FIELD OF THE INVENTION

The invention relates to methods and apparatuses for heating and pressurizing water for use in the preparation of coffee beverages, and coffee machines comprising said apparatuses.

BACKGROUND OF THE INVENTION

Hot coffee beverages are one of the most popular beverages in the world. There are a variety of ways in which coffee beverages are made that typically involve the contacting of ground coffee beans with hot water before filtering the ground beans from the water after a period of time. The hot water extracts coffee flavour and aroma providing compounds from the ground beans. Typical techniques known in the art include cafetiere, percolation, and filter coffee. One of the most popular methods of coffee preparation is the preparation of espresso coffee. Espresso coffee is commonly perceived to be one of the best tasting coffees and the majority of coffee shops all over the world generally have espresso machines for making a variety of espresso coffee containing beverages such as americanos, cappuccinos, flat whites, long blacks, lattes, espressos, macchiatos and cortados. The current espresso coffee brewing method was developed in the 20 ^th century and involves contacting finely ground and compacted coffee beans with water at a temperature of typically 90°C to 93 °C at a pressure of around 8 bar to 10 bar. These conditions cause an improved extraction of compounds from the ground coffee beans to the water. It is necessary to finely grind and compact the coffee beans in order to achieve the extraction in a short time. The finely ground and compacted beans cause resistance to water flow and so a high pressure is needed to force the hot water through the bed of coffee beans and achieve a good extraction. It is important that the temperature of the water is within the range described above. Lower temperatures do not achieve extraction of all of the desired flavour and aroma providing compounds from the coffee, whereas higher temperatures cause deterioration of the flavours present in the coffee and can lead to an unpleasant tasting beverage.

A variety of different types of espresso machine are known in the art. Espresso machines typically comprise a means for heating the brew water (water intended to contact the coffee); means for pressurizing the brew water; and often means for generating steam. The steam is often used for applications such as to heat and froth milk for later addition to the coffee beverage once prepared to produce frothy coffee beverages such as cappuccinos. The majority of espresso coffee machines use separate systems for heating the brew water, pressurising the brew water, and heating water to provide steam. Often, the brew water is heated by a single boiler with a temperature controlled electric element. The boiler may be operated at a higher temperature for the production of steam. For pressurising the brew water, a manual or electric pump is often included. An electric pump is the most common method in espresso machines by which the brew water is pressurised. The configuration of espresso machines of this type is shown in Figures 1 and 2. Figure 1 shows the typical configuration of a single boiler espresso machine where a single boiler is used with two temperature settings to heat the brew water and to generate steam. Figure 2 shows a slightly more advanced type of espresso machine where a single boiler is used for the production of steam. A conduit for containing brew water passes through the boiler and the brew water is heated by heat exchange with the steam boiling within the boiler. Figure 3 depicts a further type of espresso machine that comprises two separate boilers for generating steam and for heating brew water. Figure 4 depicts a configuration similar to that shown in Figure 1 where a single thermoblock is used to heat water instead of a boiler, and the water is subsequently used for both brew water and steam. In all of the types of coffee machine described above and depicted in Figures 1 to 4, brew water pressure is generated by an electric pump, and separate systems are used for steam generation and brew water heating. The machines often comprise complex electronic control systems and are expensive to manufacture, run and maintain.

In order to try and solve the problems associated with the types of machine discussed above, several designs have been attempted where the same system is used to both heat and pressurise the brew water. For example, in order to dispense of the need for an electric pump, certain designs have been attempted where steam produced from heating the brew water is also used to pressurise the brew water, thus obviating the need for an electric or manual pump. Such designs include the Bialetti Moka Pot™. In this coffee machine, brew water is heated in an enclosed space so as to produce steam. As more heat is applied and more steam generated, the brew water pressure increases. The pressurised brew water is then introduced to the coffee filter for the extraction. Limitations with this system were initially that it was hard to generate a pressure high enough for a good enough extraction and to force the brew water through a finely ground bed of coffee. In attempts to solve this problem, high pressure valves were included in the device in order to allow the build-up of higher pressure. However, in order to generate sufficient steam pressure to achieve a proper espresso extraction (i.e. pressures in the 8 bar to 10 bar range), it is necessary to heat the water to around 180°C. This is because water under high pressure has a much higher boiling point and so considerable heat is needed to generate sufficient steam to generate the necessary high pressure. As a result, it is then necessary to allow the water to cool down to the desirable temperature of 90°C to 100°C before using the brew water for coffee extraction. 180°C is too hot for coffee extraction as it results in an unpleasant tasting beverage and also causes the brew water to boil explosively as flash steam when it is brought to atmospheric pressure. The brew water can be allowed to cool, for example, by contacting the brew water with a reverse heat exchanger type device, or by the addition of cooler water to the brew water. The inclusion of the reverse heat exchanger adds undesirable cost and complexity to the coffee machine. Where the brew water is cooled by addition of cooler water, it is hard to cool the water to the exact desired temperature meaning that process control is lost. This is undesirable in coffee making where it may be desired to use brew water of a very specific temperature.

Another problem with coffee machines is the build-up of limescale within the chambers and conduits of the machine. This is caused by dissolved minerals and salts present in the water used to prepare the coffee. Dissolved minerals and salts present in the brew water also contribute to an unpleasant tasting beverage. As a result, many users of coffee machines prepare softened water for use in the machines by e.g. filtering or reverse osmosis. It is also possible to purchase softened water specifically intended for use in coffee machines in order to alleviate these problems.

Another problem with the use of coffee machines is that of temperature control of the brew water. Existing coffee machines where the brew water is heated by a boiler or similar heat source use convection and conduction to heat the water, which is a fairly slow process. The correct brew water temperature is typically maintained by turning the heat source on and off and cycling above and below the desired temperature. This is an inefficient process and does not provide sufficient control of the brew water temperature.

SUMMARY OF THE INVENTION

Appreciating the above, the inventor of the present invention has devised methods that address or alleviate the above-mentioned problems, and apparatuses for implementing said methods. The methods of the invention involve directly contacting the brew water with a separate volume of steam in a manner in which the brew water is heated and pressurised by the steam. By the addition of steam to the brew water, the brew water can easily be brought up to a desired temperature for coffee extraction (i.e. 90°C to 93°C) whilst also being pressurised to the desired pressure of 8 bar to 10 bar for espresso extraction. Unlike the methods discussed above where the brew water is directly heated so as to generate pressure by steam generation, there is no need for the brew water to be heated above the desired temperature in order to generate the necessary pressure for coffee extraction, meaning that there is then no need for the brew water to be actively cooled prior to the coffee bean extraction (for example by a cooling heat exchanger type device). The brew water is also effectively pressurized without the use of a manual or electric pump. Additionally, there is no need for the use of two boilers or a more complex heat-exchanger type boiler such as those discussed above. Being able to exclude these components from coffee machines means that coffee machines can be made less complex, smaller and at lower cost.

In addition to the above, it has been found that the method of the invention can provide a better tasting coffee and reduce the build-up of limescale in chambers and conduits of coffee machines. This is because the separate volume of steam that is added to the brew water subsequently condenses into the brew water before the brew water is then used for the coffee extraction. Since boiled steam does not comprise salts or minerals, the mineral and salt concentration of the original brew water is reduced upon introduction of the separate volume of steam and condensing of the steam. The result is a brew water with even lower mineral salt concentration which creates less limescale when compared to the use of harder water with higher mineral content, and also a more pleasant tasting coffee beverage. Even where softened water is used as the original brew water, the addition of steam to said brew water and condensing of the steam into the brew water still provides a brew water with even lower mineral salt concentration. In addition to the above, the method of the invention has been found by the inventor to provide enhanced temperature control of the brew water when compared to coffee machines known in the art. The addition of steam to the brew water allows instantaneous increase in the heat of the brew water. Additionally, once the brew water reaches the desired temperature, the addition of steam can then be halted or reduced meaning that the brew water can easily be raised to the desired temperature and then maintained at said temperature. This is a more efficient process than the convection and conduction that occurs in processes known in the art and also provides greater temperature control than processes known in the art. Greater temperature control means that the brew water temperature can be altered in real time, providing excellent temperature control during, for example, the pulling of an espresso shot. Temperature profiling may also be made possible meaning that different temperatures could be selected for different parts of the espresso extraction process such as the wetting, pre- infusion and main extraction phases, or for different types of coffee beans that are optimally extracted at different temperatures.

According to a first aspect of the invention, there is provided a method of preparing a coffee beverage, wherein the method comprises:

(a) heating and pressurizing a volume of brew water by directly contacting the volume of brew water with a separate volume of steam;

(b) contacting the brew water with ground coffee beans; and

(c) separating a portion of the ground coffee beans from the brew water so as to form a coffee beverage.

General methods of heating and pressurizing brew water

Typically, the method comprises heating the brew water to a temperature of from 85°C to 130°C, preferably from 85°C to 95°C, and more preferably from 85°C to 93°C by contacting the brew water with the separate volume of steam.

Typically, the method comprises pressurizing the brew water to a pressure of from 6 bar to 12 bar, and preferably from 8 bar to 10 bar by contacting the brew water with the separate volume of steam.

Most preferably, the method comprises pressurizing and heating the brew water to a pressure of from 8 bar to 10 bar and a temperature of from 85°C to 93°C by contacting the brew water with steam. These temperatures and pressures are preferred since these are the desired temperatures and pressures for brew water in espresso extraction. As described above, the pressure should ideally be within this range to force the brew water through finely ground compacted coffee in an espresso filter. Temperatures are preferably within this range since lower temperatures do not provide a sufficient extraction and higher temperatures provide a coffee beverage with unpleasant flavour. The preferred temperature in each specific instance will be dependent upon the nature of the coffee beans used in the extraction. Darker roast coffee beans (those roasted at a higher temperature) are typically extracted with water at temperatures at the lower end of the ranges described above, whereas lighter roast coffee beans (those roasted at lower temperatures) are typically extracted with water at temperatures at the higher end of the ranges described above. This is because coffee beans roasted at higher temperatures are easier to extract with water and so do not need the water to be as hot, and are more easily over extracted if water that is too high a temperature is used.

In some embodiments, the separate volume of steam is injected into the brew water.

Typically, the steam is at a pressure of from 6 bar to 12 bar; and preferably from 8 bar to 10 bar on introduction to the brew water. Typically, the steam is at a temperature of from 100°C to 200°C; preferably from 150°C to 200°C; and more preferably from 175°C to 190°C on introduction to the brew water. However, temperatures and pressures outside of these ranges may also be used if desired. Any suitable steam temperature and pressure may be used that are capable of heating and pressurising the brew water to the desired temperature and pressure.

Typically, the steam is generated in a steam generation component. Preferably, the steam generation component comprises a steam boiler comprising an internal electric heating element; a thermoblock; a thermocoil; or a combination thereof. More preferably, the steam generating component comprises a steam boiler comprising an internal electric heating element. Whilst these types of steam generation component are preferable, any type of suitable steam generating component known in the art may be used and the invention is not limited by the nature of this component.

Typically, the steam and brew water are contacted in a manner such that a portion of the steam condenses into the brew water and adds to the volume of the brew water. In some embodiments, all of the steam contacted with the brew water may condense and add to the volume of brew water.

The brew water may comprise any suitable type of water for brewing coffee. Typically, the brew water comprises softened water; mineral water; tap water, or a combination thereof. An advantage of using tap water is that, where the steam condenses into the brew water, the mineral salt content of the brew water is reduced since the brew water is diluted by condensation of steam. In the case of using softened water in the brew water, an even lower mineral salt concentration than normal softened water may be obtained by condensation of the steam into the brew water. Accordingly, the method of the invention produces brew water with a lower mineral salt concentration providing the advantages discussed above of reduced limescale deposition and improved tasting coffee. For example, using typical methods of the invention, it is possible to reduce the total dissolved solids content of tap water by around 10% to 15%. The present invention involves the contacting of a volume of brew water with a separate volume of steam. The term separate volume of steam as used herein is used to refer to the scenario where a separate volume of water to the brew water is boiled to produce steam, before said produced steam (i.e. not steam produced from boiling the brew water itself) is then added to the brew water. This is distinguished from processes known in the art where the brew water itself is brought to the boil by e.g. a boiler with an internal electric heating element and steam produced from heating the brew water is used to pressurise the remaining brew water that has not boiled. Steam produced by heating the brew water itself is thus not encompassed by the term separate volume of steam as used in the context of the present invention.

The present invention involves directly contacting the brew water with a separate volume of steam. The term directly contacting as used herein is used to refer to the brew water and steam having to be in direct physical touching contact. The term directly contacting as used herein is not used to refer to heat transfer between water and steam that never actually physically contact each other (for example in processes known in the art where steam is used to heat water via heat exchangers but where the steam and water are separated from each other and never actually touch).

In some embodiments of the method, the volume of brew water is present in an enclosed space such that the brew water increases in pressure and temperature on introduction of steam into the enclosed space. In other embodiments of the method, the method comprises injecting steam into a continuous flow of brew water, such as by using a steam injector. Examples of these methods are discussed in further detail below.

Methods of contacting brew water and coffee beans to produce coffee beverages

The method of the invention involves the contacting of coffee beans and brew water. Preferably, this contacting is done in a coffee filter present in a coffee machine. Preferably, the filter is an espresso coffee filter that contains coffee beans. Any suitable coffee filter known in the art may be used and any known method of arranging coffee beans within the filter so as to produce coffee on contact with the brew water may be used. For example, the coffee beans may be ground, compacted, and arranged within the filter using typical techniques known in the art.

The brew water is preferably at a temperature of from 85°C to 130°C, more preferably from 85°C to 95°C, and most preferably from 85°C to 93°C when the brew water and ground coffee beans are contacted. The brew water is preferably at a pressure of from 6 bar to 12 bar, and more preferably from 8 bar to 10 bar when the brew water and ground coffee are contacted.

Most preferably, the brew water is at a pressure of from 8 bar to 10 bar and a temperature of from 85°C to 93°C when the brew water and coffee beans are contacted.

In some embodiments, once the brew water has been heated and pressurised as desired, the brew water may be introduced directly into the coffee filter for contacting the ground coffee beans. In other embodiments, it may be desirable for the brew water to be stored for a period of time prior to introduction to the coffee filter and contact with the coffee beans. In some embodiments, once the brew water has been heated and pressurised as desired, the brew water may be transferred from a vessel or conduit in which the brew water has been contacted with steam to one or more intermediary vessels or conduits prior to introduction to the coffee filter. In other embodiments, once the brew water has been heated and pressurised as desired, the brew water may be transferred from a vessel or conduit in which the brew water has been contacted with steam directly to the coffee filter.

The step of contacting the brew water and ground coffee beans may include any of such steps known in the art. For example, typical methods of contacting ground coffee beans and brew water used in espresso machines known in the art may be used. The contacting of coffee beans and brew water may involve steps known in the art such as wetting, pre-infusion and extraction.

The ground coffee beans and brew water are contacted so as to achieve extraction of the desired flavours and components from the coffee beans into the brew water. Any method known in the art of how to achieve such an extraction may be used, such as extraction methods used in espresso machines known in the art. For example, any known contact times, configuration of coffee beans within the filter and methods of passing the brew water through the ground coffee beans may be used.

Once contacting of the brew water and ground coffee beans has been carried out, and extraction of the desired components from the coffee beans into the brew water has been carried out, the brew water may then be separated from the ground coffee beans so as to produce a coffee beverage. Any suitable separation technique known in the art may be used. For example, the brew water may be separated from the ground coffee beans simply by forcing the brew water with pressure such that it emerges from the opposite side of the coffee filter from which it originally entered. This separation produces a coffee beverage. The coffee beverage produced by the method of the invention can be any suitable type of coffee beverage. Preferably, the coffee beverage is an espresso coffee beverage. The espresso coffee beverage can be further treated so as to be formed into a particular type of beverage as desired such as a cappuccino, latte or flat white by the addition of milk or frothed milk to the beverage.

Methods where the brew water is contacted with steam in an enclosed space

In some embodiments, the volume of brew water is present in an enclosed space when the brew water and separate volume of steam are contacted (such as in a chamber) such that the brew water increases in pressure and temperature on introduction of steam into the enclosed space. In these embodiments, a desired level of pressure and a desired level of temperature of the brew water may be obtained independently. Alternatively, a desired level of pressure and a desired level of temperature of the brew water may be obtained simultaneously. For example, the brew water may reach a desired temperature and a desired pressure at the same time. Alternatively, it may be that the brew water is raised to the desired pressure without simultaneously being raised to the desired temperature. In these embodiments, more steam can be contacted with the brew water (e.g. by introduction into an enclosed chamber) to raise the brew water temperature further, whilst pressure is kept constant by e.g. allowing some steam to exit the enclosed space (e.g. via a valve) as more steam is introduced, or by other suitable means of releasing pressure. Alternatively, in the event that the brew water reaches a desired temperature before it reaches a desired pressure, pressure can be increased by e.g. decreasing a volume of the enclosed space in which the brew water is present (for example if the brew water is present in an enclosed chamber with an adjustable volume as discussed in further detail below).

In embodiments where the brew water is present in an enclosed space when the brew water and separate volume of steam are contacted, preferably, the enclosed space is only partially filled with brew water such that a volume of air remains above the brew water. This is so that there is room in the enclosed space for the separate volume of steam to be introduced.

In embodiments where the brew water is present in an enclosed space when the brew water and separate volume of steam are contacted, preferably, steam is introduced to the enclosed space at a rate too fast for all of the steam to be condensed by the brew water present in the enclosed space. This is so that some introduced steam remains as steam in the enclosed space and increases the pressure of the brew water within the enclosed space. However, preferably, the rate of introduction of steam to the enclosed space is sufficient for a portion of the introduced steam to condense and add to the volume of brew water within the brew chamber. As discussed above, in some embodiments, the method may comprise adjusting the volume of the enclosed space after introduction of steam into the enclosed space. This may be to adjust the pressure and/or temperature of the brew water and/or steam within the enclosed space.

In some embodiments, the method comprises the use of an apparatus comprising: a brew chamber for containing brew water; an input port for receiving steam from a source of steam; an output port for allowing outflow of brew water from the brew chamber; an input valve operable between an open position in which the brew chamber is in fluid communication with the source of steam, and a closed position in which the brew chamber is not in fluid communication with the source of steam; and an output valve operable between an open position in which brew water present in the brew chamber leaves the brew chamber via the outport port, and a closed position in which brew water and steam present in the brew chamber are prevented from leaving the brew chamber via the output port; wherein the apparatus is configured such that, when the input valve is in an open position and the output valve is in a closed position, steam from the source of steam flows through the input port and into the brew chamber to contact, heat and pressurise brew water present within the brew chamber.

Preferably, the apparatus further comprises a diffusion chamber that is in fluid communication with and contiguous with a portion of the brew chamber. More preferably, the diffusion chamber is positioned beneath the brew chamber. Typically, the input port and input valve are positioned to introduce steam from the source of steam to the diffusion chamber when the input valve is in an open position. Typically, the diffusion chamber and brew chamber are separated by a perforated diffusion grate. Preferably the perforated diffusion grate is adapted to evenly inject steam into the brew chamber via perforations in the perforated diffusion grate when steam is introduced to the diffusion chamber from the inlet port.

In an alternative to where the apparatus comprises a diffusion chamber, the apparatus may further comprise sparge tubes disposed between the input port and the brew chamber and connected to the input port; wherein the sparge tubes, input port and input valve are configured to introduce steam from the source of steam to the brew chamber via the sparge tubes when the input valve is in an open position. Preferably the sparge tubes are positioned so as to introduce steam from the source of steam to a lower portion of the brew chamber. Preferably, the sparge tubes are adapted to evenly inject steam into the brew chamber via perforations present in the sparge tubes.

In an alternative to where the apparatus comprises a diffusion chamber or sparge tubes, the input port and input valve may be positioned so as to introduce steam from the source of steam directly into the brew chamber when the input valve is in an open position. Preferably the input port is positioned so as to introduce steam from the source of steam to a lower portion of the brew chamber. In some instances of these embodiments, the input valve and input port form part of a steam injector. The steam injector is preferably configured and positioned to inject steam into brew water present within the brew chamber. In these embodiments, the water source for delivery to the steam injector may be the brew water itself present in the brew chamber. Accordingly, in some embodiments, the steam injector is configured and positioned so as to be submerged within brew water present in the brew chamber. Any type of steam injector known in the art may be used and configured to function in this way. Any of the types of steam injector discussed herein may be used as the steam injector in these embodiments.

Preferably, the brew chamber is an enclosed space when the input valve, output valve, and any additional valves connected to the brew chamber are in a closed position.

Preferably, the apparatus further comprises an input brew water port connected to the brew chamber for introducing brew water to the brew chamber. Preferably the input brew water port is closable via a valve so as to form an enclosed space within the brew chamber when both the output valve and input valve are in a closed position. The apparatus may further comprise a chamber for containing water where water can be stored prior to introduction to the brew chamber.

Typically, the output port is connected to a lower portion of the brew chamber.

The apparatus may further comprise a steam generating component for generating steam, wherein the steam generating component is in fluid communication with the brew chamber via the input port when the input valve is in an open position. The steam generating component typically comprises a steam boiler comprising an internal electric heating element; a thermoblock; a thermocoil; or a combination thereof. Preferably the steam generating component comprises a steam boiler comprising an internal electric heating element. In alternative embodiments, the source of steam can be an external heating source such as a campfire, stove or other external heating source.

Preferably, one or both of the input valve and output valve are manually or electronically adjustable between their open and closed positions by a user of the apparatus. However, typically, the input valve is adapted to move from a closed position to an open position when steam from the source of steam applying pressure to the input valve exceeds a certain threshold pressure; preferably wherein the threshold pressure is from 2.5 bar to 16 bar; and more preferably from 8 bar to 10 bar. Typically, the output valve is adapted to move from a closed position to an open position when the pressure within the brew chamber exceeds a certain threshold pressure; typically wherein the threshold pressure is from 2.5 bar to 16 bar, preferably from 6 bar to 12 bar; and more preferably from 8 bar to 10 bar.

Typically, the apparatus further comprises one or more safety valves operable to release pressure from the apparatus when a certain threshold pressure is exceeded; preferably wherein the safety valves are adapted to release pressure from the brew chamber, the steam generating component, or both.

The volume of the brew chamber may be any suitable volume. Preferably, the volume is sufficient for containing an amount of brew water to be used in a coffee extraction such as an espresso coffee extraction. The volume should also be sufficient for a volume of air to also be present in the brew chamber as well as the desired amount of brew water so that there is room for steam to enter the brew chamber and pressurise the volume of brew water therein. Typically, the volume of the brew chamber is from 50 ml to 150 ml; preferably from 80 ml to 150 ml; and more preferably from 80 ml to 120 ml.

Preferably, the volume of the brew chamber is manually or electronically adjustable by a user of the apparatus. Preferably, the apparatus is adapted so that temperature and/or pressure within the brew chamber may be adjusted by electronically or manually adjusting the volume of the brew chamber.

Preferably, the apparatus further comprises a filter for containing ground coffee beans, wherein the filter, brew chamber and output port are configured such that the filter receives brew water from the brew chamber via the output port when the output valve is in an open position. Preferably the filter is an espresso coffee filter for producing espresso coffee. Preferably, the apparatus further comprises a bypass conduit adapted to allow steam from the source of steam to bypass the brew water and be introduced to an upper portion of the brew chamber. More preferably, the bypass conduit is connected to a conduit connecting the source of steam to the input port. Excess steam can thus be diverted from passing through the brew water if desired but still be used to create pressure within the brew chamber.

Typically, the apparatus further comprises temperature and pressure sensors configured to determine the temperature and pressure of the brew water within the brew chamber.

The apparatus can be formed from any suitable material that can tolerate the pressures and temperatures encountered in the apparatus and used in the process. Suitable materials for use will be apparent to the skilled person given the benefit of the present disclosure. Preferably, a portion of the brew chamber and optionally a portion of the diffusion chamber if present are formed from a transparent material. Preferably, the interior of the brew chamber and optionally diffusion chamber if present are visible to a user of the apparatus. This is advantageous since it enables the heating and pressurising process to be witnessed by a user of the apparatus which may be aesthetically pleasing. The user is able to see the addition of steam and the rising of gas bubbles through the brew water present in the brew chamber. Preferably, the brew chamber and optionally diffusion chamber if present are formed from glass, a thermoplastic material, or a combination thereof. More preferably, the brew chamber and optionally diffusion chamber are formed from a transparent polymer that is able to tolerate the high temperatures and pressures encountered in the method such as polyether ether ketone (PEEK). Preferably, the brew chamber and optionally diffusion chamber if present are formed from a food-safe material.

The apparatus described above may be used by connecting the input port of the apparatus to a source of steam. The input valve may initially be closed so as to prevent steam entering the brew chamber. The output valve may also be closed to prevent any water present in the brew chamber leaving the chamber. The brew chamber may then be filled with brew water. Any additional valves may also be closed in the brew chamber so that it is an enclosed space. Typically, the brew chamber is not fully filled with brew water to allow space for steam to enter the brew chamber and pressurise the brew water within. On opening the input valve, steam is introduced to the brew chamber. This may be directly from the input port as discussed above where the input port is connected directly to the brew chamber. Alternatively, steam may be introduced to the diffusion chamber or sparge tubes from the input port as discussed above, before then entering the brew chamber. Typically, the apparatus is configured so that the input port introduces steam to a lower portion of the brew chamber so that the steam directly contacts the brew water upon introduction. Accordingly, the method may comprise:

(a) introducing brew water to the brew chamber of the apparatus;

(b) configuring the input valve, output valve, and any additional valves present in the apparatus so that the brew chamber is an enclosed space; and

(c) injecting steam into the brew chamber of the apparatus via the input port by opening the input valve of the apparatus.

Typically, the volume of brew water present in the brew chamber is from 50 ml to 150 ml; and preferably from 50 ml to 100 ml.

Preferably, the brew chamber is only partially filled with brew water such that a volume of air remains above the brew water.

Steam is typically injected into the brew chamber at a rate too fast for all of the steam to be condensed by the brew water present in the brew chamber. This is so that the steam passes through the water and into the space above where it generates pressure within the brew chamber and pressurises the brew water. However, preferably, the rate of steam introduction is sufficient for a portion of the injected steam to condense and add to the volume of brew water within the brew chamber.

A typical rate of steam introduction to the brew chamber is from 5 mg/s to 10 mg/s, although different flow rates may be used instead if desired. A flow rate within the range of from 5 mg/s to 10 mg/s is typically desirable when the steam is introduced at the preferred pressures and temperatures discussed above, and where the brew water amount and brew chamber capacity are within the preferred ranges discussed above.

A typical time period of introduction of steam is from 2 seconds to 10 seconds, with around 5 seconds being most preferred, although different time periods may be used if desired. A time period within the range of 2 seconds to 10 seconds is typically desirable when the steam is introduced at the preferred pressures, flow rates and temperatures discussed above, and where the brew water amount and brew chamber capacity are within the preferred ranges discussed above. Preferably, the flow rate of introduction of steam to the brew chamber is from 5 mg/s to 10 mg/s and the time period of introduction of steam is from 2 seconds to 10 seconds.

In an embodiment, the flow rate of introduction of steam to the brew chamber is from 5 mg/s to 10 mg/s; the time period of introduction of steam is from 2 seconds to 10 seconds; the temperature of the steam is from 150°C to 200°C; the pressure of the steam is from 8 bar to 12 bar; the volume of brew water is from 50 ml to 100 ml; and the volume of the brew chamber is from 80 ml to 150 ml.

In a specific example, steam is introduced at a pressure of 9 bar and a temperature of 175°C. The brew chamber has a 100 ml capacity and 60 ml of brew water at 15°C is used. A time period of steam introduction of 5 seconds is used and a steam flow rate of introduction of 7.1 mg/s is used.

As discussed above, the brew chamber volume may be adjustable. Typically, this is achieved by, for example, a wall, ceiling or floor of the brew chamber being movable. Preferably, the volume is adjustable by moving of the ceiling of the brew chamber. Accordingly, the method may further comprise adjusting the volume of the brew chamber so as to adjust the temperature and the pressure of the brew water within the brew chamber.

Where the apparatus comprises a coffee filter as described above, and the filter comprises coffee beans, the method may further comprise opening the output valve such that the brew water flows from the brew chamber into the filter via the output port thus contacting the ground coffee beans in the filter. Typically, the output valve is opened when the temperature of the brew water reaches from 90°C to 93 °C and the pressure of the brew water reaches from 8 bar to 10 bar. The output valve may be opened automatically upon the brew chamber interior reaching a threshold pressure. Alternatively, the output valve may be adjusted by a user of the apparatus once a desired pressure or temperature of the brew water is achieved. The pressure and temperature of the brew water may be indicated to a user of the apparatus by, for example, temperature and pressure sensors present within the brew chamber or another part of the apparatus.

Methods where steam is added to a continuous flow of brew water

In some embodiments, the method of the invention comprises injecting steam into a continuous flow of brew water, such as with a steam injector. Preferably, the steam is injected continuously into the brew water. In some embodiments, a pulse of steam can be injected into the continuous flow of brew water before the pulse is then stopped. In some embodiments, a plurality of steam pulses may be injected into the continuous flow of brew water.

The steam is typically injected into the brew water at a predetermined rate calculated to cause the steam to entrain the brew water and to condense within the brew water. This process is typically carried out with a steam injector.

Typically, the pressure of the steam delivered to the brew water in the steam injector is from 2.5 bar to 16 bar, preferably 8 bar to 10 bar.

Typically, the rate of injection of steam into the continuous flow of brew water is from 0.1 mg/second to 4 mg/second, and preferably 0.1 mg/second to 1 mg/second; although lower or higher injection rates may be used if desired, for example in a multiple head machine.

Typically, the rate of entrainment of brew water is from 0.5 mg/second to 40 mg/second, and preferably 0.5 mg/second to 1.5 mg/second; although lower or higher injection rates may be used if desired, for example in a multiple head machine. By rate of entrainment of brew water is meant the rate at which the brew water is delivered to the steam injector.

Typically, the amount of brew water discharged by the injector is from 0.6 ml/second to 44 ml/second, and preferably 1 ml/second to 8 ml/second; although lower or higher discharge rates may be used if desired, for example in a multiple head machine.

An important parameter is the mass ratio of water entrained (i.e. provided to the steam injector) to steam injected (i.e. provided to the steam injector). This determines the output temperature of the brew water. Typically, this ratio is from 5: 1 to 10: 1, preferably from 8: 1 to 7: 1; although lower or higher ratios may be used if desired.

The flow of steam and brew water to the injector, and the ratio between the two, can be set as desired to obtain the desired temperature and amount of brew water discharged by the injector per unit time.

Preferably, all of the injected steam condenses into the brew water and entrains the brew water. Injection of the steam into the continuous flow of brew water will increase the temperature of the brew water since the steam is hotter than the brew water and will give up its latent heat to the brew water as it condenses. The pressure is generated within the brew water by injection of the steam into the brew water. As discussed above, typically, the steam is at a pressure of from 2.5 bar to 16 bar; and preferably from 8 bar to 10 bar when the steam and brew water are contacted. Typically, the steam is at a temperature of from 100°C to 200°C; preferably from 150°C to 200°C; and more preferably from 175°C to 190°C when the steam and brew water are contacted. The injection of the steam into the flow of brew water will also cause the pressure of the brew water to rise to the desired level.

Preferably, the steam is injected into the continuous flow of brew water by way of a steam injector. More preferably, the steam injector comprises a steam cone, a combining cone and a delivery cone.

Typically, the steam is injected into the continuous flow of brew water by way of a steam injector comprising a steam cone for accelerating the flow rate and lowering the pressure of the steam, and a combining cone for receiving a flow of brew water and combining the flow of brew water and steam, wherein the steam enters the combining cone from the steam cone, and wherein the brew water enters the combining cone. This process may allow the steam to entrain the brew water and condense into it. The steam cone lowers the pressure of the steam by speeding up its flow. The pressure is further reduced by the reduction in volume as the steam condenses to water in the combining cone.

Preferably, the distance between the combining cone and steam cone is adjustable, such as by a user of the steam injector. This may be used to adjust the ratio of water and steam that are mixed in the combining cone. For example, a greater distance between the steam cone and combining cone will cause a greater ratio of water to steam to mix in the combining cone. This feature may be used to exert greater control of the temperature of the brew water exiting the steam injector. A greater ratio of steam to brew water mixing in the combining cone will cause the brew water exiting the steam injector to be at a higher temperature, and vice versa.

Typically, after the brew water has passed through the combining cone and contacted the steam therein and the steam has condensed into the combining cone, the brew water then passes from the combining cone to a delivery cone for decelerating the brew water. In the delivery cone, the flow of brew water slows, raising the pressure of the brew water again. This process typically brings the flow of brew water up to the desired pressure and temperature discussed above. Examples of suitable steam cones, combining cones and delivery cones include triple cone Giffard-type injectors such as those disclosed in US55218 and A survey of locomotive injector development, T. H. Shields, Paper No. 498, 25 October 1950, Journal of the Institute of Locomotive Engineers. Suitable adaptations to make to the injectors disclosed in these papers to make them suitable for use in the process of the invention will be apparent to the skilled person given the benefit of the present disclosure.

The angles, lengths and ratios of the cones discussed above may be calculated and varied if necessary so as to effectively condense the steam into the brew water flow and to achieve the target pressures and temperatures discussed above. How to vary these angles, lengths and ratios to achieve the desired result will be apparent to the skilled person given the benefit of the present disclosure.

Whilst cones of the type described above are preferable in the method of the invention for contacting the steam and continuous flow of brew water to heat and pressurise the brew water to the desired amount, other systems that are suitable for contacting the steam and brew water and increasing the brew water pressure and temperature may also be used and will be apparent to the skilled person given the benefit of the present disclosure. For example, other types of injector such as other triple cone Giffard type injectors may be used.

Typically, once the brew water has passed through the delivery cone, the brew water flow is then transferred to a coffee filter containing coffee beans so as to contact the coffee beans and then produce a coffee beverage. The brew water preferably contacts the coffee beans at the preferred temperatures and pressures described above. Preferably, the brew water flows directly from the delivery cone to the coffee filter. However, in alternative embodiments, the brew water may flow through one or more intermediary conduits before subsequently passing into the coffee filter.

In some embodiments, the brew water may flow to multiple coffee filters or heads.

In some embodiments, the method comprises the use of an apparatus comprising: a steam generating component connected to a steam delivery conduit; a first valve operable between an open position in which steam enters the steam delivery conduit from the steam generating component, and a closed position in which steam from the steam generating component is prevented from entering the steam delivery conduit; a steam injector in fluid communication with the steam delivery conduit and adapted to receive steam from the steam delivery conduit; a brew water delivery conduit in fluid communication with the steam injector for delivering brew water to the steam injector, wherein the brew water delivery conduit and steam injector are configured so as to entrain the brew water within the steam and to condense the steam into the brew water; and an exit conduit in fluid communication with the steam injector and for receiving brew water from the steam injector.

Typically, the steam generating component comprises a steam boiler comprising an internal electric heating element; a thermoblock; a thermocoil; or a combination thereof. Preferably the steam generating component comprises a steam boiler comprising an internal electric heating element. In alternative embodiments, the source of steam can be an external heating source such as a campfire, stove or other external heating source.

Typically, the first valve is adapted so as to move from a closed position to an open position when a threshold steam pressure value of steam pressure from the steam generating component is exceeded; preferably wherein the threshold steam pressure value is from 8 bar to 10 bar, although other threshold pressure values may be used if desired. Alternatively, the first valve may be manually or electronically operable by a user of the apparatus.

Typically, the rate of flow of steam from the steam generating component into the steam delivery conduit may be determined by the profile of the first valve.

Typically, the apparatus further comprises a water tank for storing brew water and for supplying water to the brew water delivery conduit. Alternatively, the brew water delivery conduit may be connected to a source of water flow such as a tap or water pump.

Typically, the apparatus further comprises a filter or vessel for containing ground coffee beans, wherein the filter or vessel is connected to the exit conduit and adapted to receive brew water from the exit conduit. Preferably the filter or vessel is an espresso coffee filter or vessel for producing espresso coffee. In further embodiments the apparatus may comprise multiple filters or vessels.

In cases where the steam injector comprises a delivery cone, as discussed in further detail below, the exit conduit may simply be a downstream portion of the delivery cone such that the filter or vessel for containing ground coffee beans is adapted to receive brew water directly from the delivery cone. Alternatively, the exit conduit may be a separate conduit disposed between the delivery cone and filter or vessel for containing ground coffee beans.

Typically, the apparatus further comprises a return conduit connected to the exit conduit; and a check valve operable between an open position in which brew water may enter the return conduit from the exit conduit, and a closed position in which brew water is prevented from entering the return conduit from the exit conduit, wherein the return conduit is adapted to return brew water to the steam generating component. Typically, the check valve is adapted so as to move from a closed position to an open position when a threshold pressure value of the brew water in the exit conduit is exceeded; and preferably the threshold pressure value is where the brew water pressure in the exit conduit exceeds the steam generating component pressure. Alternatively, the check valve may be manually or electronically operable by a user of the apparatus. The check valve ensures that steam can continue to be injected into the system via the injector even when resistance from the coffee filter is too high and exceeds the pressures described above. In this scenario, undesirable pressure build up from continued injection of steam can be alleviated by allowing some brew water out of the system via the check valve instead of said brew water flowing into the coffee filter. The check valve may also function as a general over pressure valve to release pressure from the system if desired.

Alternatively or additionally, other types of safety valve may also be present in the apparatus. Preferably, the apparatus comprises at least one safety valve operable to release pressure from the apparatus when a certain threshold pressure is exceeded.

Typically, the steam injector comprises a steam cone, a combining cone and a delivery cone.

Typically, the delivery cone is a tapered delivery cone. Preferably, the tapered delivery cone increases in diameter from an upstream end to a downstream end.

Typically, the steam cone is a tapered steam cone that decreases in diameter from an upstream end to a downstream end.

Typically, the combining cone is a tapered combining cone that decreases in diameter from an upstream end to a downstream end; wherein the tapered combining cone is downstream from the tapered steam cone.

Preferably, the combining cone is adapted to receive the brew water from the brew water delivery conduit and steam from the steam cone. Preferably, the delivery cone is adapted to receive the brew water from the combining cone.

Preferably, the tapered steam cone and tapered combining cone are in an overlapping configuration such that a narrowest downstream portion of the tapered steam cone overlaps with a broadest upstream portion of the tapered combining cone, although this is not essential.

Preferably, the distance between the combining cone and steam cone is adjustable, such as by a user of the apparatus. This may be used to adjust the ratio of water and steam that are mixed in the combining cone. For example, a greater distance between the steam cone and combining cone will cause a greater ratio of water to steam to mix in the combining cone. This feature may be used to exert greater control of the temperature of the brew water exiting the steam injector. A greater ratio of steam to brew water mixing in the combining cone will cause the brew water exiting the steam injector to be at a higher temperature, and vice versa.

Typically, a valve is inserted into an interior of the steam cone, wherein the valve is configured to control the rate of steam delivery to the combining cone from the steam cone and wherein the valve is operable by a user of the apparatus. Preferably the valve is a needle valve, although other suitable valve systems may also be used. Examples of alternative valves that are suitable for use will be apparent to the skilled person given the benefit of the present disclosure.

In cases where the steam injector does not comprise a valve (such as the valve described above in the interior of the steam cone), the rate of steam delivery to the combining cone can be controlled by other means such as including a flow restrictor in the steam delivery conduit or controlling the steam flow rate with the first valve.

Typically, the apparatus further comprises temperature and pressure sensors configured to determine the temperature and pressure of the brew water and/or steam within the apparatus.

Typically, the method of the invention comprises:

(a) opening the first valve to allow steam to enter the steam delivery conduit and steam injector; and

(b) providing brew water to the steam injector via the brew water delivery conduit to entrain the brew water within the steam and to condense the steam into the brew water.

Apparatuses and coffee machines of the invention

According to a second aspect of the invention, there is provided an apparatus for heating and pressurizing brew water for brewing coffee, wherein the apparatus is adapted for use with a coffee machine, and wherein the apparatus is configured to heat and pressurize a volume of brew water by directly contacting the volume of brew water with a separate volume of steam.

Preferably, the apparatus is adapted for use with an espresso coffee machine.

Preferably, the apparatus is a component of or connected to a coffee machine; and wherein the apparatus is configured to contact the brew water with ground coffee beans after the brew water has been heated and pressurized by the contact with the separate volume of steam; and subsequently separate a portion of the ground coffee beans from the brew water so as to form a coffee beverage.

In an embodiment, the apparatus comprises: a brew chamber for containing brew water; an input port for receiving steam from a source of steam; an output port for allowing outflow of brew water from the brew chamber; an input valve operable between an open position in which the brew chamber is in fluid communication with the source of steam, and a closed position in which the brew chamber is not in fluid communication with the source of steam; and an output valve operable between an open position in which brew water present in the brew chamber is allowed to leave the brew chamber via the outport port, and a closed position in which brew water and steam present in the brew chamber are prevented from leaving the brew chamber via the output port; wherein the apparatus is configured such that, when the input valve is in an open position and the output valve is in a closed position, steam from the source of steam flows through the input port and into the brew chamber to contact, heat and pressurise brew water present within the brew chamber.

Preferably, the apparatus further comprises a diffusion chamber that is in fluid communication with and contiguous with a portion of the brew chamber. More preferably, the diffusion chamber is positioned beneath the brew chamber. Typically, the input port and input valve are positioned to introduce steam from the source of steam to the diffusion chamber when the input valve is in an open position. Typically, the diffusion chamber and brew chamber are separated by a perforated diffusion grate. Preferably the perforated diffusion grate is adapted to evenly inject steam into the brew chamber via perforations in the perforated diffusion grate when steam is introduced to the diffusion chamber from the inlet port.

In an alternative to where the apparatus comprises a diffusion chamber, the apparatus may further comprise sparge tubes disposed between the input port and the brew chamber and connected to the input port; wherein the sparge tubes, input port and input valve are configured to introduce steam from the source of steam to the brew chamber via the sparge tubes when the input valve is in an open position. Preferably the sparge tubes are positioned so as to introduce steam from the source of steam to a lower portion of the brew chamber. Preferably, the sparge tubes are adapted to evenly inject steam into the brew chamber via perforations present in the sparge tubes.

In an alternative to where the apparatus comprises a diffusion chamber or sparge tubes, the input port and input valve may be positioned so as to introduce steam from the source of steam directly into the brew chamber when the input valve is in an open position. Preferably the input port is positioned so as to introduce steam from the source of steam to a lower portion of the brew chamber. In some instances of these embodiments, the input valve and input port form part of a steam injector. The steam injector is preferably configured and positioned to inject steam into brew water present within the brew chamber. In these embodiments, the water source for delivery to the steam injector may be the brew water itself present in the brew chamber. Accordingly, in some embodiments, the steam injector is configured and positioned so as to be submerged within brew water present in the brew chamber. Any type of steam injector known in the art may be used and configured to function in this way. Any of the types of steam injector discussed herein may be used as the steam injector in these embodiments.

Preferably, the brew chamber is an enclosed space when the input valve, output valve, and any additional valves connected to the brew chamber are in a closed position.

Preferably, the apparatus further comprises an input brew water port connected to the brew chamber for introducing brew water to the brew chamber. Preferably the input brew water port is closable via a valve so as to form an enclosed space within the brew chamber when both the output valve and input valve are in a closed position. The apparatus may further comprise a chamber for containing water where water can be stored prior to introduction to the brew chamber.

Typically, the output port is connected to a lower portion of the brew chamber. The apparatus may further comprise a steam generating component for generating steam, wherein the steam generating component is in fluid communication with the brew chamber via the input port when the input valve is in an open position. The steam generating component typically comprises a steam boiler comprising an internal electric heating element; a thermoblock; a thermocoil; or a combination thereof. Preferably the steam generating component comprises a steam boiler comprising an internal electric heating element. In alternative embodiments, the source of steam can be an external heating source such as a campfire, stove or other external heating source.

Preferably, one or both of the input valve and output valve are manually or electronically adjustable between their open and closed positions by a user of the apparatus. However, typically, the input valve is adapted to move from a closed position to an open position when steam from the source of steam applying pressure to the input valve exceeds a certain threshold pressure; preferably wherein the threshold pressure is from 2.5 bar to 16 bar; and more preferably from 8 bar to 10 bar. Typically, the output valve is adapted to move from a closed position to an open position when the pressure within the brew chamber exceeds a certain threshold pressure; typically wherein the threshold pressure is from 2.5 bar to 16 bar; and preferably from 8 bar to 10 bar.

Typically, the apparatus further comprises one or more safety valves operable to release pressure from the apparatus when a certain threshold pressure is exceeded; preferably wherein the safety valves are adapted to release pressure from the brew chamber, the steam generating component, or both.

The volume of the brew chamber may be any suitable volume. Preferably, the volume is sufficient for containing an amount of brew water to be used in a coffee extraction such as an espresso coffee extraction. The volume should also be sufficient for a volume of air to also be present in the brew chamber as well as the desired amount of brew water so that there is room for steam to enter the brew chamber and pressurise the volume of brew water therein. Typically, the volume of the brew chamber is from 50 ml to 150 ml; preferably from 80 ml to 150 ml; and more preferably from 80 ml to 120 ml.

Preferably, the volume of the brew chamber is manually or electronically adjustable by a user of the apparatus. Preferably, the apparatus is adapted so that temperature and/or pressure within the brew chamber may be adjusted by electronically or manually adjusting the volume of the brew chamber. Preferably, the apparatus further comprises a filter for containing ground coffee beans, wherein the filter, brew chamber and output port are configured such that the filter receives brew water from the brew chamber via the output port when the output valve is in an open position. Preferably the filter is an espresso coffee filter for producing espresso coffee.

Preferably, the apparatus further comprises a bypass conduit adapted to allow steam from the source of steam to bypass the brew water and be introduced to an upper portion of the brew chamber. More preferably, the bypass conduit is connected to a conduit connecting the source of steam to the input port. Excess steam can thus be diverted from passing through the brew water if desired but still be used to create pressure within the brew chamber.

Typically, the apparatus further comprises temperature and pressure sensors configured to determine the temperature and pressure of the brew water within the brew chamber.

The apparatus can be formed from any suitable material that can tolerate the pressures and temperatures encountered in the apparatus and used in the process. Suitable materials for use will be apparent to the skilled person given the benefit of the present disclosure. Preferably, a portion of the brew chamber and optionally a portion of the diffusion chamber if present are formed from a transparent material. Preferably, the interior of the brew chamber and optionally diffusion chamber if present are visible to a user of the apparatus. This is advantageous since it enables the heating and pressurising process to be witnessed by a user of the apparatus which may be aesthetically pleasing. The user is able to see the addition of team and the rising of gas bubbles through the brew water present in the brew chamber. Preferably, the brew chamber and optionally diffusion chamber if present are formed from glass, a thermoplastic material, or a combination thereof. More preferably, the brew chamber and optionally diffusion chamber are formed from a transparent polymer that is able to tolerate the high temperatures and pressures encountered in the method such as polyether ether ketone (PEEK). Preferably, the brew chamber and optionally diffusion chamber if present are formed from a food-safe material.

In another embodiment, the apparatus comprises: a steam generating component connected to a steam delivery conduit; a first valve operable between an open position in which steam enters the steam delivery conduit from the steam generating component, and a closed position in which steam from the steam generating component is prevented from entering the steam delivery conduit; a steam injector in fluid communication with the steam delivery conduit and adapted to receive steam from the steam delivery conduit; a brew water delivery conduit in fluid communication with the steam injector for delivering brew water to the steam injector, wherein the brew water delivery conduit and steam injector are configured so as to entrain the brew water within the steam and to condense the steam into the brew water; and an exit conduit in fluid communication with the steam injector and for receiving brew water from the steam injector.

Typically, the steam generating component comprises a steam boiler comprising an internal electric heating element; a thermoblock; a thermocoil; or a combination thereof. Preferably the steam generating component comprises a steam boiler comprising an internal electric heating element. Alternative embodiments may be adapted for use with an external heat source such as a stove top.

Typically, the first valve is adapted so as to move from a closed position to an open position when a threshold steam pressure value of steam pressure from the steam generating component is exceeded; preferably wherein the threshold steam pressure value is from 8 bar to 10 bar, although other threshold pressure values may be used if desired. Alternatively, the first valve may be manually or electronically operable by a user of the apparatus.

Typically, the rate of flow of steam from the steam generating component into the steam delivery conduit may be determined by the profile of the first valve.

Typically, the apparatus further comprises a water tank for storing brew water and for supplying water to the brew water delivery conduit. Alternatively, the brew water delivery conduit may be connected to a source of water flow such as a tap or water pump.

Typically, the apparatus further comprises a filter or vessel for containing ground coffee beans, wherein the filter or vessel is connected to the exit conduit and adapted to receive brew water from the exit conduit. Preferably the filter or vessel is an espresso coffee filter or vessel for producing espresso coffee. In further embodiments the apparatus may comprise multiple filters or vessels.

In cases where the steam injector comprises a delivery cone, as discussed in further detail below, the exit conduit may simply be a downstream portion of the delivery cone such that the filter or vessel for containing ground coffee beans is adapted to receive brew water directly from the delivery cone. Alternatively, the exit conduit may be a separate conduit disposed between the delivery cone and filter or vessel for containing ground coffee beans. Typically, the apparatus further comprises a return conduit connected to the exit conduit; and a check valve operable between an open position in which brew water may enter the return conduit from the exit conduit, and a closed position in which brew water is prevented from entering the return conduit from the exit conduit, wherein the return conduit is adapted to return brew water to the steam generating component. Typically, the check valve is adapted so as to move from a closed position to an open position when a threshold pressure value of the brew water in the exit conduit is exceeded; and preferably the threshold pressure value is where the brew water pressure in the exit conduit exceeds the steam generating component pressure. Alternatively, the check valve may be manually or electronically operable by a user of the apparatus. The check valve ensures that steam can continue to be injected into the system via the injector even when resistance from the coffee filter is too high and exceeds the pressures described above. In this scenario, undesirable pressure build up from continued injection of steam can be alleviated by allowing some brew water out of the system via the check valve instead of said brew water flowing into the coffee filter. The check valve may also function as a general over pressure valve to release pressure from the system if desired.

Alternatively or additionally, other types of safety valve may also be present in the apparatus. Preferably, the apparatus comprises at least one safety valve operable to release pressure from the apparatus when a certain threshold pressure is exceeded.

Typically, the steam injector comprises a steam cone, a combining cone and a delivery cone.

Typically, the delivery cone is a tapered delivery cone. Preferably, the tapered delivery cone increases in diameter from an upstream end to a downstream end.

Typically, the steam cone is a tapered steam cone that decreases in diameter from an upstream end to a downstream end.

Typically, the combining cone is a tapered combining cone that decreases in diameter from an upstream end to a downstream end; wherein the tapered combining cone is downstream from the tapered steam cone.

Preferably, the combining cone is adapted to receive the brew water from the brew water delivery conduit and steam from the steam cone. Preferably, the delivery cone is adapted to receive the brew water from the combining cone.

Preferably, the tapered steam cone and tapered combining cone are in an overlapping configuration such that a narrowest downstream portion of the tapered steam cone overlaps with a broadest upstream portion of the tapered combining cone, although this is not essential.

Preferably, the distance between the combining cone and steam cone is adjustable, such as by a user of the apparatus. This may be used to adjust the ratio of water and steam that are mixed in the combining cone. For example, a greater distance between the steam cone and combining cone will cause a greater ratio of water to steam to mix in the combining cone. This feature may be used to exert greater control of the temperature of the brew water exiting the steam injector. A greater ratio of steam to brew water mixing in the combining cone will cause the brew water exiting the steam injector to be at a higher temperature, and vice versa.

Typically, a valve is inserted into an interior of the steam cone, wherein the valve is configured to control the rate of steam delivery to the combining cone from the steam cone and wherein the valve is operable by a user of the apparatus. Preferably the valve is a needle valve, although other suitable valve systems may also be used. Examples of alternative valves that are suitable for use will be apparent to the skilled person given the benefit of the present disclosure.

In cases where the steam injector does not comprise a valve (such as the valve described above in the interior of the steam cone), the rate of steam delivery to the combining cone can be controlled by other means such as including a flow restrictor in the steam delivery conduit or controlling the steam flow rate with the first valve.

Typically, the apparatus further comprises temperature and pressure sensors configured to determine the temperature and pressure of the brew water and/or steam within the apparatus.

According to a third aspect of the invention, there is provided a coffee machine comprising or connected to an apparatus according to the second aspect of the invention.

Preferably, the coffee machine is an espresso machine, although this is not essential and any type of coffee machine may comprise the apparatus. The invention is not limited to any particular type of coffee machine or espresso machine and all machines known in the art of such type may be connected to or comprise the apparatus of the invention. Uses of the apparatuses and coffee machines

According to a fourth aspect of the invention, there is provided the use of an apparatus according to the second aspect of the invention or a coffee machine according to the third aspect of the invention for (i) heating and pressurizing brew water for use in the preparation of a coffee beverage; or (ii) in the preparation of a coffee beverage. Preferably, the use comprises heating and pressurizing brew water for use in the preparation of a coffee beverage and then using said heated and pressurised brew water in the preparation of a coffee beverage. Preferably, the coffee beverage is an espresso coffee beverage. Preferably, the use comprises using a method according to the first aspect of the invention.

As discussed above, in prior art systems where the brew water itself is heated so as to evaporate a portion of it into steam and said steam is used to pressurise the remaining brew water, it is necessary to heat said brew water to around 180°C in order to create sufficient pressure within the system. The pressurised brew water then needs to cool before it is contacted with the coffee beans, such as by adding a portion of cooler brew water or by a cooling type heat exchanger device. In contrast, in the present invention there is no need to heat the brew water above the desired temperature of 90°C to 100°C. The brew water is also effectively pressurized without the use of a manual or electric pump. Additionally, there is no need for the use of two boilers or a more complex heat-exchanger type boiler such as those discussed above. Being able to exclude these components from coffee machines means that coffee machines can be made less complex, smaller and at lower cost.

The use may also comprise using the apparatus or coffee machine to reduce the build-up of limescale in a coffee machine. As discussed above, the process of condensing steam into the brew water dilutes the brew water such that it contains lower quantities of mineral salts leading to less deposition of mineral salts in the form of limescale on the interior of chambers and conduits of coffee machines. Even in the case of softened water such as commercially available softened water for coffee machines, the method of the invention can dilute this softened water even further so as to further reduce the build-up of limescale. Reducing the quantity of mineral salts in a coffee beverage may also improve the taste of said beverage. Accordingly, the use may also comprise using the apparatus or coffee machine to provide a coffee beverage with improved flavour, when compared to a coffee beverage prepared by a coffee machine that does not comprise or is not connected to an apparatus of the invention. As discussed above, use according to the invention may also provide improved control of the temperature of the brew water which may provide energy efficiency savings and also allow for temperature profiling during the espresso making process.

DESCRIPTION OF THE DRAWINGS

Figures 1 to 4 depict the mechanism of operation of various coffee machines known in the art.

Figure 5 shows a boiler that may be used in accordance with the present invention.

Figure 6 shows an embodiment of an apparatus of the invention.

Figures 7 and 8 depict example designs of coffee machines of the invention.

Figure 9 shows an alternative embodiment to the embodiment shown in Figure 6 of an apparatus of the invention.

Figure 10 shows sparge tubes that may be used in accordance with the invention.

Figures 11 and 12 show steam injectors that may be used in accordance with the invention.

Figure 13 shows the dimensions and angles of a steam cone, combining cone and delivery cone that form part of a steam injector that may be used in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following described embodiments are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

In the embodiments discussed below, and in other embodiments, any suitable valves, conduits, chambers, steam injectors, and other described components known in the art may be used to implement the described methods and apparatuses and other methods and apparatuses of the invention. Any suitable material known in the art may also be used for manufacture and fabrication of the described components, provided that said materials are suitable for use with the temperatures and pressures encountered in the method of the invention. Additionally, any suitable manufacture methods known in the art for the manufacture of said components may also be used. Suitable components, materials, methods of manufacture and configurations of components within suitable apparatuses will be apparent to the skilled person given the benefit of the present disclosure.

Example 1 In an embodiment, water may be heated in an insulated boiler to a temperature of around 180°C and to a pressure of around 9 bar. A warm-up cycle may be used initially followed by full power heating. An example of a boiler 10 that may be used is shown in Figure 5. Also shown in Figure 5 is an input valve 11 and a conduit by which steam may exit the boiler. Input valve 11 may be electronically or manually adjustable by a user or may open when a threshold pressure within the boiler is exceeded. Once the pressure exceeds the threshold value, input valve 11 opens and allows steam to escape the boiler via input port 12. As shown in Figure 6, the steam enters a diffusion chamber via input port 12. The steam may rise up and out of the diffusion chamber via perforations in perforated grate 23 and pass into brew chamber 22. Brew chamber 22 is already filled with brew water 21. The steam enters the brew chamber 22 at the base and passes up through the volume of water of brew water 21. Some of the steam may condense into the brew water 21 to add to its volume. At least a portion of the steam passes up through the brew water to the portion of brew chamber 22 that is free of brew water and that contains air. The rate of steam injection may be controlled so as to ensure that some steam passes up above the brew water into the space at the top of the brew chamber, and if desired so that some steam condenses into the brew water. As more steam is added, the pressure builds in upper section of brew chamber 22 so that pressure is applied to brew water 21. The parameters affecting the rate of heating of the brew water and pressurising the chamber are set to result in a simultaneous achievement of advantageous values of both pressure and temperature of the brew water. If desired, the volume of the brew chamber 22 may be adjusted by adjusting ceiling portion 24 so as to increase or decrease the volume of the brew chamber. Typically, the ceiling portion 24 may be lowered so as to increase the temperature and pressure within the brew chamber. Ceiling portion 24 is adjustable via a control of the device handled by a user. The materials of the diffusion chamber and brew chamber are preferably transparent and able to tolerate the temperatures and pressures encountered in the system. This enables a user of the apparatus to watch the bubbles of steam rise up through the diffusion chamber and brew chamber to the upper portion of the brew chamber which may be visually pleasing to the user. Figures 7 and 8 show designs of a coffee machines that can comprise the apparatus of the invention. As can be seen in e.g. Figure 7, the diffusion chamber and brew chamber may be made visible to a user of the apparatus so that bubbles can be seen rising through the brew chamber.

An alternative embodiment to the diffusion chamber system discussed above is shown in Figure 10. Figure 10 shows sparge tubes which may be perforated and may be used to inject steam directly into the volume of brew water in the brew chamber. Figures 11 and 12 show yet further embodiments where steam injector devices can be used to inject steam directly into the brew water present in the brew chamber. These injectors may also be used to inject steam into a continuous flow of water as described below in Example 2.

Example 2

In another embodiment, a method of injecting steam into a continuous flow of water is shown in Figure 9. Steam from a boiler enters a conduit 51. The steam may be generated by a boiler such as the type shown in Figure 5, or alternatively, by other steam generating components. Typically, steam enters conduit 51 when an input valve opens when pressure from the boiler exceeds a threshold pressure value, such as 9 to 10 bar. Steam proceeds through conduit 51 until it reaches steam cone 52. Steam cone 52 has a broader upstream end and a narrower downstream end. The steam accelerates through steam cone 52 which lowers its pressure. Conduit 56 supplies a continuous flow of brew water to combining cone 54. The steam passes through the steam cone 52 and into combining cone 54. It can be seen in Figure 9 that upstream broader end of combining cone 54 overlaps lower downstream end of steam cone 52, although this is not essential. Brew water enter the combining cone 54 and where it encounters the steam as it leaves the steam cone. The steam and water contact in the space 53 inside combining cone 54 where the steam is allowed to entrain the brew water causing the steam to condense into the brew water and raising the temperature of the brew water. The steam also imparts its kinetic energy to the brew water. The water then enters delivery cone 55 which broadens in diameter towards its downstream end. In the delivery cone the water slows down and meets resistance from the finely ground coffee beans beyond the coffee filter (shown directly below delivery cone 55 in Figure 9). This increases the pressure of the brew water to the desired level of around 9 bar. Some of the brew water then passes through into the coffee filter to contact the ground beans. If the pressure in the delivery cone 55 rises to a level above the boiler’s, the fluid will leave the system via boiler return conduit 59 which returns the brew water to the boiler. Check valve 58 may open when a threshold pressure is exceeded allowing the brew water to enter the boiler return conduit 58.

Adjustments to the rate of steam injection can be made by adjusting the positioning of steam cone 52 and by opening and closing needle valve 57 which is within the steam cone 52. This is achieved via controls 56 and 60. The angles, lengths and screw threads of the cone and needle valve are such that the ratio of steam to water may be constant as flow is altered. Controls 60 and 56 turn together, but 60 can be turned independently to alter the position of the needle valve, the amount of steam entering the cone, and consequently the temperature.

As discussed above, other injection systems where steam is injected into a continuous flow of brew water may also be used.

Figure 13 depicts in greater detail an example of a steam injector that may be used in accordance with the invention. The various dimensions and angles of the cones of the injector are depicted in the figure. All dimensions depicted are in mm except the angles of the cones. In the injector depicted, the maximum output flow rate of the injector is around 8 ml/second which would be suitable for use in the present invention. This output is dependent upon the diameter of the narrowest part of the delivery cone which is 0.635 mm. The injector depicted would typically operate with a steam to water ratio of 1 to 7. The steam to water ratio is dependent on the size of the annular space around the downstream end of the steam cone. Suitable adjustments to such an injector and how to implement them in the method of the invention will be apparent to the skilled person given the benefit of the present disclosure.