally, be larger.

The advantages of the porous frozen filler medium as compared to a frozen block of liquid are the following:

- with a smaller amount of liquid medium significantly more plant material may be consumed in a given volume,

- the porous structure has less melting heat, due to which the porous frozen mixture 30 cools the hot liquid down less, and so an infusion can be made that has greater content and a higher temperature when consumed,

- the steeping liquid cools less as a consequence of environment effects, due to this more active substance can be dissolved in the same amount of time,

- as a result of more even melting the various parts of the filling 24 are subjected to nearly the same heat shock, therefore quality deterioration factors originating from steeping differences are fewer, and

- the larger part of the active substances of the filling 24 is dissolved at the optimal temperature, therefore the use of less filling 24 is sufficient to achieve the same effect.

It is obvious for a person skilled in the art that alternative solutions are conceivable as compared to the embodiments presented here, which, however, fall within the scope of protection determined by the claims.