Changes in bitterness as beer ages naturally

King, Bonnie M.; Duineveld, C.A.A.

doi:10.1016/s0950-3293(98)00040-8

Cited by 43 publications

(45 citation statements)

References 13 publications

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“…2. As reported in several studies 8,18,30,31,33,59 , significant degradation of iso-α-acids occurs during beer ageing, due to oxidative deterioration. After ageing for 60 days at 30°C, the remaining relative concentration of iso-α-acids in the beers is comparable.…”

Section: Evaluation Of Bitterness Profilesmentioning

confidence: 73%

Flavour Instability of Pale Lager Beers: Determination of Analytical Markers in Relation to Sensory Ageing

Malfliet

Opstaele

Clippeleer

et al. 2008

Journal of the Institute of Brewing

125

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Flavour changes of six Belgian pale lager beers were studied in order to estimate the importance of different parameters and reactions in relation to the ageing process. An attempt was made to link analytical data with sensory evaluation using multivariate statistical analysis. Partial least squares regression techniques (PLSR) were employed on the analytical and sensory data. As apparent from the PLSR model, significant indicators of lager beer ageing are aldehyde markers (especially total aldehydes, furfural, hexanal, 2-methylpropanal, 2-methylbutanal, and 3-methylbutanal), cold and permanent haze, and beer colour. Conversely, compounds or parameters that load negatively in the PLSR model for beer ageing are trans-isohumulones, cis-isohumulones, total bitterness, the T/C-ratio, polyphenolic markers (especially proanthocyanidins), the flavanoid content, and, to a lesser extent, the TB-index and reducing power (TRAP). The integrated analytical-sensorial methodology is proposed as a useful tool for evaluation of the flavour instability of pale lager beers.

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Section: Evaluation Of Bitterness Profilesmentioning

confidence: 73%

Flavour Instability of Pale Lager Beers: Determination of Analytical Markers in Relation to Sensory Ageing

Malfliet

Opstaele

Clippeleer

et al. 2008

Journal of the Institute of Brewing

125

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“…In contrast to the cis-iso-a-acids, the corresponding transiso-a-acids have long been known to be rapidly degraded upon storage of beer, [8,[10][11][12][13][14][15][16] thus demonstrating their stereospecificity as a key factor for the different reactivity of the iso-a-acid isomers. Early studies investigated the stereochemistry of these iso-a-acids by converting them into degradation products of known stereochemistry and showed evidence that cis-and trans-iso-a-acids (2, 3; Scheme 1) differ in the configuration at the carbon atom C4.…”

Section: Resultsmentioning

confidence: 99%

“…[3][4][5] In particular, photodegradation [6] and radical-assisted oxidation of iso-a-acids [7] are generally accepted to be responsible for the generation of potent off-odor compounds, but the available information on nonvolatile off-taste is rather fragmentary. Although aging of beer has long been known to induce a significant decrease in the intensity of the bitterness as well as a change of the bitter taste quality towards a long-lasting, lingering, and harsh bitterness and, in consequence, continues to cause severe quality problems for the brewing industry, [8][9][10] the molecular basis of the deterioration of that bitterness is not known. Multiple studies have demonstrated that the aging of beer induces a decrease of the amounts of trans-iso-a-acids (3), whereas the corresponding cis-iso-a-acids (2) seem to be comparatively stable.…”

Section: Introductionmentioning

confidence: 99%

“…Multiple studies have demonstrated that the aging of beer induces a decrease of the amounts of trans-iso-a-acids (3), whereas the corresponding cis-iso-a-acids (2) seem to be comparatively stable. [8,[10][11][12][13][14][15][16] Although numerous publications have proposed chemical structures of putative degradation products of isoa-acids obtained from model experiments, [17][18][19][20] most of these studies have been performed under rather artificial conditions, for example, iso-a-acids were degraded at highly alkaline pH values or in the presence of hydrogen peroxide. Consequently, the presence of a majority of these compounds could not been unambiguously verified in authentic beer samples.…”

Section: Introductionmentioning

confidence: 99%

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Structures of Storage‐Induced Transformation Products of the Beer’s Bitter Principles, Revealed by Sophisticated NMR Spectroscopic and LC–MS Techniques

Intelmann

Kummerlöwe

Haseleu

et al. 2009

Chemistry A European J

108

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Besides undesirable changes in the attractive aroma, a significant decrease in the intensity of the bitterness as well as a change of the taste into a lingering, harsh bitterness has long been known as a shelf-life limiting factor of beer. Multiple studies have demonstrated that the aging of beer induces a decrease of the total amount of cis- and trans-iso-alpha-acids, the well-known bitter principles of beer. Although the trans-iso-alpha-acids exclusively, not the cis-iso-alpha-acids, were found to be degraded upon storage of beer, the key transformation products formed exclusively from the trans isomers in beer are not known. In the present study, suitable model experiments followed by LC-MS/MS and sophisticated NMR spectroscopic experiments, including the measurement of residual dipolar couplings (RDCs) in gel-based alignment media as well as a novel broadband and B(1)-field-compensated incredible natural abundance double-quantum transfer experiment (INADEQUATE) pulse sequence, enabled the identification of a series of previously unknown trans-specific iso-alpha-acid transformation products, namely, tricyclocohumol, tricyclocohumene, isotricyclocohumene, tetracyclocohumol, and epitetracyclocohumol, respectively. HPLC-MS/MS analysis of these compounds, which exhibit the aforementioned harsh lingering bitter taste and have threshold concentrations ranging from 5 to 70 micromol L(-1), confirmed their generation during aging of beer and, for the first time, explained the storage-induced changes of the beer's bitter taste on a molecular level.

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“…Upon storage in the absence of light, these compounds rapidly undergo degradation in the presence of oxygen species 18,24,32 . This oxidative degradation of iso-α-acids results in a significant decline in beer bitterness intensity and a quality change towards a lingering, more harsh bitterness, accompanied by an astringent note in the taste 10,22,27,28,36 , and has been linked to the development of volatile carbonyl compounds such as 2-methylpropanal, 2-methylbutanal and 3-methylbutanal, associated with staling of beer flavour 4,17,18,33,51 . On the other hand, the oxidative decomposition of iso-α-acids during beer ageing has also been linked to the formation of a series of nonvolatile trans-specific cyclic iso-α-acid transformation products, exhibiting the aforementioned harsh lingering bitter taste 22,27,28 .…”

Section: Introductionmentioning

confidence: 99%

Influence of the Hopping Technology on the Storage-induced Appearance of Staling Aldehydes in Beer

Clippeleer

Rouck

Cooman

et al. 2010

Journal of the Institute of Brewing

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In this paper, the involvement of iso-α-acids in the appearance of stale flavour in beer during storage was examined. Flavour instability upon storage, by far the most important quality problem of beer, may be caused by a multitude of reactions, in particular, the degradation of trans-iso-α-acids is pivotal. In order to gain improved understanding of the beer ageing process, the behaviour of the stereoisomers of the bitter acids was studied for the first time in pilot beers at particularly high and low proportions of the trans-iso-α-acids concentration relative to the cis-iso-α-acids concentration. Therefore, pure trans-respectively cis-isomers were required and obtained on a pilot scale by the separation of trans-iso-α-acids as β-cyclodextrin inclusion complexes from a commercial isomerised hop extract, permitting the quantitative dosage to beer in mg/L amounts. The relationship between the storage-induced degradation of these iso-α-acids in authentic beer samples and the increase in staling aldehydes, especially 2-methylpropanal, 2-methylbutanal and 3-methylbutanal, is the subject of further investigations. A remarkable increase in the relative concentration of cis-iso-α-acids was observed in the beers bittered with purified trans-iso-α-acids, which may be ascribed to partial conversion, i.e., reverse isomerisation, of trans-iso-α-acids via α-acids into cis-iso-α-acids. In spite of the trans-specific degradation observed during ageing, the decomposition of these bitter acids leading to volatile carbonyl compounds is of minor importance. Aldehyde formation as a function of forced ageing was irrespective of the mode of bittering, emphasising that malt quality and the brewing process itself are probably the most important factors regarding the flavour instability of beer.

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Changes in bitterness as beer ages naturally

Cited by 43 publications

References 13 publications

Flavour Instability of Pale Lager Beers: Determination of Analytical Markers in Relation to Sensory Ageing

Flavour Instability of Pale Lager Beers: Determination of Analytical Markers in Relation to Sensory Ageing

Structures of Storage‐Induced Transformation Products of the Beer’s Bitter Principles, Revealed by Sophisticated NMR Spectroscopic and LC–MS Techniques

Influence of the Hopping Technology on the Storage-induced Appearance of Staling Aldehydes in Beer

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