Classifications

• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12C—BEER; PREPARATION OF BEER BY FERMENTATION; PREPARATION OF MALT FOR MAKING BEER; PREPARATION OF HOPS FOR MAKING BEER
  • C12C5/00—Other raw materials for the preparation of beer
  • C12C5/02—Additives for beer
  • C12C5/026—Beer flavouring preparations
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12C—BEER; PREPARATION OF BEER BY FERMENTATION; PREPARATION OF MALT FOR MAKING BEER; PREPARATION OF HOPS FOR MAKING BEER
  • C12C3/00—Treatment of hops
  • C12C3/04—Conserving; Storing; Packing
  • C12C3/08—Solvent extracts from hops
  • C12C3/10—Solvent extracts from hops using carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12C—BEER; PREPARATION OF BEER BY FERMENTATION; PREPARATION OF MALT FOR MAKING BEER; PREPARATION OF HOPS FOR MAKING BEER
  • C12C3/00—Treatment of hops
  • C12C3/12—Isomerised products from hops
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12C—BEER; PREPARATION OF BEER BY FERMENTATION; PREPARATION OF MALT FOR MAKING BEER; PREPARATION OF HOPS FOR MAKING BEER
  • C12C9/00—Methods specially adapted for the making of beerwort
  • C12C9/02—Beerwort treatment; Boiling with hops; Hop extraction
  • C12C9/025—Preparation of hop extracts; Isomerisation of these extracts; Treatment of beerwort with these extracts; Surrogates of the hop

Definitions

• Difficulties include unwanted variations in yeast cultures, in hops, in malt, in adjuncts, in times, in temperatures, and the human element of the brewhouse. Beer presents a subtle combination of carbonation, foam, mouth feel, bitterness, and aroma when smelted and swallowed. Whatever can be done to improve the reproducibility and control of even one variable is exceptionally important.
• Hop flavors have attracted widespread interest in recent years for use in controlling and standardizing the flavoring of beer including ale, especially by post- fermentation treatment.
• U.S. Patent No. 4,778,691 teaches that unidentified hop-derived substances, when present during fermentation, are either metabolized or removed by the yeast. However, when they are added post-fermentation, they complex or esterify with the alcohol present to give undesirable fruity-estery-fatty or stout type of aromas during normal storage of the beer. Therefore, a post-fermentation hop flavored fresh beer may be acceptable, but one aged for several weeks may not.
• U.S. Patent No. 4,778,691 also states that the prior art is not effective in removing the undesirable impurities.
• Todd U.S. Patent No. 4,002,683 removes humulinic acid, tannins, sugars, and gushing promoters.
• Humphrey U.S. Patent No. 4,302,479) performs a highly acidic wash of an organic solvent solution of extract. Neither procedure, because of the very acidic pH used for purification, removes neutral materials.
• Lance U.S. Patent No. 4,395,431 elutes these substances with the alpha acids, and does not remove or separate them.
• Westermann U.S. Patent No. 3,798,332
• the procedure of Humphrey U.S. Patent No. 3,875,316 also does not remove them.
• U.S. Patent No. 4,778,691 teaches the extraction of impurities by agitating the hop flavor with water at a pH of 4 to 12 and extracting the impurities from the organic phase into the aqueous phase. Also, U.S. Patent Nos. 5,013,572 and
• U.S. Patent Nos. 3,552,975 and 3,923,897 teach the production of tetrahydroisoalpha acids from beta acids by a process including hydrogenolysis of beta acids to form desoxyalpha acids, oxidation of desoxyalpha acids to form tetrahydroalpha acids and isomerization of tetrahydroalpha acids to form tetrahydroisoalpha acids.
• the present invention is directed to a process for preparing hop flavors that includes the removal of undesired impurities from the hop flavor.
• the process comprises an improved process for conversion of beta acids to tetrahydroisoalpha acids.
• the beta acids are hydrogenated in a (C.-C 6 )alkanol to produce desoxytetrahydroalpha acids, the desoxytetrahydroalpha acids are oxidized to produce tetrahydroalpha acids and the tetrahydroalpha acids are isomerized to produce tetrahydroisoalpha acids.
• the improvement comprises dissolving the desoxytetrahydroalpha acids in a high boiling point solvent and removing the (C,- C 6 )alkanol by azeotrope prior to isomerization.
• the alkanol is removed prior to oxidation with the peracid and the high boiling point solvent is toluene.
• the advantage of the process is that it utilizes certain solvents (e.g., toluene) to aid in the removal of alcohols used in an initial process step.
• solvents e.g., toluene
• beta acids are derived from hops where they exist as different homologs, stereoisomers, optical isomers, and combinations thereof.
• the primary homologs are those in which R is isopropyl, isobutyl or sec-butyl.
• Beta acids can be isolated from hops by a process in which the organic components of the crushed hop cones are extracted by liquid C0 2 .
• beta acids are then separated from the alpha acids using an aqueous extraction at a pH of about 8 to about 8.3.
• aqueous extraction at a pH of about 8 to about 8.3.
• synthetic production of beta acids has been described, albeit at low yields, by for example, K. G. Drewett, D. R. J. Laws, J.
• the beta acids are used to prepare desoxytetrahydroalpha acids having the following formula:
• R is isopropyl, isobutyl or sec-butyl.
• the desoxytetrahydroalpha acids are used to prepare tetrahydroalpha acids having the following formula:
• TAIAA tetrahydroisoalpha acids
• R is isopropyl, isobutyl or sec-butyl.
• THIAA as produced by the processes of this invention has two sites of optical activity in the ring, thus contains cis and trans stereoisomers.
• the process of this invention comprises the reduction of beta acids to form desoxytetrahydroalpha acids, the oxidation of the desoxytetrahydroalpha acids to form tetrahydroalpha acids and the isomerization of the tetrahydroalpha acids to form THIAA.
• a high boiling point solvent is used to remove undesirable odor forming constituents. More specifically, the reduction process involves using a reducing medium comprising hydrogen gas, preferably in the presence of a noble metal catalyst.
• the process comprises adjusting, if necessary, the pH of a solution of the beta acid to the desired range, and if necessary, adding buffering agents (described below) as desired and exposing the beta acid to hydrogen at elevated temperatures and pressures, typically in the presence of a hydrogenation catalyst.
• any source of hydrogen gas may be used in the hydrogenation of this invention.
• the reaction may be performed under a mixture of hydrogen with a safe and reaction inert gas such as nitrogen.
• a hydrogenation catalyst such as a noble metal, which increases the speed of the reaction.
• palladium is utilized as it has been found to provide high yields, good purity and short reaction times in contrast to other hydrogenation catalysts.
• the catalyst is disposed on a finely divided support material.
• Preferable support materials included finely divided carbon, barium carbonate, barium sulfate, calcium carbonate and alumina. Suitable carbon supported palladium catalysts are well known in the art.
• the reduction is performed at a pressure of about atmospheric to about 100 psig and higher (e.g., 2000 psig). Generally, a higher pressure increases the rate of reaction. Preferably, the reaction is performed at a pressure of about 40 psig to about 60 psig because of typical equipment constraints.
• Any temperature can be used at which the beta acids are in solution (e.g., those described below); however, preferably, the temperature is about 50°C to about 200°C because below about 50°C the beta acids may come out of solution and above about 200° C the reactants may be degraded.
• reaction time depends on the pressure, temperature, reactant concentration, catalyst amount, etc.; however, for typical conditions of 50 psig, 100°C, 20% by weight beta acids, and 2% by weight catalyst, reaction times of about 4 hours to about 6 hours are normal.
• a (C C 6 ) alkanol is used as a solvent and preferably methanol is used. Typically concentrated sulfuric or hydrochloric acid is added to the solution prior to hydrogenolysis.
• the thus-formed (C,-C 6 ) alkanol solution of desoxytetrahydroalpha acids is then combined with a suitable high boiling point solvent and the alcohol is removed by azeotropic distillation.
• the alcohol/ desoxytetrahydroalpha acids solution may be concentrated prior to addition of the high boiling solvent and subsequent distillation. The azeotropic distillation may be assayed to assure that the alcohol has been removed.
• the azeotropic removal of the (C.-C 6 )alkanol may be delayed until later, however, it must be performed prior to the transformation of the tetrahydroalpha acids to the isoalpha acids (e.g., the addition of base).
• the azeotropic distillation may be repeated at different times to assure removal of the alkanol.
• reaction inert solvent which is a solvent for the desoxytetrahydroalpha acids
• high boiling point is meant that the solvent has a boiling point significantly above that of the (C,-C 6 )alkanol, i.e. greater than 100°C.
• reaction inert is meant a solvent which does not interact with starting material, reagents, intermediates or the desired product in a manner which adversely affects the yield of the desired product.
• Typical solvents include C 8 -C 15 hydrocarbons, aromatics, chlorinated aliphatics of C 4 or higher, esters and ethers.
• Exemplary aromatics include toluene, xylenes, ethylbenzene, chlorobenzenes, and chlorotoluene.
• Exemplary aliphatics include isomeric octanes, isomeric nonanes, isomeric undecanes and isomeric dodecanes.
• Exemplary chlorinated aliphatics include isomeric dichlorobutanes, isomeric dichlorobutenes, isomeric dichlorohexanes and isomeric dichlorohexenes.
• Exemplary esters include propyl acetate, butyl acetate and ethyl butyrate.
• Exemplary ethers include butyl ether, isobutyl ether, diglyme and triglyme.
• Preferred solvents include toluene, xylene, isooctane, decane, diglyme, butyl acetate and 1 ,2-dichlorobenzene.
• the resulting desoxytetrahydroalpha acids solution is then oxidized using a peracid to produce tetrahydroalpha acids.
• a peracid e.g., peralkanoic acid
• any peracid e.g., peralkanoic acid
• peracetic acid is preferred. Oxidation can be facilitated by using an excess of peracetic acid at ambient or slightly elevated temperatures in one hour or less. This is described in more detail in U.S. Patent No. 3,923,897 the disclosure of which is hereby incorporated by reference.
• the resulting tetrahydroalpha acids solution is then isomerized to isoalpha acids in the above described high boiling point solvent/water solution at temperatures which are typically below about 50° C and ordinarily at ambient temperature.
• the procedure for transforming the tetrahydroalpha acids into isoalpha acids involves contact of an aqueous solution of a metal ion with the high boiling point, reaction inert, organic solvent/water solution of the tetrahydroalpha acids under conditions whereby the tetrahydroalpha acids remain dissolved in the organic solvent.
• the temperature can be and conveniently is below about 50° C; the pH of the water phase is maintained above about 7, preferably at least 8.0 and preferably 13 or below.
• a metal ion selected from the group consisting of calcium and magnesium ions is preferably present and it is especially preferred that the calcium ion is employed.
• the isomerization can occur without the addition of alkali metal cations at a temperature of about 80 °C or higher.
• the mixture is held until isomerization occurs, the solvent is removed and the metal ions are removed, preferably by washing the product contained in the solvent with dilute acid prior to removal of the solvent.
• This process removes a variety of undesired impurities from the hop flavors.
• the process is well suited for removing odor- or aroma-forming impurities or contaminants.
• these impurities impart fruity, estery, fatty, or sour type aromas, to hop flavors. It is believed these impurities are typically present at levels of about 0.1 ppm to about 100 ppm. It is believed some of these impurities are a result of using alcohols (e.g., methanol) in the production of the hop flavors.
• This process results in purified hop flavors.
• purified is meant essentially void of the odor forming impurities described above. This may be tested for by the organoleptic test described below.
• the test sample is dissolved in 95% alcohol to obtain a concentration of 1 -2% of the hop flavor.
• the exact concentration of the hop flavor in the alcohol solution is determined by HPLC.
• a 6 1 /2 oz. bottle of sparking mineral water is uncapped and a quantity of alcohol solution calculated to give an overall concentration of 5 ppm of hop flavor is added.
• the bottle is recapped and inverted 2 or 3 times to mix it.
• the bottle is stored in a refrigerator for at least 18 hours prior to tasting.
• the samples are divided into sets of four. Each set includes a control prepared from analytically pure hop flavor.
• the samples are assigned arbitrary code numbers.
• a 1-2 oz. portion of each sample of a set is poured into a clean glass marked with the code number and distributed to a panel of four tasters.
• EXAMPLE 1 Crystalline beta acids (25 gm) were added to a flask containing 200 mL of methanol, followed by 7.35 gm of concentrated sulfuric acid at 20-25 °C with stirring. The solution was stirred for 1 hour, then 5.0 gm of 5% palladium on carbon catalyst prewet with 5 gm of water was added to the solution. The mixture was placed in a Parr bottle and hydrogenated at 50 PSI and 50°C for 2 hours. It was then cooled to 0-5°C and the catalyst was filtered off. The spent catalyst was then washed with methanol. The layers were combined, and most of the methanol was stripped off under vacuum, keeping the temperature below 40° C.
• Example 2 In analogous preparations to Example 1 , the hydrogenolysis step was run with ethanol and isopropanol as solvents. This produced two materials with no fruity odor.
• Example 1 As a contrasting example to Examples 1-4, the Example 1 process was performed except, when the hydrogenolysis solution was extracted with hexane or methylene chloride instead of toluene, the final products had a fruity odor.

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• 1995
  • 1995-05-22 WO PCT/IB1995/000394 patent/WO1996000774A1/en not_active Ceased
  • 1995-05-22 EP EP95917457A patent/EP0770124A1/de not_active Withdrawn

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