HK1079235B - Apparatus for improving the bittering of the beer - Google Patents

Description

Device for improving bitter taste of beer

This application is a divisional application of the chinese patent application having application number 01810850.4 (corresponding to the international application having application number PCT/US 01/20370), and claims the right of US provisional patent application 60/215,408, filed on 30/6/2000.

Technical Field

The present invention relates to improvements in bittering, foam improving and light stabilising products prepared from hop extracts and used in beer, and to methods of improving the bittering of these products, particularly for post-fermentation of beer.

Background

Many of the types of compounds present in hops that are useful to the brewer are a class of resinous compounds known as alpha-acids. These compounds are mainly responsible for the bitterness of beerThe flavours, which are converted into their isomerized forms during wort boiling, are known as iso-alpha-acids (formula 1). Iso-alpha-acids are bitter and also contribute to the foam quality of beer. Unfortunately, the conversion of alpha-acids to iso-alpha-acids in the wort kettle is rather insufficient and the iso-alpha-acids are also subsequently lost during fermentation of the wort. Thus, many brewers use certain forms of iso-alpha-acid preparations to easily add them to already fermented wort, thereby greatly increasing the initial alpha-acid utilization. These formulations can be efficiently manufactured from hops extracts, in particular by using fluid or supercritical carbon dioxide (CO)₂) The prepared extract is prepared, thereby providing an easy and cheap method for brewers to control the bitterness of beer. Although other formulations have been described, the conventional form of making iso-alpha-acids commercially useful is an aqueous solution of potassium salts, most commonly a slightly basic solution containing 30% of the actual iso-alpha-acid, either by weight (i.e. 300g/kg) or by weight/volume (i.e. 300 g/liter) of iso-alpha-acid.

A range of products are produced after addition of iso-alpha-acid solutions for post-fermentation bittering, wherein the iso-alpha-acids are converted into chemically reduced derivatives in different forms. These derivatives are also bitter, but to a different extent than iso-alpha-acids. The differences are also apparent in their ability to promote and modify the foam characteristics of beer. The industrially available, reduced form of iso-alpha-acids also has the property of resisting light-induced damage to the iso-alpha-acid molecule, a key factor in producing "accidental exposure" or "failure" in beer exposed to sunlight or some form of artificial light. Therefore, these chemically reduced compounds are also often used as the only bittering agent in beer formulations sold in clear glass bottles.

Three types of reduced iso-alpha-acids are commercially available. These are rho-iso-alpha-acids (alternatively written rho-iso-alpha-acids, formula 2), tetrahydroiso-alpha-acids (formula 3) and hexahydroiso-alpha-acids (formula 4). (see European Brewery Convention Manual of Good Practice Manual): Hops and Hop Products (Hop and Hop Products) (1997) published by Getranke-Fachverlag Hans carl, Nurnberg). Many different methods of preparation of these compounds have been described, but a common characteristic of the preparation of rho-iso-alpha-acids is that they are prepared by reduction of iso-alpha-acids using alkali metal borohydrides, typically sodium borohydride. On the other hand, tetrahydroiso- α -acids are always prepared by catalytic reduction using noble metal catalysts, usually palladium on carbon and hydrogen. Several different methods for producing tetrahydroiso- α -acids have been described and the starting material may be an α -acid, iso- α -acid or even a β -acid (forming a sequence-like compound of the α -acids but contributing little to beer in normal brewing). Hexahydroiso-alpha-acids are prepared by catalytic hydrogenation of rho-iso-alpha-acids, or by chemical reduction of tetrahydroiso-alpha-acids using alkali metal borohydrides. Tetrahydro-iso-alpha-acids are substantially more bitter than iso-alpha-acids; hexahydroiso-alpha-acids are also more bitter, but to a lesser extent, while rho-iso-alpha-acids are actually less bitter. Hexahydroiso-alpha-acids are generally considered to be the most effective in foam enhancement when compared on an equally bitter basis, followed by tetrahydroiso-alpha-acids. When compared in this manner, iso-alpha-acids and rho-iso-alpha-acids have similar, but substantially less, foam enhancing effects. The combination of bitterness and foam stability properties expressed in particular with tetrahydroiso- α -acids makes this form of reduced iso- α -acids particularly popular worldwide, as a partial replacement for normal iso- α -acids in the production of beer with improved foam characteristics, or for brewing light stable beer.

Since the p-iso-a-acid is sufficiently soluble in wort, it is often used by adding it directly to the kettle and to the beer. They are generally similar to iso-alpha-acids and are commercially available as a slightly basic aqueous solution with a concentration of about 30%. This solution and the corresponding rho-iso-alpha-acid solution are generally prepared by the following methods: diluted with deionized water and then injected into the beer, although it is possible to inject the product itself directly, provided that the completion step ensures sufficiently vigorous and rapid mixing. A concentrated form of this product is available in which the rho-iso-alpha-acid is also in the potassium salt form, but at a concentration of about 60%. Such compositions are described in our co-pending U.S. provisional patent application 60/215,408 filed on 30/6/2000. The aim of the present invention is to enable such concentrated and necessarily rather viscous preparations of p-iso- α -acids not only to be used as pan additives, but also as post-fermentation additives or even as in-line or direct pan wort additives by providing suitable equipment, which is currently not available designed to facilitate such applications.

Tetrahydro-, and especially hexahydroiso-alpha-acids are themselves less soluble than iso-alpha-acids and rho-iso-alpha-acids. For this reason, tetrahydroiso- α -acids are generally sold as 10% slightly basic aqueous solutions of their potassium salts. Similarly, the hexahydroiso-alpha-acid formulation is also sold as a relatively dilute solution, or a stabilizer such as propylene glycol must be added-a process that is considered unacceptable by most brewers. In the case of tetrahydroiso- α -acids, Ting described in U.S. patent 5,874,633 an improved manufacturing process whereby an aqueous alkaline solution with a concentration of up to 45% could be obtained. However, Ting also reports (lines 1-7 at column 4) that, although this effect is reversible, this single phase solution will quickly separate into two phases of significantly different composition at temperatures below 28 ℃. Thus, it is expected that in most cases, the solution of Ting will not be physically stable when stored at room temperature (and certainly not at the lower temperatures of the brewer's cellar or freezer). Clearly, the use of dilute or heterogeneous solutions is inconvenient and more expensive because John Paul Maye in us patents 5,583,262 and 5,624,701 describes anhydrous salt formulations of isomerized and reductively isomerized α -acids for this reason, which he claims can reduce costs because it greatly reduces the weight of material delivered to the consumer's requirements. However, it is clear that such anhydrous, crystalline or powdered substances containing less than 2% moisture (as indicated by Maye) require additional work to be done in brewing, as these materials must first be weighed and then dissolved in water before use. Furthermore, Maye's process for producing these salts requires one to start with an aqueous solution of iso-alpha-acids or reduced iso-alpha-acids and then substantially remove the water by any of a number of different methods. Another advantage of the present invention is to provide an apparatus by which these isomerized substances can be converted from their free acid state to highly concentrated stock solutions and readily usable forms without first preparing these relatively dilute solutions, which forms are conveniently used to bitter wort or beer in the manner we describe later. Many brewers prefer to add bitter compounds to their wort rather than to the subsequent beer, because in this way they can obtain some useful protection against gram positive spoilage bacteria whose activity is inhibited in the presence of all types of isomerized α -acids. However, it is not recommended to add the tetrahydro-or hexahydro-iso- α -acids directly to the brewery kettle, although this may often be done because the poor solubility of these compounds leads to excessive losses due to precipitation on the residue. Yet another advantage of the present invention is that the concentrated product we describe to make is also particularly suitable for addition to a kettle if brewing so requires,

in the preparation of light stable beer, it is common practice to use p-iso- α -acids and tetrahydroiso- α -acids or hexahydroiso- α -acids as bittering agents, usually because the production of beer with the correct bitterness but with an excessively stable foam is avoided. In U.S. Pat. No. 5,200,227, Guzinski and Stegink describe stable, single-phase, aqueous solutions of mixtures of two or more different types of isomerized α -acids. By preparing such mixtures, Guzinski and Stegink demonstrate that when made into aqueous alkaline solutions alone, the amount of tetrahydro-or hexahydroiso-alpha-acids that can be retained in solution will exceed the individual solubility limits of these types of compounds. This phenomenon is due to the unexpected co-dissolution effect. However, the authors also show that above certain limits, these mixtures are not physically stable and may form two phases, indicating (column 6, lines 30-34) "… … that there is an upper concentration limit at which the co-dissolution effect does not work. The practical limit is about 45 vol%, and the total iso-alpha acid concentration of the preferred formulation is 25 vol% to 40 vol%. Surprisingly, we have found that in fact we can easily prepare mixtures of different types of isomerized α -acids at much higher concentrations, which are still homogeneous, have fluidity, and are therefore suitable for the work of the present invention.

Brief description of the invention the present invention relates to an apparatus for injecting a concentrated preparation of one or more isomerized α -acids directly into wort or beer, the apparatus comprising:

(a) a heat source for heating each preparation of isomerized α -acids;

(b) a dosing unit for metering the flow of each isomerized α -acid preparation into the conduit; and

(c) from this conduit is fed an injector for injecting heated single or combined preparations of isomerized α -acids into wort or beer.

Further, each of the preparations of isomerized α -acids is provided directly from a disposable or recyclable container.

The apparatus of the present invention comprises two or more supplies of each of said preparations of isomerized α -acids, wherein each of said preparations of isomerized α -acids is selectively metered into said conduit from one of said supplies, wherein said supplies are contained in disposable or recyclable containers.

In addition, the apparatus of the present invention also includes a device or apparatus for mixing and diluting the concentrated preparation of isomerized α -acids with hot water prior to wort or beer injection.

It is an object of the present invention to provide an apparatus by means of which the advantages of products with a high concentration of iso-alpha-acids or reduced iso-alpha-acids, in particular tetrahydro-iso-alpha-acids, can be utilized in the following manner: these advantages are not compromised such as the need to first dissolve the solid compound in water prior to use. We have found that these products can be readily prepared by the following process: the natural acid and the iso-alpha-acid in resin form or the reduced iso-alpha-acid are taken, heated to flow and mixed with an approximately equimolar amount of a concentrated, preferably nearly saturated, alkali metal hydroxide solution. By this method we have found that we can prepare highly concentrated, substantially homogeneous and raw liquid forms of alkali metal salts of isomerized α -acids. It is also possible to add small amounts of water to standardise the product and/or to reduce its viscosity at room temperature so that it remains fluid, but not enough to cause substantial separation of the aqueous and resinous phases in practice. In view of the above observations by Ting in U.S. patent 5,874,633, it is particularly surprising that we can do so in the case of tetrahydroiso- α -acids.

Our invention also includes an apparatus for injecting isomerized and/or reductively isomerized α -acids directly into wort or beer, which apparatus serves as a feedstock for one or more highly concentrated preparations of the above-described isomerized or reductively isomerized α -acids, mixing these salts with demineralized or softened water and injecting the resulting dilute solution directly into beer. In another aspect of the invention, a device is provided for making highly concentrated homogeneous formulations of iso-alpha-acids, tetrahydro-iso-alpha-acids and hexahydroiso-alpha-acids in the form of alkali metal salts, most preferably as their potassium salts, having a fluid consistency which is conveniently improved by heating. Furthermore, we provide a preparation apparatus for a mixture of different forms of iso-alpha-acids and reduced iso-alpha-acids, including mixtures containing rho-iso-alpha-acids.

Brief Description of Drawings

The invention is further described with reference to the accompanying drawings, wherein like numerals describe like parts, and wherein:

FIG. 1 is a flow chart illustrating one embodiment of the present invention;

FIG. 2 is a flow chart illustrating another embodiment of the present invention; and

fig. 3 is a side bottom view in cross-section showing details of the dip tube of the preferred embodiment of the present invention.

Detailed description of the preferred embodiments

Figure 1 illustrates a preferred embodiment of the apparatus for practicing the invention. It is to be understood that in the description of the operation of the apparatus and elsewhere herein, the term "iso-concentrate" is to be taken as a concentrated, substantially homogeneous mixture of the alkali metal salts of iso-alpha-acids or reduced iso-alpha-acids or any mixture containing different types of these substances, wherein the total content of these substances is concentrated and has a concentration of greater than about 40% by weight as measured by HPLC. It will be further understood and apparent to those skilled in the art that in the operation of the above-described apparatus, other useful items such as valves, vents, gauges, etc. may be added which may better facilitate the operation of the apparatus without substantially altering the basic principles of the present invention.

The iso concentrate formulation is placed in a container 41. The container is equipped with a known device for heating the contents, which comprises a sleeve for circulating hot water, an electric heating jacket, an electric hot plate or an internal heating element. The larger second container 42 is similarly equipped and contains water, in particular deionized or demineralized water. The second container may advantageously be about 5-100 times larger than the container 41, with relative dimensions related to the target concentration of diluted iso-concentrate for wort or beer infusion, thereby providing sufficient water to dilute all iso-concentrate in the container 41. Hot water and iso-concentrate are continuously pumped by adjustable metering pumps 43 and 44 into a closed pressure vessel 45 equipped with known means for vigorously stirring the contents of the vessel. The iso-concentrate is rapidly dissolved in this container, optionally also equipped with known means for heating the contents, and the pump speed is adjusted to produce a solution of known concentration, preferably substantially below the solubility limit of the iso-concentrate at the set temperature. For example, for iso-alpha-acids or rho-iso-alpha-acids, a concentration of 2 to 20 wt% is suitable, whereas for less soluble tetrahydro-and hexahydroiso-alpha-acids, a concentration in the range of 0.5 to 5 wt% is suitable. The dilute solution in the vessel 45 is then injected into the beer, preferably into the wort or beer mains, through the nozzle 46, while the wort or beer is transferred between the vessels. Typically, the pump speed is set such that the iso-concentrate is transferred to the wort or beer in at least 70% of the time the wort or beer is passed through the wort or beer mains, and typically, but not necessarily, in the case of beer, the iso-concentrate is transferred to the wort or beer prior to the filtration step. The metering pumps 43 and 44 may be of any type suitable for handling relatively viscous iso-concentrates and water, respectively, but must be fully capable of accurately metering both streams at high pressure. The pressure generated is a function of a number of factors. In particular, it depends on the pressure prevailing in the wort or beer mains, the pump speed, the temperature of the fluid and the configuration of the nozzle 46. It is desirable that the spray solution disperse rapidly into the wort or beer, otherwise there may be a tendency for certain iso-concentrate components to precipitate out of solution, resulting in a slight haze that is not readily redissolved, and may be lost in the precipitated cold residue in the case of wort or during filtration in the case of beer. For this reason, in the practice where the after-fermentation becomes bitter, a solution of iso- α -acids or the like is generally sprayed immediately before the beer master pump, and we also suggest this practice of the invention. That is, it is still desirable and preferred, but not necessary, to configure the nozzle 46 to cause vigorous mixing of the diluted iso-concentrate with the wort or beer. Since the energy required for this mixing comes from the pressure drop between the nozzle outlet and the wort or beer stream, the pressure in the vessel 45 must be substantially higher than the pressure of the wort or beer mains, which is expected to be of the order of 0.5-5 bar. The structure of the proposed nozzle is therefore advantageous for creating such a pressure difference. Other target characteristics of a good dosing system are shown in figure 1. For example, line 47 allows hot water from container 42 to be injected into container 41 through nozzle 48, thereby allowing the residual iso-concentrate in container 41 at the end of such a run to move out of the container into container 45 and from there into the wort or beer, thereby ensuring that the originally measured iso-concentrate is transferred to the wort or beer in its entirety, while ensuring that the piping is free of material that may subsequently block line, valve or nozzle 46. (this blockage is most likely to occur in the post-fermentation ingredient of beer when the temperature of the line or nozzle drops to the cellar or main beer temperature).

The iso-concentrate is advantageously provided in a plastic container, which typically holds 20kg of product. Suitable containers are drums with lids, spouts, or square polypropylene or high density polyethylene containers with screw caps. In a variant of the above solution for dosing a iso concentrate, as shown in fig. 2, the greatest advantage of the working capacity of the iso concentrate is brought about by the brewer using the iso concentrate directly from the container. Item 1 of figure 2 is a square iso-concentrate container with the screw cap removed. The interior of the container retains an insulated, electrically heated tank 3 which can be set to maintain the contents at a temperature above the room temperature of the beer cellar in which the device is operated. The second vessel 2 is similarly placed in a heated tank 4 substantially identical to tank 3, but may optionally be set to control at a different temperature. Removable dip tubes 5&6 are inserted into both containers and have connected temperature sensors 7& 8. The configuration of the two tanks is such that the vessel is preferably held at a slight angle from vertical so that the contents of each are discharged on one side, where the dip tubes 5&6 are suitably located. These dip tubes are held in place by adjustable means 11&12 in caps 13&14 screwed onto the vessel instead of the original caps provided for the vessel. These (identical) means are designed so that the tubes can be adjusted to just reach the bottom of the container. In a suitable embodiment of the invention, the tubes 5&6 have sealed ends, but the product is allowed to enter the tubes through holes 9 drilled into the sides 10 of the tubes as shown in figure 3. The dip tube 5&6 is attached to a flexible tube portion 15&16 which allows for easy removal of the dip tube from the vessel. During operation, the iso-concentrate from one of the two containers (referred to as container 1 for ease of description) passes through its associated dip tube, through the motorized three-way valve 17, and into the self-priming, adjustable rate, displacement metering pump 18. From the pump 18, the suitably heated iso-concentrate passes into the mixing chamber 19, where it encounters hot, demineralized or softened water from the pressurized supply vessel 20 and immediately begins to dissolve. The heating is done in-line by electric heater 21, the temperature is controlled by temperature probe 22 and controller 23, and the flow rate is controlled by turbine flow meter 24, controller 25 and control valve 26. The partially dissolved product of iso-concentrate and water is passed through an electrostatic mixer 27 from where it passes through a splitter valve 28 into a nozzle 29 located in a beer manifold 30. Once the contents of the container 1 are exhausted, air is drawn into the dip tube 9 causing the sensor 31 to register a change in the conductivity of the fluid which in turn triggers a signal to the drive motor of the valve 17 which then changes position to begin drawing off the iso-concentrate from the full container 2, automatically signaling the need to replace the container 1 (e.g. via the light 33).

As noted above, many brewers prefer to produce light stable beer from more than one type of reduced iso-alpha-acid. In general, such a process can of course be achieved by first preparing a concentrate in which the different types of iso-alpha-acids have been mixed together in the appropriate proportions, although some target mixtures may not always be able to accomplish the process and obtain a product that is homogeneous or has the appropriate physical characteristics. Thus, in another embodiment of the invention, we allow to increase the flexibility at the same time by slowly varying the ratio of the different types of iso-alpha-acids. We do this by adding equipment for handling the second, third or even fourth type of concentrate. Thus in the above embodiments of the dosing apparatus the number of heating tanks can be increased to four, six or eight, arranged in pairs for operating containers filled with different types of iso-concentrates, as otherwise shown in tanks 1 and 2 of fig. 2. The contents of these vessels can be discharged through dip tubes, three-way valves and metering pumps as previously described, with separate streams of different products eventually meeting in or before the mixing chamber 18.

As mentioned above, different types of iso-alpha-acids have different solubilities in aqueous solutions. These solubilities are particularly related to the pH of the solution, with lower pH values reducing solubility. At the lower pH of the beer (typically 3.8-4.5), the unmodified iso-alpha-acids and rho-iso-alpha-acids are the most soluble forms, followed by tetrahydroiso-alpha-acids, and hexahydroiso-alpha-acids may be the least soluble of them. In all cases, the solubility in beer is very low and is typically measured in parts per million. It is clearly desirable that solutions of these substances can be readily mixed into wort or beer without forming temporary or sometimes permanent precipitates, and that such ease is related to their inherent solubility and dissolution rate at which the added near neutral to weakly basic iso-alpha-acid solution is dispersed into the wort or beer. For this reason, dilute solutions of these products were found to work, most particularly in the case of tetrahydro-and hexahydro-iso-alpha-acids, although some brewers did achieve these satisfactory results using directly injected products such as 30 wt% of chemically unmodified iso-alpha-acid. If vigorously stirred, there is the possibility of dissolving more concentrated formulations of these materials, and in another variant of our invention we allow for the direct injection of fluid concentrates of the alkali metal salt form of iso-alpha-acids or reduced iso-alpha-acids, which have much higher concentrations and are essentially as described in our later examples. In this case, the required equipment is substantially simpler, consisting of, for example, a heated tank, a three-way valve, a self-priming metering pump and a nozzle. Thus, in this embodiment we even eliminate the need for a supply of demineralised or softened water and a mixing chamber. However, it must be recognized that the convenience of being able to apply direct injection of concentrate necessarily requires extremely vigorous injection into the beer main.

Iso-concentrates are easily and conveniently prepared from free acid, iso-alpha-acid in resin state or reduced iso-alpha-acid. This iso-concentrate can be obtained by the following method: the acid is first heated to about 40-80 ℃ until conveniently fluid, the fluid resin is vigorously stirred and a calculated, near equimolar amount of an appropriately concentrated, preferably near saturated, aqueous alkali metal hydroxide solution is slowly added until a homogeneous, still fluid product is formed. Optionally or sometimes necessary, a small amount of water is added before, during or after the addition of the base, but not enough to cause the formation of a separate phase in the final product. The mixture was then cooled to room temperature. The addition of water is intended to bring the concentration of the product to a favorable standard value and/or the addition of water is used to reduce the viscosity of the product so that it still flows sufficiently to allow it to be easily used in our batching plant. The concentration of the iso-alpha-acids or reduced iso-alpha-acids will obviously depend on the concentration and type of alkali metal hydroxide solution used, and the amount of water added (if any), but in any case should not be less than about 50 wt%. A potassium hydroxide solution of about 45% (w/w) is particularly advantageous as the neutralizing hydroxide, although other alkali metal hydroxides may be used. Ideally, sufficient neutralizing hydroxide should be added to completely (100%) neutralize the acid, but not so much beyond the level of neutralization, although in some cases the concentration of satisfactory product may be 70-100%. On the other hand, the addition of an excess of hydroxide solution is avoided, since it may lead to chemical instability. In most cases, the addition of the alkali metal hydroxide solution should result in a pH of 5-12, most commonly 7 and 11, when the product is dissolved in demineralized water containing about 2% by volume concentration of iso-alpha-acids or reduced iso-alpha-acids. The point at which water is added without causing significant phase separation depends on a number of factors and varies with the particular resin and the amount, type and concentration of base added. Thus, unless experimentally, it is not possible to determine the exact limit of maximum amount of water that can tolerate a particular type of product. In general, the minimum possible amount of water is of course determined by the concentration and degree of neutralization of the alkali metal hydroxide solution, but is in no way less than about 3% by weight. However, at such low moisture content, the resin is substantially solid and is not suitable for use. It is therefore necessary to add water to bring the moisture content to at least about 10 wt% to the maximum possible.

Mixtures of two or more types of iso-alpha-acids may be prepared by: the appropriate amount of free acid resin is mixed and then neutralized and optionally diluted as described above, or the various types of iso-alpha-acid formulations formed are mixed. In these cases the total amount of all types of iso-alpha-acids should be at most about 50 wt%, and the mixture must also be homogeneous and not phase separate under normal storage conditions.

The effective practice of our invention naturally depends on the provision of suitable iso-concentrate formulations, and this aspect of our invention is more readily seen by the following examples.

EXAMPLE 1 preparation of a Tetrahydroiso-alpha-acid concentrate

1.477kg of the tetrahydroiso- α -acid formulation (85.8% by HPLC and 94.8% by spectrophotometry) was heated to 50 ℃ in a glass beaker and vigorously stirred at 700RPM using a propeller-type stainless steel stirrer with an electronic drive of controlled speed. A total of 341ml of 45% (w/w) aqueous potassium hydroxide solution was added over a period of about 2 minutes. An aliquot of this mixture was found to be diluted in water to a pH of 7.7 at a calculated concentration of about 2 wt%. The product, a homogeneous flowing resin, was allowed to cool and was found to be still a suitable fluid at room temperature. Upon analysis it was found to contain 65.9% by HPLC and 72.5% by spectrophotometric analysis of tetrahydroiso- α -acid. When the product was mixed with an excess of water at room temperature to give a calculated concentration of 10 wt% (HPLC analysis), the product was found to dissolve readily and the resulting solution was found to have a pH of 8.3.

EXAMPLE 2 preparation of Iso-alpha-acid concentrate

212.7g of iso-alpha-acid in free acid form (90.5% iso-alpha-acid by HPLC) was weighed into a glass beaker, heated to 37 ℃ and then stirred at 650RPM using a 2.5 "impeller. A 45% (w/w) aqueous solution of potassium hydroxide was added in steps and the pH of an aliquot of the diluted mixture (approximately 2% iso-alpha-acid content) was determined at each step to avoid overdose of the iso-alpha-acid. The final pH of 2% iso-alpha-acid was 5.9. The resin was clear and slightly fluid at room temperature, and remained clear after cooling overnight. The iso-alpha-acid concentration was 72.4% by HPLC. An aliquot of this product was then diluted with a small ratio of demineralized water to give a calculated 60% (HPLC method) iso- α -acid concentrate. On cooling, this lower concentration of product first became opaque, and after a few days a separate, small amount of aqueous phase formed. But no such separation was observed in the undiluted concentrate.

Example 3 preparation of concentrated rho-iso-alpha-acids and tetrahydroiso-alpha-acids mixtures

A rho-iso-alpha-acid concentrate ("rho concentrate") was prepared by the following method: first 1.627kg of p-iso- α -acid in free acid form and 160mL of deionized water were heated to 45 ℃ in a 2L glass beaker, stirred at 750RPM (2.5 "impeller), and 354mL of 45% (w/w) aqueous potassium hydroxide was added. The pH of approximately p-iso- α -acid was 6.1 by HPLC analysis. According to HPLC analysis, it consisted of 53.9% reduced rho-iso-alpha-acid. A tetrahydroiso- α -acid concentrate ("Tetra concentrate") was then prepared by the following method: the hot, approximately 60 ℃ tetrahydro iso-alpha-acid in free acid form was mixed at 500RPM (2.5 "impeller) and then 23.3ml of 45% (w/w) aqueous potassium hydroxide solution in total was added. HPLC analysis of 2% tetrahydroiso- α -acids in demineralized water pH 7.1. According to HPLC analysis, the formulation consisted of 71.8 wt% tetrahydroiso- α -acid. A mixture of the above rho and Tetra concentrates was then prepared by combining 46.16g of the rho concentrate and 14.85g of the Tetra concentrate to give a 7: 3 ratio of rho-iso-alpha-acid to tetrahydroiso-alpha-acid. The pH of a diluted aliquot of 2% of the total amount of reduced isomerized alpha-acids (HPLC method) was calculated to be 6.2.

Example 4 determination of maximum amount of water allowed in tetrahydroiso-alpha-acid concentrate

Aliquots of the tetrahydroiso- α -acid concentrate of example 1 (65.9% tetrahydroiso- α -acid) were added to various amounts of deionized water. These mixtures were then heated to 50 ℃ and mixed. The samples were kept in the glass container at room temperature for about 2 weeks. Even the sample with the least amount of added water (2.0 wt%) had an aqueous layer on top of the main resin phase, indicating that homogeneity could not be maintained below a certain concentration of tetrahydroiso-alpha-acid (unless as a much lower concentration solution).

EXAMPLE 5 Effect of varying degree of neutralization in preparation of Tetrahydroiso-alpha-acid concentrates

230g aliquots of the tetrahydroiso-alpha-acids in free acid form were each heated to 50 ℃ with stirring at 650RPM (2.5 "impeller) and various amounts of 45% (w/w) aqueous potassium hydroxide solution were added. Each of the aliquots was diluted with water to a concentration of about 2% of tetrahydroiso- α -acid by HPLC. The resulting diluted samples, pH values and the form and stability of the various concentrates are provided in table 1.

TABLE 1 Effect of varying the ratio of alkali hydroxide addition in the preparation of tetrahydroiso-alpha-acid concentrates

mL of 45% (w/w) KOH	Mole KOH mole Tetra	pH of 2% Tetra	Physical form and stability of concentrates	Physical form of diluted sample
					(a)49.0	1.04	6.6	Viscous, just flowing	Resin droplet + aqueous phase
(b)51.0	1.09	7.1	Viscous, just flowing	Resin droplet + aqueous phase
					(c)52.0	1.11	7.4	Viscous, just flowing (least viscous formulation)	Translucent resin
(d)52.5	1.12	9.0	Viscous, just flowing	Translucent resin

The concentration of tetrahydroiso- α -acids (═ Tetra ") was determined by HPLC analysis.

In cold storage 3¹/²After a month, formulations a and b were still quite uniform, while formulation c had a thin layer of dark resin on top and formulation (d) had a more pronounced layer of dark resin and a thin layer of aqueous phase.

EXAMPLE 6 addition of Tetrahydroiso-alpha-acid concentrate to beer

In separate experiments, various iso- α -acid concentrates were drawn into glass syringes, hypodermic needles were placed on the syringes, and the syringes were then placed in a 60 ℃ oven for a period of time to heat the syringes and their contents. A weighed amount of each warm concentrate was poured into a 40oz cold beer (Budweiser) bottle with a replaceable screw cap and each bottle was transferred to a freezer before being re-capped and then vigorously agitated by hand for approximately 8-12 minutes during the next 2-3 days. The bottle was then opened and a 200mL (ca.) sample of beer (cold) was poured into a 400mL glass beaker. After the addition of one drop of n-octanol as a defoaming agent, the beer was sonicated using a small sonic water bath. Each degassed beer sample was then filtered through sintered glass paper (Whatman GF/F paper) to remove any insoluble reduced iso-alpha-acids or iso-alpha-acids. Finally, 4ML aliquots will be diluted to 10ML with methanol and 25 μ L will be injected onto the HPLC column for analysis. The results are given in table 2.

TABLE 2 direct addition of different types of iso-alpha-acid concentrates to beer

Added concentrate		Content (ppm) of added iso-alpha-acids	Increase in iso-alpha-acid content (ppm) in beer	% addition of iso-alpha-acids dissolved in beer
					1. Tetra concentrate of example 1		11.1	1.7	15
2. Rho concentrate of example 3		11.6	9.4	81
					3. Iso concentrate of example 2		10.9	9.4	86
4. Iso-60% concentrate		12.9	12.0	93
					5. Free acid from iso-alpha-acid of example 2		19.5	7.6	39
6. rho/Tetra concentrate (7: 3)	ρ：	8.9	3.1	35
					Tetra：	3.8	1.0	26
	7. rho/Tetra concentrate (4.25: 1)	Different:	8.2	3.8					46
Tetra：					6.5	2.1	32

not the rho/Tetra concentrate of example 3, but the composition ratios were the same.

It is clear that the efficiency of the iso-alpha-acids solubilised by simple addition to beer varies with the type of iso-alpha-acids and the form they are present. The potassium salt of iso-alpha-acids or rho-iso-alpha-acids is more soluble than the potassium salt of tetrahydroiso-alpha-acids. (compare items 2, 3 and 4 within item 1). In fact, it was observed that a very efficient solubilization was achieved by simply, non-vigorously adding a concentrate of iso-alpha-acids to beer in the above-described manner. Furthermore, as can be seen from the comparison of items 3 and 4 with item 5, when the iso-alpha-acid is used in the form of a highly concentrated potassium salt solution prepared according to our invention. The ease of solubilization is substantially greater. It is naturally to be expected that the utilization of all types of iso-concentrates is higher when beer is injected using the dispensing apparatus of the present invention, wherein it is ensured that the introduction of the heated product is achieved in a vigorous manner and optionally with the aid of a pre-dilution which further reduces the intrinsic viscosity.

EXAMPLE 7 concentrate of tetrahydroiso-alpha-acids dissolved in Hot Water

150.4g of deionized water was heated to 60 ℃ in a weighed, 400ml beaker and stirred at 400RPM using a 2.5 "diameter stainless steel impeller. Then 8.47g of hot (approximately 60 ℃) tetrahydroiso- α -acid concentrate (formulation (d) of table 1, see example 5) was added rapidly using a 10cc plastic syringe fitted with a 16 gauge stainless steel needle. The Tetra concentrate was dissolved almost immediately, yielding a pale milky solution. After stirring for 10 seconds, the beaker was weighed again and the weight of the solution was measured. The contents of the entire beaker were then filtered through Whatman1 paper and an aliquot of the filtrate was subjected to spectroscopic analysis. Considering the measured concentration of Tetra in the filtrate (6.22% w/w) and the amount of tetrahydroiso- α -acids added as a concentrate, it can be concluded that essentially all (i.e. 100%) of the added tetrahydroiso- α -acids are transferred to the filtrate.

This example clearly demonstrates that Tetra concentrate can be rapidly and efficiently dispersed and dissolved in water (e.g., by using the ingredient system shown in fig. 1& 2) to form an aqueous solution suitable for direct infusion into wort or beer without the need for solvents or other undesirable chemical additives.

Example 8 rho/Tetra concentrate in Hot Water

In example 7, 150.1g of deionized water was heated to 60 ℃ in a weighed, 400ml beaker and stirred at 400RPM using a 2.5 "impeller. 12.14g of hot (approximately 60 ℃) ρ/Tetra concentrate (7: 3 ratio of ρ -iso- α -acid to tetrahydroiso- α -acid, total 74.6% spectroscopic analysis) was then quickly discharged through a 16 gauge needle from a 10cc plastic syringe into the water. Stirring was continued for 10 seconds. It was noted that the rho/Tetra concentrate dispersed almost immediately, although some cloudy solution formed. A sample of this solution was then filtered through Whatman5 paper (a grade more moisture than paper No. 1) and the aliquot (milky white) filtrate was spectroscopically analyzed. It was found that if all the added hop acids had dissolved 5.65% (w/w), the total concentration of p-iso-alpha-acids + tetrahydroiso-alpha-acids in the measured filtrate was 5.62% (w/w), in good contrast to the theoretical concentration, indicating that almost all the isomerized hop resin acids were converted into a form suitable for efficient dissolution in wort or beer.

It will be apparent to those skilled in the art that certain changes may be made without departing from the spirit and intent of our invention. It is therefore to be understood that our invention is not limited by the scope of the description and examples given, but by the claims that follow, and wherein the term isomerized α -acids is intended to mean iso- α -acids, reduced iso- α -acids, or any mixture of these.

Claims (5)

1. An apparatus for injecting a concentrated preparation of one or more isomerized α -acids directly into wort or beer, the apparatus comprising:

(a) a heat source for heating each preparation of isomerized α -acids;

(b) a dosing unit for metering the flow of each isomerized α -acid preparation into the conduit; and

(c) from this conduit is fed an injector for injecting heated single or combined preparations of isomerized α -acids into wort or beer.

2. The apparatus of claim 1 wherein each of said preparations of isomerized α -acids is provided directly from a disposable or recyclable container.

3. The apparatus of claim 1, said apparatus comprising two or more supplies of each of said preparations of isomerized α -acids, wherein each of said preparations of isomerized α -acids is selectively metered into said conduit from one of said supplies.

4. The apparatus according to claim 3, wherein the supply is contained in a disposable or recyclable container.

5. The apparatus according to claim 1, further comprising a device or apparatus for mixing and diluting the concentrated preparation of isomerized α -acids with hot water prior to the wort or beer infusion.