Description

The present invention relates to an improved method and machine for optimizing the quality of extracted coffee drink. In particular the invention relates to an improved method and coffee machine, wherein the flow characteristics of the extracted coffee drink into the receptacle is monitored and if found to be deviating from reference value, the brewing temperature and time are corrected to improve the flavours extracted from the ground coffee powder.

Background Art

Espresso coffee machines that extract coffee drink from a dose of ground coffee powder, by passing water:

under pressure,

within an optimum temperature range and

in a short time of approx. 20-30 seconds, extract different flavours from the ground coffee powder very well. Therefore, espresso coffee and espresso based milk drinks are gaining in popularity in many parts of the world.

Espresso coffee is normally made from approximately 5-9 grams of ground coffee for a single serving, and when prepared well, it has excellent flavours. It has a small serving size of approximately 15-40 ml, a thick consistency as compared to other brewing methods, a higher concentration of dissolved solids and thick foam commonly known in the trade as "Crema'. In addition to the above mentioned relevant parameters of pressure, temperature and time, many other factors also affect the espresso coffee brewing process, either on their own or by influencing the other parameters or both, e.g. type of coffee or coffee mixture, roast level and roast profile, moisture content, ambient humidity, time after roasting and grinding etc.

Technical Problems

In order to produce a high quality espresso drink with an optimum percentage of dissolved solids, the brewing parameters have to be carefully adjusted to optimize some or all the above mentioned factors, which may normally affect the brewing process.

Often these adjustments are not accurately made, due to the manual intervention required and because of the limited understanding of the brewing process being used. This results in either of the following two undesirable conditions:

the first condition is associated with a weak brew, underdeveloped flavours and high sourness, which are caused by a low extraction pressure and/or low temperature, and

the second condition is associated with a very strong brew and highly unpleasant bitterness, which are caused by a high extraction pressure and/or high temperature.

Normally, it is known in the existing art to adjust or modify the brewing parameters, e.g. pressure and time, which are deviating from the reference/desired values. Most commonly, the brewing pressure of more than 9 bar is developed by the action of the pump acting on the dose of ground coffee powder placed on a filter member. The function of this filter member is to allow the extracted beverage to flow through, but to disallow the ground coffee powder to pass to the beverage receptacle, e.g. a coffee cup.

The pressure is normally adjusted by regulating:

the particle size of the ground coffee powder, the dose weight of the ground coffee powder and the pressing force applied to compact the dose of ground coffee powder. Prior Art

Patent document DE 10 2009 049229 Al (WMF, Casado Gomez Sebastian+) describes a coffee machine, which calculates the grind particle size of the ground coffee coming out of the grinder by checking the volume and mass of the ground coffee and which corrects the brewing pressure for the subsequent brewing cycle by changing the grind particle size by adjusting the mean distance between the two grinding discs in the coffee grinder.

Patent document WO 2009/0101909 (De'Longhi SPA, De Longhi Giuseppe+) discloses a method for controlling a coffee machine grinder by measuring the percolation time, percolation rate and percolation pressure and by changing the grind particle size by adjusting the mean distance between the two grinding discs in the coffee grinder. Both the above patent documents have the following limitations:

Once the brewing cycle starts, only the subsequent brewing cycle can be corrected or improved, because the grind particle size for the current brewing cycle cannot be changed after starting the brewing cycle,

By their own nature, coffee mixtures differ in terms of their quality, consistency, degree of roasting and humidity etc. At the same time, it is very difficult to control the grinding process accurately and thus, the resulting ground coffee is generally formed by a distribution of small grains, the shape and dimensions of which vary. As a result, a dose of ground coffee taken from the grinder is never exactly the same as another,

Frequent adjustments to the mechanical elements of the grinder are not a desirable or practical solution.

Patent document EP 2314182 Al (Gruppo Cimbali, Coccia Andrea) describes a system for controlling the brewing/dispensing pressure by varying the pump output flow rate.

Patent document WO2011/055189A (La Marzocco Sri., Bianchi Roberto; Ellul-Blake Jacob) describes an improved method for preparing espresso coffee by manually adjusting or manually setting the automatic control of the brewing water pressure developed by the pump to suit different types of coffee.

However, adjusting the pressure developed by the pump also has limitations, because if the dose of coffee is not offering enough resistance to the flow of water and the water is flowing too fast through the dose of coffee, then reducing the pressure/rate of flow will, to an extent, help in extracting an increased percentage of flavours from the ground coffee powder but at the same time, the reduced pressure will not be adequate enough to extract the flavours from the ground coffee powder properly, resulting in a coffee beverage that is still too thin, sour and with underdeveloped flavours.

Normally, espresso coffee is to be extracted within an optimum temperature range around 90 degrees. The temperature is controlled by suitable temperature sensing devices, which are commonly known in the art.

Patent document EP2050372Al(Gruppo Cimbali, Coccoa Andrea) describes a system, in which the optimum temperature is maintained constant throughout the brewing process by means of a controlled mixing of cold water into the hot water line disposed downstream of the heat exchanger.

Optimum extraction time can range from 20-30 sees for a 15-40 ml of beverage extracted from a dose of approximately 5-9 grams of ground coffee powder, depending on coffee, roast, grind, moisture etc... and such other factors, already listed above. The extraction time is normally controlled manually by a visual inspection of the extracted beverage, or is a "fixed" time value - programmed into the machine control system.

In fact, an experienced espresso machine user/operator routinely/intuitively monitors the flow characteristics visually on a manually operated espresso machine in order to determine, whether the extracted beverage is of high/desired quality or not.

Some prior art machines also monitor the flow volume by means of a flow sensing device, which measures the volume of water pumped into the heating device. In such monitoring process, it is assumed that the volume delivered to the beverage receptacle is equal to the volume delivered to the heating device. However, this assumption does not always hold good, because some of the water delivered to the heating device ends up as residue or is captured by absorption or other losses taking place in the brewing device and other parts of the hydraulic circuit of the machine.

Commonly, the heating devices in usual espresso machines are either a boiler vessel which hold some volume of water at a constant temperature, or a thermo-block which consists of a thin long water tube and a heater element cast together in order to form a heat exchanger.

Objects of the Invention

It is an object of the present invention to provide a method for extracting the desired flavors optimally from a dose of ground coffee powder.

It is another object of the present invention to provide a method to produce a high quality espresso coffee drink more consistently, by employing a method for monitoring and controlling the brewing process continuously during the brewing cycle.

It is yet another objective of the present invention to provide a method in which the flow characteristics of the extracted coffee drink collected in its receptacle are monitored continuously and if required, the brewing temperature and time are either increased or decreased accordingly in order to adjust the rate of coffee extraction, so that the desired flavors are extracted in the coffee drink. It is a further object of the present invention to provide a method in which optimizing the extracted beverage is based on the output of the weighing device for the extracted beverage, and outputs of a plurality of sensors - which are disposed in the hydraulic and coffee powder delivery circuit - for detecting various relevant parameters, such as, pressure, temperature, position and flow.

It is still another object of the present invention to provide a method to correct any relevant brewing parameter after completion of the brewing cycle, to be ready for the subsequent brewing cycle.

It is yet another object of the present invention to provide an espresso coffee machine incorporating a weight sensing device for monitoring the flow characteristics of the extracted coffee drink as it flows into the beverage receptacle, by means of the temperature sensor, time clock in the control device and a plurality of sensors and actuators disposed in the hydraulic and coffee delivery circuit of the coffee machine.

Summary of the Invention

In accordance of the present invention, the method for optimizing quality of extracted coffee beverage comprising the steps of: a) Feeding a ground coffee dose in a brewing chamber, b) Compacting said coffee dose in said brewing chamber, c) Feeding hot water into said brewing chamber under pressure, d) Extracting coffee beverage in a beverage receptacle e) Weighing said extracted beverage continuously and communicating said weight to a control device for controlling the brewing cycle further for optimal coffee extraction from said coffee dose, wherein said weight of the extracted beverage is obtained as a difference of the tare weight and the total weight of the beverage receptacle continuously obtained during the brewing cycle, and comparing said extracted beverage weight continuously in terms of its flow characteristics, i.e. weight over time with respect to the reference flow characteristics stored in said control device, and if the flow characteristics of the extracted beverage are deviating from the reference values, accordingly modifying the brewing temperature and time during the same brewing cycle.

Typically, the compacting force on the coffee dose, volume and/or weight of the coffee dose and particle size and particle size distribution of the ground coffee dose are all controlled in a subsequent brewing cycle for obtaining the extracted coffee beverage of a high quality, which comprises the flow characteristics similar to the stored reference flow characteristics.

In accordance of the present invention, an espresso coffee machine continuously controllable during the brewing cycle comprises:

a coffee feeding device,

a hot water delivery unit, a beverage extraction unit,

- a beverage receptacle placed on a support,

- a weighing unit placed under said support,

- a plurality of sensors monitoring and providing all relevant brewing parameters detected from said units,

- a plurality of connection lines, and

a control device configured with a reference set of brewing parameters stored for controlling the temperature and time or if required pressure and volume of hot water as well, in order to optimally extract the desired flavors from a dose of ground coffee powder in a coffee drink.

Typically, the coffee feeding device is an auger feeder fitted with a position sensor for issuing output signal to said control device and fitted with an actuator which receives an input signal from said control device for adjusting the volume/weight of the ground coffee powder dose to be fed to said coffee extraction unit.

Typically, the hot water delivery unit comprises:

a water reservoir,

a water pump for pumping water received from said water reservoir,

a water heating unit for heating water being pumped from said pump fitted with at least one temperature sensor, a device for monitoring the flow of water,

a device for controlling flow of water, and

a plurality of connection lines. Typically, the beverage extraction unit comprises:

a brewing chamber fitted with a positioning screw at the top end and a filtering member at the bottom end, a pressing plunger connected and driven by said positioning screw according to its position detected by a position sensor, a pressure sensor for sensing the pressure on the pressing plunger.

Typically, the water heating unit is configured as a thermo-block or boiler vessel.

Typically, the ground coffee powder dose is fed into the brewing chamber manually, or automatically by the machine, or said dose is contained in a single serve package, e.g. a pod, capsule, cartridge or a cup being disposed therein.

Typically, the control device is configured to store as reference brewing parameters, all the relevant optimum brewing parameters, e.g. pressure, temperature and time, for different types of coffees and coffee mixtures and which can be recalled, as and when required, for example-during a changeover of the type of the coffee or the coffee mixture.

Typically, the control device comprises a feedback control system of any configuration.

Brief Description of the Accompanying Drawings

The present invention will be described in more detail in the following with the help of the figures in the accompanying drawings, which illustrate a preferred but non-inclusive and non-limiting embodiment thereof.

Figure 1- shows a schematic diagram of the espresso coffee machine in accordance with the present invention, which is configured to optimally extract the desired flavors from a dose of ground coffee powder during the brewing cycle, by carrying out the method according to the present invention.

Figure 2- shows typical flow characteristic curve for a particular high quality coffee, which is used as a reference for modifying a brewing cycle by the espresso machine in accordance with the present invention.

Figure 3- shows an alternative embodiment of the espresso machine having a preferred position of the load cell sensor.

Detailed Description of the drawings

Figure 1 shows a schematic diagram of an exemplary embodiment of the espresso machine in accordance with the present invention. The espresso machine includes: a support (101) for a beverage receptacle (102) placed on a weight sensing device (103). The weight sensing device (103) issues an output signal to the control system (105) which monitors the flow characteristics of the extracted coffee drink, temperature, pressure flow rate etc... continuously during the entire brewing cycle. Optionally, a sensor (106) to detect, whether the beverage receptacle has been placed in its required position, can also be added. The ground coffee powder is delivered to the brewing chamber (107) by means of a coffee feeding device (108) in the form of an auger feeder, which incorporates a position sensor (109) to issue an output signal to the control unit (105) and an actuator (not shown) in the form of a motor which receives an input signal from the control unit (105) to make the required adjustment to the weight/volume of the coffee dose (114) to be fed to the brewing chamber (107).

Optionally, the coffee machine can also be equipped with a coffee grinding device (110), in which the roasted coffee seeds are ground between a non- rotating disc (111) and a rotating disc (112). The non-rotating disc (111) and the rotating disc (112) include cutting teeth on their mating faces. The mean ' particle size of the ground coffee powder in the coffee dose (114) being fed i to the brewing chamber(107) can be adjusted by adjusting the distance (113) between the non-rotating disc (111) and the rotating disc (112) by moving any one of the discs by means of another actuator (not shown), for example, a motor driven on receiving an input signal from the control unit (105) which in turn is based on the output signal given by the weight sensing device (103) ' continuously, during the brewing cycle, arid a position sensor (129) for the 1 adjustable disc, to adjust the particle size of the ground coffee for the subsequent brewing cycle.

The pressing force on the ground coffee dose (114) can be adjusted by adjusting the position of the pressing plunger (115) as determined by a position sensor (104) and by means of a positioning screw (117), which in turn is moved by a motor (130), based on the output signal issued to the control unit (105) by the pressure sensor (116) disposed under the pressing plunger (115). The pressure required for brewing the coffee dose is developed by the pump

(118) acting against the coffee dose (114) stored above a filtering member

(119) . For developing this pressure, the pump (118) delivers the hot water to the brewing chamber (107) by drawing it from the water reservoir (120). The flow monitoring device (121) in the inlet line of the pump (118) issues an output signal to the control unit (105). Alternately, a flow monitoring device (122) can also be disposed in the output line of the pump (118).

The temperature of the hot water being fed to the brewing unit (107) is adjusted by the control unit (105) by regulating the power delivered to the heating element (123) based on :

- the output signal received from temperature sensor/s (124) in the thermo-block (125)

- the reference temperature curve for the type of coffee/coffee mixture being extracted, as explained in more detail with the help of figure 2

- the output signal received continuously during the brewing cycle, from the weight sensing device (103) for the beverage receptacle (102), which detects any differences between the actual flow characteristics of the extracted beverage and the reference flow characteristics for any particular type of coffee/coffee mixture. Based on this difference in flow characteristics the control unit (105) adjusts the power supplied to the heating element (123) in the thermoblock (125) to either increase or decrease the temperature of the water being fed to the brewing chamber (107) to adjust/correct the extraction rate accordingly and extract the desired flavours. The brewing time is controlled by the clock in the microprocessor/microcontroller embedded in the control unit (105).

The espresso machine is also equipped with a plurality of hoppers (126) to accommodate different coffee/coffee mixtures or flavoring agent/s at the same time.

Additionally, the espresso machine can also be equipped with a milk delivery circuit (127) and a unit (128) for delivering a beverage by dissolving flavor/s and/or flavoured beverage/s obtained from a soluble powder.

Figure 2 shows a typical reference flow characteristic curve (Br) as read by the weight sensor for the beverage receptacle and a typical reference temperature curve (Tr) for a particular high quality Indian coffee mixture, containing 40% wet processed Arabica coffee, 40% dry processed Arabica coffee and 20% dry processed Robusta coffee. The other curve (Bm) represents the flow characteristic curve as modified by means of the control system in accordance with the present invention, in order to at least partially improve flavours in the extracted beverage by increasing the temperature as shown by the curve (Tm) and at the same time, stopping the brew cycle a few seconds earlier.

During the brewing cycle denoted by curve (Bm), when the beverage starts flowing into the beverage receptacle, the control system senses that the beverage has started flowing into the beverage receptacle a little earlier than the reference time value. This means that the water is flowing too fast through the coffee powder dose and if the brewing cycle is allowed to proceed without interruption from the control system as in prior art machines the beverage would be weak and with underdeveloped flavours and a high sourness, compared to a well extracted beverage. To correct this, the control system of the invention increases the temperature in the heating unit in order to increase the temperature of the water being fed to the brewing chamber and thereby the rate of extraction/percentage of flavours extracted and also stop the brewing cycle a few seconds earlier to avoid too weak/watery beverage.

Additionally, the brewing cycle can also incorporate an initial wetting of the coffee powder dose at the start of the brewing cycle for approx. 3 seconds, and a subsequent stopping of the brewing cycle for approx. 5 seconds, before proceeding with the brewing cycle as shown in the curve. This is commonly known in the art as pre-infusion.

Figure 3 shows a preferred position of the load cell sensor in the espresso machine. This embodiment has an alternate location of the weight sensing device (203) for the beverage receptacle (202) by which the weight sensing device (203) is disposed away from the beverage delivery area. This arrangement avoids any damage to the weight sensing device (203) which is a very delicate device and this also avoids soiling of the device by the prepared beverage.