A freeze-dried coffee article and a method for the production thereof

Abstract

There is provided a method for the manufacture of a coffee article having a mass of at least 0.5 g, the method comprising:(i) providing an unfoamed, aqueous coffee extract comprising from 30 to 40wt% coffee solids; (ii) filling the unfoamed, aqueous coffee extract into a mould; (iii) freezing the unfoamed, aqueous coffee extract in the mould to form a frozen coffee body at a temperature below -30°C; (iv) releasing the frozen coffee body from the mould; (v) annealing the released frozen coffee body at a temperature in a range of from -15 to -28°C for at least 20 minutes, (vi) subliming water from the annealed frozen coffee body to form a coffee article.

Description

[0001] A freeze-dried coffee article and a method for the production thereof

[0002] The present invention relates to the provision of a moulded freeze-dried coffee article. The articles can be made from an aqueous coffee extract comprising increased amounts of coffee oil and fine coffee particles. In particular, the freeze-dried coffee articles can be produced with the desired darker colour for coffee compositions, without the need for grinding, filtering, or aeration steps. As a result, the articles can also be made at a lower energy cost without compromising the product quality or appearance.

[0003] Freeze-dried coffee is well known in the art and the products are generally considered to be a premium soluble coffee product. The drying process is typically gentler than spray-drying, with a reduced loss of volatile flavour components due to the low temperatures used. Accordingly, while it is generally more expensive to produce freeze-dried coffee than spray- dried coffee due to the energy costs associated with the freeze-drying process, the product is generally more desirable.

[0004] A conventional freeze-drying system for preparing soluble coffee is well known in the art. Such a system takes an aqueous soluble coffee extract, typically having from 40 to 50wt% soluble coffee solids, and cools it down. The cooled coffee extract is then typically foamed, which provides a number of benefits. These include improved dissolution, colour control and the density of the final freeze-dried product. The foamed, cooled coffee extract is then loaded onto cooling trays and frozen to a temperature of less than minus 40°C and typically less than minus 50°C. The frozen material is ground to increase its surface area and then subjected to a freeze-drying process with added heat under a reduced pressure. An exemplary freeze-drying process is disclosed in EP3448166.

[0005] As a consequence of the freeze-drying process steps, the final product has a sharp fragmented structure, with edges where the frozen sheets of soluble coffee were fragmented and broken up before drying. The freeze-dried coffee has flat angular faces and generally has an open pore structure due to the water leaving the structure during the drying process (c.f. spray-drying). The conventional freeze-drying process produces a large amount of fines, particularly from the grinding step, which need to be sorted out of the fragmented material and recycled back into the soluble coffee extract. The fines are typically removed by sifting out the frozen fine material. No soluble coffee is therefore wasted.

[0006] While the freeze-drying process allows fine-tuning of the beverage strength, it also provides an opportunity for significant variance in the final beverage quality. In order to address this problem, it has been suggested to provide the soluble beverage ingredients in a tablet form. This ensures that each beverage produced is identical and of the high quality intended by the beverage ingredient manufacturer.

[0007] However, the provision of ingredients in tablet form has not yet been perfected. In particular, there are commonly problems with the dissolution of the ingredients; the presence of an undissolved residue at the bottom of a beverage is not appealing for consumers. Tablets are commonly formed using a powdered ingredient since this avoids drying issues and allows for easier shaping. In order to produce a tablet of, for example, soluble or instant coffee, it is generally necessary to either provide considerable compaction or use a binder to hold a soluble coffee powder together. However, the high compaction can prevent the tablet from dissolving and the presence of a binder can cause similar problems or affect the flavour of the final beverage.

[0008] For tablets prepared with low compression and / or without the use of a suitable binder, there is a further risk of damage or fracturing of the tablet. This is especially the case for pellets with sharp edges; the chance of fracturing, leading to a loss of the original shape, is increased. If the consumer opens a tube of tablets and finds that they are chipped or broken, then the impression of quality is significantly diminished.

[0009] There exists a prejudice amongst consumers who consider soluble coffee products, such as freeze-dried coffee, to be inferior to the coffee produced in cafes or produced in beverage machines. Therefore, the use of tablets as a distribution form for beverage ingredients has not been popular amongst consumers. In particular, consumers prefer coffee beverages which possess a darker colour similar to the colour of beverages produced by ground or roasted coffee.

[0010] Various previous attempts have been made to provide freeze-dried articles that address these problems. US7794771 B2 relates to a method of forming a soluble coffee tablet in which a coffee composition is moulded whilst adding gas. It is then frozen, demoulded and dried. The colour of the coffee composition is preferably altered by using a colourant.

[0011] JPS5668351 A relates to a method of manufacturing freeze-dried coffee granules in the shape of coffee beans. The coffee extract is poured into a mould, frozen inside the mould and then dried under reduced pressure. GB1240842 A relates to a method of manufacturing a dried instant coffee in which aqueous coffee extract is chilled to precipitate wax solids. These solids are separated by centrifugation. The extract is further cooled to separate ice, providing a concentrated extract having a solids content in excess of 35%. This extract is frozen and freeze-dried to produce a freeze-dried instant coffee.

[0012] WO2022215744A1 relates to a method for producing a freeze-dried beverage solidified product, where dextrin is mixed into the extract to improve moldability, shape retention, moisture resistance, and instant solubility of the product.

[0013] DE1906924 provides a method for changing the surface colour of a freeze-dried coffee product. Droplets (3mm diameter) of coffee extract are frozen to approximately minus 40°C, and then scraped onto a heat-emitting surface at a temperature of about -10°C for a few seconds. The contact causes the frozen droplets to darken. The frozen droplets are then fully frozen again and subjected to freeze-drying.

[0014] CN116636573 relates to a freeze-dried coffee product comprising maltodextrin and having the taste of blueberries. The method involves an annealing step performed on droplets, but this is performed at a colder temperature than the preceding steps.

[0015] FR1563136 discloses a method of forming a frozen tablet product in two steps, where the first step is a freeze-concentration step followed by conventional freezing and freeze-drying.

[0016] US6428833 describes a process in which coffee extract with a 35 to 45wt% solids content is foamed to a foam weight of 450 to 750 g / l and then dropped onto a cooled belt for the formation of pellets. The pellets are frozen on the belt to temperatures below minus 30eC and then freeze-dried. The product is preferably dropped onto the cooled belt in quantities such that, after freezing, pellets with a diameter of 4 to 7 mm are obtained.

[0017] When the inventors reproduced the method of US6428833, they found that the product appearance was overly light. Rather than a conventional dark coffee colour, the pellets were light, creamy or beige in colour. This did not meet with consumer expectations.

[0018] Accordingly, it is an object of the present invention to provide a freeze-dried coffee tablet that addresses the problems of the prior art, whilst maintaining a suitable colour profile, or at least provides a commercially viable alternative thereto. According to a first aspect there is provided a method for the manufacture of a coffee article having a mass of at least 0.5 g, the method comprising:

[0019] (i) providing an unfoamed, aqueous coffee extract comprising from 30 to 40wt% soluble coffee solids;

[0020] (ii) filling the unfoamed, aqueous coffee extract into a mould;

[0021] (iii) freezing the unfoamed, aqueous coffee extract in the mould to form a frozen coffee body at a temperature below -30°C;

[0022] (iv) releasing the frozen coffee body from the mould;

[0023] (v) annealing the released frozen coffee body at a temperature in a range of from -15 to -28eC for at least 20 minutes,

[0024] (vi) subliming water from the annealed frozen coffee body to form a coffee article.

[0025] The present disclosure will now be described further. In the following passages different aspects / embodiments of the disclosure are defined in more detail. Each aspect / embodiment so defined may be combined with any other aspect / embodiment or aspects / embodiments unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0026] Through this combination of steps the inventors have been able to provide a tablet-like coffee product which has a wide range of advantages. These include: sufficient solubility performance; a sufficient strength and integrity (from a higher density) such that it can be sold and transported without damage; an attractive darker appearance than expected for a just-frozen product; a surface structure that can retain its configuration; and an improved aroma profile. The improved appearance and aroma result from the annealing process.

[0027] The method results in the production of a coffee article having a mass of at least 0.5 g. Preferably the coffee article has a mass of at least 2 g, preferably from 2 g to 20 g, more preferably from 2.5 to 5g. These sizes are enough that the coffee article can be used as a single serve article to provide a beverage by dissolving a single coffee article. Typically a mug of coffee ~250ml will be prepared with around 3g of coffee.

[0028] The method comprises providing an unfoamed, aqueous coffee extract comprising from 30 to 40wt% coffee solids. Aqueous coffee extracts are well known in the art and are typically prepared by the extraction of roasted coffee beans with hot water and / or steam in a multistage industrial process. Depending on the process the coffee extract may need to be concentrated before use. However, it is normally the case that conventional freeze-drying is performed with a higher solids coffee extract (such as 45-55wt%). This is because it is generally desirable to have less water present, since water removal is more expensive as part of the freeze-drying process than when performing an evaporation step on the aqueous coffee extract.

[0029] The inventors have found that it is necessary to form the coffee article using an aqueous coffee extract comprising from 30 to 40wt% coffee solids. This represents a balance between having enough solids that the freeze-drying step is not unduly expensive, and having a good solubility of the final article. The lower the solids content the larger the proportion of voids formed in the final product by the removal of ice crystals. Preferably the coffee extract comprises from 32 to 38wt%, more preferably 34 to 36wt% and most preferably about 35wt%.

[0030] For the avoidance of doubt, coffee solids are the material which remains after total removal of water from the extract. Therefore, a 35wt% solids extract contains 65wt% water. The coffee solids are primarily soluble coffee material obtained by extraction processes, but there will also be insoluble material, including coffee oils and roast and ground coffee particles. The oil and particles may be present as a result of the extraction process or they may be added as a supplement. Preferably the aqueous coffee extract comprises from 1 to 10 wt.% coffee oil, preferably from 1 .5 to 5 wt.%. Preferably the aqueous coffee extract comprises at least 3 wt.% roast and ground coffee particles, preferably 5 to 20wt%. The presence of oil and / or particles improves the final beverage flavour.

[0031] Preferably the aqueous coffee extract does not comprise any non-coffee material other than water. That is, the extract is preferably devoid of any further ingredients such as sugar, sweeteners, Whiteners, creamers or the like and, in particular, is devoid of binders. Similarly, it is preferred that the final coffee article consists of coffee from the original coffee extract.

[0032] The coffee extract is unfoamed. That is, the coffee extract does not have a foamed or bubble-containing structure. Rather, it is provided without bubbles. The coffee extract is generally provided at atmospheric pressure into the mould, and therefore it preferably does not contain any more gas than would normally dissolve in water under such conditions. For the avoidance of doubt, preferably no gas is added prior to filling the extract into the mould.

[0033] The unfoamed, aqueous coffee extract is filled into a mould. It is necessary that the extract is a liquid at this stage so that it can readily fill the mould. Nonetheless, it is desirable that the extract is chilled to facilitate the freezing step and, accordingly, it is typically provided at 15 to -5eC, preferably 10 to -2eC (the coffee solids depress the freezing point so that the extract at these negative temperatures is still a liquid). Using an unfoamed liquid helps to ensure that the detail within the mould is all represented in the final product. Suitable moulds and filling mechanisms are well known in the food industry. The mould may be flexible aid demoulding of the frozen material. The mould size will be determined by the final product weight desired. The mould may be selected such that the coffee article is disc-shaped or shaped to resemble a coffee bean.

[0034] The method involves freezing the unfoamed, aqueous coffee extract in the mould to form a frozen coffee body at a temperature below -30eC. The freezing may be performed by direct cooling of the mould with a refrigerant or by placing the moulds into a freezer or cold room at a suitable temperature. The freezing needs to be performed to a sufficiently low temperature that the frozen bodies do not stick to the mould. Preferably this step is performed to form a frozen coffee body at a temperature of from -32 to -50°C, preferably -40 to -45°C.

[0035] After the extract is frozen there is a step of releasing the frozen coffee body from the mould. This may be achieved by inverting the moulds and / or pushing the bodies from the moulds and / or distorting the moulds. The released frozen coffee bodies can be collected in trays or on a belt.

[0036] The released frozen coffee body is then annealed at a temperature in a range of from -15 to -28eC for at least 20 minutes. Preferably the annealing step is performed at a temperature of from -20 °C to -28 °C, preferably -22 °C to -26 °C. Preferably the annealing step is performed for 30 minutes to 5 hours, preferably 1 to 2 hours. This temperature range means that the frozen coffee bodies have to be warmed or allowed to warm after the preceding freezing step. Preferably the annealing step is performed at atmospheric pressure.

[0037] It is preferred that there is a single annealing step (v) between the release step (iv) and the subliming step (vi). That is, there is a single step in which the frozen coffee body is allowed to warm before having the water sublimed away, rather than having the temperature of the frozen coffee body repeatedly cycled.

[0038] During the annealing step the frozen coffee bodies typically remain on the trays or on a belt. The frozen coffee bodies are preferably not subjected to any additional agitation or coating steps. In this way the surface of the final tablet consists of coffee from the coffee extract. Finally there is a step of subliming water from the annealed frozen coffee body to form a coffee article. This is a conventional freeze-drying step and suitable vacuum and heating conditions and apparatus are well known in the art.

[0039] It may be possible to directly freeze-dry the annealed frozen coffee bodies or, alternatively, it may be desirable to further cool them before the sublimation starts. Since sublimation involves adding heat under a low pressure it may be desirable to start with a colder coffee body to prevent localised melting. Preferably a further cooling step involves cooling the annealed frozen coffee bodies to a temperature below -30eC, preferably -32 to -50°C, preferably -40 to -45°C before the step of subliming water away.

[0040] Preferably the coffee article has a surface colour of 18 to 30 La. Preferably from 20 to 28 La. “La” colour measurements can be performed using a Dr Lange LK 100 unit (Hach-Lange GmbH). The standard operating procedure of the unit involves spreading a layer of the sample flat in a standard sample holder before measurement.

[0041] Preferably the coffee article has a density of at least 1 .2 g / cm3, preferably 1 .3 to 1 .5g / cm3. This density reflects the lack of a pre-foaming step.

[0042] Without wishing to be bound by theory, it is believed that the colour of the freeze-dried product is determined by its surface structure and, specifically in this case, the surface pore configuration. It is well known in the art that the colour of freeze-dried coffee can be changed by foaming the coffee extract before drying. An increased number of larger surface pores gives rise to a darker coloured product via a light scattering phenomenon. It is generally understood that the surface of conventional freeze-dried granules are dominated by pores derived from gas bubbles and this is why changing the foam structure is generally used to achieve darker powders.

[0043] For the present unfoamed coffee extract there is no gas-bubble structure to help darken the appearance of the product. The inventors have now found that they can also affect the surface appearance by controlling the ice-crystal surface pores on the freeze-dried coffee surface. Whereas ice pores are generally smaller than the gas bubbles in the product and therefore less involved in the light scattering, the inventors have found that a slow cooling or annealing step can help the ice crystals grow and mature such that there is a meaningful effect on the colour. The inventors have found that performing the cold-annealing step allows the provision of a product that is darker than normally achievable using a conventional freeze-drying, avoiding the need for new equipment or a change in procedure. Furthermore, there is an improved aroma content which seems to be the surprising result of the annealing step.

[0044] Fioures

[0045] The invention will now be described further in relation to the following non-limiting figures, in which:

[0046] Figure 1 shows an illustrative temperature profile during the cooling of the present invention. In particular, this shows an embodiment in which the chilled coffee extract is a liquid poured into the moulds, frozen (with phase change ~ -6eC) to -50eC, followed by annealing at a raised temperature to ~ -25eC.

[0047] The invention will now be described further with reference to the following non-limiting examples.

[0048] Chilled liquid coffee extract at 35% concentration was poured into food-grade open moulds. The filled mould was then placed in a cold room maintained at -50eC until the coffee was fully frozen. Remaining in the cold room, the frozen coffee pieces were removed from the mould. Half of the frozen pieces were then transferred to a cabinet freezer controlled at -20eC for 1 hour. The other half of frozen pieces were kept at -50eC.

[0049] After the period of 1 hour, all the frozen pieces were placed in a freeze dryer tray and dried with a gentle and slow profile.

[0050] The samples that underwent the annealing step showed interesting surface finishes with dark patches resembling stripes. This irregularity was appealing and gave an artisanal, crafted appearance. The annealed pieces were also slightly darker in colour.

[0051] The dark appearance is believed to be caused by a change in ice crystal structure during the annealing process. The observed dark patches could correspond to respective regions of varying ice growth. For example, a sharp contrast in colour could be sign along the boundary between regions where ice crystals tended to align in different directions.

[0052] The term “comprising” as used herein can be exchanged for the definitions “consisting essentially of” or “consisting of”. The term “comprising” is intended to mean that the named elements are essential, but other elements may be added and still form a construct within the scope of the claim. The term “consisting essentially of” limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the claimed invention. The term “consisting of” closes the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith.

[0053] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.

[0054] For the avoidance of doubt, the entire contents of all documents acknowledged herein are incorporated herein by reference.

Claims

Claims1 . A method for the manufacture of a coffee article having a mass of at least 0.5 g, the method comprising:(i) providing an unfoamed, aqueous coffee extract comprising from 30 to 40wt% coffee solids;(ii) filling the unfoamed, aqueous coffee extract into a mould;(iii) freezing the unfoamed, aqueous coffee extract in the mould to form a frozen coffee body at a temperature below -30eC;(iv) releasing the frozen coffee body from the mould;(v) annealing the released frozen coffee body at a temperature in a range of from -15 to -28eC for at least 20 minutes,(vi) subliming water from the annealed frozen coffee body to form a coffee article.

2. The method according to claim 1 , wherein the coffee article has a mass of at least 2 g, preferably from 2 g to 20 g.

3. The method according to claim 1 or claim 2, wherein the coffee article has a surface colour of 18 to 30 La.

4. The method according to any preceding claim, wherein the coffee article is discshaped or shaped to resemble a coffee bean.

5. The method according to any preceding claim, wherein the coffee article has a density of at least 1 .2 g / cm3, preferably 1 .3 to 1 .5g / cm3.

6. The method according to any preceding claim, wherein the aqueous coffee extract comprises from 1 to 10 wt.% coffee oil, preferably from 1 .5 to 5 wt.%.

7. The method according to any preceding claim, wherein the aqueous coffee extract comprises at least 3 wt.% roast and ground coffee particles, preferably 5 to 20wt%.

8. The method according to any preceding claim, wherein the aqueous coffee extract does not comprise any non-coffee material other than water.

9. The method according to any of claims 8 to 12, wherein step (iii) is performed to form a frozen coffee body at a temperature of from -32 to -50°C, preferably -40 to -45°C.

10. The method according to any preceding claim, wherein the annealing step is performed at a temperature of from -20 °C to -28 °C, preferably -22 °C to -26 °C.11 . The method according to any preceding claim, wherein the annealing step is performed for 30 minutes to 5 hours, preferably 1 to 2 hours.

12. The method according to any preceding claim, wherein the annealing step is performed at atmospheric pressure.

13. The method according to any preceding claim, wherein the step of subliming water from the annealed frozen coffee body to form a coffee article involves first cooling the annealed frozen coffee body to a temperature below -30eC, preferably -32 to -50°C, preferably -40 to -45°C.

14. The method according to any preceding claim, wherein a gas is not added prior to filling the extract into the mould.

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