Process for coating powder compacts, in particular for the preparation of capsules containing beverage powders

Abstract

A method for coating powder compacts, in particular for producing capsules containing powdered beverages, comprising: i) providing a powder compact of a powder containing at least one polysaccharide; ii) providing a vessel having a vessel wall of perforated material surrounding a cavity, the vessel having an inlet opening for introducing a coating liquid into the cavity; and iii) placing the powder compact within the cavity of the container, the powder compact being smaller than the volume of the cavity, the method further comprising: iv) introducing a coating liquid containing a coating material into the cavity through the inlet port; v) immersing the container filled with the powder compact and the coating material in a curing agent liquid containing a curing agent compound, wherein the viscosity of the curing agent liquid is lower than the viscosity of the coating liquid; and the method further comprises: vi) removing the container from the hardener liquid and removing the coated powder compact from the container.

Description

[Technical Field]

[0001] The present invention relates to a method for coating powder compacts to produce capsules containing beverage powders, particularly suitable for preparing beverages such as cocoa, tea or coffee. [Background technology]

[0002] In recent years, coffee capsules, whose capsule walls are typically made of stainless steel, aluminum, or plastic, have increasingly been used in addition to coffee pods for preparing beverages, especially individual cups of brewed coffee. Such capsules allow coffee powder to be stored for longer periods without loss of aroma. Additionally, they allow for the rapid and user-friendly production of a cup of coffee with a desired flavor by inserting a capsule containing the desired coffee type into an adapted coffee machine, where hot water is then forced through the capsule to produce brewed coffee. However, such capsules are relatively expensive, in part due to the capsule material used and their production-intensive capsule design. Furthermore, such capsules are environmentally problematic. On the one hand, capsules are not recyclable and are typically disposed of by consumers as residual waste after use. Therefore, coffee capsule recycling is virtually nonexistent, which is particularly concerning for aluminum-based coffee capsules, since aluminum production is very energy-intensive and the CO₂ balance for such capsules is particularly poor. Another major drawback is that such capsules are not biodegradable and therefore cannot be biologically disposed of. Considering that over 2 billion coffee capsules are consumed each year in Germany alone, this is a serious problem.

[0003] Capsules made from alternative materials have already been proposed to at least partially avoid the above problems.

[0004] For example, WO 2010 / 006979 A1 discloses a capsule filled with coffee or tea and including a capsule wall containing water as a structuring component in addition to the capsule contents. However, to form a stable capsule wall, the capsule must be cooled below the freezing point of the structuring component, because the structuring component melts above its freezing point and wets the capsule contents. This, of course, significantly limits the use of such capsules.

[0005] WO 2009 / 053811 A2 describes a capsule that can contain ground coffee, cappuccino powder, chocolate powder, milk powder, or tea powder. The capsule includes two half shells that form a capsule wall. Here, the capsule wall is made of a material that is soluble in water and dissolves during the brewing process. In this concept, the capsule wall material dissolves during the brewing process and therefore becomes part of the prepared beverage, which can have an undesirable effect on the taste. Apart from this, the production of such capsules is complex and expensive.

[0006] To overcome the above drawbacks, EP 3 115 316 A1 has also proposed capsules particularly suitable for coffee production, including compacts of a powder containing at least one polysaccharide, such as coffee powder, coated with at least one coating layer containing a cross-linked polysaccharide. Preferably, the coating layer is made of alginate, obtained by immersing the thus-treated compacts in an alkali metal alginate solution before immersing them in an alkaline earth metal salt solution. In this process, the alkaline earth metal ions act as cross-linking agents, forming coordinate or ionic bonds with the alginate groups. This provides a water-insoluble coating that does not affect the taste of the beverage produced from the capsule, and provides capsule stability sufficient to ensure transport and contact protection without significant loss of flavor to the capsule contents. Due to the relatively high viscosity of the alkali metal alginate solution, the coating material does not adhere well to the hydrophobic coffee powder compacts. This makes it difficult to transfer the powder compacts from the alkali metal alginate solution to the alkaline earth metal salt solution for immersion. Even when this is done carefully and with specially designed holders, it is difficult, if at all possible, to obtain a sufficiently uniform coating thickness on the powder compact. Summary of the Invention [Problem to be solved by the invention]

[0007] Based on this, the present invention is based on the problem of providing a method for coating powder compacts, in particular a method for producing capsules containing beverage powder for preparing single-serving beverages from beverage powders such as cocoa, tea and coffee, whereby coated powder compacts with a uniform coating thickness are obtained in a simple and reliable manner. [Means for solving the problem]

[0008] According to the invention, this problem is solved by a method for coating powder compacts, in particular for producing capsules containing beverage powder, which method comprises the following steps: i) providing a powder compact of a powder containing at least one polysaccharide; ii) providing a vessel having vessel walls of perforated material surrounding a cavity, the vessel having an inlet opening for introducing a coating liquid into the cavity; and iii) placing the powder compact within the cavity of the container, the powder compact being smaller than the volume of the cavity, the method further comprising: (iv) introducing a coating liquid containing a coating material into the cavity through the inlet port; v) immersing the container filled with the powder compact and the coating material in a curing agent liquid containing a curing agent compound, wherein the viscosity of the curing agent liquid is lower than the viscosity of the coating liquid; and the method further comprises: vi) removing the container from the hardener liquid and removing the coated powder compact from the container.

[0009] This solution is based on the finding that by using a container having a container wall made of perforated material surrounding a cavity and having an inlet opening for introducing a coating liquid, the powder compact can be easily and reliably coated while obtaining a uniform coating thickness for the powder compact. Because the powder compact introduced into the container cavity in step iii) has a smaller volume than the cavity, the powder compact fits into the cavity, forming a space between the powder compact and the inside of the perforated container wall that bounds the container cavity. This space can be filled with the coating liquid by introducing the coating liquid in step iv). Due to the perforations and the inlet opening, the air initially present in the intermediate space is replaced by the coating liquid, allowing the entire intermediate space to be completely filled with the coating liquid in step iv). Because the powder compact floats on the introduced coating liquid, the powder compact is surrounded by a uniformly thick layer of the coating liquid once the interstitial space is completely filled with the coating liquid. Thus, by immersing the container filled with the powder compact and coating material in the hardener liquid, a uniform coating thickness can be easily and reliably obtained. Since the hardener liquid has a lower viscosity than the coating liquid, during step v), the hardener liquid can quickly and uniformly enter the container through the perforated material, i.e., through its small holes, over the surface of the container, and thus contact the coating liquid, while the coating liquid does not exit the container through the perforated material due to its higher viscosity. This makes it possible to easily and reliably obtain a coated powder compact having a uniform coating thickness.

[0010] For purposes of the present invention, perforated material means a material having a plurality of small holes, the holes being regularly arranged in the material and each having at least substantially the same shape and size.

[0011] The present invention is not particularly limited with respect to the polysaccharide-containing material constituting the powder compacts provided in step i). In particular, good results are obtained when the powder compacts comprise, or preferably consist of, a material selected from the group consisting of coffee, tea, drinking chocolate, cocoa, and milk powder. In particular, good results are obtained when the powder compacts consist of ground coffee powder.

[0012] For the purposes of the present invention, the powder compact is understood to be a compressed powder. In particular, good results are obtained when the powder compact prepared in step i) is produced by pressing a powder, in particular coffee powder, at a pressure of 1 to 100 MPa, particularly preferably at a pressure of 5 to 50 MPa, and very particularly preferably at a pressure of 15 to 30 MPa. This provides sufficient compression to ensure that the powder compact is reliably coated and a good oxygen barrier is achieved. At lower pressures, the compaction is insufficient, while at higher pressures, the compaction is excessive, which, under certain circumstances, may relax again after release from the pressure, leading to capsule rupture.

[0013] In principle, the powder compacts can have any shape. Preferably, the powder compacts are spherical. In particular, good results are obtained when the diameter of the spherical powder compacts is 1 to 10 cm, preferably 1 to 5 cm, particularly preferably 2 to 4 cm, and most preferably 2.7 to 3.7 cm.

[0014] Accordingly, it is (likely) preferred that the cavity of the container is also spherical in shape, ie the inner surface of the container is spherical.

[0015] In a further development of the invention, it is proposed that the diameter of the cavity in the container is larger than the diameter of the spherical powder compacts used by 0.5 to 10.0 mm, preferably 1.0 to 8.0 mm, particularly preferably 3.0 to 6.0 mm.

[0016] According to a particularly preferred embodiment of the present invention, the perforated material constituting the container wall of the container is a wire mesh. For the purposes of the present invention, a wire mesh is understood to be a flat structure having similar holes in a regular arrangement, the holes being formed by crossing longitudinal and transverse wires at right angles. On the one hand, wire mesh is relatively cheap and easy to process or form, and on the other hand, the holes contained therein are particularly regularly arranged and have the same shape and size.

[0017] Preferably, the porous material, preferably a wire mesh, has holes of a size or mesh size such that when the container is immersed in the sclerosant fluid, the more viscous coating fluid passes through the perforated material, preferably the wire mesh, and does not exit the container cavity and therefore the container, but the less viscous sclerosant fluid passes into the container, through the perforated material, preferably the wire mesh, and quickly and uniformly across the surface of the container.

[0018] In particular, good results can be obtained when the pore diameter of the porous material of the container wall, or the mesh size of the wire mesh, is 0.01 to 0.30 mm, preferably 0.02 to 0.21 mm, more preferably 0.04 to 0.08 mm, even more preferably 0.05 to 0.075 mm, and most preferably 0.058 to 0.068 mm, for example, about 0.063 mm.

[0019] Thus, it is preferable to use a wire mesh as the porous material for the container wall. Preferably, the wire mesh is made of steel or stainless steel. In a further development of the idea of ​​the present invention, it is proposed that the wire mesh has a wire thickness of 0.01 to 0.30 mm, preferably 0.02 to 0.20 mm, particularly preferably 0.03 to 0.10 mm, most preferably 0.04 to 0.06 mm, and most preferably 0.045 to 0.055 mm.

[0020] According to the present invention, the container provided in step ii) comprises an inlet opening for introducing the coating liquid into the cavity. In order to be able to introduce the coating liquid into the cavity of the container through the inlet opening, according to a further preferred embodiment, it is proposed that a pipe is arranged above the inlet opening of the container, which is fixedly connected to the container and preferably has its longitudinal axis arranged radially on the container wall.

[0021] In principle, the tube can be made of any material, such as the same material as the container, i.e. preferably steel or stainless steel, etc. However, the tube is preferably not perforated.

[0022] In principle, the present invention is not limited with respect to the shape of the tube. For example, the tube may have a rectangular, square, circular, elliptical, oval, or polygonal cross section. Preferably, the tube is a rectangular or circular tube having a length of 1.0 to 5.0 cm, preferably 2.0 to 4.0 cm. Particularly good results are obtained with circular tubes having an inner diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, most preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

[0023] In order to facilitate the introduction of the powder compact into the cavity of the container and the removal of the coated powder compact from the cavity, a further development of the concept of the present invention proposes that the container be composed of two halves connected to each other by a connecting element, such as a hinge, and thus easily joined to form a closed container. In the case of the preferred spherical configuration of the container, the container preferably has two half-carrots connected to each other via a hinge. Both half-carrots preferably have the same dimensions and are formed from the same perforated material. When the two half-carrots are placed on top of each other with their equators closely aligned, they define a spherical cavity, except for the entrance opening, which is preferably formed in only one of the two half-carrots. Particularly good results are obtained when the entrance opening is provided at the pole of one of the two half-carrots.

[0024] The lower, equatorial regions of the two half-callots may also have a slightly different radius of curvature than the upper regions, as viewed in cross section.

[0025] To facilitate accurate and complete placement of the two half-carrots on top of each other, both half-carrots may have an outward collar at their equator that surrounds each half-carrot in a circular ring shape.

[0026] In principle, the present invention is not limited with respect to the shape of the inlet opening. For example, the inlet opening may have a rectangular, square, circular, elliptical, oval, or polygonal cross section. Preferably, the inlet opening has a circular cross section, and the diameter of the inlet opening is preferably 0.1 to 5.0 mm, more preferably 0.5 to 2.5 mm, even more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

[0027] To facilitate and speed up the simultaneous or parallel coating of several powder compacts, the process can also be carried out using multiple containers, whereby a container designed as described above is connected to one or more other containers of the same dimensions in a rack. In this way, multiple containers can be simultaneously immersed in a bath of hardener liquid in a single step. In this embodiment, the rack preferably contains 2 to 100, in particular 5 to 50, containers.

[0028] In principle, the process is not particularly limited with respect to the chemical nature of the coating material contained in the coating liquid and the hardener compound contained in the hardener liquid, as long as the hardener liquid has a lower viscosity than the coating liquid. Examples of suitable coating materials include those selected from the group consisting of starch, cellulose, chitin, carrageenan, agar, and alginate.

[0029] The viscosity of the curing agent liquid is preferably 0.01 to 100 mPa·s, more preferably 0.1 to 20 mPa·s, and most preferably 0.5 to 10.0 mPa·s, for example, 1 mPa·s, and the viscosity of the coating liquid is preferably greater than 100 to 10,000 mPa·s, particularly preferably 200 to 5,000 mPa·s, and most preferably 300 to 1,000 mPa·s, for example, 500 mPa·s.

[0030] The curing compound is selected to crosslink the coating material, preferably via i) covalent bonds or ii) ionic and / or coordinative bonds.

[0031] According to a very particularly preferred embodiment of the present invention, alginate is used as the coating material in the process. This has the advantage that a homogeneous coating is easily and quickly formed by cross-linking with alkaline earth metal ions, i.e., a water-insoluble coating that does not impair the taste of beverages produced from the coated powder compacts, such as coffee. In addition, this provides sufficient stability for the coated powder compacts to ensure transport and contact protection without appreciable loss of flavor of the contents. In addition, calcium alginate is highly biodegradable. Another advantage is that calcium alginate is an approved food additive with E-number E405, meaning it is harmless to health.

[0032] Therefore, it is particularly preferable to use a coating liquid containing an alkali metal alginate (particularly sodium alginate) as the coating material and a hardener liquid containing an alkaline earth metal salt (particularly a calcium salt such as calcium chloride) as the hardening compound.

[0033] For example, good results can be obtained when an alkali metal alginate solution is used as the coating liquid, preferably a 0.5 to 5 wt% aqueous alkali metal alginate solution, particularly preferably a 0.5 to 5 wt% aqueous sodium alginate solution, and an alkaline earth metal salt solution, preferably a 1 to 7 wt% aqueous alkaline earth metal salt solution, particularly preferably a 1 to 7 wt% aqueous calcium chloride solution, is used as the hardener liquid.

[0034] According to another very particularly preferred embodiment of the invention, the method comprises the following steps: i) providing a powder compact of a powder containing at least one polysaccharide; ii) providing a vessel having a wire mesh vessel wall surrounding a cavity, said vessel having an inlet opening for introducing a coating liquid into said cavity, said wire mesh having a mesh size of 0.01 to 0.30 mm, preferably 0.02 to 0.21 mm, more preferably 0.04 to 0.08 mm, even more preferably 0.05 to 0.075 mm, and most preferably 0.058 to 0.068 mm; and iii) placing the powder compact within the cavity of the container, the powder compact being smaller than the volume of the cavity, the method further comprising: (iv) introducing a coating solution containing an alkali metal alginate into the cavity through the inlet port; v) immersing the container filled with the powder compact and the coating material in a hardener liquid containing an alkaline earth metal salt, the viscosity of the hardener liquid being lower than the viscosity of the coating material; vi) removing the container from the hardener liquid and removing the coated powder compact from the container.

[0035] In any of the above embodiments, steps i) to vi) may be performed in the order mentioned. It is equally possible for step ii) to be performed before or simultaneously with step i).

[0036] In addition to the above steps, the process may further comprise, as step vii), drying the coated powder compact obtained in step vi).

[0037] According to a further preferred embodiment, the coating thickness of the dried coated powder compact is 10 to 600 μm, particularly preferably 20 to 40 μm.

[0038] The invention will now be described with reference to the drawings which illustrate the invention in a non-limiting manner. [Brief explanation of the drawings]

[0039] [Figure 1] 1 shows a vessel suitable for a process according to the present invention in an open position, the vessel having a vessel wall formed of a perforated material according to an embodiment of the present invention. [Figure 2] The container shown in Figure 1 is shown in a closed state. DETAILED DESCRIPTION OF THE INVENTION

[0040] A vessel 10, shown in Figure 1, suitable for use in the process according to the present invention includes two half-carrots 12, 12' connected to one another by a hinge 14. The two half-carrots 12, 12' each have the same dimensions and are each formed of the same perforated material, preferably stainless steel wire mesh. The equators 16, 16' of the two half-carrots 12, 12' each have a radially outwardly projecting collar 18, 18' that surrounds the half-carrot 12, 12' in the shape of a circular ring. An inlet opening 20 is provided at the pole of the upper half-carrot 12', above which a tube 22 is disposed that is fixedly connected to the vessel. The two half-carrots 12, 12' form a vessel wall 24.

[0041] In the open state shown in Figure 1, powder compacts can be easily introduced into cavity 26 of container 10 according to process step iii), and the coated powder compacts can be easily removed from cavity 26 of container 10 according to process step v). By folding the two half carrots 12, 12' together via hinge 14, the two half carrots 12, 12' can be brought together and closed with their equators fitting tightly together, as shown in Figure 2. In this state, coating liquid can be introduced into container cavity 26 via tube 22 and inlet opening 20 according to process step iv), and container 10 filled with powder compacts and coating material can be immersed in a hardener liquid container according to process step v).

Claims

1. 1. A method for coating a powder compact, comprising: i) providing a powder compact of a powder containing at least one polysaccharide; ii) providing a container (10) having a wall (24) with a plurality of holes surrounding a cavity (26), said container (10) having an inlet opening (20) for introducing a coating liquid into said cavity (26), said method further comprising: iii) placing the powder compact within the cavity (26) of the container (10), the powder compact being smaller than the volume of the cavity (26), the method further comprising: iv) introducing a coating liquid containing a coating material into the cavity (26) through the inlet opening (20); v) immersing the container (10) filled with the powder compact and the coating material in a curing agent liquid containing a curing agent compound, wherein the viscosity of the curing agent liquid is lower than the viscosity of the coating liquid, and the plurality of holes are sized such that the coating liquid does not pass through the wall to leave the container, while the curing agent liquid having a lower viscosity passes through the wall to enter the container, and the method further comprises: vi) removing said container (10) from said hardener liquid and removing said coated powder compact from said container (10).

2. 2. The method according to claim 1, characterized in that the powder compacts are spherical and are made by pressing a powder of a substance selected from the group consisting of coffee, tea, drinking chocolate, cocoa and milk powder at a pressure of 0.01 to 1.000 MPa, preferably 0.05 to 500 MPa, more preferably 0.1 to 100 MPa, even more preferably 0.5 to 100 MPa, even more preferably 1 to 100 MPa, even more preferably 5 to 50 MPa, and most preferably 15 to 30 MPa.

3. 3. The method according to claim 1 or 2, characterized in that the container (10) has a spherical cavity (26).

4. 4. The method according to any one of claims 1 to 3, characterized in that the material of the wall (24) is a wire mesh having a mesh size of 0.01 to 0.30 mm, preferably 0.02 to 0.21 mm, more preferably 0.04 to 0.08 mm, even more preferably 0.05 to 0.075 mm, most preferably 0.058 to 0.068 mm.

5. 5. The method according to claim 4, characterized in that the wire mesh is made from stainless steel and has a wire thickness of 0.01 to 0.30 mm, preferably 0.02 to 0.20 mm, more preferably 0.03 to 0.10 mm, most preferably 0.04 to 0.06 mm, most preferably 0.045 to 0.055 mm.

6. 6. The method according to any one of claims 1 to 5, characterized in that a pipe (22) firmly connected to the vessel (10) is placed above the inlet opening (20) of the vessel (10).

7. The method according to claim 6, characterized in that the tube (22) is a rectangular tube (22) or a circular tube (22) with a length of 1.0 to 5.0 cm, preferably 2.0 to 4.0 cm.

8. 8. The method according to claim 6 or 7, characterized in that the tube (22) is a circular tube (22) with an inner diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, most preferably 0.95 to 1.05 mm.

9. 4. The method according to claim 3, characterized in that the container (10) comprises two half-carrots (12, 12'), each of the same dimensions, each formed from the wall provided with the plurality of holes, and connected via a hinge (14), the two half-carrots (12, 12') enclosing a spherical cavity (26) when placed on top of each other with their equators snugly fitting together, one of the half-carrots (12, 12') having the inlet opening (20) at its pole.

10. 10. The method according to any one of the preceding claims, characterized in that the inlet opening (20) has a circular cross section with a diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

11. 11. The method according to any one of claims 1 to 10, characterized in that the container (10) is connected to one or more other containers (10) of the same dimensions in a rack, so that several powder compacts can be coated simultaneously.

12. 12. The method according to any one of claims 1 to 11, characterized in that a coating liquid is used which contains a coating material selected from the group consisting of starch, cellulose, chitin, carrageenan, agar and alginate.

13. 13. The method according to any one of claims 1 to 12, characterized in that a hardener liquid is used which contains a hardener compound which crosslinks the coating material i) via covalent bonds or ii) via ionic and / or coordinate bonds.

14. The method according to any one of claims 1 to 13, characterized in that a coating liquid containing an alkali metal alginate is used as the coating material, and a hardener liquid containing an alkaline earth metal salt is used as the hardener compound.

15. An alkali metal alginate solution, preferably a 0.5 to 5 wt % aqueous solution of alkali metal alginate, particularly preferably a 0.5 to 5 wt % aqueous solution of sodium alginate, is used as the coating liquid, and an alkaline earth metal salt solution, preferably a 1 to 7 wt % aqueous solution of alkaline earth metal salt, particularly preferably a 1 to 7 wt % aqueous solution of calcium chloride, is used as the hardener liquid. The method according to claim 14, wherein the composition is used as a base.

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