CH630956A5 - Preparation of iso-alpha-acids from hop extract - Google Patents

Description

This invention relates to the preparation of an iso-a-acid preparation which is suitable for use in the manufacture of beer and isomerized from a-acids extracted from hops. The general procedure today is to extract various constituents from hops and to use these extracted constituents instead of hops in the production of beer. The main components extracted in this way are the resins and in particular the a-acid fraction of the soft resins. In a chemical rearrangement, these produce iso-a-acids, which are the most important bittering components of beer. The main advantage of extracting a-acids is that the a-acids can be used in a much more efficient way than is possible in traditional beer production. In traditional beer production, typically only 25 to 35% of the a-acids are used in the original hops. If one extracts the 65 a-acids, isomerizes them separately from the beer and adds the produced iso-a-acids to the beer after fermentation, the use of the a-acid can be much higher, typically from 60 to 85%. Another important advantage of using extracts is that they can be stored for longer periods without the presumably oxidative degradation that occurs in hops when they are stored for a long time, in particular the degradation of the main bitter constituents, including the a-acids.

Common hop extraction processes work with organic solvents such as methylene chloride, trichlorethylene, hexane and methanol. These solvents not only dissolve the desired a-acids, but also relatively large proportions of ß-acids, tannins, chlorophyll and various other hop components.

A primary extract, which was prepared by extracting hops with an organic solvent, typically has the following composition:

% By weight

a acids 8-45

ß acids 8-20

non-characterized soft resins 3-8

hard resins 2-10

Hop oil 1-5

Fats and waxes 1-2

total resins 15-60

Tannins 0.5-5

Chlorophyll to 1

fine material (cellular fragments) 2-5

inorganic salts 0.5-1

residual solvent (usually CH2CI2 or CH3OH) 1.5-2.2

Water 1-15

In order to obtain high-quality a-acids suitable for isomerization, the crude extract must be thoroughly cleaned, which often requires other organic solvents and always involves many and often complex stages. It is also difficult to completely remove the organic solvent from the extract; typical commercial extracts can contain over 1% by weight of solvent. While it is believed that residual solvents, especially methylene chloride and methanol, are completely released during beer production, it is not entirely satisfactory to rely on such an "accidental" elimination of potentially harmful materials during food production. While there is still no major technical difficulty in meeting public health requirements for the concentration of residual solvents, there may be significant difficulties in the future.

An organic solvent extract that had been purified to be suitable for isomerization to produce an iso-a-acid preparation suitable for use in bittering beer would typically have the following composition:

% By weight

a-acids 60-80

β-acids 0.3-0.5

non-characterized soft resins 1-2

hard resins 1-5

Hop oil up to 1

Fats and waxes approx. 0.1

total resins 70-90

Tannins about 0.1

Chlorophyll approx. 0.1

fine material essentially no inorganic salts

no residual solvent * 0.5-1

Water up to 10

* In addition to CH2CI2 and CH3OH, which are usually both

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used in the extraction and cleaning, these solvent residues can contain solvents such as ethyl acetate, butanol and trichlorethylene.

Liquid carbon dioxide has been suggested as either a liquid or a supercritical gas as an extraction medium for hops. Thus, the specification of British Patent No. 1,388,581 discloses a process for producing a hop extract by extracting hops with a plurality of supercritical gases in temperature and pressure. Carbon dioxide is said to be the most preferred gas. Extraction under such supercritical conditions with CO2 typically results in an olive-green, pasty product which contains a-acids, ß-acids, uncharacterized soft resins, hard resins and small amounts of tannins. The extraction conditions can be varied so that the yields of a-acids are correspondingly higher than the concentrations in the starting hops, although the best extracts described contain only about a third of a-acids. The optimal extraction conditions state that they contain the extraction under a pressure substantially above the critical pressure, which for CO2 is approximately 72.8 atmospheres, preferably more than 100 atmospheres (atmospheric pressure) and temperatures of 40 to 50 ° C. It is stated that by appropriately selecting the extraction conditions, it is possible to extract substantially all of the soft resins and the essential hop oils, while minimizing the extraction of hard resins, or that the corresponding extraction of β-acids is reduced may, however, at the expense of increasing the ratio of hard resins extracted. It is further stated that it is possible to extract hops with liquid CO2, but this does not form part of the invention of this earlier patent because "its resolving power is less great than that of supercritical CO2".

The extract as described in the specification of British Patent No. 1,388,581 advantageously compares to typical primary extracts obtained using organic solvents and would be of use in brewing Beer seems suitable, for example by adding copper. However, the extract described would not be suitable for isomerization without substantial purification in order to remove the components, which would result in an unfavorable taste under typical isomerization conditions and would also lead to the formation of substantial amounts of haze when added to the beer. (It is not practical to do the post-isomerization purification because the mixture is even more complex than the impure extract.) At the current level of extraction technology, this would require the use of organic solvents, which is one of the main advantages of using supercritical CO2 is released when extracting hops.

Liquid CO2 is described in USSR Inventor's Certificate No. 167,798 under the names of Pekhov, Ponamarenko and Prokopchuk and Pekhov in Masloboino-Zhirovanaya Promyshlemnost Vol. 34, Part 10 (1968) pages 26-29 as an extraction medium for hops. The product obtained by extracting hops with liquid CO2 at 20 to 25 ° C is referred to in the author's certificate as a light brown, viscous mass. Shafton and Naboka in ISU Sev-Kauk Nauchn Tsentra UGssh Shk, Ser Tekh Nauk 1975.3 (3), 29-31 [Chem Abs Vol. 84 (1976) 120046a] describe CCh extracts of hops as complex mixtures of a-, ß- and y-acids, a-, ß- and y-soft resins and hard resins, which are subject to a substantial deterioration, especially by rather rapid ones

Auto-oxidation during storage. The purity and stability of such CCh extracts is not completely reliable; although it is possible to use them in the production of beer by adding them to copper, it is still clear that they could not be isomerized to produce an iso-a-acid preparation without substantial purification, and that in any case they could be used in storage are considerably less stable than the conventional hop extracts made using organic solvents. So far it has not been recognized that a primary hop extract could be obtained which would be satisfactory for direct isomerization to produce an iso-a-acid preparation suitable for bittering beer. The present invention is based on the discovery that the extraction of hops can be carried out with liquid CO2 (i.e. under subcritical conditions) so that a primary extract is obtained which can be satisfactorily isomerized without the need for prior purification.

It is an object of the present invention to provide an improved process for the preparation of iso-a-acid preparations which are suitable for addition to beer, and in particular to produce high-quality preparations which are suitable for addition to beer after-lightening Filtration are suitable.

The present invention accordingly provides a process for producing an iso-a-acid preparation, which is characterized in that hops are brought into contact with liquid carbon dioxide at a temperature of not less than -5 ° C., thereby at least a proportion of those contained in the hops a-acids extracted into the liquid carbon dioxide, a high-purity primary hop extract isolated from the liquid carbon dioxide and the a-acids present in the hop extract isomerized to iso-a-acids.

In practicing the present invention, the high purity primary hop extract, which has been isolated as an intermediate, generally contains a-acids, ß-acids, hop oil, usually small amounts of water and generally no more than trace amounts of the major contaminants involved primary organic solvent extracts are seen, namely uncharacterized soft resins, hard resins, tannins and chlorophyll.

Table 1 shows the purity of the primary extract, as measured by the amounts of impurities which have a disruptive effect on the subsequent isomerization. Column A shows the maximum permissible content of the above impurities, at which it was found that the impurities significantly interfere with the subsequent isomerization, Column B shows the expected maximum content of the impurities, which is caused by the liquid CO2 below the general conditions were extracted, and column C shows numbers which are typical of what is expected to be obtained.

Table 1

Contamination '"amount of contamination,

% By weight on the extract

ABC

not characterized soft

Resins

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0.1

<0.1 <2)

hard resins

0.5

0.1

no

Tannins

0.5

0.1

no

Chlorophyll

0.2

0.1

no

Fats and waxes

0.2

0.1

<0.1®

fine particles

0.5

none no inorganic salts

0.5

0.1

<0.1 (2)

Total

4%

0.3

0.1

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(I) See below for a summary of the analytical methods used.

! 2) These figures indicate that the contamination of some primary extracts could only be determined qualitatively using the analytical methods used, but the amounts were too small to be assessed with any degree of accuracy. The numbers shown as maximum values represent the analysis limit; the actual amounts of contaminants present can be even smaller.

The main components of the primary extract are, as stated above, a-acids, ß-acids, and the hop oil extract has the following composition with regard to these components:

% By weight (1)

a-acids 40 to 75 (3)

ß acids 20 to 40

total resins 70 to 98 hop oil up to 10 (3>

Water up to 5

(1) These numbers are based on analyzes for the resins, which were carried out according to the method described in Analytica EBC, published by Schweizer Brauerei Rundschau, third edition, 1975, page E49; the analyzes for the non-resin components, in particular the tannins and the chlorophyll, were carried out according to the method described by J. Jerumanis in Bulletin Association Anciens Etudiants Brasserie Louvain, 1969, Vol. 65, page 113.

(3) The maximum analytical values for α-acids and hop oils will generally only be achieved with hops, which contain unusually high proportions of these materials. Very often the upper limits will be around 65% for a-acids and around 3% for hop oil.

The term “primary extract of high purity” means that the undesirable impurities given in Table 1 are present in amounts which are smaller than the values given in column A of Table 1. Under the conditions compiled here, under which hops were extracted with liquid CO2, results were obtained which are much better than the maximum values given in column A.

For practical purposes, the composition of the extract can be summarized as follows:

% By weight

α-acids 40 to 75 very common 40 to 65 β-acids 20 to 40 very common 25 to 35 total resins 70 to 95 very common 80 to 95 hop oil up to 10 very common up to 3 water typically

2-5

The composition contains essentially no organic impurities from hops.

The amount of water present in the extract is not itself critical; however, as noted below, if substantial amounts of water are present in the carbon dioxide at the time of extraction, tannins can be extracted from the hops. It appears that if appropriately dried liquid CO2 is used, the amount of water in the extract will depend on the amount added in the hops and thus, while the numbers given above are common, amounts outside of the specified range can be obtained in certain circumstances.

The high quality primary extract has the golden yellow color of a-acids and is usually a solid or semi-solid crystalline material at ambient temperature, the exact form depending on the particular extraction conditions and the type of hop extracted. Another indication of purity is

that typical, primary extracts precipitate identifiable crystals of a- and ß-acids on cooling to approx. 4 ° C. Conventional primary solvent extracts show no signs of such crystallization.

It should be noted that this primary extract is a much cleaner material than primary extracts with typical organic solvents; in particular with regard to the hard resin and the uncharacterized soft resin components, it is much purer than the conventional extracts with organic solvents, even after cleaning. A major difference is that the extract obtained using liquid carbon dioxide contains significantly more ß-acids than typical, conventional, purified extracts. It seems that the ß-acids can be tolerated at these much higher levels because the extract has the otherwise excellent cleanliness and purity. Thus, the high content of β-acids does not prevent the satisfactory isomerization of the α-acids in the preparation of an iso-a-acid preparation, and the β-acids can be removed from such an iso-a-acid preparation by filtration at a suitable pH.

As far as is known, this was not previously published, on the contrary, the content of the preceding explanations regarding the amounts of β-acids tolerable in the extracts to be isomerized actually shows that the maximum permissible quantities of β-acids were very small, typically less than 1%. In the present invention, it is believed that it is possible to isomerize a-acids because the levels of the other materials that could interfere with the isomerization are so low.

The general physical conditions of pressure and temperature used in the extraction step are somewhat critical to the invention. If the extraction is carried out at temperatures below -5 ° C, undesirable organic compounds tend to be extracted. These compounds appear to be mostly fats and waxes. At higher temperatures, however, increasing amounts of hard resin and presumably tannins are extracted. At subcritical temperatures above -5 ° C one is able to obtain extracts of high purity. The extraction temperature is subcritical because the use of supercritical temperatures results in the extraction of substantial amounts of hard resins, chlorophyll, tannins, etc. (as is clear from the description of British Patent No. 1,388,581).

Good results can be obtained within this temperature range, but in general it is not preferred to use temperatures close to the critical temperature in order to avoid the possibility that CO2 happens to become supercritical. The generally preferred temperature range is between -5 ° C and 20 °.

Clearly, the pressure at which the extraction is carried out must be sufficient to keep the CO2 liquid and not so high that the CO2 behaves like a supercritical liquid, as described in the specification of British Patent No. 1,388 581 is described. In general, it is both convenient and preferred to operate below the vapor pressure of liquid CO2 at the extraction temperature. The pressure will normally be slightly, for example up to 10%, above the vapor pressure, so that small temperature differences between the different parts of the extraction apparatus are possible, especially if temperatures below room temperature are used for the extraction, and thus hydrostatic pressure differences within the apparatus are also permitted can. The change in vapor pressure of liquid CO2 with temperature is shown in Table 2.

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Table 2

Steam pressure temperature

° C atmospheres (absolute)

31 ° (critical temperature) 7 2.8

30 71.2

20 56.5

10 44.4

0 34.4

-5 30.1

From the point of view of the engineer, it is desirable to have the lowest possible pressure and a temperature which is as close as possible to the ambient temperature. These requirements are not strictly compatible, and in practice a compromise will usually determine the best possible working temperature, taking into account these considerations as well as the speed of extraction, the selectivity and the purity of the extract.

The form in which the hops are extracted is not particularly critical in that effective extractions can be achieved from green or dried hops, hop cones, ground, powdered, tableted and powdered hops from crushed hop tablets.

However, the bulk density of hop cones is very low and powdered or tableted hops are preferably used as the practical material for the extraction. Powdered hops appear to be satisfactory for the extraction in the invention and for the further work required for tableting the hop seeds, so that no particular advantage is created in the extraction. The optimal extraction conditions can vary, depending on the particular form used; however, determining the correct, best possible seeds seems to be a simple matter.

Of course, the hops themselves should be of a suitably high quality. Low quality hops or spoiled hops cannot produce satisfactory extracts. The particular type of hop used (versatility of breeding) does not appear to be critical with regard to the extraction itself; both seed-bearing or seedless hops can be extracted satisfactorily. The special composition of the extract and the yield obtained are a function of the extracted, versatile growing hop, whether it carries seeds or is seedless. Satisfactory extracts were made from the following different breeding hops: Wye Northdown, Wye Saxon, Northern Brewer, Wye Challenger, Bullion,

Comet, Pride of Ringwood and Styrian Golding.

The amount of liquid CO2 required to extract the hops appears to be a function of the solubility of the a-acids in the CO2, the type of extraction system, and the exact conditions used. The limits of the solubility of a-acids in liquid CO2 have not yet been determined. However, there were no difficulties in reaching concentrations of 3.7 g / liter; higher concentrations could well be possible. The effectiveness of the extraction, both in terms of the content of the extracted a-acids and the amount of CO2 required to extract them, is increased by the increase in the effective contact time between the CO2 and the hops. This can e.g. B. by simply circulating the CO2 over an extraction bed. Alternatively, this can be done using a semi-continuous or continuous extraction process, for example using counter

current process. Although it is desirable to increase the effective contact time between the liquid CO2 and the hops, it has been found that an essentially complete extraction can be obtained in the laboratory at times comparable to the contact times found in conventional commercial solvents -Extractions are needed. One can actually assume that liquid CO2 will extract the hops much faster than is the case with conventional organic solvents, and that this has not appeared specifically in the relatively small range in which the tests have been carried out to date. The causes are the limitations of the relative and absolute flow rate, which are due to the small range of the equipment used for the extraction.

The extent of the extraction of a-acids is a function of the assumed, specific method. More than 90% of the available a-acids have been successfully extracted without difficulty and it is believed that even higher extraction ratios are possible without greater difficulty.

The extracted a-acids can be easily recovered from the liquid C02 extract by "boiling away" the CO2 as a gas. This can conveniently be done by heating the solution under constant pressure so that the liquid CO2 boils. This is how you work under almost isothermal conditions. Alternatively, the vaporization of the gaseous CO2 can be carried out by reducing or releasing the pressure, i.e. H. about adiabatic. These two processes are satisfactory on a small scale, and the quality of the product is not reduced. It is preferred, particularly in the case of commercial operation, to recover the CO2 and to condense and reuse it as the extraction liquid. It is easier, thermodynamically effective and therefore more economical to carry out this cycle under approximately constant pressure, taking advantage of the low specific heat and the latent heat of vaporization of the CO2 to achieve the necessary changes in state. The large pressure and temperature changes in adiabatic evaporation make it rather less preferred in this regard.

When the extract is isolated by heating the liquid CO2 for evaporation, it is desirable to use a heat source at a moderately high temperature, e.g. B. 30 to 40 ° C to ensure sufficient heat transfer is ensured. As the extract further tends to become quite viscous, and even at low temperatures, e.g. B. can begin to crystallize below about 5 ° C, it is therefore desirable to isolate the extract close to or slightly above ambient temperature so that these potential problems are avoided.

The primary hop extract thus obtained is an actually pure mixture of a-acids and ß-acids, together with a part of the essential oil ("hop oil") which is present in the hops; however, it does not usually contain hard resins, chlorophyll or tannins. There was no difficulty in isolating the crude extracts, which are essentially free of hard resins, chlorophyll, tannins, etc. This purity of the product is a characteristic advantage over the products obtained by the hop extraction processes mentioned above.

A quantitative examination of the crude product shows that there is a fairly higher ratio of the a-acids compared to the ß-acids in the product than would have been expected simply because of the relative ratios of the a-acids in the hops. The extent of this selectivity is significantly higher than that which was published in the description No. 1 388 581; one cannot explain why the conditions used for extraction are so special5

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are advantageous. The same applies to the other aspects of purity.

As already stated above, the primary extract produced by the process according to the invention is usually a mixture of α-acids, β-acids and at least 5 a substantial proportion of the essential oil from hops. The mixture will normally contain moisture; however, this is not considered to be a contaminant for further processing, although it may be expedient and / or desirable to dry the extract if it is to be stored for long periods. The product of high purity is yellow in color, i.e. H. the color of the a-acids is present and there is no green, brown or other dark color, as is customary in conventional primary hop extracts, including those which are described in the description No. '5 1 388 581. The extract is typically a solid or a viscous part or a liquid, the exact form being strongly dependent on the temperature.

The extract contains some hop oil; since this can itself be a valuable product, it can be removed from the primary extract by steam distillation under vacuum, for example, under the general conditions of temperature and pressure described in the specification of U.S. Patent No. 3,979,527 to Laws and Pickett is specified. The separation can thus be conveniently accomplished by mixing the extract 25 with water and distilling the mixture under vacuum at a temperature of less than 50 ° C, typically 20 to 25 ° C. The distillate, an emulsion of hop oil in water, can be collected as a dispersion in ice by cooling the steam to below 0 ° C, usually to -20 ° C or lower. Hop oil, which has been distilled from the extract in this way, can be used to add hop flavor and taste to the beer. However, it has been found that using liquid CO2 essentially all of the hop oil is removed from the 35 hops, so care must be taken to select only the desired fractions in steam distillation as described, as described in the description above is executed. It also appears that some of the more volatile components of hop oil are extracted very quickly by the liquid 40 CO2; If no precautionary measures are taken, these components can be lost; this can even occur during the time when the remaining air is flushed out of the extraction apparatus. For these reasons, when hop oil is desired as a separate product, it appears to be advantageous to extract the hop oil from the hop with liquid CO2 prior to extraction. In any case, it is likely that the liquid CO2 extract will contain at least some of the hop oil components. Since some components 50 of the hop oil are broken down during the isomerization and contribute to an unfavorable (off) taste and aroma, it is usually desirable to remove the hop oil from the extract.

As illustrated in U.S. Patent No. 3,979,527, the quantities of hop oil that are normally desired in beer to produce a hop aroma and taste as obtained by dry hops are in the range of 0.5 to 2 ppm . The amount of hop oil in the primary CÖ2 extract is usually such that, if all of the hop oil were retained, the amount of oil that would have been obtained using the final product, i. H. of the iso-a-acid preparation would be added, substantially in excess of what is desired to produce a beer hop aroma or taste. This is especially true if the type of hop extracted is one that has a high ratio of accessible hop oil. It is therefore desirable to remove at least enough hop oil to prevent this from becoming a serious problem.

Another practical aspect that favors the separation of the hop oil prior to use of the iso-a acid preparation is that a brewer is generally preferred to use essentially pure materials. Thus, if he wishes to use the iso-a acid preparation made in accordance with the present invention, and also hop oil isolated from the primary extract, he will prefer that these materials be supplied separately for use rather than a pre-determined, as-is mixture to obtain.

When using the preferred mode of isomerization, which is described in detail below, it is not necessary and indeed not preferred to specifically remove the hop oil from the extract prior to isomerization. However, if it is desired to purify the extract in this way, this can be done by steam, with all hop oils distilling away. However, care should be taken to avoid excess heating as this will damage or destroy the bitterness of the extract. Such damage can be done by steam distillation at a suitably reduced pressure, e.g. B. so that the temperature is not more than 50 ° C can be avoided.

In connection with the purity of the extract, it has been found that the extract easily forms complexes with a number of metals such as iron and copper. Passing the extract containing liquid CO2 through moderate steel or copper tubing, particularly in the presence of moisture, will result in the copper or iron being leached from the walls of the tubing. This is undesirable because corrosion problems and salt crystallization can arise in the extraction apparatus, especially with copper, which forms blue, crystalline salts with the soft resin acids and contaminates the product with heavy metals. Although iron, like copper, is not toxic, this is undesirable because other heavy metals, which can be toxic, can be carried with the iron; the presence of iron in the extract appears to reduce the stability of the product, particularly with regard to oxidative degradation. Extracts contaminated with iron are typically brown, i.e. H. different from the otherwise yellow color. The problem of metal contamination can be solved by using a suitably inert material for the extraction equipment or its lining. It has been found that if the extraction equipment consists primarily of red-free steel, glass (for viewing parts) and suitable inert plastic materials, this problem is solved. Other materials are undoubtedly suitable and the selection of suitable inert materials is within the knowledge of a chemical engineer.

As mentioned briefly above, the quality of the extract can be adversely affected if there is an excess of water in the CO2 which is used as the extraction liquid, in particular insofar as tannins, which are relatively soluble in water, can be extracted into the water , which is contained in the liquid CO2. The commercial quality of liquid CO2 in the United Kingdom, as available from Distillers Company (Carbon Dioxide) Limited, is a high quality product whose water content is measured in parts per million (typically about 20 ppm). Such CO2 is sufficiently dry for the use according to the invention. The purity of such liquid CO2 is well within the relevant British Standard (BS No. 4105/1967). It is believed that liquid CO2 which meets this British standard is of sufficient purity for the use according to the invention. The use of less pure liquid CO2 can lead to problems regarding the quality of the extract.

The possibility of heavy metal pollution

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and the pressure of water and / or other impurities-unconcentrated solution of a-acids was carried out, because genes in liquid CO2, it is believed, can at least then increase the solubility of the iso-a-acids in the acidic

Part of the lack of previous proposals for extraction pH is quite low, so the a-acids are

of hops with liquid CO2 to produce a product, it may be necessary to use the isomerized, alkaline

tes, which the purity of the primary 5 see extract solution according to the invention before dilution to dilute

Extract almost reached, be responsible. to avoid an undesirable loss of iso-a-acids.

The isomerization step in the process according to the invention is thus optimally acidified to about pH 4, where it can be carried out by any suitable method. Iso-a acids are soluble up to about 0.5% by weight (about 5 g / liter);

will. Some operations, such as the photoisomerization-alkaline isomerization solutions, are more concentrated than this

However, methods may require the extract to be before 10, should be diluted before acidification to

Isomerization is purified and even to a further lung and thus a possible loss of iso-a acids too

Stage leads, although avoid using those obtained according to the invention. The preferred concentration of iso-a acids in

Extractions of high purity such purification in this state is pH dependent; nevertheless, it is generally

is relatively simple. This further stage is not necessary in the range from 0.5 to 5 g / liter and optimally between

dig if the preferred method of isomerization 15 see 3 and 5 g / liter.

is set. Other ways of working often include use. Conveniently, the solution is

formation of organic solvents and are therefore not filtered like diatomaceous earth. After filtration, the iso is preferred. In the preferred extract, organic solvents are added directly to the beer in order to bitter it,

driving the isomerization is not necessary. as detailed below. The iso extract is

The preferred method is to keep the a-acids 20 not very stable when stored at acidic pH by heating, and preferably by boiling an aqueous th; especially if the extract is not added directly to the beer solution of the extract which has been made alkaline, it is therefore preferred to alkali isomerize the pH moderately. Typically the extract is made alkaline in alkali, for example by adding a suitable e.g. sodium and / or potassium hydroxide or pre-alkali, e.g. B. sodium and / or potassium hydroxide and / or -Car-Zug-carbonate dissolved so that a solution with a pH 25 bonat to adjust a pH of 8 to 10, preferably from 8 to 11 arises. For solutions that do not have a subsequent way about 9.0. The solution will require dilution to the desired extent (see below), which is concentrated (usually 10 to 40% iso-a-acids). Concentration of α-acids typically 0.5 to 5 g / liter. It has been found that if the isomerization is rapid and the concentration of sodium and / or potassium carbonate is completed, a small proportion of the hop oil will not be from 0.01 n to 0 , 5 n. The solution is then, for. B. during 5 30 the steam can be boiled away. If a full minute to 2 hours is desired to isomerize the a-acids to iso-remove the hop oil, then this can be boiled by a-acids. During the boiling, the hop oil will continue to boil the alkaline mixture, driven off with the steam. It is known that the alkali is concentrated. However, if the iso-extract is concentrated before use, as isomerization of a-acids in a relatively concentrated manner described below, it has been found that any trated solutions can be carried out, e.g. B. up to about 35 35 remaining hop oil conveniently with the iso wt .-% a-acids. Such high concentrations can be removed when extracting evaporated water. Isomerization step of the present invention, if the concentrating can be carried out to use solid, kri-desired. Obtaining the use of high stalline iso-a-acids, as well as the concentration, if necessary, can be useful in reducing the heating condition 'useful alkali metal salts. Since iso-a acids may be beneficial due to overheating during the isomerization and the requirement for subsequent connection, especially during cooling down, and also that the entire gene may be lost by evaporation, it is pre-alkali amount which in order to maintain the desired pH of 8, the solution is required for evaporation to not more than 11 or, in the case of more dilute solutions, to be heated slightly below 50 ° C., in particular to not more than 40 °. It is less than necessary. This latter point can be important, there were no difficulties in the execution of the evaporator since a reduction in the amount of inorganic material was found at 45 ° C at 35 ° C. Rapid evaporation can be reduced by the likelihood of inorganic salts, which can be done under a partial vacuum. The KCl or NaCl crystallized out, for example, when the even concentration of the iso-extract to produce the solid iso-tual iso-a-acid preparation is substantially concentrated, e.g. B. a-acids do not need to be carried out, of course, between 30 and 40% by weight. Thus, in the present case, for the storage and transportation, an invention is generally the concentration of the a-acids during the isomer concentration to form 10 to 40% concentration is not a limitation; Concentrations up to at- (weight per volume) satisfactory. Assuming that for example 400 g / liter will be considered. The particular, there is no undue delay, the chosen concentration is a matter of choice depending on the stage of preparation of the alkaline iso-extract solution, depending on the particular circumstances; one, or possibly even during the narrowing, is not expected to have any authority in this regard.

are going to have serious difficulties. Concentration The use of the preferred mode of operation of the isomer

will typically be in the range of 0.5 to 300 g / liter, rization is particularly advantageous because the inventive

mostly between 3 and 100 g / liter. perform moderate procedures in a particularly elegant manner

The solution is then preferably at least possible. A particularly preferred aspect of the invention

Practice temperature and optimally in the range of 0 60 manure results in a process for producing an isomerized and cooled to 10 ° C. The pH of the solution is then acidic hop extract, the process being carried out in the following stages, e.g. B. from 2.5 to 5, preferably from 3.5 to 4.5 and optionally contains:

sometimes about 4.0. This can conveniently be done by (i) extracting the hops, preferably in the form of

to add a suitable amount of acid, such as hydrochloric acid to smaller tablets, with liquid CO2 at one temperature. At this acidic pH, the β-acids are much less soluble than the iso-a acids from -5 ° C to 30 ° C, preferably from -5 ° C to 20 ° C; they will precipitate out and can operate at a pressure slightly above that of the

for example, by filtering or centrifuging, the vapor pressure of liquid CO2 is removed during the extraction

the. Where the isomerization is at a relatively high temperature;

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(ii) recovering a high purity primary hop extract by evaporating the liquid CO2;

(iii) without further purification, an alkaline, aqueous solution is prepared which preferably contains the extract in an amount corresponding to 1 to 100 g / liter of the a-acids, these containing sodium and / or potassium carbonate, preferably in a concentration of 0 , 01 to 0.5 n, and preferably has a pH of 8 to 11;

(iv) this solution is boiled to convert substantially all of the a-acids contained therein to iso-a-acids and to remove the hop oil components, this operation preferably being carried out over a period of 5 minutes to 2 hours;

(v) this solution is preferably cooled to a temperature of 0 to 10 ° C;

(vi) if necessary, the alkaline solution is diluted to a concentration of not more than 5 g / liter of iso-a acids and the pH of the solution is adjusted to about 2 to about 5, preferably about 4.0, by adding acid;

(vii) filter this acidified solution to remove the precipitated β-acids from it while keeping the iso-a-acids in solution;

(viii) if appropriate, the solution of the iso-a acids thus obtained is concentrated by evaporation to a predetermined extent, preferably at a temperature of not more than 40 ° C., and

(ix) the pH of the filtered solution is adjusted to 8 to 10, preferably to about 9.0, either before, during or after the concentration by adding alkali.

The isomerized extract, which was prepared by the process according to the invention, is of excellent quality and can be obtained in high yield. It has been possible to extract 85-95% of the a-acid from the hops without any difficulty; higher extraction yields are expected to be possible. Usually up to about 70% of the ß-acids are extracted. Although the levels of soft resin acids vary from different hop species, there have been no difficulties in extracting a number of different hop cultivars as indicated above.

The conversion of the a-acid content from the extract to iso-a-acid can be carried out essentially qualitatively by the preferred method according to the invention used, the losses in the filtration to remove the β-acids being low. Losses during evaporation are usually not significant, provided that the temperature is kept below about 40 ° C. Thus, the real yield of the process according to the invention can typically be as high as 90%; higher yields will probably be achievable without great difficulty.

It is an outstanding advantage of the iso-a-acid preparation obtained by the process according to the invention that it does not produce any measurable turbidity when added to the beer. This compares very advantageously with commercially available isomerized extracts. The isomerized product produced in accordance with the invention is of a sufficiently high quality that it can be added to bright beer after filtration without significant clouding. To date, this has been practically impossible; even the best commercial isomers that had to be added latest before final filtration due to their tendency to cause turbidity. The effective utilization of the bitterness of the hops is reduced. With commercial isomerized extracts,

the utilization, which is available under normal conditions, is between 70 and 75%, and under carefully controlled and optimized conditions a maximum of about 85% is obtained; with non-isomerized extracts added to the copper, the utilization is typically 27 to 35%, compared to about 25 to 30% when the hops are used without extraction. There were no major difficulties in achieving utilization values better than 80% without specifically optimizing the conditions; it is believed that values of 90% and more are obtained by optimizing the addition processes.

When commercial, isomerized extracts are used to make beer bitter, there are sometimes difficulties with flowing out. The main promoters of the swelling are oxidation products of hop resins, which are present in the hop and / or are formed during processing. Another advantage of the new process is that the resulting isomerized extracts show no tendency to swell. Thus, the wells are not extracted from the hops or formed during processing.

The quality of the iso-a-acid preparations obtained according to the invention is verified by analysis. Examination of typical samples prepared as described above by column chromatography as described by Otter, Silvester and Taylor, J. Inst. Brew. 78 (1972) 57, describes the presence of iso-a acids, but it does not show a-acids, β-acids or humulic acids. These components can generally still be determined using thin layer chromatography. Commercially available iso extracts generally reveal much higher levels of these undesirable compounds. Furthermore, the iso-a acids produced according to the invention contain no detectable amounts of polyphenol compounds. These are usually present in commercial extracts and are believed to contribute to the poorer properties of previous materials, particularly in terms of haze formation.

The invention will be further described in connection with the accompanying drawings.

Fig. 1 illustrates the apparatus for the quantity extraction of hops with liquid CO2 and

2 schematically illustrates the apparatus for semi-continuous extraction of hops with liquid CO2.

Fig. 3 shows schematically the apparatus for converting a primary extract into an iso-a-acid preparation, which is suitable for addition to beer.

In Fig. 1 the hop 1 is contained in a pressure cell 2, which has the following parts:

Inlet 3 connected to valve 4;

Outlet 5, including the sintered metal filter 6, said outlet 5 being connected to outlet valve 7;

Observation window 8 and pressure indicator 9.

To extract the hops, tap 7 is closed and liquid CO2 is introduced into cell 2 via inlet 3 and valve 4. Tap 4 is closed and cell 2 is shaken to mix the hops with the liquid CO2 in order to extract the soft resins (α-acids and β-acids) into the liquid CO2. When the extraction is complete, the extract can be transferred to the second pressure cell 10, which contains the bottle 11, the observation window 8 and the drain line 12, which is provided with the heating device 13 and the valve 14. To transfer the extract, valve 14 is closed and valve 7 is opened; the extract flows through filter 6 (this prevents any fine material from being carried along with the extract) in bottle 11 in cell 10. After the transfer has ended, valve 7 is closed. This extraction and transfer procedure can be repeated to extract the hops if necessary or desired. The extract can be separated from the liquid CO2 by opening valve 14, the cell 10 being controllable with the aid of the heating device 13

8th

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

9 630 956

Atmosphere is opened. to a certain extent from the extraction temperature

2 shows the liquid CO2, which is stored in the tank 20; this will be chosen so that it is pumped uniformly by pump 21 at a pressure which ensures the transfer of heat with the indicator 22 and insulation is tracked, via the heat exchanger 23, in which extract is avoided at a temperature, which either sets the temperature of the liquid CO2 to that for extraction 5 which is so low that it is very viscous or solid, or the desired temperature. One of the commercial goals is that it be degraded or decomposed. The extract, wave extractor, storage tank 20 will normally be cooled to more typically a liquid at the contact temperature - a temperature between -15 ° C and - 20 ° C. For tur inside the evaporator, in the evaporator or small-scale extractions, the storage container, a collection vessel connected to it, can be conveniently collected by a number parallel to each other 10 and it can from time to time through the tap 26 ent arranged cylinders of liquid CO2 can be replaced. When to be removed.

due to the small size C02 cylinders are used, The gaseous CO2, which from the evaporator 25 when these are usually not intentionally cooled; Outlet 28 comes, is moved by condenser 29,

by being at ambient temperature, the gaseous CO2 is liquefied for re-liquefaction and it cools a higher internal pressure than the vapor pressure of the 15. The liquid CO2 will have liquid CO2 in the storage container 20 at the extraction temperature and will move it. From the tank 20, the liquid CO2 is pumped with pump 21. Excess pressure in the cylinders can be pumped through the heat exchanger 25 and thus circulated through the system through a suitable column 24 to the evaporator 25. Fri flow rate to drive, where you need the liquid CO2 can be met through valve 30 in the circuit unity of a pump. 20 to replace CO2, which when removing

As a practical matter, it is expedient that the extract was lost via valve 26 or when the extrac temperature of the liquid CO2 was refilled when the heat emission column was discharged.

2 to show any temperature differences. FIG. 2 shows how liquid CO2 moves upwards through zen between the ambient temperature and the actual extraction column 24. While taking into account machine extraction temperature. It is believed that 25 technical reasons prefer that the liquid CO2 move to the extractions in 11 generally below rather than upwards, it is possible that it will be carried down through half the ambient temperature and that the column will flow.

Liquid CO2 is thus cooled to compensate for the absorption of heat. Other forms of equipment can be used to achieve environmental compensation. Due to the fact that the extraction with liquid CO2 is used and the erfin environment is at ambient temperature, this extraction step up to 30 according to the invention is not limited by a temperature 20 ° C. warmer than the liquid CO2 in the extraction column of the form of the device in which the extraction will be. To carry out such an undesirable transfer of heat.

to the liquid CO2 to a minimum, the primary hop extract 40 is of high quality in FIG.

Extraction column and the associated pipework in liquid CO2, which is normally insulated, for example, under use valves, etc., in order to provide a suitable degree of thermal insulation for the device described in FIG. 1 or 2. Has been put together with an alkali, e.g. B. sodium or suitably isolated column needs the liquid CO2 more common potassium carbonate solution of a suitable concentration, eg. B. wise not more than about 2 or 3 ° C cooler than the desired 0.01 to 0.5 n, introduced into a vessel 42 which should be at the heating extraction temperature. It was found that coils 43 and capacitor 44 are provided. The 3 ° C generally a suitable range for a solution of the hop extract in the alkali, which are typically small-scale extraction apparatus. Where there are problems of 0.5 to 2 g / liter of a-acids at a pH of 8 to 11, with regard to the absorption of heat as a result of the proportionally larger areas of the surface that are soaked for 5 minutes to 2 hours, for example, the Isomerize acids in the extract to iso-a-acids. than is the case with commercial equipment. The vapor that escapes during this vaporization

From the heat exchanger 23, the liquid CO2 is drawn through 45 and the hop oil present in the primary extract is carried with it to the extraction column 24, which carries the hops in one. The steam and the hop oil are in the condensable form, e.g. B. condensed as powder or reduced tablets, tor 44 and they can be collected at 45, contains. In the illustrated apparatus, the column is vertical. After completion of the isomerization, the alkaline is arranged, the liquid CO2 being removed upward through the solution from the vessel 42 via valve 46 and through the

Column moves. 50 coolers 47 moves where the solution is preferably heated to a temperature

Although only one extraction column shown in Fig. 2 is cooled between 0 and 10 CC. After cooling, others can be set up in parallel, for example the solution 48 is fed into the vessel 49, which with the between B and B '; by equipping the (Xh flow with a stirrer 52 and the pH meter 51. The acid 50, a plurality of columns is guided (the necessary valves etc., for example hydrochloric acid, in a suitable concentration is not in that shown), it is possible to introduce the apparatus semi-continuously 55 in order to acidify the isomerized extract, for example if the columns which are fermenting, for example to a pH of 2.5 to 5. The acidic contain used hops, the mixture is stirred and the β-acids are precipitated, which are separated in order to feed them again with fresh hops, mixture which may be a filter aid, during extraction by the other column or other such as diatomaceous earth contains, is then continued via valve 53 through the filter ren columns, thus being able to pass 60 or the centrifuge 54. The filtered or centrifuged, a continuous extraction z u received. Solution 55 is then introduced into the vessel 56, which with

The liquid stirrer 59 and the pH meter 58 are equipped from the uppermost part of the extraction column. The sige CO2, which contains the extract, to an evaporator 25 Alkali 57, z. B. sodium and / or potassium hydroxide and / or where the CO2 is boiled away through the tube 28. The carbonate is introduced into the vessel 56 to make the solution of the evaporator alkaline, for example by warm 65 iso-a-acid, e.g. B. heated to adjust a pH water, which occurs at 27a and at 27b away from 8 to 10. This alkaline solution is then via valve 60th

flows. This warm water can be conveniently directed to the enrichment device 61, which is more convenient-40 ° C, although the temperature of the heating medium is up to a relaxation evaporator that with

630956

10th

Heating coil 62, steam separator 63, vacuum pump 64 and condensate collector 65 is provided. The temperature inside the evaporation device is preferably not more than 40 ° C. in order to avoid degradation of the iso-a acids. The concentrated iso-a-acid preparation can be removed from the collector via valve 66.

Although the apparatus illustrated in Figure 3 is said to produce a concentrated iso-a acid preparation, it is appreciated that, if desired, the isomerized a-acid solution may be from an earlier stage of manufacture, e.g. B. after the filter 54 or from valve 60, if desired, can be removed. The device was further described in batch mode; if necessary, a continuous or partially continuous operation can be accomplished.

The design of the individual parts of the equipment for use in such equipment is simple; actually suitable (although perhaps not the best possible equipment), one assumes, will be accessible «away from the subject». A truly continuous operation may require custom-built equipment, but it is believed that designing such equipment will not be a major difficulty for a chemical engineer in the field. An apparatus which is different from that specified can be expedient to meet special requirements; the isomerization step of the process according to the invention is not restricted by a special form of the device in which it is carried out.

The invention is further described in the following examples.

example 1

Extraction of hops (batch process) and transfer to an isomerized extract

100 g of powdered Wye Northdown hops containing 7.3% a-acid were generally extracted in the apartment shown in Fig. As described below.

1.0 liter of the liquid carbon dioxide was introduced via inlet 3 and associated valve 4 at a pressure of 730 p.s.i.g. introduced into cell 2. At this pressure, the temperature inside the cell was about 16 ° C. The cell was shaken for 15 minutes during which the pressure on 745 p.s.i.g.

was increased. Tap 7 was opened and the liquid was then moved through the sintered filter 6 in bottle 11, which was in the second cell 10. Tap 7 was closed; then tap 14 was opened and the liquid carbon dioxide was evaporated as a gas which was released into the atmosphere over a period of 45 minutes. The hops were extracted a further seven times using this procedure; the extracts containing residual solid carbon dioxide were piled up. The bottle was removed from the pressure vessel and the remaining solid carbon dioxide was evaporated via a Bunsen size to leave a yellow, viscous extract (15.8 g).

The extract was examined by thin layer chromatography using the method described by the European Brewery Convention (J. Inst. Brewing 1970, 76, 386); the presence of only a-acids and ß-acids was determined to be two distinct spots when the plate was sprayed with ferric chloride reagent. When the products obtained by extracting hops with organic solvents are examined by this method, the chromatogram is usually complicated and it consists of more than ten spots.

The extract was shown to contain 40.7% a-acid when evaluated by a conductometric method (J. Inst. Brewing 1970, 76, 343) using methanolic lead acetate. Thus, 88.1% of the accessible a-acids are extracted from the hops using carbon dioxide. Examination of the extract by column chromatography on Sephadex (J. Inst. Brewing, 1972, 78, 57) showed that 70.2% of the β-acid added in the hops had been extracted.

A 10.0 portion of the extract was steam distilled using the procedure similar to that described by Io Howard (J. Inst. Brewing, 1970, 76, 391); a total of 450 mg of hop oil was collected. In this experiment, the liquid carbon dioxide extracted 83% of the accessible oil from the hops.

Similar yields of oils and resins were obtained 15 when powdered Wye Challenger hops were extracted using liquid carbon dioxide using this procedure. This solvent was used to make whole hop cones of the Wye Challenger type and also cones that had not been dried, i.e. H. greener so hops to extract. Hop resins and oils were successfully extracted from these samples.

A 1.1 g portion of the extract, which was obtained from Wye-Northdown hops and contained 40.7% a-acid,

was placed in a bottle via a cohobic head, 25 which was provided with a condenser. 500 ml of 0.1N sodium carbonate was added and the mixture was soaked under a nitrogen atmosphere for 15 minutes. The hop oil was discarded and the mixture cooled to about 0 ° C; the pH was adjusted to 3o 4.0 by adding 2N hydrochloric acid. The mixture was stirred at a constant pH for one hour; Diatomaceous earth (10 g) was added; A nitrogen stream was passed through the mixture for 5 minutes to promote flocculation of the a-acids. The mixture was filtered through a diatomaceous earth bed (40 g) which had been washed with water. The filtrate 1 and the washing liquid were combined and the pH of the solution was adjusted to 9.0 by adding 2N potassium carbonate to give a dilute solution of the required isomerized extract. A qualitative examination of the to extract by thin layer chromatography showed the presence of iso-a-acids and ß-acids. A quantitative analysis of this extract using the method of Otter et al. (J. Inst. Brewing, 1972, 78, 57) showed that the yield of the iso-a acids 45 obtained from the hop extract was 79.9%. Thus 70.4% of the accessible a-acids, which were present in the Wye-Northdown hops, were converted into iso-a-acids.

The extract was concentrated to 15% iso-a acids (weight / volume) using a rotary evaporator without loss of iso-a acids (both temperature 35 ° C, 15 mm / Hg).

Example 2

Production of an isomerized extract (semi-continuous extraction of hops)

200 g of powdered Northern Brewer hops containing 6.1% α-acids were placed in the column of the semi-continuous extraction device shown in Fig. II. Liquid carbon dioxide was 60 for 5 hours at a pressure of 890-910 p.s.i.g. circulated by the system. The pressure in the system was released and the extract, which had been collected in the evaporator (40 ° C.), was recovered.

Another five 200 g samples of hops were extracted in the same way; the extract obtained from the six extractions was collected (157.8 g). The extract was examined using the procedures described in Example 1. The following results were obtained:

11

630 956

a) Only a-acids, ß-acids, could be determined with thin layer chromatography.

b) 93% of the accessible a-acids and 60% of the available ß-acids were extracted with the help of the liquid carbon dioxide.

c) 70% of the available hop oil was present in the extract.

28 g of hop extract containing 43% a-acids were isomerized in the same manner as described in Example 1; after filtration through diatomaceous earth, a yield of 98% iso-a-acid was obtained. Only trace amounts of a- and ß-acid were found in the extract.

The volume of the aqueous iso extract at pH 4 (8.2 liters) was reduced to less than one liter by evaporation at 50 ° C./15 mm Hg. The pH was then adjusted to 9 with 0.2N sodium carbonate solution; the volume was brought to one liter to give the isomerized extract as a black-yellow solution (overall yield of iso-a-acid 88%, i.e. 1.06 weight / volume (w / v)).

The additions to unhopped beer by adding the isomerized extract (diluted to 0.5% w / v iso-a-acid) before bottling were made in a ratio of 30 mg iso-a-acid per liter of beer. The bitterness of the resulting beer, which was measured by the recommended analytical method (J. Inst. Brew., 1971, 77, 181), was 26 EBU. The utilization of iso-a-acid in beer was 86%.

An isomerized extract was also added to the Hellbier container in a ratio of 42 mg iso-a-acid per liter of beer to beer before being bottled. The bitterness of the bottled beer measured as above was 35 EBU. The usability of the iso-a-acid in beer was therefore 83%.

A commercial, isomerized hop extract was added to a further filling of the same beer in the Hellbier container, this being done at the same dilution and in the same addition ratio as in the Iso extract used above. The initial turbidity readings of the resulting bottled beers as measured by the recommended analytical methods (]. Inst. Brew., 1971,77,181) were 0.60 EBC units for the beer made with that in this example Iso extract was made bitter, and 4.42 EBC units for the beer containing the commercial, isomerized hop extract. The turbidity indicator of the beer which had been obtained with the iso-extract produced in this example did not exceed 105 EBC units after 15 weeks of storage.

The beer was reckoned to have satisfactory storage stability in terms of haze formation if the haze reading after 12 weeks of storage was no more than 205 EBC units.

5 Induced swelling tests were carried out according to the method of Laws and McGuinness (J. Inst. Brewing, 1972, 78, 303) on the bottled beers when the beer loss was given as 0.4 g (Vi Schoppen) for the beer, which contained the iso extract produced in this example ent-10, and with 117.4 g / 'A Schoppen (pint) for the beer which contained the commercial, isomerized hop extract. For comparison, an equivalent bottled beer that has been traditionally brewed (ie it does not contain the addition of the extract or iso-extract after 15 brews) typically loses from 0.5 to 5 gl Vi point (point) in similar testing . Thus, the beer which had been made bitter with the new, isomerized extract had no tendency to swell.

20 Example 3

Semi-continuous extraction of hops in an industrial scale facility

830 g of powdery Wye Northdown hops containing 7.1% a-acid was placed in the column of a semi-25 continuous extractor, which is illustrated in FIG. 2. Liquid carbon dioxide was released at a rate of 6.4 liters / hour and a pressure of 870 p.s.i.g. passed through the system for 5 hours. The pressure in the system was released using exhaust valve 30; the extract (114.8 g) collected in the evaporator was isomerized using the procedure described in Example I; analysis of the product showed that the overall effectiveness of α-acid extraction and isomerization was 88%.

35

Example 4

Samples from a variety of hop species were extracted with liquid CO2 and isomerized according to the two methods described above. The extracts and isomerized extracts were of a similarly high purity. The results of the extractions and isomerizations are summarized in Table 3; the results of the tests for haze formation, swelling, bitterness and utility of these isomerized extracts when added to the beer are shown in Table 4.

Table 3

Hop species

Extraction time (hours)

Yield of the extract (% by weight on the hops)

Ratio of a-acids in the extract (% a-acids)

accessible extracted hop component (%)

Yield in isomerization (%)

a-acids' ß-acids hop oil

'' Overall yield of iso-a-acids yield (%)

Northern Brewer

5

13.2

46.0

96

87

67

97.4

93.5

Comet

3rd

13.8

39.9

95

60

71

70.0

66.5

Wye Northdown

2nd

15.4

43.5

92

81

83

79.9

73.5

Wye Target

1

13.8

54

81

56

86

95.1

77

630956

12

Table 4

Haze added haze (E.B.G. units) Induced bitterness of use

Iso-a acids ppm pour beer (E.B.U (%)

at the beginning after the addition (beer loss) (4) units)

Northern Brewer

24.5

0.52

0.55

none

21.4

87.3

Comet

24.8

0.52

0.52

none

20.5

82.7

Commercial Iso Extract A

25.3

0.52

3.8

69.7

19.1

75.5

Commercial Iso Extract B

25.0

0.52

4.1

78.2

18.9

75.7

Control (5)

-

0.52

-

0.5

-

-

(4) Weight loss from the bottles containing 278 ml of beer.

(5> unhopped beer

G

3 sheets of drawings

Claims (10)

630956 1. Process for the preparation of an iso-a-acid preparation, characterized in that hops are treated with liquid CO2 at a temperature of not less than -5 ° C., as a result of which at least some of the a-acids contained in the hops enter the Carbon dioxide is extracted, that a primary hop extract with high purity is isolated from the liquid carbon dioxide, and that the a-acids present in the hop extract are isomerized to iso-a-acids. 2. The method according to claim 1, characterized in that the temperature at which the hops are extracted with the liquid CO2 is in the range from -5 ° C to +20 ° C. 2nd PATENT CLAIMS 3. The method according to any one of claims 1 and 2, characterized in that the a-acids in the primary extract by boiling an aqueous solution of the extract for 1 s, which is adjusted to pH 8 to 11 with sodium and / or potassium carbonate, isomerized for a period of 5 minutes to 2 hours. 4. The method according to claim 3, characterized in that the aqueous solution is then cooled to a temperature of at most 40 ° C, that a pH value of 2 to 5 is set by adding acid, so that the β-acids from of the solution are precipitated, and the solution is filtered or centrifuged to remove the precipitated β-acids. 5. The method according to claim 4, characterized in that the filtered aqueous solution by evaporation, before. added under vacuum, at a temperature of at most 50 ° C., and that the pH of the solution is adjusted to 8-10 by adding alkali before, during or after the concentration. 6. The method according to claim 4, characterized in that the concentration of iso-a acids in the solution before acidification is not more than 5 g / liter. 35 7. Preparation, prepared by the method according to claim 1. 8. Preparation according to claim 7, produced by the method according to one of claims 2 to 6. 9. Use of the preparation according to claim 7 for making bitter 40 beer. 10. Use according to claim 9 of a preparation according to claim 8.