Method for coating an compacted powder cake

Abstract

The invention relates to a method for coating a compacted powder cake, in particular for producing a capsule containing beverage powder. The method comprises the following steps: a) providing a compacted powder cake made of a powder containing at least one polysaccharide, b) providing a coating solution made of at least one polysaccharide for coating the compacted powder cake, c) applying the highly viscous coating solution to the compacted powder cake, and d) drying the coated compacted powder cake. The coating solution has a viscosity of between at least 400 mPas and at most 4000 mPas, preferably between 600 and 2500 mPas and particularly preferably between 800 and 1500 mPas, measured using a rheometer. The invention also relates to a capsule for preparing beverages.

Description

[0001]Method for Coating a Powder Pellet The present invention relates to a method for coating a powder pellet, in particular for producing a capsule containing beverage powder, and to a capsule according to the preambles of the independent claims. Capsules are known in the prior art which consist of a pellet with an encapsulating layer. For example, DE 102014 000 187 B4 describes an encapsulating layer made of a polysaccharide with a polyol spacer and an associated crosslinker. EP 3115 316 A1 describes a capsule for preparing a beverage from a pellet and at least one coating layer made of a crosslinked polysaccharide without a polyol spacer.EP 3225 566 A1 describes a capsule for preparing a beverage from a capsule body composed of at least one polysaccharide, filled with a polysaccharide powder, and comprising a coating layer of a cross-linked polysaccharide. All these capsules have in common that the coating is produced by dipping and / or coating the capsule body with a polysaccharide solution and subsequently immersing it in a cross-linking solution. Low-viscosity polysaccharide solutions are generally used for this purpose so that they can be pumped, poured over, and recirculated. Dilute solutions have the disadvantage of resulting in a very thin coating. To achieve a specific coating thickness, the coating step must be repeated several times. This is associated with a high expenditure of time and energy.Furthermore, dipping and coating processes are only possible up to a yield strength of 15 Pa, with dipping becoming difficult even at 10 Pa. Above a yield strength of 20 Pa, it is no longer possible to obtain a coating by dipping and / or coating. It is therefore an object of the present invention to overcome the disadvantages of the prior art. In particular, it is an object of the invention to provide a method that enables more efficient and cost-effective coating of a powder pellet. It is also an object of the invention to provide a capsule consisting of a powder pellet and a coating. These objects are achieved by the independent claims. Preferred embodiments are described in the dependent claims. A first aspect of the invention relates to a method for coating a powder pellet, in particular for producing a capsule containing a beverage powder.The process comprises the following steps: a) providing a powder pellet from a powder containing at least one polysaccharide, b) providing a highly viscous coating solution from at least one polysaccharide for coating the powder pellet, c) applying the coating solution to the powder pellet, in particular in the form of a highly viscous layer, d) drying the coated powder pellet. The coating solution, particularly when provided in step b), has a viscosity between at least 400 mPas and at most 4000 mPas, preferably between 600 and 2500 mPas and particularly preferably between 800 and 1500 mPas, as measured with a rheometer with a plate-plate measuring system.The viscosity is determined by recording the viscosity curve via shear rheological measurements (5-1001 / s linear shear rate, t=56 s) at 30°C using a rheometer with a plate-to-plate measuring system with a 50 mm plate diameter, followed by evaluation using Casson-Steiner regression. For example, the viscosity can be determined using an MCR 72 rheometer from Anton Paar. This method allows the use of highly viscous polysaccharide solutions, especially highly viscous alginate solutions. Due to its high yield strength, highly viscous alginate for spray formulations is difficult to apply to the substrate using conventional manufacturing methods (immersion or coating with an alginate solution). By using alternative application techniques, such as spraying, highly viscous alginate can be utilized. This allows powder pellets to be coated quickly and efficiently in a single step.The process is cost-effective and has lower energy consumption. Furthermore, unlike conventional manufacturing processes, a very homogeneous layer application around the compact is possible. Preferably, after drying step d), the resulting layer thickness is so homogeneous that the relative standard deviation of the layer thickness is no more than 20%, preferably no more than 16%, and most preferably no more than 14%. The relative standard deviation is calculated as the relative dispersion of a data set of several measured layer thicknesses in relation to the mean value and is determined by dividing the standard deviation (SD) by the mean value (MW) and multiplying the result by 100. rel= (SD / MW)*100. Specifically, at least three, preferably exactly three, layer thicknesses are considered at the thinnest and thickest areas of the layer of a capsule. In the thinnest and thickest areas of the layer, only one layer thickness value is included in the calculation for each area of ​​a local minimum or maximum layer thickness. The improved homogeneity of the layer thickness enhances the mechanical stability of the pressed capsules and reduces the consumption of coating solution. Alternatively or additionally, the capsule may have a substantially homogeneous color, and the mean value of the color deviation "Delta E" according to CIELAB, measured at least three times at an optically brightest, optically medium, and optically darkest point within the capsule, is less than or equal to 6, preferably less than or equal to 5, and particularly preferably less than or equal to 4.CIELAB (also known as Lab color space) is a perceptual color space used to represent colors perceived by the human eye. It consists of three axes: - L (luminance): brightness of the color (0 = black, 100 = white) - a: color information between green (−) and red (+) - b: color information between blue (−) and yellow (+) The Lab color space is device-independent, making it particularly useful for color comparisons and color corrections. Delta E is a measure used to numerically quantify a visually assessed color difference. The delta symbol represents the difference. The value of Delta E between the color coordinates (L*, a*, b*)p ​​and (L*, a*, b*)v is calculated according to EN ISO 11664-4 as the Euclidean distance (* denotes the transformed values ​​from the CIELAB color space). A substantially homogeneous color is advantageous for quality assurance, among other things, because defective products can be detected and rejected more reliably. For example, surface bubbles, which lead to a less homogeneous color, are easier to detect, even with automated means. Furthermore, any markings on the product, such as printed codes or designations, are more reliably readable against a homogeneous colored background, even with automated means. The application in step c) can be carried out at least partially, preferably over the entire surface, with the coating solution from step b). Step c) is preferably performed only once, so that only one layer of the at least one polysaccharide results. However, it is also possible toThe compact is printed with ink. The corresponding area can then be coated again. This optimally protects the print and prevents it from being washed into the beverage during dispensing. Application in step c) can refer specifically to spraying or a spraying technique. However, other application techniques are also possible. For example, the solution is sprayed on under pressure using an atomizing medium, applied via slot nozzle coating, extrusion coating, blade coating, and / or by encapsulation using an injection mold. When spraying, the viscosity is ideally chosen so that the nozzles do not clog, but the powder compact is still coated with sufficient material. Application in step c) can be achieved by placing the compact into a partial shell and then overmolding it. For this purpose, a partial shell in the shape of a hemispherical is provided, for example.in which the compact is placed. The partial shell and the compact are placed in a hemispherical mold, preferably made of metal, and enclosed in another mold with a hemispherical recess. The mold can then be filled with the coating solution via an access point, so that the compact is completely coated. Before separating the molds, they, along with the enclosed and coated compact, can be cooled. For the production of the partial shell, a predetermined quantity of the highly viscous coating solution can preferably be filled under pressure into a mold with a hemispherical recess. A partial shell can be formed in the mold by means of a punch. The mold and punch are preferably made of metal. Before separating the mold and punch, they, along with the formed partial shell, can be cooled, e.g., to allow for hardening. It goes without saying thatthat the partial shell does not need to form a half-shell, but only a part thereof. For the production of the partial shell and / or during overmolding, a gap width of 100 to 1000 µm, preferably 250 to 800 µm, and particularly preferably 400 to 600 µm, can be formed between the mold and the die or between the compact and the mold. An identical coating solution can be used for the production of the partial shell and the overmolding. Before the actual application of the high-viscosity alginate in step c), a moistening step of the compact, for example with water, can be carried out. The moistening can help to ensure that the coating forms fewer or no holes at the contact points of the compact. The moistening can also counteract possible blistering during the drying step. Blistering can also be reduced or completely prevented if the compact is heated before coating. The moistening is preferably carried out mainly with water.In particular, deionized water or an aqueous solution as a humectant, wherein the water content is greater than or equal to 90%, preferably greater than or equal to 95%, and particularly preferably greater than or equal to 99%. However, it is also possible to use non-aqueous solutions, for example, alcohols or polyols. Aqueous solutions of alcohols and / or polyols are particularly preferred, e.g., 50% glycerol and 50% water or a 96% ethanol solution. It is also possible to add flavoring(s) to the humectant. Alternatively, hygroscopic compounds are also possible as humectants. In principle, all food-grade hygroscopic compounds, whether as a solution, dispersion, or solid, are suitable.conceivable as a wetting agent. The wetting can be considered a priming or priming step. The wetting step prevents bubble and pitting, regardless of the application technique in step c). The at least one polysaccharide of the coating solution can be selected from the group consisting of: alginates, starches, modified starches, celluloses, chitin, chitosan, carrageenans, pectins, agar, xanthan gum, gellan gum, dextrans, galactomannan, glucomannan, guarana, carob, gum arabic, scleroglucan, pullulan, derivatives, or mixtures thereof, preferably alginate. The polysaccharide is preferably present in an aqueous solution. According to the present invention, a "pressed pellet" is understood to be a core material that has been compressed under pressure. Providing the core material of the capsule as a pressed pellet is advantageous if the core material is produced according to the invention by immersion,The core material is at least partially encased by coating or spraying with the coating according to the invention, so that it does not disintegrate during the coating process. The core material therefore preferably exhibits a certain tensile strength. This can preferably be achieved by compressing the core material with a compression pressure in the range of 1-100 MPa, preferably 5-50 MPa. The compression pressure to be applied for producing the pellet depends on the properties of the core material; in the case of coffee powder, for example, on the grind, roast level, and moisture content of the powder. Particularly with coffee powder, it can be observed that powders with a lower fat or oil content, e.g., decaffeinated coffee powder or coffee powder with a light roast color, require a higher compression pressure to achieve a stable pellet. The strength of the pellet is determined by...The pressing is performed by positioning the pellet between two plates of a compression-tensile testing machine (for example, with an Xforce P force transducer from Zwick / Roell) and determining the force required to break the pellet. This method is also described in WO 2008 / 123775 A1, p. 3. The pellet can be shaped like a sphere, cube, cuboid, prism, pyramid, truncated cone, cone, cylinder, torus, or ellipsoid, preferably a sphere or a truncated cone. Advantageously, the coating solution is additionally crosslinked with a crosslinking agent in or after step c). It is possible to apply a crosslinking agent first. However, it is also conceivable toThis crosslinking agent is applied together with the coating solution or after application of the coating solution. Furthermore, the crosslinking agent can be applied in solid form by dusting or powder coating. Crosslinking can be covalent, ionic, and / or coordinative. Crosslinking via covalent bonds enables a very durable coating. Crosslinking via covalent bonds typically occurs through the reaction of at least one polysaccharide with a suitable crosslinker. Particularly suitable as crosslinkers are difunctional organic compounds, where the functional groups are selected, for example, from the group consisting of carboxylic acids, salts of carboxylic acids, activated carboxylic acids, amines, alcohols, aldehydes, and ketones. In this context, activated carboxylic acids include carboxylic acid halides, active esters of carboxylic acids,Anhydrides of carboxylic acids or other reactive derivatives of carboxylic acids are understood. Polysaccharides cross-linked by ionic and / or coordinate bonds are particularly easy to produce and do not impair the biodegradability of the polysaccharide used. Ionic and / or coordinate cross-linking can be achieved, for example, using polysaccharides that have anionic groups, such as carboxylate or sulfonate groups. By introducing divalent or higher-valent cations, especially alkaline earth metal ions, ionic or coordinate cross-linking of the anionic groups of the polysaccharide then occurs to form a stable coating. In this context, a coordinate bond refers to an interaction between an electron pair donor and an electron pair acceptor.such as can occur between lone pairs of electrons on oxygen atoms in hydroxyl groups and cations. A crosslinking agent is particularly preferred as an alkaline earth metal ion solution, and calcium chloride is especially preferred. The crosslinking agent can be applied by immersion in a bath containing the crosslinking agent. However, spraying the solution is also conceivable. Optionally, the crosslinking agent can also be mixed with the coating solution or applied in solid form by dusting or powder coating. When using a calcium chloride bath, the residence time of the coated pellet in the bath can vary between 2 and 30 seconds. Bath concentrations of less than 50% are preferably used; 5 to 30% (w / w) solutions are particularly preferred. The crosslinking agent can be integrated into the coating solution and trigger crosslinking in a delayed manner.In particular, the process can be simplified by using sparingly soluble alkaline earth salts with a defined amount of suitable complexing agents, by lowering the pH value and / or the temperature. Integrating the crosslinking agent into the coating solution further simplifies the process. Delayed crosslinking does not affect the actual coating process. Furthermore, this allows the timing of crosslinking to be specifically determined by external factors. The yield strength of the coating solution can be between at least 1 Pa and a maximum of 170 Pa, preferably between 25 Pa and 150 Pa, and particularly preferably between 50 Pa and 100 Pa, measured at 30°C using a plate-plate rheometer with a 50 mm plate diameter. For example, an MCR72 rheometer from Anton Paar can be used. For the present invention,A higher yield strength is particularly advantageous for applying a coating by spraying. A yield strength greater than 10 Pa is especially advantageous, preferably greater than 15 Pa, and most preferably greater than 25 Pa. The yield strength is the force required to make a substance or mixture of substances flow. In this case, it is the force required to make the coating solution flow. Advantageously, in step c), the powder pellet rests on support points, preferably on at least one set of tips. A set preferably comprises at least three tips. The powder pellet can be moved and / or rotated on the support points, particularly when spraying the powder pellet with the coating solution. The support points can be mounted on a turntable.so that the compact, along with the support points, can rotate. Preferably, the support points have only very small contact areas with the powder compact, so that the powder compact can be coated as uniformly and without holes as possible. It is also possible to wet the support points with the coating solution, thus preventing defects in the coating. It is also conceivable to provide the support points with a hydrophobic or even a superhydrophobic coating, for example, with PTFE or PP. Ideally, the coated powder compact can be ejected from the support points after step d). The ejection can take place directly into the bath containing the curing agent. During the fall, any holes in the coating resulting from the support points can be closed by the viscosity of the solution. It is also possible for the powder compact to be held between at least two sets of support points,preferably from points, is moved. This has the advantage that different positions can be sprayed, thus achieving complete coating. It is also possible that the powder compact is moved by means of an airflow during the application of the coating in step c) and is preferably kept suspended on an air bed. This also enables 360° coating of the powder compact, and on the other hand, it allows the powder compact to be transported without bringing any still-liquid coatings into contact with other surfaces and thus damaging the coating or contaminating the surface of the powder compact. Gelation would be possible in the airflow. In step c), the powder compact can be moved by means of an airflow with a mass application of less than 5 g, preferably less than 3 g,Based on a spherical pellet with a diameter of approximately 27 mm, the pellet is sprayed with at least one spray nozzle and a spray rate of at least 0.05 g to 0.7 g / s. A two-component nozzle is suitable, for example. With such a nozzle, a fine coating can be achieved without damaging the surface of the pellet or creating coating thickenings that could promote blistering during the drying process. The "drying" in step d) can be carried out as active or passive drying. Active drying includes, in particular, drying at elevated temperatures, microwave drying, vacuum drying, freeze-drying, or combinations thereof. Passive drying includes, in particular, drying by storage, especially at room temperature. The drying in step d) can be carried out in a binder oven at 60–90°C, preferably 70–80°C.Drying is preferably carried out at 75 °C. The drying time can be between 1 and 120 minutes, preferably 10 to 120 minutes, particularly preferably between 20 and 90 minutes, and most preferably between 30 and 60 minutes. It is also possible to apply temperature ramps during drying. For example, heating from 50 °C to 80 °C followed by cooling from 75 °C to 30 °C is possible. Drying at room temperature or lower temperatures, for example by freeze-drying, is also possible. The drying temperature is preferably selected to achieve an optimum between drying time and energy consumption. The powder compact is preferably produced from a powder or powder mixture at a pressure of 1 to 100 MPa, preferably 5 to 50 MPa, and particularly preferably 15 to 30 MPa. Alternatively, the process can be used to coat a capsule body.in particular for the production of a capsule containing a beverage powder. The process comprises the steps: a) providing a capsule body composed of at least one polysaccharide, b) filling the capsule body with a powder pellet or a powder, c) optionally: closing the capsule body with a lid, d) providing a coating solution containing at least one polysaccharide for coating the capsule body and / or lid, e) applying the coating solution to an outside of the capsule body and / or lid, f) drying the coated capsule body obtained after step e), wherein the coating solution, particularly when provided in step d), has a viscosity between at least 400 mPas and at most 4000 mPas, preferably between 600 and 2500 mPas and particularly preferably between 800 and 1500 mPas, measured with a rheometer with a plate-plate measuring system. It is possible tothat the capsule body is sealed with the coating solution in step e), so that step c) is not strictly necessary. Alternatively, it is also possible to provide a method for coating a capsule body, in particular for producing a capsule containing beverage powder, as follows: a) providing a capsule body composed of at least one polysaccharide, b) providing a coating solution containing at least one polysaccharide for coating the capsule body, c) applying the coating solution to an inside and / or outside of the capsule body, d) drying the coated capsule body obtained after step c), e) Optional: filling the capsule body with a powder pellet or a powder, f) Optional: sealing the capsule body with a lid, wherein the coating solution, in particular when provided in step b), has a viscosity between at least 400 mPas and at most 4000 mPas.preferably between 600 and 2500 mPas and particularly preferably between 800 and 1500 mPas, measured with a plate-plate rheometer. Applying the coating solution to an outer and / or inner surface of the capsule is particularly advantageous to slow down aging over time. Barrier measurements have shown a significantly improved barrier. The at least one polysaccharide of the capsule body can be paper. The capsule body can be shaped as a sphere, cube, cuboid, prism, pyramid, truncated cone, cone, cube, cylinder, torus, or ellipsoid; preferably as a sphere or a truncated cone. The remaining embodiments, in particular with regard to the coating solution, crosslinking, application, drying, and mass deposition,The same applies to the alternative methods. Another aspect of the invention relates to a capsule made from a coated powder pellet produced according to a method as described above. Another aspect of the invention relates to a capsule made from a capsule body produced according to a method as described above. Another aspect of the invention relates to a capsule, in particular as described above, comprising a powder pellet made from a powder containing at least one polysaccharide and, in particular, exactly one layer of at least one polysaccharide. Preferably, the layer is a coating layer, more preferably a fully coating layer. The single layer has a thickness of at least 50 µm, preferably at least 80 µm, and more preferably at least 100 µm. The layer thickness is therefore nowhere less than 50 µm.Preferably at least 80 m and particularly preferably at least 100 m. Preferably, the mean layer thickness is 50 m, preferably at least 80 m, and particularly preferably at least 100 m. The layer thickness refers to the dry layer. The dried layer has a moisture content of preferably at least 7%, preferably in the range between 7 and 12% w / w. The total residual moisture of the product containing coffee after appropriate drying is preferably less than 5% w / w. "Exactly one layer of at least one polysaccharide" refers to a single layer of the same at least one polysaccharide. Another aspect of the invention relates to a capsule, in particular as described above and preferably produced according to one of the methods described above, wherein the capsule has such a homogeneous layer thickness that the relative standard deviation of the layer thickness does not exceed 20%.preferably not more than 16% and particularly preferably not more than 14%, as described above. The capsule can alternatively or additionally have a substantially homogeneous color, and the mean value of the color deviation "Delta E" according to CIELAB is less than or equal to 6, preferably less than or equal to 5, and particularly preferably less than or equal to 4, over at least three measurements at an optically brightest, optically medium, and optically darkest point within the capsule, as described above. A further advantage of the invention is that, due to the high viscosities, practically no water absorption occurs in the powder compact. This enables a method for coating a powder compact,that requires no active drying step. In this case, the layer can have a moisture content greater than 12%. The total residual moisture of the product with coffee inside preferably remains below 5% (w / w). The capsule can be understood as the pellet with at least one layer. However, it is also possible for the pellet to have several layers and / or to be additionally surrounded by a capsule body as described above. A capsule with, in particular, exactly one layer, especially a single layer of the same polysaccharide, can be produced particularly easily and ecologically. Coating steps do not need to be repeated unnecessarily; the single coating layer provides very good transport protection and a good oxygen barrier. The coated powder pellet, in its dry state, can withstand a maximum force of at least 50 N in a breaking strength test.preferably at least 80 N and particularly preferably at least 100 N. For the tensile strength test, the capsule is positioned between two parallel plates of a tensile-compression testing machine (for example, equipped with an Xforce P force transducer from Zwick / Roell). The capsule is positioned centrally on the lower plate in the extraction direction, or, in the case of a rotationally symmetrical compact, for example, with a spherical or cubical shape, in the compression direction. The plates have a diameter that is at least 50% larger than the maximum capsule diameter. The parallel plates are slowly brought together, and a force-displacement diagram is recorded. The load is increased until the shell is damaged. Simultaneously with this crack or fracture, a drop in force is observed. If the measured force falls below the force drop threshold of 40% of the maximum force,The tensile strength test is terminated. The maximum measured force without damage to the shell is reported as the tensile strength. The powder pellet, or alternatively the powder, preferably consists of a powder or powder mixture and particularly preferably contains ground coffee, instant coffee, grain coffee, malt coffee, tea, tea granules, drinking chocolate powder, or milk powder. The at least one polysaccharide of one layer can be selected from the group consisting of: alginates, starches, modified starches, celluloses, chitin, chitosan, carrageenans, pectins, agar, xanthan gum, gellan gum, dextrans, galactomannan, glucomannan, guarana, carob, gum arabic, scleroglucan, pullulane, derivatives, or mixtures thereof, preferably alginate. The at least one polysaccharide is preferably in solution. The concentration of polysaccharide and especially alginate for the coating solution can range between 0.5 and 10.0%.Preferably between 0.8 and 5.0% and particularly preferably between 2.0 and 3.0% (w / w). The layer may contain fibers, preferably selected from the group consisting of: alginate fibers, cellulose fibers, viscose fibers, PLA fibers, mineral fibers, preferably of silicon dioxide; plastic fibers, preferably aramid, polyethylene, and polyamide fibers; or derivatives thereof. Hydroxypropyl methylcellulose (HPMC), for example, is a suitable cellulose derivative. The fibers provide additional reinforcement of the coating. The fiber content in the coating solution can be, for example, between 0.1 and 20.0%, preferably between 0.1 and 10.0% (w / w), and more preferably between 0.5 and 10.0%.The concentration of fibers is particularly preferably between 0.5 and 7.0% and most preferably between 1.0 and 5.0% (w / w). Besides reinforcing the coating, fibers in the coating solution can also reduce or completely prevent blistering in the coating. The layer can further contain at least one polyol. Coating solutions can be used that preferably have a concentration between 1 and 30%, preferably 5 and 25%, and particularly preferably 10 and 20% of at least one polyol. The permeability of the coating can be influenced by the choice of polyol. Defects in the coating, such as blistering, can also be influenced. Advantageously, the at least one polyol is selected from the group consisting of aliphatic polyols, preferably ethyl glycol, propanediol, butylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, sorbitol, erythritol,Xylitol, and particularly preferably glycerol and sorbitol; cyclic polyols, preferably glucose, fructose, mannose, galactose, oligofructose, inulin, isomaltulose, trehalose; sugar substitutes, preferably mannitol, isomalt, maltitol, lactitol; and aromatic polyols, preferably cyanidin, corilagin, digallic acid, tannic acid, and gallic acid; and combinations thereof. The polyol can serve as an additional crosslinking agent or be incorporated into the coating, e.g., by electrostatic interaction. The mechanical properties of the coating with regard to elasticity can be adjusted by means of the polyol. A further aspect of the invention relates to a container comprising at least two capsules as described above. The at least two capsules in the container have such a homogeneous layer thickness that the relative standard deviation of the layer thickness across all capsules in the container does not exceed 25%.preferably not more than 20% and particularly preferably not more than 18%. Another aspect of the invention relates to the use of a capsule as described above for producing a beverage. The invention is explained in more detail by means of examples. The examples serve to illustrate the invention and are not to be understood as limiting. Example 1: A spherical pellet was produced from 6.2 g of coffee powder by pressing with a press plunger. After pressing, it was lightly moistened on the surface with tap water using a conventional spray bottle. The following coating composition was used to coat the pellet: 2.5% sodium alginate (medium viscosity), 3% cellulose fibers (LC 200), 14.3% sorbitol (w / w). The viscosity was 899 mPas with a yield strength of 80 Pa.Measured at 30°C using an Anton Paar MCR72 rheometer with a plate-to-plate measuring system and a 50 mm diameter plate. The coating solution was applied to the compact using a spray technique. To ensure complete coverage of the powder compact, it was rotated between two sets of tips with hydrophobic tips. The tip sets were mounted on a rotary table rotating at 120 rpm. The coating solution was applied using two two-component nozzles, each equipped with a PF2850-SS liquid cap and a PA70 full-cone air cap (Spraying Systems Co.). The nozzles were oriented at angles of -30.5° and 40.5° to the horizontal and at a distance of 60 mm from the rotating compact. The compact was thus sprayed on all sides.without damaging the pellet surface. A spray time of 10 seconds resulted in a mass application of 2.1 g. The pellet was then immersed in a calcium chloride dihydrate bath. The residence time of the pellet in the bath was 6 seconds, the concentration was 20% w / w, and the bath temperature was 25 °C. After complete immersion in the calcium chloride dihydrate bath, the gelled, coated pellet was rinsed with softened water. To cure the coating and achieve the desired residual moisture content,The pellet was dried for 60 minutes at 75°C in a conventional dryer-heater (ventilation and dehumidification down to 5% RH). After 5 minutes, the coated pellet was turned over, and after the drying time was complete, it was cooled in a desiccator at room temperature. Using the method described above, a single-layer, hole- and bubble-free coated pellet with a residual moisture content of < 5% w / w and a breaking strength of at least 100 N was produced. This coated pellet was compared with a pellet produced using a low-viscosity coating in an alginate bath with a concentration of 1.5% w / w alginate. The use of highly viscous alginate formulations in an alginate bath leads to uncontrollable layer thicknesses with a significant drying disadvantage. Conventional high-viscosity (low-viscosity) coating, coating, 1-layer 3-layer A, lginat [%] 1.3 2.5Cellulose [%] 0.7 3.0 Sorbitol [%] 8.0 14.3 Water [%] 90.0 80.2 Sorbitol / Alginate 6.2 5.7 Cellulose / Alginate 0.5 1.2 Dry matter [%] 10.0 19.8 Mass application [g] (wet) 3.2 2.1 It was shown that the wet mass application can be significantly reduced compared to the manufacturing method with low-viscosity alginate solutions, while simultaneously resulting in a higher dry matter content. This results, on the one hand, in a very efficient coating process and, on the other hand, in lower energy consumption for drying due to single-layer coating (high viscosity) versus three-layer coating (low viscosity). Furthermore, the breaking strength of the single-layer coated pellet was tested according to the procedure described above, and stabilities of > 100 N were achieved with a single layer. Example 2: A spherical pellet was produced from 5.7 g of coffee powder. After pressing, it was moistened with 0.2 ml of demineralized water using a spray bottle.The following coating composition was used to coat the compact: 2.5% sodium alginate (medium viscosity), 3% cellulose (LC 200), 7% sorbitol, and 7% glycerol (w / w). The viscosity was 898 mPas with a yield strength of 91 Pa. The coating solution was heated at 50°C with constant stirring and the addition of 0.04% calcium ions in the form of calcium chloride dihydrate. The temperature was maintained at 50°C to prevent the coating from gelling due to the calcium ions. 0.75 g of the warm, highly viscous coating solution was poured into an aluminum mold with a hemispherical cavity. A hemispherical aluminum plunger was inserted from above into the cavity containing the coating solution, displacing it into the gap between the hemispherical cavity and the plunger. The gap width was 500 µm. The mold and die were then cooled to 5°C, causing the calcium alginate in the gap to gel. The die was then rotated and withdrawn from the alginate.The pellet was then placed into the opening created by the first mold. A second aluminum hemisphere was placed over the pellet, again resulting in a gap width of 500 µm. Through an opening at the top, the mold was filled with 0.75 g of warm, highly viscous coating solution to coat the pellet from above as well. The upper aluminum hemisphere was then cooled until the mixture gelled at approximately 5°C. The pellet, now completely coated with calcium alginate, was then immersed in a calcium chloride dihydrate bath with a residence time of 6 seconds and a concentration of 20% w / w to ensure complete gelation. After the calcium chloride dihydrate bath, the gelled, coated pellet was rinsed with softened water. Analogous to example 1, the coated pellet was dried for 60 min at 80°C in a conventional dryer-heating cabinet (ventilation and dehumidification down to 5% RH) to achieve the desired residual moisture content.After 5 minutes, the coated pellet was turned over, and after the drying time was complete, it was cooled in a desiccator at room temperature. Example 3: A spherical pellet was produced from 6.2 g of coffee powder by pressing with a press ram. After pressing, the pellet was lightly moistened on the surface with 0.2 g of tap water using a conventional spray bottle. The following coating composition was used to coat the pellet: 2.6% sodium alginate, 4% cellulose fibers (LC 200), 10% glycerol (w / w). The viscosity was 1400 mPas with a yield strength of 70 Pa, measured at 30°C using an Anton Paar MCR72 rheometer with a 50 mm diameter plate-plate measuring system. The coating solution was applied to the pellet using a spray technique. To completely spray the powder pellet, it was placed on a rotating ball holder, which rotated at 150 rpm.For this purpose, holder A with 10 metal tips and holder B with hydrophobic plastic tips were used. The coating solution was applied using two two-component nozzles, each equipped with a PF2850-SS liquid cap and a PA70 full-cone air cap (Spraying Systems Co.). The nozzles were oriented at angles of -30.5° and 40.5° to the horizontal and at a distance of 60 mm from the rotating pellet. The pellet was thus sprayed on all sides without damaging its surface. A spray time of 3 seconds resulted in a mass application of 1.5 g. The pellet was then dropped into a calcium chloride dihydrate bath. The residence time of the pellet in the bath was 6 seconds, the concentration was 20% w / w, and the bath temperature was 25 °C.After complete immersion in the calcium chloride dihydrate bath, the gelled, coated pellet was rinsed with softened water. To cure the coating and achieve the desired residual moisture content, the pellet was dried for 30 minutes at 75°C in a conventional drying oven (ventilation and dehumidification down to 5% RH). After drying, it was cooled in a desiccator at room temperature. The coated pellets, produced and dried according to the above procedure in a reproducible sample size of 18 pieces using holders A and B, were 100% free of bubbles and holes, regardless of the holder. Example 4 Experiment on the influence of the alginate type on the rheological properties of an alginate solution Alginate 359, Alginate 187, Alginate 152, Alginate 135, Alginate 20, Alginate 2 and Alginate 16 were in 2.A 5% (w / w) aqueous solution was mixed and the viscosity and yield point at 30°C were determined using an Anton Paar MCR72 rheometer with a 50 mm diameter plate measuring system. Table 1 shows the recorded yield points and viscosities. Table 1: Viscosity and yield point of 7 different alginate solutions in 2.5% w / w aqueous solution (MW = mean, STD = standard deviation). Viscosity Yield Point Alginate type* MW [mPas] STD MW [Pa] STD [mPas] [mPas] Alginate 359 993.9 2.8 18.3 0.4 Alginate 187 797.2 13.7 10.0 0.7 Alginate 152 829.6 10.1 7.5 0.1 Alginate 135 707.8 1.5 2.7 0.1 Alginate 20 45.9 7.6 0.3 0.1 Alginate 21 22.9 2.8 0.0 0.0 Alginate 16 22.1 1.2 0.1 0.0*The alginate type is determined by the characteristic viscosity of a 1% (w / w) aqueous standard solution in water, measured with a Brookfield viscometer at 60 rpm 20°C; the number indicates the corresponding viscosity value.Table 1 shows that the yield point and viscosity do not always correlate linearly. Table 2 shows the yield point and viscosity of a high-viscosity alginate spray formulation A consisting of 2.6% Alginate 359, 4.0% cellulose fibers (LC 200), and 14% sorbitol (w / w) in comparison to coating formulations B and C from the dip-coating process. Formulation B contains 1.4% Alginate 359, 1.1% cellulose fibers (LC 200), and 11% sorbitol (w / w). Formulation C contains 1.8% Alginate 359, 0.9% cellulose fibers (LC 200), and 9% sorbitol. The specified yield point limit in the dip-coating process is 15 Pa. Thus, the yield strength of the alginate in spray formulation A is more than 5 times higher than the limit of 15 Pa specified on a system for dip coating. Table 2: Viscosity and yield strength of 3 different alginate formulations for spray and dip coating Process Viscosity Yield strength Alginate formulation MW [mPas] Stability MW [Pa] Stability [mPas] [mPas] Spray formulation 879.7 27.6 79.7 0.5A Formulation B 389.0 18.8 2.7 0.3 Formulation C 641.1 10.0 7.0 0.1 As can be seen from Table 2, the yield point also increases with viscosity, but the two parameters do not correlate linearly. While the viscosity of spray formulation A is slightly more than twice as high as the viscosity of formulation B, the yield points differ by a factor of 26. This has a significant influence on the application method used. Example 5 Calculation of the color difference Delta E Three balls each, produced using the spray method and the conventional method by dipping with 2 and 3 layers, were measured at three locations each (light, dark, and medium areas). The measurements were carried out according to CIELAB. The color difference Delta E was calculated for each ball and measuring point. calculated and then averaged. The results are summarized in Table 3. Based on the values ​​in Table 3, it is evident that the spray method shows the smallest color deviation. Table 3 – Color space measurements and determined values ​​according to CIELAB - - - osssrsss pg 1 2 3 e ) e ) e )n M 2 M 3 M 3 t tu ettt ( , ( , ( , rr nl . tkkk 1 1 2 ee el rrnnn EEE w E w re N euuueeell ht - wpppatatateae as lbssstktktkttt fr lrssslnlnlntlt re aaeeeeueueuieie HBFMMMD p D p D p MDMV 1L* 44 38 36 6 8 2 6 5y arp S a * 9 11 11 b* 20 21 202 L* 43 41 42 3 6 4 4a* 8 10 11b* 19 20 243 L* 41 36 37 6 4 4 5 a* 9 11 9 b* 20 22 191 L* 38 40 59 2 22 20 15 13t hcihc S - 3 a * 7 6 3 b* 9 10 162 L* 44 47 46 4 14 12 10 a* 3 5 5 b* 6 8 20 3 L* 40 56 38 16 7 19 14 a* 5 3 7 b* 7 8 13 1 L* 37 41 43 4 10 7 7 12t hcihc S - 2 a* 8 7 6 b* 10 11 182 L* 39 45 53 6 17 11 11 a* 8 7 7b* 10 11 193 L* 27 41 51 14 25 12 17 a* 11 8 7b* 14 13 19 Example 6 Paper Capsules: Initially, 20 paper capsules were brewed as a reference. It was observed that all but 6 capsules remained stuck in the coffee machine after brewing. Subsequently, 20 paper capsules were sprayed on the outside with alginate (recipe according to Example 1 and mass application 0.8g) and then cross-linked with a 10% calcium solution by immersing the capsule to just below the sealing edge for 5 seconds. They were then dried in a dryer at 60°C for 5 minutes. Afterward, the capsules were brewed in the same way as the reference. No capsules remained stuck in the brewing chamber. Thus, the coating solution prevents the paper from becoming saturated and provides a smooth surface for brewing. Example 7 Determination of the relative standard deviation of the layer thickness: 5 balls per method (conventional by immersion or spray method) were measured with a micrometer.Six thickness measurements were taken for each ball: three measurements at an optically thin point and three at an optically thick point. The mean (MW) and standard deviation (SD) were then determined for each ball, followed by the relative standard deviation (SD). rel ) according to SD rel = (SD / MW)*100. determined. Table 4a shows the measured values ​​according to the conventional method, Table 5a according to the spray method. Tables 4a and 5a also show the MD, SD and SD relover all 5 measured balls. Table 4b shows the values ​​determined using the conventional method and Table 5b shows the values ​​determined using the spray method for the individual capsules. Table 4a: Measured values ​​for determining the layer thickness using the conventional method. Ball No. Optical Value 1 Value 2 Value 3 Layer (in mm) (in mm) (in mm) 1 thick 0.18 0.17 0.21 2 0.2 0.21 0.23 3 0.14 0.22 0.23 4 0.17 0.15 0.21 5 0.22 0.19 0.21 1 thin 0.11 0.11 0.13 2 0.08 0.11 0.13 3 0.08 0.11 0.13 4 0.13 0.12 0.14 5 0.12 0.1 0.13 MW (in mm) 0.156 SD (in mm) 0.049 SD rel (in %) 31.7 Table 4b – Mean values, standard deviation and relative standard deviation for the balls according to Table 4a after the conventional procedures B all-Nr. Mittelwert Standard deviation (mm) Standard deviation (%) 10.152 0.037 23.72 0.160 0.056 353 0.152 0.055 36.24 0.153 0.038 24.85 0.162 0.046 28.4 Table 5a: Measured values ​​for determining the layer thickness using the spray method. B all-Nr. OptischeValue 1 Value 2 Value 3 Layer (in mm) (in mm) (in mm) 1 thick 0.16 0.18 0.21 2 0.19 0.22 0.17 3 0.17 0.17 0.19 4 0.16 0.18 0.22 5 0.21 0.16 0.14 1 thin 0.12 0.14 0.12 2 0.14 0.13 0.16 3 0.13 0.14 0.14 4 0.15 0.14 0.17 5 0.15 0.15 0.15 MW (in mm) 0.165 SD (in mm) 0.028 SD rel (in %) 17.2 Table 5b – Mean values, standard deviation and relative standard deviation for the balls according to Table 5a the spray method. B all-Nr. MittelwertStandard deviation (mm) Standard deviation (%) 10.168 0.030 17.82 0.157 0.021 13.43 0.173 0.034 19.64 0.170 0.026 15.35 0.160 0.023 14.4 Tables 4a, 4b, 5a and 5b show that the spray method results in less variation in the relative standard deviation in the layer thickness of the individual balls. A container with a corresponding number of coffee balls also shows a lower relative variation using the spray method than using the conventional method. It is thus evident that the layer thicknesses are more homogeneous using the spray method than with the conventional method.

Claims

1. Claims 1. A method for coating a powder pellet, in particular for producing a capsule containing beverage powder, comprising the following steps: a) providing a powder pellet made from a powder containing at least one polysaccharide, b) providing a highly viscous coating solution made from at least one polysaccharide for coating the powder pellet, c) applying the coating solution to the powder pellet, d) drying the coated powder pellet, characterized in that the coating solution has a viscosity between at least 400 mPas and at most 4000 mPas, preferably between 600 and 2500 mPas and particularly preferably between 800 and 1500 mPas, as measured by a plate-plate measuring system.

2. The method according to claim 1, wherein the application in step c) is carried out at least partially, preferably over the entire surface, with the coating solution from step b). 3.Method according to claim 1 or 2, wherein step c) is performed only once.

4. Method according to any of the preceding claims, wherein the compact is formed in the shape of a sphere, a cube, a cuboid, a prism, a pyramid, a truncated cone, a cone, a cube, a cylinder, a torus, or an ellipsoid, preferably a sphere or a truncated cone.

5. A method according to any one of the preceding claims, wherein the application in step c) is carried out by inserting the compact into a partial shell and subsequent overmolding.

6. A method according to any one of claims 1 to 4, wherein the application in step c) is carried out using a spray technique.

7. A method according to any one of the preceding claims, wherein the coating solution is additionally crosslinked with a crosslinking agent in or after step c).

8. A method according to claim 7, wherein the crosslinking agent is an alkaline earth metal ion solution.

9. A method according to claim 7 or 8, wherein the crosslinking agent is integrated into the coating solution and the crosslinking is delayed, in particular by the use of sparingly soluble alkaline earth salts with a defined amount of suitable complexing agents, by lowering the pH value and / or the temperature. 10.A method according to any one of the preceding claims, wherein the yield strength of the coating solution is between at least 1 Pa and at most 170 Pa, preferably between 25 Pa and 150 Pa, and particularly preferably between 50 Pa and 100 Pa, measured at 30°C using a plate-plate rheometer with a plate diameter of 50 mm.

11. A method according to any one of claims 6 to 10, wherein the powder-pressed component rests on support points, preferably on at least one set of points, in step c).

12. The method of claim 11, wherein the coated powder compact is ejected from the support points after step d).

13. The method of claim 11 or 12, wherein the powder compact is moved between at least two sets of support points.

14. The method of any one of the preceding claims, wherein the powder compact is moved by means of an airflow during the application of the coating in step c).

15. The method of any one of the preceding claims, wherein the powder compact is sprayed in step c) with at least one spray nozzle and a spray rate of at least 0.05 g to 0.7 g / s at a mass application of less than 5 g, preferably less than 3 g.

16. The method of any one of the preceding claims, wherein the powder compact is produced from a powder or powder mixture at a pressure of 1 to 100 MPa, preferably 5 to 50 MPa and particularly preferably 15 to 30 MPa. 17.Capsule, in particular made of a coated powder pellet, obtainable according to a method according to one of claims 1 to 16.

18. Capsule, in particular according to one of the preceding claims, comprising a powder pellet made of a powder containing at least one polysaccharide and in particular exactly one layer of at least one polysaccharide, preferably made of a highly viscous coating material, characterized in that one.

19. A capsule according to claim 17 or 18, wherein the coated powder pellet, in the dry state, exhibits a maximum tensile strength in a breaking strength test of at least 50 N, preferably at least 80 N, and particularly preferably at least 100 N.

20. A capsule according to any one of claims 17 to 19, wherein the powder pellet consists of a powder or powder mixture and preferably contains ground coffee, instant coffee, grain coffee, malt coffee, tea, tea granules, drinking chocolate powder, or milk powder. 21.Capsule according to any one of claims 17 to 20, wherein the at least one polysaccharide of one layer is selected from the group consisting of: alginates, starches, modified starches, celluloses, chitin, chitosan, carrageenans, pectins, agar, xanthan gum, gellan gum, dextrans, galactomannan, glucomannan, guarana, carob, gum arabic, scleroglucan, pullulan, derivatives or mixtures thereof, preferably alginate.

22. Capsule according to any one of claims 17 to 21, wherein the layer contains fibers, preferably selected from the group consisting of: alginate fibers, cellulose fibers; viscose fibers; PLA fibers; mineral fibers, preferably of silicon dioxide; plastic fibers, preferably aramid, polyethylene and polyamide fibers; or derivatives thereof.

23. A method for coating a capsule body, in particular for producing a capsule containing a beverage powder, comprising the steps of: a) providing a capsule body composed of at least one polysaccharide, b) filling the capsule body with a powder pellet or a powder, c) optionally: closing the capsule body with a lid, d) providing a coating solution containing at least one polysaccharide for coating the capsule body and / or lid, e) applying the coating solution to an outside of the capsule body and / or lid, f) drying the coated capsule body obtained after step e), wherein the coating solution has a viscosity between at least 400 mPas and at most 4000 mPas, preferably between 600 and 2500 mPas and particularly preferably between 800 and 1500 mPas, measured with a plate-plate rheometer. 24.A method for coating a capsule body, in particular for producing a capsule containing a beverage powder, comprising the steps of: a) providing a capsule body composed of at least one polysaccharide, b) providing a coating solution containing at least one polysaccharide for coating the capsule body, c) applying the coating solution to an inner and / or outer surface of the capsule body, d) drying the coated capsule body obtained after step c), e) Optionally: filling the capsule body with a powder pellet or a powder, f) Optionally: closing the capsule body with a lid, wherein the coating solution has a viscosity between at least 400 mPas and at most 4000 mPas, preferably between 600 and 2500 mPas and particularly preferably between 800 and 1500 mPas, measured with a plate-plate rheometer.25.

26. A capsule made of a coated capsule body, obtainable according to a method according to any one of claims 24 to 25.

27. A capsule according to any one of claims 17 to 22 or 26, wherein the capsule has such a homogeneous layer thickness that the relative standard deviation of the layer thickness is not more than 20%, preferably not more than 16%, and particularly preferably not more than 14%.

28. A capsule according to any one of claims 17 to 22 or 26 to 27, wherein the capsule has such a homogeneous color that the mean value of the color deviation “Delta E” according to CIELAB over at least three measurements at an optically brightest, optically medium, and optically darkest point within the capsule is less than or equal to 6, preferably less than or equal to 5, and more preferably less than or equal to 4.

29. Container comprising at least two capsules according to one of claims 17 to 22 or 26 to 28, wherein the at least two capsules in the container have such a homogeneous layer thickness that the relative standard deviation of the layer thickness across all capsules in the container does not exceed 25%.

30. Use of a capsule according to one of claims 17 to 22 or 26 to 28 for producing a beverage.

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