Beverage mixing device

Abstract

The present invention relates to a mixing device (1) comprising a whipper housing (2), a whipper (3), and a rear wall (4), and a drive shaft (81) for driving the whipper, wherein the whipper housing has a front wall (21) facing a radially forward surface (32) of the whipper, the whipper (3) being disk-shaped, and at least a portion of the surface of the radially forward surface (32) of the whipper being rough and having an arithmetic maximum surface roughness (Sz) of at least 200 μm.

Description

[Technical Field]

[0001] The present invention relates to plant-based milks and their use in coffee drinks. [Background technology]

[0002] Many foamed beverages, such as dairy drinks and chocolate drinks, are often prepared by mixing a food soluble powder or a food liquid concentrate with a diluent. Mixing devices are known for more rapid preparation of such beverages by mixing soluble food ingredients with a diluent, such as water. These devices typically include a mixing chamber into which the soluble ingredients and the diluent are supplied. The diluent can be introduced into the dissolving chamber to create a vortex for efficiently dissolving the soluble ingredients in hot water, or the hot diluent can be introduced in the form of a jet that provides mixing, dissolving, and frothing. The mixture is then typically whipped by a whipper in a whipping chamber to reconstitute the beverage and generate foam. The beverage then exits the whipping chamber through the bottom of the chamber and is dispensed into a drinking container.

[0003] In the prior art, different types of whipping chambers have been developed to improve the quality of beverage foam. European Patent Nos. 1,476,060 and 1,639,924 describe similar whipping chambers in which the whipper has a tapered shape. While multiple grooves or multiple ribs exist on the surface of the whipper, the rear wall of the whipping chamber may have protrusions or ribs. These whipping chambers were designed to froth various soluble powder ingredients, and in particular, these chambers were configured to froth dairy and coffee beverages depending on the operating speed of the whipper. Therefore, these whipping chambers are not specifically optimized for frothing milk. Additionally, due to the fine grooves on the whipper and the ribs on the rear wall, these whipping chambers cannot be easily and quickly cleaned.

[0004] WO 2003 / 005868 describes a whipping chamber in which the inner wall surface of the chamber is provided with depressions. These depressions cause cavitation when the whipper is activated. The whipper may also exhibit breakers. This whipping chamber can be used interchangeably for preparing lattes, cappuccinos, or espressos, and therefore is not specifically optimized for frothing milk.

[0005] WO 2013 / 149942 describes a whipping chamber in which the front wall of the whipper housing has flat bumps with sharp edges that rise from the surface of the front wall, which makes it possible to prepare large amounts of high-density milk foam from milk powder and water.

[0006] Today, consumer demand for plant-based or non-dairy milks, such as oat milk, almond milk, soy milk, and coconut milk, is increasing. These milks are difficult to foam, and even when using the above-described whipping chamber with these plant-based milk powders, it is not possible to prepare a large amount of high-density milk foam. Furthermore, the properties of the milk foam are important in the preparation of milk-based, especially frothed milk-based specialty beverages, such as cappuccino, latte macchiato, or cocoa-based beverages. The properties of the milk foam in these beverages play an important role in the quality of the final beverage, whether it is related to the visual aspect or mouthfeel of the beverage.

[0007] However, none of the prior art whipper chambers have been able to provide genuine, high quality frothed milk.

[0008] The object of the present invention is to propose a mixing device dedicated to the foaming of milk in order to provide a high-quality vegetable milk foam for the preparation of frothed milk drinks.

[0009] For example, it would be advantageous to provide a new mixing device that can be easily implemented into currently existing beverage dispensers by replacing the existing mixing device with a new one. Summary of the Invention

[0010] In a first aspect of the present invention, there is provided a mixing device comprising: a whipper housing, a whipper, and a rear wall, the whipper housing and the rear wall forming a whipper chamber in which the whipper is housed; a whipper housing having a beverage inlet and a beverage outlet; a drive shaft for driving the whipper, the drive shaft being supported by the rear wall; Equipped with a whipper having a radially rearward surface facing a rear wall of the whipper housing and a radially forward surface opposite the radially rearward surface; a whipper housing having a front wall facing a radially forward surface of the whipper; The whipper is disc-shaped; At least a portion of the radially front surface of the whipper is rough and has an arithmetic maximum surface roughness (Sz) of at least 200 μm, preferably at least 400 μm; A mixing device is provided.

[0011] The mixing device of the present invention comprises a whipper housing and a rear wall configured to form a whipper chamber when assembled together. The device also comprises a whipper, such as an impeller or a rotating disk, for whipping the beverage being prepared. The whipper is driven by a drive shaft supported by the rear wall of the whipper assembly. The whipper housing has a front wall facing the radial front surface of the whipper. The whipper housing comprises a beverage inlet through which the different components of the beverage are introduced to be whipped by the whipper. The beverage inlet is generally located in the front wall of the whipper housing. The front wall preferably has the form of a truncated cone tapering from the beverage inlet to the periphery of the front wall. The whipper housing also has a peripheral side wall generally parallel to the drive shaft. This peripheral side wall has the form of a general cylinder and surrounds the periphery of the whipper. The whipper housing also comprises a beverage outlet through which the beverage whipped by the whipper is discharged. A conduit or nozzle can be attached to the beverage outlet for dispensing into a drinking cup.

[0012] In the present invention, The term "rear" refers to the portion of the mixing device located near the rear wall that supports the whipper drive shaft; The term "front" refers to the portion of the mixing device located near the whipper housing beverage inlet; The terms "radial" and "axial" are defined relative to the axis of rotation of the whipper.

[0013] According to the invention, the whipper is disc-shaped and the material surface at the radial front of the whipper is not smooth but rough, which can be quantified by:

[0014] An arithmetic maximum surface roughness (Sz) of at least 200 μm, preferably at least 400 μm, even more preferably 400 to 750 μm.

[0015] An arithmetic mean surface roughness (Sa) of at least 30 μm, preferably at least 40 μm, even more preferably between 40 and 100 μm.

[0016] This roughness increases the foaming of sparkling drinks, especially low-carbon drinks such as plant-based milks.

[0017] In one preferred embodiment, the roughened surface of the radially forward surface of the whipper has a pattern, preferably a geometric pattern, which is engraved into the surface of the radially forward surface of the whipper.

[0018] In this embodiment, the radial front surface combines a continuous roughened surface with a pattern etched into the roughened surface, typically with a pattern design resulting from lines etched into the roughened surface and having a maximum pit depth compared to the pits in the continuous roughened surface.

[0019] Preferably, the front face of the whipper is provided with a plurality of grooves extending radially on the surface.

[0020] Typically, the grooves are equally spaced from one another.

[0021] Preferably, these grooves extend from the centre of the disc to the periphery of the disc and have a depth of 1 to 2 mm and a width of 2 to 6 mm.

[0022] Preferably, the grooves present a smooth surface in contrast to the front surface of the whipper, which extends between the grooves and is rough.

[0023] Preferably, the front wall of the whipper housing has bumps extending from the surface of the front wall, each of which has a flat upper surface and a sharp edge, and such a whipper housing is similar to the housing described in WO 2013 / 149942.

[0024] The bumps rise from the surface of the front wall of the whipper housing that faces the front face of the whipper. The bumps then face the front face of the whipper. The top surface of each bump, i.e., the most raised portion of the bump above the surface of the front wall of the whipper housing, is flat, with sharp edges.

[0025] According to a preferred embodiment, the beverage outlet is located at the lowest point on the front wall of the whipper housing.

[0026] Preferably, the bumps are regularly radially arranged on the front wall of the whipper housing around the whipper central axis, except in the region of the beverage outlet, and in particular, the edges of both bumps surrounding the beverage outlet are preferably arranged at a distance of more than 2 mm, preferably more than 5 mm, and even more preferably 9 mm, from the edge of the beverage outlet.

[0027] Preferably, all the bumps have the same shape and size.

[0028] Preferably, each bump extends along the entire radial length of the front wall. Since the beverage inlet of the mixing device typically corresponds to an axial opening in the front wall of the whipper housing, this means that the bumps can extend radially on the surface of the front wall from the front wall opening corresponding to the mixing device inlet to the periphery of the front wall.

[0029] Preferably, the top surface of each bump is parallel to the surface of the front wall, and each bump appears as a localized protuberance on the surface of the front wall.

[0030] Preferably, for each bump, its width is greater than its height.

[0031] According to a preferred embodiment, the bump has the shape of a hexahedral solid with quadrilateral faces, such as a trapezoidal solid, a rectangular solid, or a cube. It has been found that such a solid with a flat top surface, a flat raised surface, and straight edges effectively improves the formation of good quality foam. The bump preferably has the shape of a rectangular solid, which is a hexahedral solid with quadrilateral faces composed of three pairs of rectangles.

[0032] The width and number of bumps on the front wall of the whipper housing can vary, with the sum of the surface of all bumps generally being 20-75%, preferably 25-50%, and even more preferably 30-40% of the surface of the front wall of the whipper housing.

[0033] The front wall may include 3 to 11 bumps, preferably 5 to 11 bumps, and according to a preferred embodiment 6 to 8 bumps.

[0034] The bumps may rise above the surface of the front wall by 0.5 to 2 mm, preferably 0.8 to 1.3 mm.

[0035] According to certain embodiments, the mixing device may comprise a dissolving chamber attached to the beverage inlet of the whipper housing. The dissolving chamber and the whipper housing may be molded as a single piece. The outlet of the dissolving chamber emerges within the whipper housing. Preferably, the dissolving chamber comprises at least an inlet for the beverage ingredient and an inlet for the diluent.

[0036] Preferably, the whipper has a radial front surface having a shape substantially corresponding to the surface of the front wall of the whipper housing. The shear gap between the radial front surface of the whipper and the surface of the front wall of the whipper housing is preferably 0.4 to 1.4 mm.

[0037] Particularly good results are obtained with a mixing device as described above, the beverage outlet is located at the lowest point on the surface of the front wall of the whipper housing; The front wall of the whipper housing has 6 to 8 bumps evenly spaced on the surface of the front wall around the beverage outlet, The seven bumps have the same rectangular shape. The seven bumps are raised 0.6 to 1.3 mm above the surface of the anterior wall. The whipper is a disk having six radially extending grooves on its radial front surface, the six grooves being equally spaced from one another; The surface of the groove is smooth, The surface of the whipper between the grooves is rough and has an arithmetic maximum surface roughness (Sz) of at least 400 μm and an arithmetic mean surface roughness (Sa) of at least 30 μm.

[0038] The front wall of the whipper housing of the mixing device is frusto-conical in shape tapering from a diameter of about 40 mm to about 31 mm, and the whipper has a diameter of about 30 mm. Any other smaller or larger mixing devices having the same proportional ratio between the different diameters of the front wall frustum and the whipper are encompassed by the present invention.

[0039] According to a second aspect, there is provided a whipper for a mixing device, the whipper being disc-shaped; a central bore configured to cooperate with a drive shaft; A back surface and a front surface, and The surface of the radially forward surface (32) of the whipper is rough and has an arithmetic mean surface roughness (Sa) of at least 40 μm, and having an arithmetic maximum surface roughness (Sz) of at least 400 μm, A whipper for the mixing device is provided.

[0040] Preferably, the radially forward surface comprises a plurality of grooves extending radially thereon, the plurality of grooves being equally spaced apart from one another.

[0041] This whipper device can be used in the mixing device described in WO 2013 / 149942 to improve the foaming function of the whipping device, especially when soluble plant-based milk powder is mixed with a diluent such as water for dissolution and foaming. Corresponding beverage machines equipped with such type of mixing device can be retrofitted with this new impeller.

[0042] According to a third aspect, there is provided a beverage preparation machine comprising: A mixing device as described above, a diluent supply, preferably a water supply, configured to deliver diluent to the mixing device; a beverage ingredient container configured to deliver ingredients to the mixing device, preferably through an open top; a motor having a drive shaft connected to the whipper through a rear wall of the whipper housing; A beverage preparation machine is provided comprising:

[0043] The machine may comprise a device for restricting the cross section of the beverage outlet downstream of the mixing chamber.

[0044] The machine may comprise a device for opening or closing the beverage outlet, such as a pinch valve cooperating with a deformable tube attached to the beverage outlet. According to a fourth aspect, there is provided a method of preparing a beverage using a beverage preparation machine as described above, the method comprising: introducing a diluent and beverage ingredients into a mixing device; rotating the whipper; Including, The method is closing the beverage outlet before the diluent is introduced into the mixing device and keeping the beverage outlet closed during rotation of the whipper. A method is provided, comprising:

[0045] Preferably, the beverage ingredient is a soluble beverage powder such as milk powder, vegetable milk powder, cocoa powder, etc. Other soluble powders are such as soluble coffee, soluble fruit powder, etc.

[0046] Preferably, the diluent is water.

[0047] According to a preferred method, the whipper is rotated at a speed of at least 9000 rpm, preferably at least 10000 rpm.

[0048] In an alternative embodiment, the beverage ingredient may be a liquid, such as a liquid concentrate (milk concentrate or chocolate concentrate or syrup) that requires dilution and foaming or frothing.

[0049] In another alternative embodiment, the beverage ingredient may be a liquid that requires foaming or frothing, such as milk or vegetable milk.

[0050] According to another aspect, the invention relates to the use of a mixing device as described above for preparing a frothed cocoa drink or a frothed milk or plant-based milk drink.

[0051] The above-described aspects of the invention may be combined in any suitable combination. Moreover, various features herein may be combined with one or more of the above-described aspects to provide combinations other than those specifically shown and described. Further objects and advantageous features of the invention will become apparent from the claims, detailed description, and accompanying drawings. [Brief explanation of the drawings]

[0052] The features and advantages of the present invention will be better understood in connection with the following figures. [Figure 1] 1 illustrates a beverage dispenser with a mixing device. [Figure 2] 1 depicts a mixing device in which features of the present invention may be implemented. [Figure 3] 1A and 1B are rear and perspective views of a whipper housing of a mixing device according to a preferred embodiment of the present invention; [Figure 4] 1A and 1B are rear and perspective views of a whipper housing of a mixing device according to a preferred embodiment of the present invention; [Figure 5A] 1 shows a whipper according to the present invention. [Figure 5B] 1 shows a whipper according to the present invention. [Figure 6] 1 shows a device for opening or closing a beverage outlet. [Figure 7] 1 shows a device for restricting the cross section of a beverage outlet; DETAILED DESCRIPTION OF THE INVENTION

[0053] 1, the beverage dispenser comprises two food ingredient storage units 113a, 113b connected to respective input units 114a, 114b capable of providing food ingredient doses to a common dissolution chamber 6. According to another embodiment, the beverage dispenser may comprise a single input unit connected to different storage units. The storage units may be disposable tanks such as cartridges, cans or tins, pouches... or non-disposable canisters that are refilled with powdered food ingredients.

[0054] The food ingredient may be any ingredient that forms a beverage when mixed with a liquid diluent. It may be a soluble powder or a soluble liquid concentrate. According to the invention, it is preferably chocolate or milk. If different storage units are present, they preferably contain different food ingredients.

[0055] The dosing unit comprises means for dosing the food ingredients, which may be a dosing screw for beverage concentrates, a dosing auger, a perforated disc or a peristaltic pump, and is located at the bottom of the storage unit from which it receives the beverage ingredients by gravity.

[0056] The doses of food ingredients dispensed from the dosing units 13a, 13b are delivered to the dissolving chamber 6 where they are mixed with diluent, typically water, introduced through the diluent inlet 12. The mixture is mixed by a mixing device 1 attached to the dissolving chamber, which comprises a whipper housing 2 and a rear wall 4. The assembly of the whipper housing 2 and the rear wall 4 forms a chamber in which a whipper 3, such as an impeller, is housed. The whipper is connected to a drive shaft 41 fixed to the frame 10 of the dispenser. The drive shaft is powered by a motor 8. The whipped beverage exits the mixing device 1 through an outlet 7 which can be connected to an outlet tube 9 and is delivered to a cup 15.

[0057] FIG. 2 is a more detailed view of the mixing device 1 that can be easily mounted in the dispenser of FIG. 1. The mixing device 1 includes a whipper housing 2, a whipper 3, and a rear wall 4. The whipper housing and the rear wall form a whipper chamber in which the whipper is housed. The whipper 3 is attached to a drive shaft 81, which is supported by the rear wall 4. The drive shaft 81 is driven by a motor 8. The whipper 4 has a radial rear face 33 facing the rear wall 4 of the whipper housing and a radial front face 32 opposite the radial rear face. The whipper front face 32 faces the mixing device inlet 11. The whipper housing includes a front wall 21 (underlined with a dotted line) at the mixing device inlet. The front wall has an opening 22 corresponding to the mixing device inlet 11. The front wall 21 is radially tapered from its periphery to the edge of the opening 22, and preferably has a frusto-conical shape. The whipper housing has a peripheral side wall extending parallel to the axis XX' from the periphery of the front wall. The end of the peripheral side wall rests against the rear wall 4 to close the mixing chamber. The inlet 11 of the whipper housing is attached to the melting chamber 6. The whipper housing and the melting chamber can be made from one integral single piece of material.

[0058] 3 and 4 show a whipper housing 2 exhibiting preferred features. The front wall 21 has a plurality of bumps 5 rising from its surface 211. The top surface of each bump is parallel to the surface of the front wall such that each bump appears as a localized elevation on the surface of the front wall.

[0059] In the illustrated preferred embodiment, the front wall has six bumps. All bumps have the same rectangular parallelepiped shape, with a flat top surface 51 and flat sides with sharp edges between the different surfaces. For optimal foaming performance, the edges of the bumps should not be curved or smooth. All bumps preferably have the same size. The bumps preferably extend the entire axial length of the front wall surface 211 of the whipper housing, from the opening 22 to the periphery of the front wall. According to the present invention, there are no bumps on the peripheral side wall of the whipper housing parallel to the axis XX'. For each bump, its width is greater than its height. Due to the small height of the bumps above the front wall surface 211 (0.5 to 2 mm, preferably 0.8 to 1.3 mm), the bumps have the shape of rectangular plates rising from the front wall surface 211 of the whipper housing. The outlet 7 of the whipper housing is located at the lowest part of the front wall, and the bumps 5 are equally spaced on the surface 211 of the front wall around the outlet 7. Overall, the sum of the surfaces of all the bumps is about 35% of the surface of the front wall of the whipper housing. According to a preferred embodiment, the two bumps surrounding the beverage outlet should be directly adjacent to the outlet. Preferably, these two bumps are located at a distance d of at least 2 mm, preferably at least 5 mm, from the beverage outlet. The outlet 7 of the whipper housing is provided with a tube that is angled slightly downwards to aid in the discharge of the beverage.

[0060] Figures 5A and 5B show a whipper 3 that is preferably used with the mixing device of the present invention, particularly with the whipper housing of Figures 3 and 4. The whipper is a 31 mm diameter disk, the front surface 32 of which is provided with six grooves 31. These grooves are equally spaced apart. Preferably, the grooves extend from the center of the disk to the periphery of the disk and have a depth of 1 to 2 mm and a width of 2 to 6 mm. The surfaces of these grooves are smooth.

[0061] In the whipper of Figure 5A, the surface of the radially forward facing surface 32 of the whipper is rough except for the smooth surfaces of these grooves.

[0062] In the whipper of FIG. 5B, the surface of the radially forward face 32 of the whipper, except for the surfaces of these grooves, is rough and also has a geometric pattern (snake skin type).

[0063] Both whipper whippers were made of plastic and produced by injection molding. Part of the surface of the mold was textured to provide the final rough surface and geometric pattern. The mold texturing was obtained by laser surface texturing. Further processes such as chemical etching can be used.

[0064] For both whipper, the surface roughness of the radial front surface 32 between the two grooves 32 (as shown by surface A1 in FIG. 5B) was analyzed using a non-contact profilometer system, Keyence VR5200 3D Profilometer.

[0065] The whipper in Figure 5A is an arithmetic mean surface roughness Sa of 37 μm, and Arithmetic maximum surface roughness Sz 220μm showed.

[0066] The whipper in Figure 5B an arithmetic mean surface roughness Sa of 85 μm, and Arithmetic maximum surface roughness Sz 740μm showed.

[0067] In comparison, a whipper with a smooth surface, i.e., no surface texturing within the mold, an arithmetic mean surface roughness Sa of 24 μm, and Arithmetic maximum surface roughness Sz 139μm showed.

[0068] Cappuccinos were prepared from coffee and frothed rice milk using different whipper housings (FIGS. 3 and 4) of the beverage dispensers (FIGS. 1 and 2). 30 mL of coffee was produced by extraction of roast and ground coffee in a specific brewing chamber, and 130 mL of rice milk was produced from 30 g of soluble rice flour in the mixing devices (FIGS. 2, 3, and 4) with different whipper types. The frothed milk was dispensed into a container, and then the coffee was dispensed into the frothed milk. The whipper rotated at a speed of approximately 10,000 rpm.

[0069] The height of the rice milk foam above the liquid mixture of coffee and milk was measured in the final drinking cup with the following results:

[0070] [Table 1]

[0071] As shown schematically in Figure 6, the beverage outlet 7 may be connected to an outlet tube 9 and the beverage preparation machine may comprise a closure device 10 for either opening or closing the tube. The closure device may comprise a movable pinch valve 141 housed within a valve assembly body 142. The pinch valve 141 is movable to pinch the tube 31, which is a deformable tube. Thus, the tube can be pinched closed or opened without being pinched.

[0072] In the preparation process using this machine configuration, the following steps are preferably performed: First, the beverage outlet 7 is closed. The diluent and beverage ingredients are then introduced into the mixing chamber and the whipper is rotated.

[0073] Once the beverage is sufficiently foamed, the whipper is stopped and the beverage outlet 7 is opened to dispense the beverage.

[0074] Figure 7 shows the presence of a restrictor 91 inside the tube 9 attached to the beverage outlet of the mixing device. A restrictor is a means for restricting the diameter of the outlet tube. In a preferred embodiment, the restrictor may be a tapered section of the outlet conduit. The tapered section is configured to restrict the flow of fluid therethrough, thereby reducing the velocity of the liquid product flow through the output conduit, which in turn extends the exposure of the fluid to the whipper.

[0075] While the invention has been described with reference to the above illustrated embodiments, it will be understood that the invention as claimed is in no way limited to these illustrated embodiments.

[0076] Variations and modifications can be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist for specific features, such equivalents are incorporated as if specifically referred to herein.

[0077] As used herein, the terms "comprises," "comprising," and similar terms should not be construed in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to." [Explanation of symbols]

[0078] 1 Mixing device 11 Beverage entrance 12 Diluent inlet 2 Whipper housing 21 Front wall 3 Whipper 31 Groove 32 Front 33 Rear 34 holes 4 Back wall 5. Bump 51 Top side 52 Edge 6. Melting Chamber 7 Beverage outlet 8 motors 81 Drive shaft 9 tubes 91 Restrictor 10 Pinch Valve 113a, 113b storage units 114a, 114b Insertion unit

Claims

1. A mixing device (1), comprising: a whipper housing (2), a whipper (3), and a rear wall (4), the whipper housing and the rear wall forming a whipper chamber in which the whipper is accommodated, the whipper housing having a beverage inlet (11) and a beverage outlet (7); a drive shaft (81) for driving the whipper, the drive shaft being supported by the rear wall; Equipped with the whipper has a radial rear surface (33) facing the rear wall (4) of the whipper housing and a radial front surface (32) opposite the radial rear surface; the whipper housing has a front wall (21) facing the radial front surface (32) of the whipper; The whipper (3) is disc-shaped, at least a portion of the surface of the radially front face (32) of the whipper is rough and has an arithmetic maximum surface roughness (Sz) of at least 200 μm, preferably at least 400 μm; Mixing device (1).

2. 2. A mixing device according to claim 1, wherein the rough part of the surface of the radially front face (32) of the whipper has an arithmetic mean surface roughness (Sa) of at least 30 μm, preferably at least 40 μm.

3. 3. A mixing device according to claim 1 or 2, wherein the rough surface of the radially front face (32) of the whipper has a pattern, preferably a geometric pattern, which pattern is engraved into the surface of the radially front face (32) of the whipper.

4. 4. The mixing device of claim 3, wherein the arithmetic maximum surface roughness (Sz) is related to the engraved pattern.

5. A mixing device according to any one of the preceding claims, wherein the front face (32) of the whipper is provided with a plurality of grooves (31) extending radially thereon.

6. 6. A mixing device according to claim 5, wherein the surfaces of the grooves (31) are smooth.

7. 7. The mixing device according to claim 1, wherein the front wall (21) of the whipper housing has bumps (5) protruding from a surface (211) of the front wall, the upper surface (51) of each bump being flat and the edges (52) of the upper surface being sharp.

8. A whipper for a mixing device, said whipper (3) being disc-shaped; a central bore (34) configured to cooperate with a drive shaft; a back surface (33) and a front surface (32); and the surface of the radially front face (32) of the whipper is rough and has an arithmetic maximum surface roughness (Sz) of at least 200 μm, preferably at least 400 μm; Whip.

9. 9. The whipper of claim 8, wherein the radially forward surface (32) includes a plurality of grooves (34) extending radially thereon, the grooves being equally spaced apart from one another.

10. 1. A beverage preparation machine comprising: A mixing device according to any one of claims 1 to 7; a diluent supply, preferably a water supply, configured to deliver a diluent to the mixing device (1); a beverage ingredient container adapted to deliver ingredients to said mixing device (1), preferably through an open top; a motor (8) having a drive shaft (81) connected to the whipper (3) through the rear wall (4) of the mixing device; Optionally, a device (91) for restricting the cross section of said beverage outlet downstream of said chamber; Optionally, a device (10) for opening or closing said beverage outlet (3), A beverage preparation machine comprising:

11. 11. A method of preparing a beverage using a beverage preparation machine according to claim 10, said method comprising: introducing a diluent and beverage ingredients into the mixing device; rotating the whipper; Including, The method comprises: closing the beverage outlet (7) before the diluent is introduced into the mixing device and keeping the beverage outlet closed during rotation of the whipper (3); A method comprising:

12. 12. The method of claim 11, wherein the diluent is introduced into the mixing device before the beverage ingredients.

13. 13. The method according to claim 11 or 12, wherein the beverage ingredient is a milk powder, a vegetable milk powder, or a cocoa powder.

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