TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method of preparing a beer concentrate, said method comprising: a) introducing a beer into a closed system while leaving a headspace; and b) producing a decarbonated beer by contacting the gas phase that is present in the headspace with a carbon dioxide capturing (CDC) material to remove dissolved carbon dioxide from the beer, said CDC material comprising a metal hydroxide selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and combinations thereof; c) producing a beer concentrate by removing water from the decarbonated beer by means of freeze concentration and/or membrane filtration; wherein the gas phase is contacted with the CDC material by continuously removing gas phase from the headspace, transporting the removed gas phase to a chamber comprising the CDC material, and returning decarbonated gas phase from said chamber to the headspace.

The present method effectively removes carbon dioxide before the concentration step c) and thereby improves the efficacy of that concentration step.

BACKGROUND OF THE INVENTION

Beer is a universally popular beverage, consumed worldwide. Beer is commonly produced by a process that comprises the following basic steps: mashing a mixture of grain and water to produce a mash; separating the mash in wort and spent grain; boiling the wort in the presence of, to produce a boiled wort; fermenting the boiled wort with live yeast to produce a fermented wort; subjecting the fermented wort to one or more further process steps (e.g. maturation and filtration) to produce beer; carbonating the beer; and packaging the carbonated beer in a sealed container, e.g. a bottle, can or keg. During fermentation of the boiled wort, carbon dioxide is produced by the yeast. A part of the carbon dioxide produced remains in the beer after fermentation.

At home consumers typically drink beer from a bottle or a can. Disadvantages of beer in bottles and cans experienced by these consumers are the space they take up during storage and transportation, and their considerable weight. These disadvantages can be overcome by providing consumers with a beer concentrate that can be used at home to prepare a ready-to- drink beer by mixing the beer concentrate with carbonated water in a dispensing device and dispensing the beer therefrom.

It is known in the art to produce beer concentrates using freeze concentration. Freeze concentration technology aims at solely removing water, in the form of ice, from a given aqueous solution. The basic principle of freeze concentration is the simple fact that the structure of an ice crystal does not leave space to include impurities. The growing ice crystals will reject the existing dissolved components in a solution. When an aqueous solution is cooled down, the first crystallizing component will be ice. By operating at temperatures and concentrations just prior to reaching the eutectic point of a certain solution, ice will remain the only crystallizing component while all other dissolved components will stay in the solution.

Freeze concentration offers the advantage that volatile components, such as volatile flavour molecules, are retained in the concentrate. Furthermore, freeze concentration does not involve any heating steps that may have an adverse effect on product quality.

US 3,193,395 describes a process for concentrating beer, comprising:

• injecting into said beer a liquid polydimethylsiloxane antifoam agent,

• cooling the beer containing the antifoam agent to form a crystal slurry of ice in a mother liquor beer concentrate,

• subjecting said slurry to sub-atmospheric pressure, thereby inducing removal of substantially all of the CO2 from said slurry,

• passing said slurry into a confined zone wherein said ice crystals are passed in a compact mass into a body of crystal melt formed by melting said ice crystals in a downstream portion of said zone while melt is displaced into said crystal mass and mother liquor is withdrawn as a concentrated solution from an upstream portion of said zone.

In the US patent it is mentioned that evolution of carbon dioxide during freeze concentration adversely affects the efficiency of this concentration method. It is also known in the art to produce beer concentrates using membrane filtration (e.g. nanofiltration or reverse osmosis).

WO 2016/130607 describes a method for forming a concentrate from an alcoholic beverage, comprising:

• providing an alcoholic beverage including a solids concentration of 20% or less, and alcohol concentration of 30% or less, and water;

• subjecting the alcoholic beverage to a membrane process by which at least some water and alcohol pass through a membrane to be part of a permeate and other components of the alcoholic beverage do not pass through the membrane and are part of a retentate;

• freezing water in the retentate to form ice; and

• removing ice from the retentate to reduce water content and form a beverage concentrate having a solids concentration of at least 30% and an alcohol concentration of 20% or less.

WO 2018/100049 describes a method for preparing a beer concentrate, comprising the steps of: a) subjecting beer to a first concentration step comprising nanofiltration or reverse osmosis to obtain a retentate and a permeate comprising alcohol and volatile flavour components; b) subjecting the permeate comprising alcohol and volatile flavour components to a next concentration step comprising freeze concentration, fractionation or reverse osmosis, to obtain a concentrated fraction comprising alcohol and volatile flavour components, and a leftover fraction; c) subjecting the leftover fraction to a fractionation, an adsorption or a freeze concentration to obtain a second fraction comprising alcohol and volatile flavour components and a second leftover fraction.

The beer, permeate or left-over fraction may be decarbonated by exposure to a vacuum. Since such decarbonation method has the drawback that apart from carbon dioxide, volatile flavour components are also removed from the liquid, such decarbonation is preferably performed over a membrane, whereby beer, cider, permeate or left-over fraction is directed over one side of the membrane, while a vacuum or nitrogen stream is provided at the other side of the membrane, thereby removing carbon dioxide from the liquid through the membrane. Decarbonation of the beer, cider, permeate or left-over fraction is especially preferred when the beer, cider, permeate or left-over fraction is subjected to freeze concentration.

It is known in the art to remove carbon dioxide from gas mixtures using so called carbon dioxide scrubbers. These carbon dioxide scrubbers employ different types of carbon dioxide capturing components, such as amines (e.g. monoethanolamine), calcium oxide, sodium hydroxide, lithium hydroxide and activated carbon.

Yoo et al. (Carbon dioxide capture capacity of sodium hydroxide aqueous solution, Journal of Environmental Management 114 (2013) 512 — 519) describes a study in which aqueous NaOH solutions (1 %, 3% and 5%) were applied as an absorbent to capture carbon dioxide from a feed gas. The feed gas contained approximately 31.5% CO2. The amount of CO2 absorbed in the solution (at 25 °C) was slightly less than the theoretical value.

WO 2014/169378 describes a method of producing a fermented beverage comprising:

• fermenting the beverage in a fermentation container to produce a headspace comprising carbon dioxide gas and volatile flavour compounds; and

• recirculating the headspace over carbon dioxide absorbing material to selectively remove carbon dioxide.

WO 2020/104674 describes a process for obtaining a concentrated flavour mixture from a malt-based beverage, the process comprising:

• providing a malt-based fermented liquid;

• subjecting the malt-based fermented liquid to a CO2 or N2-stripping step or, at least partially, degassing the malt-based liquid, thereby creating a gas stream comprising volatile flavour components;

• collecting the gas stream comprising volatile flavour components; and

• separating, by a carbon dioxide or N2 scrubber, at least partially, the CO2 or N2 in the gas stream from the volatile flavour components, obtaining a concentrated volatile flavour fraction;

• collecting said volatile flavour fraction and packaging the volatile flavour fraction.

SUMMARY OF THE INVENTION

The inventors have developed a method for the preparation of beer concentrates using freeze concentration and/or membrane filtration, in which the beer is decarbonated prior to the concentration step by removing carbon dioxide via the beer’s headspace. More particularly, the carbon dioxide is removed from the beer by contacting the gas phase that is present in the headspace with a carbon dioxide capturing material that contains metal hydroxide selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and combinations thereof. It was unexpectedly found that in this manner carbon dioxide can be removed from beer very effectively.

Accordingly, the present invention relates to a method of preparing a beer concentrate, said method comprising: a) introducing beer into a closed system while leaving a headspace, said beer containing 80-99 wt.% water, 0-16 wt.% ethanol and 0.5-8 mg/g dissolved carbon dioxide; and b) producing a decarbonated beer by contacting the gas phase that is present in the headspace with a carbon dioxide capturing (CDC) material to remove dissolved carbon dioxide from the beer, said CDC material comprising a metal hydroxide selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and combinations thereof; c) producing a beer concentrate by removing water from the decarbonated beer by means of freeze concentration and/or membrane filtration; wherein the gas phase is contacted with the CDC material by continuously removing gas phase from the headspace, transporting the removed gas phase to a chamber comprising the CDC material, and returning decarbonated gas phase from said chamber to the headspace.

The method of the present invention enables efficient production of beer concentrates by minimising the detrimental effect of carbon dioxide on the concentration step. The presence of carbon dioxide adversely affects freeze concentration as its presence lowers the temperature at which the water starts crystallising and thereby decreases separation efficiency. Carbon dioxide also has a negative effect if the beer is concentrated by means of nanofiltration or reverse osmosis. These membrane filtration techniques require the application of pressure and presence of carbon dioxide may result in a beer concentrate that contains a substantial amount of dissolved carbon dioxide which complicates handling of this concentrate.

Surprisingly, in the present method both the rate at which carbon dioxide is removed from the gas phase by the CDC material and the rate at which carbon dioxide in the gas phase is replenished from the beer are so high that carbon dioxide that remains in the beer after fermentation can be removed very rapidly therefrom. The chemical reactions involved in the capture of carbon dioxide by the metal hydroxide in the CDC material can be described as follows:

• 2NaOH + CO ₂ Na ₂ CO ₃ + H ₂ O; Na ₂ CO ₃ + H ₂ O + CO ₂ 2NaHCO ₃

• 2KOH + CO ₂ K ₂ CO ₃ + H ₂ O; K ₂ CO ₃ + H ₂ O + CO ₂ 2KHCO ₃ • Ca(OH) ₂ + CO ₂ CaCO ₃ + H ₂ O; CaCO ₃ + H ₂ O + CO ₂ Ca(HCO ₃ ) ₂

• Mg(OH) ₂ + CO ₂ MgCO ₃ + H ₂ O; MgCO ₃ + H ₂ O + CO ₂ Mg(HCO ₃ ) ₂

To capture 1 kg of CO2, theoretically the following amounts of metal hydroxide are needed:

NaOH 0.91 kg

KOH 1 .23 kg

Ca(OH) ₂ 0.84 kg

Mg(OH) ₂ 0.66 kg

The present concentration method offers the additional advantage that it enables removal of carbon dioxide with minimum loss of flavour volatiles. The method can suitably be used to concentrate both alcoholic and non-alcoholic beers.

The invention also relates to a beer concentrate that is obtained by the concentration method described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a freeze concentration system that can be used to prepare a beer concentrate in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, a first aspect of the invention relates to a method of preparing a beer concentrate, said method comprising: a) introducing beer into a closed system while leaving a headspace, said beer containing 80-99 wt.% water, 0-16 wt.% ethanol and 0.5-8 dissolved carbon dioxide; and b) producing a decarbonated beer by contacting the gas phase that is present in the headspace with a carbon dioxide capturing (CDC) material to remove dissolved carbon dioxide from the beer, said CDC material comprising a metal hydroxide selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and combinations thereof; c) producing a beer concentrate by removing water from the decarbonated beer by means of freeze concentration and/or membrane filtration; wherein the gas phase is contacted with the CDC material by continuously removing gas phase from the headspace, transporting the removed gas phase to a chamber comprising the CDC material, and returning decarbonated gas phase from said chamber to the headspace.

The term “beer” as used herein refers to a yeast fermented malt beverage that has optionally been hopped.

The term “alcohol-free beer” as used herein, unless indicated otherwise, refers to a beer having an ethanol content of 0-1 % ABV.

The term “beer concentrate” as used herein refers to beer from which water has been removed, e.g. by nanofiltration, reverse osmosis, forward osmosis and/or freeze concentration.

The term “membrane filtration” as used herein refers to a separation method in which molecules are separated by passing a single feed stream through a filtration membrane that separates it into two individual streams, known as the permeate and the retentate, said filtration membrane having a molecular weight cut-off of not more than 500 Da.

The beer that is decarbonated in the present method preferably contains 1-6 mg/g, more preferably 1.5-5 mg/g and most preferably 1.8-4 mg/g dissolved carbon dioxide.

In the present method, preferably at least 0.5 g/L, more preferably at least 1 g/L and most preferably 1.5-5 g/L of the dissolved carbon dioxide is removed from the beer.

In the decarbonation step b) of the present method preferably at least 25%, more preferably at least 35% and most preferably at least 40% of the dissolved carbon dioxide is removed from the beer.

As mentioned above, the present method offers the advantage that it enables removal of carbon dioxide with minimum loss of flavour volatiles. Acetate esters, such as ethyl acetate, isoamyl acetate and 3-methylbutyl acetate are examples of flavour volatiles that are typically present in beer. According to a particularly preferred embodiment, decarbonation step b) reduces the combined concentration of ethyl acetate, isoamyl acetate and 3-methylbutyl acetate in the beer with not more than 50 wt.%, more preferably with not more than 25 wt.%, even more preferably with not more than 15 wt.% and most preferably with not more than 10 wt.%. The CDC material that is employed in the present method preferably contains at least 30%, more preferably at least 50% even more preferably at least 80% and most preferably at least 90% by weight of dry matter of the metal hydroxide.

The CDC material may be a solid material, such as a granulate. Alternatively, the CDC material may be a liquid such as an aqueous solution of the metal hydroxide. Most preferably, the CDC material employed in the present method is an aqueous solution of the metal hydroxide.

In case the CDC material is an aqueous solution of the metal hydroxide, the aqueous solution preferably contains at least 10 g/L, more preferably at least 20 g/L and most preferably 30-300 g/L of dissolved metal hydroxide selected from sodium hydroxide, potassium hydroxide and combinations thereof.

According to a particularly preferred embodiment, the aqueous solution contains at least 10 g/L, more preferably at least 20 g/L and most preferably 30-300 g/L of dissolved sodium hydroxide.

The gas phase can be contacted with the aqueous solution of metal hydroxide by passing it through the aqueous solution or by passing it over the surface of the aqueous solution. Most preferably, the gas phase is contacted with the aqueous solution of metal hydroxide by passing it through the aqueous solution of metal hydroxyde.

In an alternative embodiment the CDC material is a granulate, more preferably a granulate containing calcium hydroxide. Preferably, the granulate contains at least 50 wt.%, more preferably at least 60 wt.% most preferably at least 70 wt.% calcium hydroxide.

The granulate preferably contains at least 80 wt.% of granules having a diameter in the range of 0.5-10 mm, more preferably in the range of 0.7-8 mm and most preferably of 1-7 mm.

Advantageously, the granulate further contains 1-30 wt.%, more preferably 1.5-20 wt.% and most preferably 2-10 wt.% of metal hydroxide selected from sodium hydroxide, potassium hydroxide and combinations thereof. The present method can suitably be used to decarbonate and concentrate both alcoholic and non-alcoholic beers.

In one embodiment of the present method is used to decarbonate and concentrate a nonalcoholic beer containing 92-99 wt.% water, 0-1 wt.% ethanol and 0.5-8 mg/g dissolved carbon dioxide. Even more preferably, the non-alcoholic beer contains 93-98 wt.% water, 0- 0.5 wt.% ethanol and 1-6 mg/g dissolved carbon dioxide.

The non-alcoholic beer may be produced by a method that comprises preparing the beer by subjecting a wort to yeast fermentation to produce an alcoholic beer having an ethanol content of 3-12 wt.%, followed by removal of ethanol to produce the non-alcoholic beer.

Alternatively, the non-alcoholic beer may be produced by a method that comprises preparing the non-alcoholic beer by subjecting a wort to a restricted yeast fermentation.

In another embodiment the present method is used to decarbonate and concentrate an alcoholic beer containing 80-95 wt.% water, 3-16 wt.% ethanol and 0.5-8 mg/g dissolved carbon dioxide. More preferably, the alcoholic beer contains 82-92 wt.% water, 4-12 wt.% ethanol and 1-6 mg/g dissolved carbon dioxide.

In yet another embodiment of the invention the present method is used to decarbonate an alcoholic beer and ethanol is removed from the decarbonated alcoholic beer to produce a decarbonated non-alcoholic beer before removing water from the decarbonated nonalcoholic beer to produce the beer concentrate. Removal of carbon dioxide prior to removal of ethanol facilitates ethanol removal, especially when such ethanol removal is carried out on an industrial scale using, for instance, vacuum distillation.

The inventors have found that the present method is capable of removing dissolved carbon dioxide from beer at a surprisingly fast rate. The rate of removal decreases over time as carbon dioxide is bound by the metal hydroxide Typically, the dissolved carbon dioxide is removed from the beer in step b) at an initial rate of at least 50 g/hl/hr. More preferably, the dissolved carbon dioxide is removed at an initial rate of at least 100 g/hl/hr, even more preferably at a rate of at least 150 g/hl/hr, most preferably at a rate of at least 200 g/hl/hr. Here the “initial rate” refers to the rate at which carbon dioxide is removed when the the gas phase that is present in the headspace is first contacted with the CDC material. According to a particularly preferred embodiment, the decarbonation step b) of the present method is carried out in a closed system. In accordance with this embodiment, during step b), the beer, the headspace and the CDC material are all present within the same closed system. In other words, in such a closed system the driving force for the removal of dissolved carbon dioxide from the beer is the absorption of carbon dioxide by the CDC material and not a vacuum that is created by removing gas phase from the system.

The decarbonation step b) is preferably carried out at a temperature in the range of 0-50°C, more preferably in the range of 5-35°C, and most preferably in the range of 8-30°C.

According to a particularly preferred embodiment, the decarbonation step b) is carried out at a pressure in the range of 50-400 kPa, more preferably in the range of 90-300 kPa, most preferably in the range of 95-150 kPa.

In the concentration step c), preferably at least 70%, more preferably at least 75% and most preferably 80-90% of the water contained in the decarbonated beer is removed.

In one embodiment of the present invention, the decarbonated beer is concentrated by means of membrane filtration. Examples of membrane filtration that may suitably be employed in the present method include nanofiltration, reverse osmosis and forward osmosis. Preferably, the membrane separation employed in the present method is reverse osmosis and/or nanofiltration. Most preferably, the present process employs reverse osmosis to remove water.

Membrane filtration of the decarbonated beer is preferably carried out at a temperature in the range of -2°C to 40°C, more preferably in the range of 3-22°C.

The pressure employed during membrane filtration is preferably in the range of 6 to 80 bare, more preferably in the range of 10 to 75 bar, and most preferably in the range of 15 to 70 bar.

In a preferred embodiment, the membrane filtration is carried out with a membrane having a magnesium sulphate rejection of 80-100%, more preferably 90-100% and most preferably 95-100% when measurement is carried out using 2,000 mg/L aqueous magnesium sulphate solution at 0.48 MPa, 25°C and 15% recovery. In a further preferred embodiment, membrane filtration is carried out using a membrane with a glucose rejection of 80-100%, more preferably 90-100% and most preferably 95-100% when measurement is carried out using 2,000 mg/L aqueous glucose solution at 1.6 MPa, 25°C and 15% recovery.

According to a particularly preferred embodiment, membrane filtration is carried out by means of reverse osmosis or forward osmosis using a membrane with a sodium chloride rejection of 80-100%, more preferably 90-100% and most preferably 95-100% when measurement is carried out using 2000 mg/L sodium chloride solution at 10.3 bar, 25°C, pH 8 and 15% recovery.

In another embodiment, the decarbonated beer is concentrated by means of freeze concentration. In this method, water is withdrawn from the beer by the phase transformation from liquid to ice crystal. This process has mainly three stages: crystallization of water, growth of water crystals and separation of water crystals, performed in specially designed equipment for each purpose. For instance, scraped-surface heat exchanger, growth recrystallizer and separation wash column, respectively. Basically, the temperature of the alcohol-free beer is reduced to a value such as to freeze at least a part of its water without reaching the eutectic point of the mixture. When the ice crystals are sufficiently large, e.g. not smaller than 100 pm in diameter, said crystals can be separated from the concentrated liquid for example using wash-columns. Because of the low process temperature, lower than 0 °C, thermal degradation and aroma losses by evaporation are avoided.

According to a preferred embodiment, freeze concentration of the decarbonated beer is carried out in a plant comprising a scraped surface heat exchanger and a separation unit. The separation unit preferably is a separation wash column or a separation filter (e.g. a vacuum belt filter). Most preferably, the separation unit is a wash column. According to a particularly preferred embodiment, the plant further contains a stirred crystallizer that is located downstream of the scraped surface heat exchanger and upstream of the separation unit.

Figure 1 shows a freeze concentration apparatus comprising a feed tank (1), a cooling system (2), a crystal growth unit (3), a separation unit (4) and a melter (5).

Beer is fed from the feed tank (1) into the cooling system (2), in this embodiment a scraped surface heat exchanger. Cooled beer is fed from the cooling system (2) to the crystal growth unit (3), in this embodiment a stirred crystallizer. A slurry containing ice crystals is fed from the crystal growth unit (3) to the separation unit (4), in this embodiment a washing column. Beer concentrate is removed from the separation unit (4). A slurry consisting of water and ice crystals is also removed from the top of the separation unit (4) and heated in the melter (5) to melt the ice crystals. Part of the melt water so produced is recirculated to the separation unit (4), while the other part is removed as essentially pure water.

In some embodiments, a single pass through the freeze concentration apparatus (1) will produce a beer concentrate of suitable quality. However, in other embodiments, the beer concentrate may be recirculated from the separation unit (20) to the cooling system (10) to produce a more concentrated beer concentrate.

In the present method, freeze concentration of the decarbonated beer preferably comprises the steps of:

(a) cooling the decarbonated beer to freezing point in a scraped surface heat exchanger;

(b) introducing the cooled beer into a stirred crystallizer to produce a slurry containing ice crystals;

(c) returning the slurry to step (a) until the ice crystals in the slurry have reached a mass weighted average diameter of 100 pm or more; and

(d) removing ice crystals from the slurry in a separation unit to produce a liquid concentrate.

Preferably, the slurry has a temperature in the range of -1 °C to -12°C, more preferably in the range of -2°C to -10°C at the beginning of step (d).

The total residence time in the stirred crystallizer preferably exceeds 10 minutes, more preferably it is in the range of 15 minutes to 3 hours.

The invention also relates to the beer concentrate obtained by the concentration method as described herein before.

The invention is further illustrated by the following non-limiting examples.

EXAMPLES

Example 1

A lager type beer (698 L, 7.17 % alcohol ABV, containing 4.45 g/L CO2) was kept at -1 °C and subjected to decarbonation by continuously leading the headspace through a solution of 15 % w/w NaOH (150 L, 15°C) for a total of approximately 6 hours, during which time the NaOH solution was stirred.

The CO2 content of the beer was measured by withdrawing samples at regular intervals. The results are shown in Table 1 .

Table 1

The composition of the beer was analysed before and after decarbonation. The results are shown in Table 2.

Table 2

Example 2

A beer concentrate is produced by subjecting both the lager beer and the decarbonated lager beer of Example 1 to freeze concentration using the procedure that is disclosed in US 3,193,395, except that no antifoam is added to the beers prior to freeze concentration. The apparatus that is used for freeze concentration of the beers is schematically depicted in Figure 1.

Beer is supercooled in a scraped surface heat exchanger and the supercooled beer is subsequently introduced in a stirred crystallizer to form a slurry of ice crystal in a mother liquor.

This slurry is fed into a washing column in which the crystals are passed in a compact mass into a body of melt water which is displaced back into the crystal mass. The washing column includes an upstream concentrate removal zone, a middle reflux zone, and a downstream ice crystal removal zone. Mother liquor is removed in the concentrate removal zone. A slurry consisting of water and ice crystals is removed in the ice crystal removal zone. The slurry of water that is removed from the washing column is heated to melt the ice crystals. A portion of the melt water is withdrawn and the remainder is forced back into the crystal mass in the reflux zone.

It is found that the decarbonated lager beer can be concentrated without problems to possible to 25 weight percent of its original weight. However, the lager beer that has not been decarbonated cannot be concentrated as easily as a result of carbon dioxide evolving from the mother liquor in the purification column.

Example 3

A beer concentrate is produced by subjecting both the lager beer and the decarbonated lager beer of Example 1 to reverse osmosis using the procedure that is disclosed in WO 84/03102.

The beers are recycled through the reverse osmosis apparatus until the volume of the retentates has been reduced to 20% of the original volume.

It is found that in case the lager beer has not been decarbonated prior to reverse osmosis, recovery of the retentate is complicated by the fact that carbon dioxide evolving from the retentate during depressurization causes excessive foaming.