Fundamentals of beer and hop chemistry

Keukeleire, Denis De

doi:10.1590/s0100-40422000000100019

Cited by 216 publications

(225 citation statements)

References 8 publications

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“…Compounds characterization relied on UV spectra and reasonable molecular formulae calculated from mass measurements, both obtained from HPLC-DAD-ESI-MS/MS analysis and comparison of these data with the metabolites previously reported for this specie and literature data (Verzele & Keukeleire, 1991;GarciaVillalba et al, 2006;De Keukeleire, 2000). Combination of the UV and ESI data allowed the characterization of oxidation products of bitter acids, flavonoids and a procyanidin dimmer.…”

Section: Resultsmentioning

confidence: 99%

“…Likewise, there are cohulupone and hulupone the oxidation corresponding to colupulone and lupulone/adlupulone in five member ring structure (De Keukeleire, 2000). The α-acids and the corresponding iso-α-acids, as well as the β-acids, each occur in six different congeners differing in the carbon skeleton of the alkanoyl side chain.…”

Section: Introductionmentioning

confidence: 99%

“…Isohumulones are optically active molecules which occur as cis-and transisomers and gives rise to two epimeric isohumulones, which are distinguished as cis-isohumulones and transisohumulones, depending on the spatial arrangement of the tertiary alcohol function at C(4) and the prenyl side chain at C(5) (Bohr et al, 2008). Tetrahydro-iso-α-acids are obtained by hydrogenation of the double bonds in the side chains of the iso-α-acid and hexahydro-iso-α-acids are accessible by a combination of the reduction of the side-chain carbonyl group and hydrogenation of the double bonds (De Keukeleire, 2000). Iso-α and reduced iso-α-acid contribute to bittering values and antimicrobial property in beer and are easily deprotonated, being commonly referred to as acids, due to their beta triketo moiety (Garcia-Villalba et al, 2006;Hall et al, 2008), having pronounced bacteriostatic activity; they strongly inhibit the growth of Gram-positive bacteria (De Keukeleire, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Bitter acids from hydroethanolic extracts of Humulus lupulus L., Cannabaceae, used as anxiolytic

Negri¹,

Santi²,

Tabach³

2010

Rev. bras. farmacogn.

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RESUMO:Humulus lupulus L., Cannabaceae, é usada como sedativo e ansiolítico na medicina popular. O método de HPLC-DAD-ESI-MS n representa uma ferramenta poderosa para a análise de produtos naturais, desde que ela fornece o espectro de UV e informações estruturais sobre os constituintes da mistura. O objetivo deste trabalho foi o de caracterizar os constituintes encontrados no extrato hidroalcoólico. Os constituintes 1-9 foram tentativamente caracterizados através do UV/DAD e ionização por electrospray (MS/MS) depois da separação usando fase reversa, tempo de retenção e dados da literatura. Os principais compostos fenólicos (baseados na área dos picos) foram caracterizados como ácido hulupínico (9), coulupona (8), dois alfaácidos amargos oxidados (principais constituintes), um deles sendo um derivado da coumulinona oxidada (5) e o outro um derivado da humulinona oxidada (7), junto com uma procianidina B (3) e os flavonoides rutina (4) e o canferol-7-O-rutinosídeo (6). Esta planta conhecida devido às suas propriedades ansiolíticas e por ser um componente da cerveja, mostrou derivados oxidados de alfa-ácidos, como principais constituintes do extrato hidroalcoólico. Unitermos: Humulus lupulus, flavonoides glicosídeos, derivados de alfa-ácidos amargos oxidados, HPLC/DAD/MS/MS.ABSTRACT: Humulus lupulus L., Cannabaceae, is commonly used as light sedative and anxiolytics in folk medicine. HPLC-DAD-ESI-MS n represents a powerful tool for the analysis of natural products, since it can simultaneously provide a UV chromatogram and significant structural information about compounds in complex mixture. The aim of this work was characterize the constituents present in hydroethanolic extract. Compounds 1-9 were tentatively characterized on the basis of UV, MS/MS, after reversed phase separation, retention time and literature data. The main phenolic compounds (based on peak area) were characterized as hulupinic acid (9), cohulupone (8), two oxidized hop alfa-bitter acids (principal constituents), one being a oxidized cohumulinone (5) and the other an oxidized humulinone (7) derivatives, together with a procyanidin dimer B (3), flavonoids rutin (4) and kaempferol-7-O-rutinoside (6). This plant known, due to anxiolytic property and beer flavoring, showed oxidized hop bitter acids, as principal constituents, in its hydroethanolic extract.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bitter acids from hydroethanolic extracts of Humulus lupulus L., Cannabaceae, used as anxiolytic

Negri¹,

Santi²,

Tabach³

2010

Rev. bras. farmacogn.

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“…To identify the source of the intrinsic fluorescence at excitation wavelengths >300 nm, comparisons were made with various types of hops, a rich source of iso-a-acids which are known to impart a unique bitterness and aroma to beer 9,13 . The steady-state fluorescence spectra for 'Target' hops, which have been pre-isomerised and are thus already bitter, are shown in Fig.…”

Section: )79087 %2( (-7'977-32 *Pysviwgirgi Glevegxivmwxmgw Sj Fiivmentioning

confidence: 99%

Beer Fluorescence and the Isolation, Characterisation and Silica Adsorption of Haze-Active Beer Proteins

Apperson

Leiper

McKeown³

et al. 2002

Journal of the Institute of Brewing

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The fluorescence spectra and lifetimes of diluted beer have been explored and found not to report on protein removal either by silica or tannic acid, nor polyphenol uptake by PVPP. Comparing the fluorescence spectra of beer with that of tea and hops, it seems that proteins, complex polyphenols and iso-a-acids can contribute to the intrinsic fluorescence of beer, although the contribution from polyphenols must be minimal since treatment with PVPP does not dramatically change the background fluorescence. To eliminate the problem of background fluorescence haze-active protein was isolated. Steady-state and time-resolved fluorescence techniques were used to characterise these and to monitor their uptake by different silica gels as a function of pH. Heat treated large pore volume, small surface area silicas were the more effective adsorbers for the proteins under study, with pH 4 being optimum. Using both intrinsic amino acid fluorescence and the extrinsic fluorophore fluorescamine, the timeresolved fluorescence anisotropy has been measured and the radius of the isolated haze protein found to be ~ 35 Å. Comparisons have been made with proteins of known size and structure such as human and bovine serum albumins (HSA and BSA). Key words:Beer, fluorescence, haze-active protein, polyphenols, silica adsorption. -2863(9'8-32The intrinsic fluorescence characteristics of beer are expected to be complex due to the overlap of emissions from numerous species. Nevertheless once the different origins of the fluorescence have been identified, by comparison with the isolated species, new insights may be found into the brewing and stabilisation processes. With this goal in mind, various constituents in beer have been studied and compared using steady-state and time-resolved fluorescence techniques.The interaction of protein with amorphous silicas, eg., silica hydrogels, silica xerogels, is of interest to the beverage industry. Of importance is its role in the prevention of chill haze, and subsequent risk to permanent haze formation in fruit-based beverages or cereal based beverages, such as beer. Chill haze forms as a result of the interaction of haze-active proteins with polyphenols. In order to maintain the clarity of beer and to extend colloidal shelf life, the brewing industry selectively removes these proteins from beer by adsorption onto and into amorphous silicas. Information regarding the detailed structure and amino acid sequence of these haze-active proteins is limited. In general terms, there are two types of protein present in beer: hydrophilic and hydrophobic. The hydrophilic proteins are responsible for haze formation and need to be removed whereas the hydrophobic proteins provide foam stability and must remain 16 . Bentonite removes both hazeactive and foam-active protein whereas silica gel offers specificity for haze-active proteins 20 . This specificity is a result of the proline residues in the haze-active proteins. These proline rich proteins are known to originate from malt and have an isoelectric point in the re...

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“…A further approach to reduce losses is the use of downstream products. Besides the traditionally used iso-extract, which is added just before filtration, the use of reduced isohumulones such as rho-, tetrahydro-or hexahydro-isohumulones can reduce the risk of production of a skunky lightstruck flavour in bottled beer and also improve foam stability 27 .…”

Section: Introductionmentioning

confidence: 99%

Degradation of Iso-α-Acids During Wort Boiling

Kappler

Krahl

Geißinger

et al. 2010

Journal of the Institute of Brewing

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A detailed study on the degradation of iso-α-acids was conducted. Because of the complexity of the wort matrix and interfering interactions during real wort boiling, the investigation of degradation kinetics was performed in an aqueous solution. Degradation was investigated as a function of time (0-90 min), temperature (80-110°C), pH value (4-7), original gravity (10-18°P) and ion content of the water (0-500 ppm Ca 2+ and Mg 2+ ). After 90 min of boiling, over 20% of the dosed iso-α-acids could no longer be detected. A strong dependence of degradation could be shown due to high temperature, low pH, high original gravity and a high Mg 2+ content. The cis:trans ratio and co-iso-α-acid content did not change significantly. Losses of isohumulones could be lowered by reducing the temperature and original gravity, as well as by heightening the pH value. High amounts of Ca 2+ and Mg 2+ salts also led to an increase in degradation products. Solutions to decrease degradation and thereby possible improvements in sensory bitter quality are discussed.

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Fundamentals of beer and hop chemistry

Cited by 216 publications

References 8 publications

Bitter acids from hydroethanolic extracts of Humulus lupulus L., Cannabaceae, used as anxiolytic

Bitter acids from hydroethanolic extracts of Humulus lupulus L., Cannabaceae, used as anxiolytic

Beer Fluorescence and the Isolation, Characterisation and Silica Adsorption of Haze-Active Beer Proteins

Degradation of Iso-α-Acids During Wort Boiling

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