The present invention relates to a mixing chamber for preparing edible thickened aqueous compositions. These thickened edible aqueous compositions are viscosity-controlled mixtures of at least one aqueous liquid and at least one solid thickener. Furthermore, the present invention relates to a device comprising such a mixing chamber, wherein said device is used to prepare and optionally 3D-print such edible thickened aqueous compositions. The present invention additionally relates to a process for preparing edible thickened aqueous compositions from at least one aqueous liquid and at least one solid thickener using said device comprising the mixing chamber and, optionally, to 3D-print these compositions. Additionally, the present invention relates to the use of the mixing chamber and/or device for the preparation of edible thickened aqueous compositions and, optionally, to 3D-print them. Dysphagia patients suffer from a swallowing problem which impairs their ability to swallow food in a controlled manner. Dysphagia can be a symptom of a multitude of neurological, muscular and structural pathologies. Dysphagia can lead to serious complications, including malnutrition and dehydration, as well as severe respiratory problems, for instance aspiration pneumonia resulting from the aspiration of food or fluids into the airways.

One of the most widely used interventions in the management of dysphagia is the thickening of low-viscosity liquids, as these normally present the greatest risk of aspiration for the patient, especially due to delayed pharyngeal swallow or oral motor impairment. The thickener increases the viscosity of the liquids and thereby significantly reduces the flow rate of the bolus during swallowing. This increases the chances of the airways being secured in time during the swallowing process to prevent aspiration of the liquid into the airways.

Depending on the severity of the swallowing impairment, the viscosity required for safe swallowing varies from patient to patient. Consequently, several levels of thickening have been established, the most common and accepted classification being that given by the National Dysphagia Diet Task Force (NDD) and published by the American Dietetic Association in 2002. According to this classification, which is based on viscosity values determined at a shear rate of 50 s ^-1 and a temperature of 25°C, a liquid or liquid food with a viscosity in the range of 1 to 50 mPa-s is classified as a "thin liquid", with a viscosity in the range of 51-350 mPa-s as "nectar-like", with a viscosity in the range of 351-1750 mPa-s as "honey-like", and finally, with a viscosity exceeding 1750 mPa-s it is classified as "spoon-thick".

Commercial products for thickening low viscosity beverages or liquid foods are provided either as dry powders or aqueous gels of starch- or gum-based thickeners. The provision of thickeners as aqueous gels instead of dry powders requires extra measures for insuring a sufficient shelf-life of the gels. These pre-gelled products are usually provided in small, pre-packaged doses, which makes them relatively costly and produces significant amounts of waste packaging material after use. Additionally, as a dose of premixed gel comprises a relatively low amount of thickener dissolved in a large amount of a liquid base, shipping costs, relative to the amount of thickener provided, are significantly increased in comparison with the dry powder products, which are usually mixed manually into a beverage or liquid food by the patient, a caregiver or nursing staff immediately before consumption.

Commercial dry powder products are provided with instructions to the users on how to prepare thickened beverages or liquid foods with a viscosity within the above defined categories. Manual mixing of the thickener into the beverage or liquid food is relatively time-consuming and requires careful adherence to the mixing instructions, e.g. the amount of thickener required to obtain the desired viscosity and the time required by the thickener to increase the viscosity of the mixture. If these instructions are not adhered to by the person mixing the powder into the beverage or liquid food, the viscosity of the thickened product may not fall into the required category. Additionally, at higher viscosities, it becomes increasingly difficult to avoid the entrapment of air and the formation of bubbles in the thickened liquid. Air bubbles in the thickened liquid can lead to a significant reduction of the viscosity of the mixture, which therefore - although using the recommended amount of thickener - may not have the desired target viscosity.

Another problem that is encountered in dysphagia patients who consume a major part of their daily food in the form of thickened liquid nutrition is the development of "diet fatigue". Due to the limited sensorial attributes of thickened liquid nutrition, patients may tire of this food rather quickly and compliance to the dietary regime based on thickened beverages and thickened liquid food may be reduced.

Consequently, there exists a need to provide means for the preparation of viscosity-controlled thickened beverages or liquid food that overcomes or lessens the above-described problems. Especially there is a need for a means to prepare more reliably thickened beverages or thickened liquid food having a predetermined viscosity, especially thickened compositions of nectar- or honey-like viscosity or spoon-thick compositions. Additionally, there is a need for a process by means of which such compositions can be prepared easily and in a less-time consuming way by users, especially caregivers or nursingstaff. There is also a need to provide thickened food with increased sensory attributes compared to thickened liquid food.

The present invention solves or lessens at least some or all the problems outlined above. The present invention provides a mixing chamber and a device comprising said mixing chamber. The chamber/device allows the reliable automated preparation of viscosity-controlled mixtures of at least one solid thickener and at least one aqueous liquid. In one aspect of the invention, the device according to the present invention is a 3D-printer, allowing to 3D-print the viscosity-controlled compositions. The device comprising the corresponding mixing chamber may be operated in continuous or sequential mode to prepare either large batches or single doses of the viscosity-controlled mixtures. Additionally, the present invention provides a process for preparing viscosity-controlled mixtures of at least one solid thickener and at least one aqueous liquid, said process making use of the mixing chamber and/or device of the present invention. A further aspect of the present invention relates to the use of the mixing chamber in a 3D-printing device, especially as part of the printing head of such a 3D-printer.

The mixing chamber for preparing an edible, viscosity-controlled mixture of at least a solid thickener and at least one aqueous liquid according to the present invention comprises: a casing, defining with its inner walls an inner volume comprising three cylindrical areas which are sequentially arranged along a central axis, whereas the three cylindrical areas are a) a solid dosage area having an inlet for solids, b) a liquid dosage area having an inlet for liquids, and c) a transport area having an outlet for the prepared mixture. The mixing chamber further comprising a rotation element arranged in the casing and extending along a long axis through the cylindrical areas, wherein the rotation element is rotatable arranged in the mixing chamber, said rotatable element comprising flanks arranged helically along the direction of the long axis. Furthermore, said mixing chamber comprises at least one counter flank arranged on at least a part of the inner wall of the casing, engaging with at least one of the flanks of the rotation element.

In the context of the present invention "edible" indicates that a mixture can be swallowed and safely consumed by a human. Such edible mixtures include nutritional compositions or foodstuff, including beverages, as well as mixtures comprising pharmaceutically active ingredients and/or at least one component selected from the group consisting of macro- and/or micronutrients, e.g. protein, fat, carbohydrates, vitamins and minerals and other nutritional supplements. Nutritional compositions include nutritional compositions defined as Food for Special Medical Purposes, FSMP, e.g. nutritional supplements or complete nutritional compositions, as for instance defined in the European Union in Commission Directive 1999/21/EC.

"Viscosity-controlled" means, that the mixture has a viscosity that lies within a predefined target range. The desired texture or viscosity is predefined by the respective amounts of solid thickener and aqueous liquid used in the mixture, i.e. the ratio between solid thickener and aqueous liquid. By mixing an aqueous liquid with a suitable solid thickener, thin liquids with a viscosity value of 1-50 mPa-s, nectar-like mixtures with a viscosity value between 51- 350 mPa-s, honey-like mixtures with a viscosity value of 351-1750 mPa-s and spoon-thick mixtures with a viscosity value >1751 mPa-s can be provided. In compliance with the classification established by the National Dysphagia Diet Task Force, these values relate to a shear rate of 50 s ^-1 and a temperature of 25°C. The viscosity-controlled mixtures may also be mixtures with a viscosity that is sufficiently high for the mixtures to essentially maintain a three- dimensional form over time into which the mixture has been brought during preparation. Put in other words, such mixtures have a viscosity that is high enough for the mixture to essentially self-sustain a defined three-dimensional form or shape over time. Such form-stable mixtures include for instance gellike mixtures. The three-dimensional stability at such viscosities allows to model the viscosity-controlled mixtures, e.g. a beverage or nutritional composition, into predefined three-dimensional shapes, for instance to imitate the form of a solid food or any other form that is considered pleasing and/or interesting by the person consuming the mixture, especially a person suffering from dysphagia. Such shapes can for instance be formed by 3D- printing of the viscosity-controlled mixtures.

"Aqueous liquid" as understood in the context of the present invention includes any water-based liquid, e.g. pure water or solutions of additional ingredients in water. Examples for such "aqueous liquids" are water, fruit juice, milk, milk-substitutes such as rice or oat milk, tea, herbal infusions, coffee, chocolate drinks, liquid food, e.g. soup or broth, or, for instance, solutions of one or more pharmaceutically active ingredients and/or one or more nutritional supplements, e.g. vitamins, minerals, etc. in water or other edible, aqueous liquids.

A "solid thickener" as used herein is meant to encompass a single solid thickener or a mixture of two or more solid thickeners, each preferably in pulverulent or granular form. Additionally, the term "solid thickener" may be understood as a mixture of at least one solid thickener and additional solid nutrients, such as macronutrients or micronutrients, all of which are preferably in pulverulent or granular form, more preferably in the form of a powder. The solid thickener preferably is a powder thickener or a powder mixture of two or more thickeners. Any edible thickener can be used, especially thickeners that are commonly used for thickening food, e.g. starch- , gum-, protein, and/or mucilage-based thickeners. Examples of such thickeners which can be used as solid thickeners include gum arabic (E414), carbo/locust bean gum (E410), guar gum (E412), pectin (E440), sodium carboxymethyl cellulose (E466), starch (E1401-1451), agars (E406), alginates (E400-404), carrageenans (E407), gellan gum (E418), xanthan gum (E415), collagen and gelatin and mixtures thereof. Examples of commercially available powder thickeners provided for diet modification of dysphagia patients are for instance described by J.M. Garcia et al., in Dysphagia 20:325-335 (2009) and include the product "Thick & Easy®", available from Hormel Health Labs, „Thick-it®", available from Kent Precision Foods Group, Inc., „Thicken Up®", available from Nestle Corporation, and „Thik& Clear®", available from Nutra Balance. Another powder thickener that can be used in the present invention is Fresubin Clear Thickener® (FCT), available from Fresenius Kabi.

It is clear to the person skilled in the art that the amount of solid thickener necessary for modifying the viscosity of a specific amount of an aqueous liquid such that the resulting mixture will have a specific consistency, e.g. a viscosity falling within the NDD classifications, will differ depending on the nature of the solid thickener as well as the aqueous liquid. According to one embodiment of the invention, the mixing chamber comprises a casing defining with its inner walls an inner volume. The inner volume comprises three cylindrical areas which are sequentially arranged along a long axis. In other words, the inner volume of the mixing chamber has areas of cylindrical shape, wherein the diameters of these cylinders may be the same or may differ for one or each of said cylindrical areas. The different cylindrical areas follow one another along a central axis from a first end of the inner volume to a second end of the inner volume. Preferably, the long axis the rotation element extends along, is superimpose with the central axis.

The three areas defined by the three respective cylindrical spaces in the casing are a solid dosage area, a liquid dosage area and a transport area. The outermost inner wall of the solid dosage area defines the first end of the inner volume. The solid dosage area is followed by the liquid dosage area which is followed by the transport area. The outermost inner wall of the transport area defines the second end of the inner volume. The solid dosage area comprises an inlet for solids, i.e. a solid thickener or a mixture of solid thickeners. The liquid dosage area comprises at least one inlet for an aqueous liquid. The transport area comprises an outlet by means of which the prepared mixture of solid thickener and aqueous liquid leaves the mixing chamber. Preferably the inlets are arranged at an upper part of the casing. Such an arrangement helps to reduce the probability of clogging of only partially wetted and/or dissolved solid thickener. The outlet is arranged at a lower part of the casing close to the second end of the inner volume. This arrangement is favorable because in the area of the outlet the weight of the prepared mixture supports its transport out of the mixing chamber. If the viscosity of the prepared mixture is sufficiently low, the mixture could simply flow out of the outlet and not require the transportation via a rotatable element.

According to one embodiment of the invention additional inlets for liquid and / or additional inlets for solids are arranged in the liquid dosage area, the solid dosage area respectively. Additional liquid and solid feeds can therefore be connected to these additional inlets. Such an embodiment is advantageous for independently controlling the concentration of selected ingredients of the mixture, such as macro- and micronutrients, pharmaceutical effective agents or additional ingredients such as colorants, flavors, stabilizers, or the like.

A rotation element is arranged within the inner volume of the mixing chamber. The rotation element is rotatable arranged in the mixing chamber. The rotation element extends through all three areas of the inner volume of the mixing chamber. The rotation element can alternatively be described as a mixing screw which will drive and mix the material during its flow through the mixing chamber.

The rotation element comprises flanks, arranged helically along at least parts of its long axis. "Helical arranged flanks" or "helical flanks" are to be understood that the outer surfaces of the flanks describe a curve that winds around the jacket of a cylinder, preferably with a constant slope. Within this invention, the diameter of the (imaginary) cylinder the outer surfaces of the flanks wind around is referred to as the outer diameter of the helical flanks. It is not mandatory that the outer surface of the flanks describe a continuous helix or cylindrical spiral along the entire rotation element. Instead, the flanks may only be present in specific sections along the long axis of the rotation element.

The diameters D _s , D _l and D _t may all be identical or different from each other. In one embodiment of the invention, the diameter D _s of the solid dosage area is smaller than the diameter D _l of the liquid dosage area and smaller than the diameter D _t of the transport area. Preferably, the diameter D _t of the transport area is smaller than the diameter D _l of the liquid dosage area, too. In other words, in this embodiment the solid dosage area has the smallest diameter of all three cylindrical areas. The ratio of D _s / D _l is preferably less than or equal to 0.5, more preferably less than or equal to 0.4. The ratio of D _l /D _t is preferably in the range of 1.5 to 5, more preferably in the range of 1.6 to 1.8.

Preferably, the mixing chamber has cylindrical areas of different diameters, to enhance each of the mixing stages. The central zone, i.e. the liquid dosage zone, is the largest in diameter, thereby creating a large reservoir in which solid thickener and aqueous liquid are brought into contact to effectively dissolve the thickener in the liquid.

If the solid thickener is a powder mixture of at least one solid thickener and one or more macro- or micronutrients, the mass to be transported into the liquid dosage area might have to be increased. In such a case, it may be beneficial to increase D _s in relation to D _l to allow a higher mass flow from the solid dosage area into the liquid dosage area, especially if the additional solid component is a macronutrient, i.e. protein, fat, or carbohydrate, or a mixture thereof.

In one embodiment of the invention the flanks of the rotation element differ depending on the cylindrical area they are arranged in. Preferably, the outer diameter of the helical flanks corresponds to the diameter of the respective cylindrical area they are arranged in. In other words, an outer diameter Di of the flanks in the solid dosage area corresponds to the diameter D _s . An outer diameter D ₂ of the flanks in the liquid dosage area corresponds to the diameter D _l and an outer diameter D3 of the flanks arranged in the transport area corresponds to the diameter D _t .

Preferably, the outer diameter of the helical flanks is equal to or only slightly smaller than the diameter of the cylindrical area they are arranged in. Hence, dead zones in which solids or highly viscous, partially dissolved solids can accumulate are minimized. Also, dead zones, where there is no movement in the mixture, i.e. in which the mixture is not transported in the direction of the outlet, are minimized. The adhesion of solid or partially dissolved solid to the inner wall is thereby effectively reduced or prevented. Minimizing the dead zones in the mixing chamber ensures an effective contact between all of the solid thickener and the aqueous liquid fed into the liquid dosage area and thereby enables the solid thickener to be effectively mixed into the aqueous liquid and subsequently to be effectively dissolved therein. This allows the preparation of mixtures having an increased homogeneity and ensures that effectively all of the solid thickener fed into the liquid dosage area is utilized to thicken the aqueous liquid, thereby minimizing variability in the concentration of thickener in the mixture and therefore its viscosity. This is of great importance for reliably producing mixtures of solid thickener and aqueous liquid having a predetermined, aimed-for viscosity.

According to one embodiment of the invention, the outer diameter of at least some of the helical flanks is equal to or slightly longer than the diameter of the cylindrical area they are arranged in, and the outer area is of a flexible material. For example, the outer area of the flanks may be designed as flexible wing elements which brush over the inner wall of the mixing chamber, as the rotation element rotates. Thus, solid thickener or only partially dissolved thickener that adheres to the inner wall is scraped off the inner wall of the casing whilst dead zones are again minimized.

According to one further embodiment of the invention there is a transition area between the liquid dosage area and the transport area. In other words, the transition between the liquid dosage area and the transport area is continuous. In this transition area the inner wall is tapered with decreasing diameter from the liquid dosage area towards the transport area. The transition area is shaped as a truncated cone. This allows the mixture to flow continuously form the liquid dosage area into the transport area. No dead zones are created where the mixture can accumulate without movement. Preferably, a flank is arranged on the section of the rotation element that is positioned in this transition area. More preferably the outer surface of the flank is tapered, corresponding to the decreasing diameter of the transition area.

In the mixing chamber according to the invention, at least one or, preferably, an array of counter flanks is arranged on at least parts of the inner wall of the casing, engaging with at least one of the flanks of the rotation element. Preferably, the counter flank or the array of counter flanks is arranged on the upper part of the inner wall of the casing. "Engaging", as used here, means that while the rotation elements rotates one or more counter flanks are brought into contact or into very close proximity to at least one of the flanks of the rotation element to wipe over their surface at a distance that is small enough to scrape off any solid or only partially dissolved solid that adheres to said flanks. In other words, the counter flanks and the flanks engage with each other, such that the counter flanks scrape off solid or only partially dissolved solid that adheres to the flanks and vice versa. If both the flanks and counter flanks are made of a rigid material, e.g. of metal or plastic material, the flanks and counter flanks may only be brought into close proximity to each other (e.g. 1 mm or less) so not to touch each other whilst any solid or only partially dissolved thickener is scraped off their surface. If either the flanks or counter flanks, or both, are made of a sufficiently flexible material, e.g. of a silicone-type material, flanks and counter flanks may come into contact with each other whilst solid or semi-solid material is scraped off their surfaces.

According to one embodiment of the invention the at least one counter flank is a baffle, which, preferably, is arranged only in the upper half of the casing, especially in the liquid dosage area. Preferably, there is an array of baffles arranged only in the upper half of the casing. By placing the baffle or preferably, an array of baffles, only in the upper half of the casing, the accumulation of any solid or only partially dissolved thickener in the bottom half of the casing is reduced or avoided.

In one embodiment of the invention the part of the rotation element extending through the solid dosage area is designed as a screw conveyor for transportation of the solid thickener. The flanks in this part of the rotation element continuously wind around the long axis of the rotation element.

In one embodiment of the invention the at least one counter flank or, preferably, the array of counter flanks, are only present in the liquid dosage area. In the liquid dosage area, the aqueous liquid and the solid thickener come into contact with each other, the surface of the solid thickener is initially wetted by the aqueous liquid and may form a highly viscous film on the surface of the thickener particle. Such wetted particles may adhere to the inner walls of the casing or the flanks. Similarly, as the aqueous liquid further penetrates the thickener particle during the dissolving process, the particle may swell and form a highly viscous body of only partially dissolved thickener, which again may adhere to the inner wall of the casing or the flanks. Thus, there is an increased need for preventing the solid thickener to adhere to the inner walls of the liquid dosage area or the flanks of the rotation element situated in the liquid dosage area. Additionally, the at least one counter flank or, preferably, the array of counter flanks hinder aqueous liquid to pass through the inlet for solids into an attached solid feed, which could result in a clogging up of the inlet for solids by highly viscous, only partially dissolved thickener. Additionally, as already discussed above, the counter flank or flanks, especially when formed as baffles arranged only in the upper half of the casing, help to reduce or avoid the accumulation of solid or only partially dissolved thickener at the bottom of the casing.

The provision of the one or more counter flanks only in this area of the mixing chamber has proven to be sufficiently effective in reducing or minimizing the adherence of solid or only partially dissolved thickener to the inner walls of the mixing chamber, the surface of the flanks of the rotation element, and for hindering liquid passing through the solid inlet into an attached solid feed.

Preferably the flanks of the rotation element in the liquid dosage area are designed as truncated helical flanks. These truncated flanks can be described as radially cut discs, each of which is stretched or distorted by pushing apart the two cutting edges resulting from the cut, said stretched or distorted discs then being arranged along the long axis of the rotation element in this area. Thus, the one or more counter flanks can engage with the truncated flanks and scrape or wipe over their front surfaces during movement of the rotation element, as described above.

In one embodiment of the invention the part of the rotation element extending through the transport area is designed as a shaftless spiral conveyor. Thus, the helical flanks wind continuously around an open axis. This form is similar to the form of a dough hook and is therefore especially suitable for exerting force onto thickened mixtures, resulting in an effective transport thereof in the direction of the outlet.

All the different kind of flanks present of the rotation element wind around the long axis of said element in the same direction. Hence, when the device according to the invention is assembled and running, the rotation element generates a mass flow through the cylindrical areas from the first end to the second end of the inner volume.

In one embodiment of the invention the casing of the mixing chamber is divided into two detachable halves, preferably an upper and a lower half. This allows an easy assembly or disassembly of the mixing chamber, the insertion and removal of the rotation element, as well as the easy cleaning of all components. Such ease of cleaning is of great importance as the mixtures produced using the mixing chamber are intended for human consumption, especially for patients with an already impaired health. Additionally, it reduces the time required for the maintenance of the mixing chamber.

According to one embodiment of the invention, the upper and the lower half of the casing each comprises a circumferential collar to build a sealed, detachable connection to one another. For this purpose, connection elements, such as screws or clamps, can be used.

According to another embodiment of the invention the upper and the lower half of the casing are pivotably attached to another along one axis. In other words, the casing can be opened like a chest.

In the following, a device according the invention, i.e. a device for preparing edible, viscosity-controlled mixtures of at least an aqueous liquid and at least a solid thickener is described. Using the device, it is possible to prepare different edible mixtures within a broad viscosity-range.

The device comprises a mixing chamber as it is described above. Where it contributes to understanding, different advantageous features of embodiments of the mixing chamber are repeated and/or added in the following description of the device according to the invention.

A solid feed, for example a hopper, is attached to the inlet for solids, i.e. an inlet through which the solid thickener can be transported into the mixing chamber. A liquid feed is attached to the inlet for liquids, i.e. an inlet through which the aqueous liquid can enter the mixing chamber. A motor is connected to the rotation element. Furthermore, the device comprises a control unit for regulating the dosage of the aqueous liquid and/or the dosage of the solid thickener. Preferably, the control unit is connected to a user interface, via which the control unit can, for instance, be programmed by the user or by means of which a specific software script, e.g. program regulating the different elements of the device can be selected and started. By regulating the different elements of the device accordingly mixtures having different viscosity and viscoelastic properties can be prepared using the device of the present invention.

The device with the corresponding mixing chamber allows the preparation of single doses as well as in situ and continuous mixing of a solid thickener and an aqueous liquid to prepare batches comprising multiple doses of viscosity- controlled mixtures. The control unit can regulate the dosage of the liquid and the dosage of the solid thickener separately.

According to one embodiment of the invention the liquid feed is a pump for liquids with an associated motor and reservoir for liquids. The control unit controls the motor of the pump to provide a mass flow of the liquid to the inlet for liquids. The liquid feed may further comprise a heating or cooling unit, preferably regulated via the control unit, to heat or cool the aqueous fluid to a predetermined temperature, which might be required to aid the dissolution of the solid thickener in the aqueous liquid.

The solid feed may be any device providing a constant supply of solid thickener, for example a hopper. It is attached to the inlet for solids. The hopper may for instance comprise a receptacle area extending therethrough, said receptacle area being designed in such a way that the mixing chamber can be inserted into the receptacle area such that the rotation element of the chamber can be connected to the motor positioned at the lower end of the hopper. Once the mixing chamber has been inserted into the receptacle area of the hopper, the opening at the bottom of the hopper is situated above the solid inlet of the mixing chamber. Solid thickener may then enter the solid dosage area of the mixing chamber via the solid inlet. Together with the rotation element which, in the solid dosage area, is designed in the form of a screw conveyor, a certain mass flow, or in other words a flow rate of the solid, can be provided. Therefore, the control unit regulates the motor driving the rotation element connected thereto. Since the total mass of the solid thickener needed to achieve a target viscosity is always small compared to the total mass of the aqueous liquid, the flow rate of the solid needs to be lower than the flow rate of the liquid.

It is clear to those skilled in the art that mass flow of the solid depends on the size of the inlet and the solid dosage area, the design of the rotation element in said area, and the rotation speed of the rotation element. Lower rotation speed results in a lower flow rate of the solid thickener. The rotation element will also mix and transport the material of the mixture during its flow through the inner volume of the mixing chamber.

It is advantageous to choose a diameter D _s for the solid dosage area that is smaller than the diameter D _l of the liquid dosage area. Therefore, a low flow rate for the solid can be provided at a sufficiently high rotation speed to ensure homogeneous mixing of the material, e.g. the solid thickener and aqueous liquid during its flow through the inner volume of the mixing chamber.

According to one embodiment of the invention the control unit of the device is part of a 3D-printer.

Three-dimensional ("3D") printing can be described as a process by which three-dimensional objects are manufactured via an additive process, where successive layers of material are deposited by a print head in a build area, or print bed, in different patterns to form the object. The patterns are derived from a digital or virtual blueprint of the object generated via computer-aided design software by slicing the object into multiple digital cross-sections of the object. The 3D-printer then successively deposits the material according to these patterns to form the object. At the end of the process the digital or virtually designed object has been printed as 3D-object. Different kinds of basic 3D-printer constructions are known, which achieve the movement of print head and build area relative to each other by different constructional principles. These types of 3D-printers are known as "Cartesian", "Delta", "Polar" or "Scara" 3D-printers, as for instance described by Jie Sun et al. in "Extrusion-based food printing for digitalized food design and nutrition control” (2018), Journal of Food Engineering, 220, 1-11.

During the process the material is deposited by the print head of the 3D- printer on a build area or building plate. The 3D-printer comprises different frame elements on which the print head and the build area are mounted, respectively. In a Cartesian 3D-printer for instance, the print head is mounted movably on a frame element of the printer for instance in such a way that it can be moved in two directions (e.g. x- and z-direction of a three-dimensional coordinate system) parallel and/or perpendicular to a building area, e.g. a building plate, which is mounted movably on another frame element of the printer in such a way that it can be moved in a third direction perpendicular to the other two directions (e.g. y-direction of a three-dimensional coordinate system). Alternatively, the print head can be mounted movably in one direction (e.g. z-direction) and the build area moveably in the other two directions (x- and y-direction) perpendicular to the first direction. The print head and building area are both motor-driven and their respective motion is configured to move in horizontal and vertical directions to control deposition of the printed material using a computer-aided manufacturing or computer- aided design (CAD) program running on the control unit of the 3-D printer. By moving the print head and the build area relative to each other in all three directions, any point within a 3D-construction space can be accessed by the print head and material be deposited thereon.

According to one embodiment of the present invention the device is a 3D- printer for printing edible, viscosity-controlled mixtures of at least an aqueous liquid and at least a solid thickener comprising a build area and a print head, wherein the mixing chamber, the solid feed and the motor driving the rotation element together form the print head of the 3D-printer. The build area and the print head are movable in relation to each other. This may be achieved in any conventional manner used in 3D-printers. For instance, either the print head or build area may be constructed to be independently movable in all 3 directions (x, y, and z) of a threedimensional coordinate system or, preferably, either the print head or the build area may be movable in two directions (e.g. directions x and z) whilst the other is movable only in the remaining third direction (e.g. direction y). The liquid feed may be attached to the mixing chamber for providing the aqueous liquid. The control unit of the device is preferably configured to regulate the movement of the building area and the printer head as well as the dosage of aqueous liquid and solid thickener into the mixing chamber in the printer head. If provided, any heating units present in the device, e.g. a conventional hot end at the outlet of the mixing chamber or a heating device forming part of the liquid feed, can also be regulated via the control unit. The 3D-printer device can for instance be build using conventional 3D-printer design and using conventional and commercially available mechanical and electronic components such as controller boards, frame construction parts, motion controllers, such as belts and stepper motors, threaded rods and end stops, power supply units, print beds used as the building area, including heated and non-heated print beds, heating units including thermocouples, cooling fans, and user interfaces.

In such embodiments, the mixing chamber is designed and manufactured to be adapted to a 3D-printer and controlled by its firmware, allowing the continuous and automatic in-situ mixing of at least one solid thickener and at least one aqueous liquid, fed into the mixing chamber via the respective feeds. The device can simply be used as an automatic mixer controlled via software, to obtain mixtures having a viscosity in a predetermined range. For instance, a conventional fused filament 3D-printer can be modified by replacing the original filament extruder with the mixing chamber mounted on the carriage using a custom designed holder. The solid feed and the motor driving the rotation element are then attached to the mixing chamber.

Preferably the 3D-printer control unit is directly connected to the motor of the liquid feed pump, e.g. a syringe pump, which is to be controlled as a conventional extruder. The mixing screw, i.e. rotation element, with its part extending beyond the mixing chamber, is directly attached and driven by a motor which, like the one in the liquid feed pump, is configured as a conventional extruder to be controlled via software running on the 3D-printer acting as the controller. The mixing screw is for example directly attached and driven by a NEMA 17 stepper motor, available from different commercial vendors. When used to obtain highly viscous mixtures with viscosities that allow them to self-sustain a defined three-dimensional form, the mixing chamber coupled to a 3D-printer can be used to design e.g. gel models with appealing shapes or simulating conventional food, which can help to make e.g. clinical nutrition more attractive to patients, thereby increasing compliance of patients to a prescribed texture-modified diet.

All parts of the mixing device must be clean and dry before assembly. The two casing halves are secured with screws, having previously placed the rotation element inside. The mixing device is then coupled to the solid feed, so that the motor shaft fits with the cavity made for this purpose in the rotation element. Once this is done, the solid feed is loaded with the solid thickener and the liquid feed, previously loaded with the liquid to be thickened, is connected to the liquid inlet in the upper half of the casing. When the device is loaded and ready for use, the desired flow ratio is set via software running on the control unit.

Preferably the process further comprises a calibration sequence for the control unit to configure the dosage of the solid thickener and the dosage of the aqueous liquid.

According to one embodiment both the liquid feed and solid feed, working as conventional extruders, can operate simultaneously and independently due to the creation in Repetier-Host of a virtual extruder for which the flow ratio of both feeds can be controlled by means of a simple software script.

When a conventional 3D-printer has two extruders, they are usually of the same type and geometry, so the flow ratio can be assigned directly. That is, by setting a weight of 50 (over 100) for each extruder, the material flow for each extruder would be the same. This is not the case here, where the liquid feed and the solid feed are feeding systems with completely different geometries, that for equal motor movement, provide different material flows. Thus, individually calibration of each of the feeds is necessary. The firmware of the 3D-printer used as the control unit measures the advance of the motors (their rotation) in units of length. Thus, by sending orders to the printer to print different distances and weighing the amount of material printed in each case, a flow rate value in g/mm can be obtained. This flow rate value, in turn, can be converted into mass flow rate directly by means of the printing speed used (Eq. 1): [1] mass flow rate [g/min] flow rate [g/mm] printing speed [mm/min]

Since the geometries of the two feed systems are different, as are the flow rate values for the liquid solvent (fr,) and the solid (Jr _SO Hd) _f therefore each of the flows has to be calibrated independently by weighing the amount of material supplied by the liquid pump, for example a syringe pump, and the mixing screw, i.e. rotation element for given motor advance lengths, for example resulting in:

Once the characteristic flow rate of each feed system is known, a weight from 0 to 100 is applied to each motor to control mixing ratio. A weight of 1 is assigned to the liquid pump motor (wl), as it is the one with higher feeding capacity. Then, the weight for the motor driving the mixing screw, i.e. rotation element (w _solid ) is calculated to get the correct ratio in each case. However, the sum of the weights of the different motors is required to be equal to 100, so that a third 'ghost' motor is defined in order to absorb the excess weights. Different mass flows can be achieved by multiplying the weights for the solid and liquid solvent. For instance, considering the nectarlike concentration (1.6 wt.%): weight for liquid solvent feeding motor weight for solid feeding motor weight for "ghost" motor

Thus, mixing mass flow rate also named as total mass flow rate is then calculated by means of Eq. [2: [2]

Printing speed is set for example at 600 mm/min for nectar-like blends and slightly variated to compensate for the increased solid flow for the two higher concentrations.

In a further aspect the present invention relates to the use of a mixing chamber and/or a device according to the present invention for the preparation of preparing edible, viscosity-controlled mixtures of at least an aqueous liquid and at least a solid thickener.

The solid thickener used in the different aspects of the present invention is preferably selected from starch-, gum-, protein, and/or mucilage-based thickeners, preferably selected from the group consisting of gum arabic, carbo/locust bean gum, guar gum, pectin, sodium carboxymethyl cellulose, starch, agars, alginates, carrageenans, gellan gum, xanthan gum, collagen, gelatin, and mixtures thereof, preferably from the group consisting of starch, gums, and carrageenans. The solid thickener is preferably in pulverulent or granular form. Preferably the solid thickener is a dry powder thickener.

The aqueous liquid used in the different aspects of the present invention is preferably selected from the group of water, beverages, liquid food, liquid enteral nutritional compositions or supplements.

The aqueous liquid used in the different aspects of the invention may further comprise at least one additive selected from the group of pharmaceutical active ingredients, micronutrients, preferably vitamins and minerals, amino acids, colorants, stabilizers and flavors.

The edible, viscosity-controlled mixture prepared using the different aspects of the present invention has a viscosity in the range of 1-50 mPa-s, 51-350 mPa-s, 351-1750 mPa-s, or >1751 mPa-s, preferably >1751 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C. In a preferred embodiment of the use according to the invention the viscosity of the edible, viscosity-controlled mixture is higher than 1751 mPa-s, preferably higher than 1800 mPa-s, even more preferably of at least 1850 mPa-s when measured at a shear rate of 50 s ^-1 and a temperature of 25°C and is sufficiently high for the mixture to self-sustain a defined three-dimensional form.

The skilled person is aware that for an edible, viscosity-controlled mixture to be able to self-sustain a defined three-dimensional form over time, not only viscosity, but also viscoelastic properties are of importance, e.g. gel strength. Gel strength of such mixtures must be sufficiently high that the mixture does not flow, once it has been printed into the desired three-dimensional form. The skilled person is aware that viscoelastic properties of mixtures of thickeners in aqueous liquids will depend on the nature of the thickener and may depend on additional parameters, such as thickener concentration in the mixture, pH-value, additives etc.

Preferably, the viscosity of the edible, viscosity-controlled mixture prepared using the different aspects of the present invention has a viscosity of up to 10.000 mPa-s, preferably of up to 8000 mPa-s, more preferably of up to 6000 mPa-s, most preferably of up to 5000 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C.

In preferred embodiments according to the invention, the viscosity of the edible, viscosity-controlled mixture prepared using the different aspects of the present invention has viscosity in the range from more than 1751 mPa-s to 10.000 mPa-s, preferably from 1800 mPa-s to 10.000 mPa-s, more preferably from 1850 mPa-s to 10.000 mPa-s when measured at a shear rate of 50 s ^-1 and a temperature of 25°C. In further preferred embodiments according to the invention, the viscosity of the edible, viscosity-controlled mixture prepared using the different aspects of the present invention has a viscosity in the range from more than 1800 mPa-s to 10.000 mPa-s, preferably up to 8000 mPa-s, more preferably of up to 6000 mPa-s, most preferably of up to 5000 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C. In yet further preferred embodiments according to the invention, the viscosity of the edible, viscosity-controlled mixture prepared using the different aspects of the present invention has a viscosity in the range from more than 1850 mPa-s to 10.000 mPa-s, preferably up to 8000 mPa-s, more preferably of up to 6000 mPa-s, most preferably of up to 5000 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C. By using this new preparation device, mixing does not cause air to enter the system and air bubbles entrapped in the final mixture are due solely to the air entering the device trapped between the solid particles. By controlling the granulometry of the solid thickener this can be further minimized. Additionally, it has surprisingly been found that when using the mixing chamber and/or device according to the present invention, less thickener is required compared to manual mixing to obtain mixtures having comparable rheological properties, e.g. viscosity or viscoelasticity.

According to a further aspect of the invention, a process for preparing an edible, viscosity-controlled mixture of at least an aqueous liquid and at least a solid thickener is provided, said process comprising the steps of providing a device according to an embodiment as it is described above, providing a suitable aqueous liquid, for example water, juice, milk within the liquid feed and providing a suitable solid thickener within the solid feed. Afterwards, depending on the aqueous liquid and the solid thickener as well as the target viscosity, a suitable software routine is chosen via the control unit, to provide a mass transport via the liquid feed and the solid feed suitable into the mixing chamber of the device to give a mixture having a target viscosity. The solid thickener and the aqueous thickener are then mixed in the device and dispensed therefrom via the outlet of the device. Preferably, the process further comprises 3D-printing the edible, viscosity-controlled mixture into a predefined three-dimensional form. The skilled person understands that this step requires that the edible, viscosity-controlled mixture has a suitable viscosity and viscoelasticity to self-sustain such a predefined three- dimensional form over time.

In a further aspect of the invention an edible, viscosity-controlled mixture comprising at least one aqueous liquid and at least one solid thickener is provided which is obtainable by the process according to the invention, wherein the edible, viscosity-controlled mixture has a viscosity of above 1800 mPa-s when measured at a shear rate of 50 s ^-1 and a temperature of 25°C, preferably above 1850 mPa-s. Embodiments of the invention

Embodiment 1: Mixing chamber (1) for preparing an edible, viscosity- controlled mixture comprising at least one aqueous liquid and at least one solid thickener, said mixing chamber (1) comprising: a casing (10), defining with its inner walls an inner volume comprising three cylindrical areas which are sequentially arranged along a central axis, whereas the three cylindrical areas are; a solid dosage area (12) having an inlet for solids (34), a liquid dosage area (14) having an inlet for liquids (32), a transport area (16) having an outlet (42) for the prepared mixture, a rotation element (20) arranged in the casing (10), and extending along a long axis through the cylindrical areas, wherein the rotation element (20) is rotatable arranged in the mixing chamber (1), and comprises flanks (22), arranged helically in the direction of the long axis, wherein at least one counter flank (38) is arranged on at least a part of the inner wall of the casing (10), engaging with at least one flank (22) of the rotation element (20).

Embodiment 2. Mixing chamber (1) according to embodiment 1, wherein the three cylindrical areas differ in diameter.

Embodiment 3. Mixing chamber (1) according to any of the preceding embodiments, wherein the diameter (D _s ) of the solid dosage area is smaller than the diameter (D _l ) of the liquid dosage area and smaller than the diameter (D _t ) of the transport area.

Embodiment 4. Mixing chamber (1) according to any one of the preceding embodiments, wherein the diameter (D _t ) of the transport area is smaller than the diameter (D _l ) of the liquid dosage area. Embodiment 5. Mixing chamber (1) according to any one of the preceding embodiments, wherein the flanks (22) of the rotation element (20) differ according to the cylindrical area they are arranged in.

Embodiment 6. Mixing chamber (1) according to any one of the preceding embodiments, wherein the part of the rotation element (20) extending through the solid dosage area (14) is designed as a screw conveyor (24).

Embodiment 7. Mixing chamber (1) according to any one of the preceding embodiments, wherein the part of the rotation element (20) extending through the liquid dosage area (14) comprises truncated helical flanks (26).

Embodiment 8. Mixing chamber (1) according to any one of the preceding embodiments, wherein the part of the rotation element (20) extending through the transport area (16) is designed as a shaftless spiral conveyor (28).

Embodiment 9. Mixing chamber (1) according to any one of the preceding embodiments, wherein the counter flanks (38) are only arranged in the liquid dosage area (14).

Embodiment 10. Mixing chamber (1) according to any one of the preceding embodiments, wherein the casing (10) is divided into two detachable halves (30, 40), preferably an upper (30) and a lower half (40) of the casing (10).

Embodiments 11. Mixing chamber (1) according to any one of the preceding embodiments, wherein the upper (30) and the lower half (40) of the casing (10) each comprise a circumferential collar (50) to build a detachable connection to one another using connection elements.

Embodiment 12. Mixing chamber (1) according to any one of the preceding embodiments, wherein the inlet for liquids (32) and the inlet for solids (34) area located in an upper part of the casing, and the outlet (42) is located in a lower part of the casing. Embodiment 13. Device for preparing edible, viscosity-controlled mixtures comprising at least one aqueous liquid and at least one solid thickener, comprising: a mixing chamber (1) according to one of the preceding claims, a solid feed attached to the inlet for solids (34), a liquid feed attached to the inlet for liquids (32), a motor (60) connected to the rotation element (20), and a control unit for controlling the dosage of the liquid and/or the dosage of the solid.

Embodiment 14. Device according to the embodiment 13, wherein the solid feed is a hopper (36).

Embodiment 15. Device according to any one of embodiments 13 or 14, wherein the liquid feed comprises a pump for liquids.

Embodiment 16. Device according to any one of embodiments 13 to 15, wherein the control unit controls the motor (60) the rotation element (20) is connected to and the motor of the pump for liquids.

Embodiment 17. Device according to any one of embodiments 13 to 16, wherein the control unit is part of a 3D-printer (80).

Embodiment 18. Device according to any one of embodiments 13 to 17, wherein the device is a 3D-printer (80) comprising a build area (84) and a print head (90), wherein the mixing chamber (1), the solid feed and the motor (60) together form the print head of the 3D-printer.

Embodiment 19. Device according any one of embodiments 13 to 18, wherein the outlet (42) of mixing chamber (1) comprises a heating unit (96) for heating the viscosity-controlled mixture transported through outlet (42) to a predefined temperature. Embodiment 20. Process for preparing edible, viscosity-controlled mixtures comprising at least one aqueous liquid and at least one solid thickener, comprising the steps of providing a device according to one of the embodiments 13-19, providing an aqueous liquid within the liquid feed, providing a solid thickener within the solid feed, choosing a software routine within the control unit, to provide a mass transport via the liquid feed and the solid feed into the mixing chamber suitable to give a mixture having a target viscosity.

Embodiment 21. Process according to embodiment 20, further comprising the steps of mixing the solid thickener and the aqueous liquid in the device and dispensing it therefrom via the outlet of the device.

Embodiment 22. Process according to any one of embodiments 20 and 21, wherein the process further comprises 3D-printing the edible, viscosity- controlled mixture into a predefined three-dimensional form.

Embodiment 23. Process according to any one of embodiments 20 to 22, further comprising a calibration sequence for the control unit to control the mass transport of the aqueous liquid feed and the mass transport of the solid thickener into the mixing chamber of the device.

Embodiment 24. Use of a mixing chamber according any one of embodiments 1 to 12 and/or a device according to embodiments 13 to 19 for the preparation of preparing edible, viscosity-controlled mixtures of at least an aqueous liquid and at least a solid thickener.

Embodiment 25. Use according to embodiment 24, wherein the solid thickener is selected from starch-, gum-, protein, and/or mucilage-based thickeners, preferably selected from the group consisting of gum arabic, carbo/locust bean gum, guar gum, pectin, sodium carboxymethyl cellulose, starch, agars, alginates, carrageenans, gellan gum, xanthan gum, collagen, gelatin, and mixtures thereof, preferably from the group consisting of starch, gums, and carrageenans. Embodiment 26. Use according to any one of embodiments 24 or 25, wherein the aqueous liquid is selected from the group of water, beverages, liquid food, liquid enteral nutritional compositions or supplements.

Embodiment 27. Use according to any one of embodiments 24 to 26, wherein the aqueous liquid further comprises at least one additive selected from the group of pharmaceutical active ingredients, micronutrients, preferably, and vitamins, minerals, amino acids.

Embodiment 28. Use according to any one of embodiments 24 to 27 wherein the edible, viscosity-controlled mixture has a viscosity in the range of 1-50 mPa-s, 51-350 mPa-s, 351-1750 mPa-s, or >1751 mPa-s, preferably >1751 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C.

Embodiment 29. Use according to any one of embodiments 24 to 28, wherein the viscosity of the edible, viscosity-controlled mixture is higher than 1751 mPa-s and sufficiently high for the mixture to self-sustain a defined three-dimensional form.

Embodiment 30. Use according to any one of embodiments 24 to 29, wherein the edible, viscosity-controlled mixture has a viscosity of up to 10.000 mPa-s, preferably of up to 8000 mPa-s, more preferably of up to 6000 mPa-s, most preferably of up to 5000 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C.

Embodiment 31. Use according to any one of embodiments 24 to 30, wherein the edible, viscosity-controlled mixture has viscosity in the range from more than 1751 mPa-s to 10.000 mPa-s, preferably from 1800 mPa-s to 10.000 mPa-s, more preferably from 1850 mPa-s to 10.000 mPa-s when measured at a shear rate of 50 s ^-1 and a temperature of 25°C.

Embodiment 32. Use according to any one of embodiments 24 to 31, wherein the viscosity-controlled mixture prepared using the different aspects of the present invention has a viscosity in the range from more than 1800 mPa-s to 10.000 mPa-s, preferably up to 8000 mPa-s, more preferably of up to 6000 mPa-s, most preferably of up to 5000 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C.

Embodiment 33. Use according to any one of embodiments 24 to 32, wherein the edible, viscosity-controlled mixture has a viscosity in the range from more than 1850 mPa-s to 10.000 mPa-s, preferably up to 8000 mPa-s, more preferably of up to 6000 mPa-s, most preferably of up to 5000 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C.

Embodiment 34. Use of a mixing chamber according to any one of embodiments 1 to 12 in a 3D-printing device, especially as part of the printing head of such a 3D-printer.

Embodiment 35. An edible, viscosity-controlled mixture comprising at least one aqueous liquid and at least one solid thickener obtainable by the process according to any one of embodiments 20 to 23, wherein the edible, viscosity- controlled mixture has a viscosity of above 1800 mPa-s when measured at a shear rate of 50 s ^-1 and a temperature of 25°C, preferably above 1850 mPa-s.

Embodiment 36. The edible, viscosity-controlled mixture according to embodiment 35, wherein the viscosity of the mixture is higher than 1800 mPa-s, preferably higher than 1850 mPa-s and sufficiently high for the mixture to self-sustain a defined three-dimensional form.

Embodiment 37. The edible, viscosity-controlled mixture according to any one of embodiments 35 or 36, wherein the edible, viscosity-controlled mixture has a viscosity in the range from more than 1850 mPa-s to 10.000 mPa-s, preferably up to 8000 mPa-s, more preferably of up to 6000 mPa-s, most preferably of up to 5000 mPa-s, when measured at a shear rate of 50 s ^-1 and a temperature of 25°C. Embodiment 38. The edible, viscosity-controlled mixture according to any one of embodiments 35 to 37, wherein the solid thickener is selected from starch-, gum-, protein, and/or mucilage-based thickeners, preferably selected from the group consisting of gum arabic, carbo/locust bean gum, guar gum, pectin, sodium carboxymethyl cellulose, starch, agars, alginates, carrageenans, gellan gum, xanthan gum, collagen, gelatin, and mixtures thereof, preferably from the group consisting of starch, gums, and carrageenans .

Embodiment 39. The edible, viscosity-controlled mixtures according to any one of embodiments 35 to 38, wherein the aqueous liquid is selected from the group of water, beverages, liquid food, liquid enteral nutritional compositions or supplements.

Embodiment 40. The edible, viscosity-controlled mixtures according to any one of embodiments 35 to 39 wherein the aqueous liquid further comprises at least one additive selected from the group of pharmaceutical active ingredients, micronutrients, preferably, and vitamins, minerals, amino acids.

The invention is described in detail below by way of exemplary embodiments in connection with the drawings, in which:

Fig. 1 shows a vertical cross section along the long axis of a mixing chamber according to a first embodiment of the invention,

Fig. 2 shows an outside view of an upper half of a casing according to one embodiment of the casing;

Fig. 3 shows an inside view of the upper half of the casing;

Fig. 4 shows a side view of a rotation element according to a first embodiment;

Fig. 5 shows a three-dimensional view of a mixing chamber, hopper and motor according to one embodiment of the invention; Fig. 6 shows a star-shaped body printed with thickened liquid achieved with a device and process according to the invention;

Fig. 7 shows the results of the measurement of viscoelastic response of different thickener/water-mixtures;

Fig. 8 shows the results of measurement of viscosity and viscoelastic response of different thickener/aqueous liquid-mixtures (water/skimmed milk/orange juice);

Fig. 9 shows a schematic diagram of a 3D-printer according the present invention.

Reference signs

1 mixing chamber

2 central axis

3 first end

4 second end

10 casing

12 solid dosage area

14 liquid dosage area

16 transport area

17 transition area

18 inner volume of casing

19 inner wall of upper half 30

20 rotation element

22 flanks

23 outer surfaces of flanks 22

24 screw conveyer

26 truncated helical flanks

28 shaftless screw conveyer

30 upper half of casing 10

32 inlet for liquids 34 inlet for solids

36 hopper

38 counter flank

39 screws

40 lower half of casing 10

42 outlet

50 collar

53 screw holes

60 motor

70 star

80 3D-printing device

82 base incl. drive mechanism and control unit

84 build area

86 static vertical frame element

88 movable horizontal frame element

90 print head

92 liquid feed including pump

94 user interface

Fig. 1 shows a vertical cross section along the central axis 2 of a mixing chamber 1 according to the invention. The three arrows in Fig.l indicate solid thickener and aqueous liquid input into mixing chamber 1 and output of the prepared mixture out of the mixing chamber. The mixing chamber 1 comprises a casing 10 which defines with its inner walls an inner volume comprising three cylindrical areas. The three areas follow one another, along the central axis 2, starting with the solid dosage area 12 at a first end 3, followed by the liquid dosage area 14 and the transport area 16 at a second end 4 of the inner volume. In other words, the liquid dosage area 14 is arranged between the solid dosage area 12 and the transport area 16.

In the example shown in Fig. 1 each of the three area has a different cross- sectional diameter. The cross-sectional diameter D _s of the solid dosage area 12 is smaller than the cross-sectional diameter D _t of the transport area 16, and smaller than the cross-sectional diameter D _l of the liquid dosage area 14. The cross-sectional diameter D _t of the transport area 16 is smaller than the cross-sectional diameter D _l of the liquid dosage area 14.

The liquid dosage area 14 comprises an inlet for liquids 32. The inlet for the liquids 32 is arranged at an upper part of the casing 10, which in one embodiment is in the upper half 30 of a casing 10 comprising detachable upper and lower halves.

The transport area 16 comprises an outlet 42 for the mixture. The outlet 42 is arranged at a lower part or lower half of the casing 10, close to the second end 4 of the casing 10. The outlet 42 ends in a nozzle. Hence, gravity guides the mixture to the nozzle.

A rotation element 20 is rotatably arranged in the casing 10, extending through the inner volume of the mixing chamber 1 with its three areas. In Fig. 1 the rotation element 20 is screw-like and extends with its long axis along the central axis 2 of the inner volume. Flanks are arranged helically along the direction of the long axis of the rotation element 20.

The part of the rotation element 20 which extends through the solid dosage area 12 and beyond is designed as a screw conveyor 24. Thus, the helical flanks wind around the long axis of the rotation element 20 in spiral turns. An inlet 34 for the solid thickener is arranged at an upper part of the casing 10 and close to the first end 3 of the inner volume. Furthermore, a solid feed is arranged at the inlet for solids. Here, the solid feed is a hopper 36. The solid thickener provided in the hopper 36 falls through the inlet for solids 34 onto the flanks of the screw conveyer 24.

The casing 10 of the mixing chamber is attached to the hopper 36 by means of a snap-in coupling (not shown), and the rotation element 20 is also fitted in this way to a motor 60 incorporated in a mount (not shown) The motor 60 is electronically coupled to a control unit. By rotating the rotation element 20, solid thickener, in general in powder form, is transported via the spiral turns of the screw conveyer 24 towards the liquid dosage area.

The spiral turns or helical flanks of the screw conveyer 24 end where the solid dosage area 12 meets the liquid dosage area 14.

The part of the rotation element 20 which extends through the liquid dosage area 14 comprises truncated flanks 26. These truncated flanks 26 can be described as radially cut discs, each of which is stretched or distorted by pushing apart the two cutting edges resulting from the cut, said stretched or distorted discs then being arranged along the long axis of the rotation element 20 in this area. Counter flanks 38, as shown in Fig. 3, engage with the truncated flanks 26. These counter flanks 38 protrude into the spaces between the surfaces of the cutted discs. While the rotation element 20 rotates, the faces of the cutted discs brush against the counter flanks 38, either with direct contact or at a small distance of less than 2 mm, preferably less than 1 mm.

The part of the rotation element 20 which extends through the transport area 16 is designed as a shaftless screw conveyor 28. This design is favorable for further mixing of the solid and the liquid that have met in the liquid dosage area 14 and for homogenization of the mixture.

Fig 2 and Fig. 3 show an upper half 30 of the casing 10 of the mixing chamber 1.

Fig. 2 shows a top view on the outside of the casing, whereas Fig. 3 shows an inside view of the upper half 30 of the casing 10. The solid feed inlet is arranged in the solid dosage area, the liquid inlet is arranged in the liquid dosage area. In Fig. 2 the counter flanks 38 are shown, which are arranged on the inner wall 19 of the upper half 30 of the casing. As described above, the counter flanks 38 are designed and arranged such, that they engage with the truncated helical flanks 26 of the rotation element 20. This means, that in an assembled state, during rotation of the rotation element, the counter flanks 38 brush against the truncated helical flanks of the rotation element. Thus, undissolved solids or only partially dissolved thickener are removed from the surface of the helical flanks 26, promoting solid flow and mixing.

Inner volume 18 of the mixing chamber 1 is designed to minimize dead zones and to avoid the adhesion of solid or only partially dissolved thickener to the surfaces of the rotation element 20 and the inner walls 19 of the casing 10.

Therefore, inner volume 18 of casing 10 comprises sections/areas with different diameters. One of these sections is solid dosage area 12, another is liquid dosage area 14, and yet another one is transport area 16. In the embodiment of the mixing chamber shown in Figs. 1-3, the transition between solid dosage area 12 and liquid dosage area 14 is abrupt. The cylindrical solid dosage area 12 with a diameter D _s ends and changes into the cylindrical liquid dosage area 14 with the diameter D _l . Thus, where the solid dosage area 12 meets the liquid dosage area 14, the inner wall 19 is disc- shaped, perpendicular to the long axis 2 of the mixing chamber. Contrary to this, there is a transition area 17 between the liquid dosage area 14 and the transport area 16. In other words, the transition between the liquid dosage area 14 and the transport area 16 is continuous. In this transition area 17, the inner wall 19 is tapered with decreasing diameter from the liquid dosage area 14 towards the transport area 16. The transition area 17 is shaped as a truncated cone. This allows the mixture to flow continuously form the liquid dosage area into the transport area 16. No dead zones are created where the mixture can accumulate without movement.

Fig. 4 shows a rotation element 20 according to one preferred embodiment. The rotation element comprises flanks 22 arranged helically along the long axis of the rotation element 20.

Helically arranged flanks 22 means, that the outer surfaces 23 of the flanks 22 describe a curve that winds around the jacket of a cylinder, preferably with a constant slope. Within this invention, the diameter of the (imaginary) cylinder the outer surfaces 23 of the flanks 22 wind around is referred to as the outer diameter of the flanks 22. The diameter of the (imaginary) cylinder the outer surfaces of the flanks 22 wind around is referred to as the outer diameter Di, D2, D3 of the flanks 22. As it is shown in Fig. 4, it is not mandatory, that the outer surface 23 of the flanks 22 describe a continuous helix or cylindrical spiral along the entire length of rotation element 20. There are three different kind of flanks 22 shown. Namely flanks that continuously wind around the long axis of the rotation element 20, forming a screw conveyor 24, flanks 22 that are designed as truncated open flanks 26, winding along the long axis, and flanks winding along the open long axis of the rotation element 20, forming a shaftless screw conveyor 28. The flanks 22 of the screw conveyer have an outer diameter Di, the truncated open flanks 26 have an outer diameter D2 and the flanks of the shaftless screw conveyer 28 have an outer diameter D3.

All different kinds of flanks 22 wind themselves around the long axis of the rotation element 20 in the same direction. Hence, when the whole device according to the invention is assembled and running, the rotation element 20 generates a mass flow through the cylindrical areas from the first end 3 to the second end 4 of the inner volume, as indicated by the open arrows in Fig 4. In other words, the rotation element 20 exerts a force on both the solid thickener and the final mixture, transporting the mixture through the entire chamber 10.

Fig. 5 shows a three-dimensional view of a mixing chamber 1 as described above, coupled to a hopper 36 and a motor 60. The entire mixing chamber 1 can be easily disengaged form the hopper 36 and the motor 60, as they are only fastened by a press fit. The hopper 36 is fastened to the motor 60 by two screws 39. The casing 10 is divided into two halves, which are held together by seven additional screws inserted into screw holes 53 in the collar 50 of the casing 10. The assembly of mixing chamber 1 coupled to hopper 36 and motor 60 may act as a print head in a 3D-printer, as will be described in the following.

Fig. 9 shows a schematic representation of a 3D-printer according to the present invention. The Figure shows only selected elements of the device. The skilled person will understand that additional constructions elements are required to run the device, e.g. additional motors to drive the build area and print head including e.g. transmission belts for moving the print head, power supply, etc. The 3D printing device 80 comprises a base 82 housing e.g. the control unit of the printer and one or more drive mechanisms for moving selected parts of the 3D-printer, e.g. print head 90, build area 84, and/or movable vertical frame element 88. Connected to the control unit of 3D-printer 80 is a user interface 94, via which the user can operate the 3D-printer 80. The interface may also comprise means of uploading software for operating the 3D-printer. In the schematic drawing of Fig. 9, build area 84 is movable only in one direction (y-direction) as indicated by the arrow above it. Build area 84 is located between two static vertical frame elements 86 onto which a movable horizontal frame element 86 is mounted in such a way that it can be moved by a drive mechanism (not shown) in vertical direction (z-direction) relative to the surface of build area 84, as indicated by the arrow shown beside it. Build area 84 is a flat rectangular heatable or non-heatable work plate made of any material suitable for depositing the printed material thereon, e.g. ceramic, plastic, metal, etc. Mounted onto movable horizontal frame element is print head 90. Print head 90 comprises mixing chamber 1, including liquid inlet 32, outlet 42, including heating unit 96, motor 60, and hopper 36, acting as the solid feed. Before use, hopper 36 is loaded with solid thickener. Liquid inlet is connected, e.g. via suitable tubing, to liquid fed 92, e.g. a syringe pump run by a pump motor, which is connected to the control unit in base 82. Motor 60 and heating unit 96 are also connected to the control unit for regulating the speed of the rotating element connected thereto and extending into mixing chamber 1, and for regulating the temperature of heating unit 96, acting as hot-end, during use. Print head 90 is mounted movably using a custom made holder (not shown) on movable horizontal frame element 88 in such a way that it can be moved along at least a part of the length of movable horizontal frame element 88 in a direction (x-direction) parallel to the surface of movable build area 84, by means of a driving mechanism (not shown). During use, the control unit in base 82 may simultaneously regulate the movement of build area 84, print head 90. Furthermore, it controls the mass transport rate of aqueous liquid from the liquid feed into mixing chamber 1 by controlling the pump comprised in the liquid feed, and the mass transport rate of solid thickener from the solid feed, i.e. hopper 36, into mixing chamber 1, by regulating the rotation speed of motor 60 to which the rotation element of the mixing chamber is attached. If required, the control unit may at the same time regulate the temperature of heating unit 96 in outlet 42. Using a corresponding software script run on the control unit, an edible mixture of a solid thickener dissolved in an aqueous liquid, having a desired self-sustaining three-dimensional form, may be obtained.

Whilst the 3D-printer 80 according to the present invention has been described based on the embodiment shown in Fig. 9, it is to be understood that device 80 may be modified in many ways, e.g. by incorporating the device into a suitable outer housing etc.

In the following, examples for the preparation of viscosity-controlled mixtures of aqueous liquids and solid thickeners are described.

Rheological characterisation of the samples printed using the device of the present invention was carried out with a controlled stress rheometer (Physica MCR-301, Anton Paar, Austria). Viscous flow measurements were performed within a range of shear rates of 0.01-100 s ^-1 , at 25 °C, using a 50 mm serrated plate geometry and a gap of 1 mm.

Same plate-plate geometry was used to perform small-amplitude oscillatory shear (SAOS) tests, inside the linear viscoelastic region, in a frequency range of 100-0.03 rad/s.

Example 1

In this example the preparation of nectar-, honey-, and spoon-thick mixtures of destilled water and Fresubin Clear Thickener® (FCT), available from Fresenius Kabi, is described.

The mixing chamber comprised in the device used in this and the following examples was obtained by printing all parts of the mixing chamber (excluding the screws) using a conventional BQ Hephestos 3D-printer. These parts were designed using AutoCAD 2018 software and Tinkercad online app. The slicing of the 3D models was carried out using Ultimaker Cura software.

The 3D-printer used in the device was a commercially available BQ Hephesos 3D printer DIY kit (BQ Spain) which was modified with the mixing chamber. A commercially available Arduino Mega 2560 microcontroller board and a RAMPS 1.4 board were used to control the modified 3D-printer set-up, which was operated using Repetier-Host software.

The device comprised a syringe pump, which was also designed and assembled from 3D printed parts and non-printable components supplied by 3DEspania (Spain).

All parts of the mixing chamber were cleaned and dried before assembly. The two halves of the casing are secured with screws, having previously placed the feeder screw, i.e . rotation element, inside. The mixing chamber is then coupled to the solid feed, i.e. a hopper including a NEMA 17 stepper motor, by fitting the motor shaft in a corresponding cavity provided for this purpose in the rotation element, i.e. mixing or feeder screw. Subsequently, the hopper is loaded with the FCT powder and the syringe pump (previously loaded with distilled water) is connected to the solid inlet on the upper half of the casing. When the device is loaded and ready for use, the desired flow ratio is configured via software. This step can be replaced by the loading of previously compiled a. geode file, with all the necessary information for printing, allowing the use of the device by non-specialized personnel.

To obtain a thickened mixture of the FCT and distilled water having a nectarlike viscosity, the total mass flow rate of the device was set at 4 g/min with a concentration setpoint of approx. 1.55 wt.-%. The mixture thus obtained had a viscosity of 233 mPa-s (50 s ^-1 , 25°C).

To obtain a mixture having a honey-like viscosity, the total mass flow rate of the device was set at 4.1 g/min with a concentration setpoint of approx. 5 wt.-%. The resulting mixture had a viscosity of 1034 mPa-s (50 s ^-1 , 25°C).

To obtain a mixture having a spoon-thick viscosity, the total mass flow rate of the device was set at 4.3 g/min with a concentration setpoint of approx. 10 wt.-%. The resulting mixture had a viscosity of 3707 mPa-s (50 s ^-1 , 25°C).

Example 2

In this example, the preparation of a form-stable mixture of K-carrageenan and water using the device according the invention is described. The solid thickener used for the preparation star 70 was K-carrageenan (Mw 193-324 kDa), the aqueous liquid was water. The resulting thickened liquid has a sufficiently high viscosity to maintain the three-dimensional shape it was formed into using the device of the present invention using the mixing chamber of the present invention as part of the print head in the 3D-printer.

As in example 1, the hopper is loaded with a dry powder thickener, here K- carrageenan powder. The syringe pump (previously loaded with tap water) acting as the liquid feed is connected to the liquid inlet on the upper half of the casing. Since typical procedures to prepare K-carrageenan gels involve heating the mixture at 70-90 °C, a hot end, i.e. a heating unit, is placed at the nozzle forming the outlet of the mixing chamber, i.e. at the end of the transport zone. The hot end is connected to the control unit and its temperature is also regulated via software. In this example, the hot end temperature was fixed at 80°C. When the device is loaded and ready for use, the desired flow ratio is configured via software. To obtain the self-sustained defined three-dimensional form, the concentration setpoint was approximately 3 wt.-%, and the total mass flow rate of the device was set at 0.3 g/min.

Fig. 6 shows the resulting form-stable printed body in form of a three- dimensional star. As can be seen in Fig. 6 the mixture having the appropriate viscoelastic characteristics/properties to maintain its three-dimensional shape over time, is highly transparent due to the absence of bubbles of entrapped air in the mixture.

Example 3:

The viscoelastic properties of manually prepared thickened liquids were compared to those of thickened liquids using the device according to the invention.

The manually prepared samples were prepared by mixing water and Fresubin Clear Thickener® (FCT), available from Fresenius Kabi, according to the instructions provided for the product, at a concentration of 1.6 wt.-% (nectarlike), 5.0 wt.-% (honey-like), and 9.5 wt.-% (spoon-thick). The samples prepared using the device and process according to the present invention were also prepared using Fresubin Clear Thickener® (FCT) and water, at a concentration of 1.3 wt.-% (nectar-like), 4.3 wt.-% (honey-like), and 9.8 wt.-% (spoon-thick) and were printed at a total mass flow rate of 2.0 g/min, 2.1 g/min, and 2.2 g/min, respectively.

Figure 7 shows several graphs comparing the linear viscoelasticity of manually mixed thickened liquids and thickened liquids prepared using the device and process according to the present invention.

A well-developed plateau region, with low values of the slope in G' and G" vs frequency plots, characteristic of strong gels, is apparent in the spoon-thick system, whereas a tendency to reach a crossover between G' and G' curves can be observed at low frequencies for the nectar-like system. However, in all cases, a predominant solid-like behaviour was exhibited, i.e., the storage modulus (G') higher than the loss modulus (G") over the whole frequency range considered. This confirms that all mixtures studied are above the overlap concentration since, below this concentration, the diluted solutions must show a viscoelastic response characterised by G" values higher than G' in a wide frequency range, as well as a high dependence of both SAGS functions with frequency.

The nectar- and honey-like samples obtained using the device according to the invention show values of both moduli very close to those obtained by manual mixing, although they use a lower thickener concentration compared to their manually prepared counterparts. In the spoon-thick sample preparation using the device according to the present invention resulted in higher values of SAGS moduli than in those obtained by manual mixing. Without wanting to be bound by theory, it is assumed that this effect is due to the lower amount of air bubbles incorporated in the mixture compared to the spoon-thick sample prepared manually.

Example 4:

In this example, common beverages were thickened either manually or using the device according to the present invention. The device according to the present invention, comprising the mixing chamber as the printing head of a 3D-printer, a syringe-pump a liquid feed, and the 3D-printer as the control unit, was used to thicken distilled water, skimmed milk (Covap, Spain), and orange juice with no added sugar (Juver SA, Spain) , using a flow rate of 2 g/min. The solid thickener was again Fresubin Clear Thickener® (FCT), available from Fresenius Kabi. For the preparation using the device according the present invention, the thickener was used at the following concentrations: 9.7 and 9.8 wt-% in water; 7.3 and 8.4 wt-% in orange juice, and 8.1 and 7.0 wt.-% in skimmed milk. The samples were investigated by measuring viscosity vs. shear rate and linear viscoelasticity vs. angular frequency. These samples were compared with manually mixed samples using the same materials, but each using the thickener at a concentration of 9.5 wt-%.

The results of these measurements are shown in Figure 8:

Higher viscosity and linear viscoelastic functions values were obtained for thickened juice and milk than for thickened water. This is not surprising, since the influence of the dispersing fluid on the rheological properties of thickened fluids is a well-known issue, the thickening effect of a given hydrocolloid being differently affected by each dispersing medium.

Similar viscosity and linear viscoelastic values to those shown by a 9.5 wt.% hand-prepared thickened milk have been achieved by using 8.1 wt.% (for viscosity) and a 7.0 wt.% (for linear viscoelasticity functions) skimmed milk, respectively, with the 3D printing device. In the case of orange juice, the viscosity of the manually thickened fluid (9.5 wt.-%) has been matched by using just 7.3 wt.% thickener concentration. On the other hand, 8.4 wt.% thickener, mixed using the 3D printing device, provides storage and loss moduli values that are even slightly higher than those obtained by manually mixing 9.5 wt.% thickener concentration.