Compounds In Beer Research Articles

Analysis of flavour compounds in beer with extruded corn starch as an adjunct

Analysis of flavour compounds in beer with extruded corn starch as an adjunct

Kinetic Models for the Role of Protein Thiols during Oxidation in Beer.

Thiol-containing proteins have been suggested to have antioxidative properties in beer. A kinetic model has been setup for the reactivity of thiols during early stages of oxidative degradation of beer. Kinetic analysis based on the proposed reaction mechanism allowed evaluation of the relative reactivity of beer components, such as bitter acids from hops and polyphenols. The rate constants for the reaction of 1-hydroxyethyl radicals, which are generated during radical mediated oxidation of ethanol in beer, with hop bitter acids and thiols were very similar, and the concentration of these compounds in beer is therefore essential for the relative reactivity. For a standard pilsner beer with 35 international bitter units with typical concentrations of thiols and hop bitter acids, thiols were found to react with ca. 9% of 1-hydroxyethyl radicals, while bitter acids from hops accounted for ca. 88% of the reaction with 1-hydroxyethyl radicals. Polyphenols were not found to account for any major part of the reaction with 1-hydroxyethyl radicals due to low reaction rates and low concentrations in pilsner beer compared to the other components. The kinetic model suggests that the concentration of thiols has to be increased in order to contribute with any significant antioxidative protection and that the fate of thiols during oxidation must be considered since some thiol oxidation products may induce further damage.

Intracellular metabolite profiling of industrial yeast and the synthesis of flavour compounds in beer

Beer quality is largely guaranteed by a rational ratio of different flavour compounds. In this study, we present intracellular metabolic profiles in the light of lager beer flavour compound synthesis on an industrial scale. A total of 62 intracellular metabolites were identified and quantitatively analysed. Among these, amino acid was identified as the most dominant category of metabolites. We also report gene expression profiling of relevant genes encoding six representing amino acids, including serine, alanine, lysine, valine, leucine and asparagine. Nine genes involved in the amino acid synthesis – ALT1, ALT2, ASN1, ASN2, BAT1, SER2, SHM1, SHM2 and LYA1 – displayed significantly higher level of expression at various fermentation stages in an industrial lager fermentation. However, concentrations of the recovered amino acids decreased towards the end of fermentation. Our results suggested that the defined amino acids could be assimilated by the yeast to be utilized for synthesis of aroma-active metabolites at different stages in fermentation. Copyright © 2017 The Institute of Brewing & Distilling

Optimalizace stanovení obsahu dimethylsulfidu v mladině a pivu

Sulphur compounds present in barley, malt and beer are mostly non-volatile substances (amino acids, proteins, inorganic sulphates) from which volatile sensory active substances can be produced under certain conditions. The presence of these substances in beer can adversely affect its organoleptic properties. Dimethyl sulfi de (DMS) is one of the most studied volatile sulphur compounds in beer; therefore a suitable analytical method for monitoring DMS content is necessary. The static headspace method coupled to gas chromatography with fl ame photometric detector (HS-GC-FPD) used for the determination of DMS content in wort and beer was optimized and validated. Optimal yield of HS extraction was achieved after 30 minutes at 50 °C. DMS contents moved from 9.6 to 59.6 μg.l-1 in the analysed worts, from 6.1 to 34.9 μg.l-1 in beers.

Ethanol Content Has Little Effect on the Sensory Orthonasal Detection Threshold of Hop Compounds in Beer

Many factors contribute to the complexity of beer flavor, including odor-active hop oil compounds. Best estimate thresholds of 10 hop compounds were reported in unhopped pale ale beer with ethanol contents of 5 and 10% alcohol by volume (ABV) using ASTM E679 threshold methodology. Although the solvating properties of ethanol had the potential to impact solubility, this study concluded that variation in the ethanol content had little effect on the sensory orthonasal detection thresholds of hop compounds in beer. Seven of the compounds were not influenced by ethanol concentration. Ethanol had a statistically significant effect on the threshold concentrations of β-damascenone (195 μg/L in 5% ABV to 74 μg/L in 10% ABV), but the practical significance of the 36 ppb difference between the two ethanol contents is uncertain. The threshold concentrations of geraniol and linalool significantly increased when more ethanol was present, from 141 to 305 μg/L and from 83 to 205 μg/L, respectively. The potential ethanol suppression of terpene alcohols was relatively small, 2.5-fold, and would likely have little impact on the odor activity values (OAVs). The results of this study can be used for OAV calculations across a wide range of ethanol concentrations in beer.

Identification of volatile organic compounds extracted by headspace solid-phase microextraction in specialty beers produced in Brazil

Beer is a very complex mixture, being an alcoholic beverage obtained by fermentation processes. The consumption and production of specialty beers in Brazil have increased in the past years; however, most Brazilian brewers still depend on imported commercial starter yeast strains and raw materials. Our data also indicate that volatile profile of Brazilian beers is more influenced by raw materials. The analysis of volatile compounds in beer is important for its quality control, and the presence of aromatic substances is related to the beverage acceptance and quality. In this study, headspace solid phase microextraction in combination with gas chromatography coupled to mass spectrometric detection was used for the identification of the volatile organic compounds in 30 samples of Brazilian Pilsen and ale beers. Ninety-nine volatile compounds were identified and grouped into ketones, terpenes, esters, higher alcohols, aldehydes, fatty acids, hydrocarbon and other minority compounds. Analysis of the principal components showed that the majority of specialty beers have similar chemical characteristics, their volatile profile being characterized mainly by esters and higher alcohols. Additional studies are necessary to better characterize Brazilian specialty beers; however, our results open perspectives for future research of possible indicators and markers that may serve for the purposes of certification, as well as quality control of the beverage. Copyright © 2017 The Institute of Brewing & Distilling

Iso-α-acids, Bitter Components of Beer, Prevent Inflammation and Cognitive Decline Induced in a Mouse Model of Alzheimer's Disease

Alongside the rapid growth in aging populations worldwide, prevention and therapy for age-related memory decline and dementia are in great demand to maintain a long, healthy life. Here we found that iso-α-acids, hop-derived bitter compounds in beer, enhance microglial phagocytosis and suppress inflammation via activation of the peroxisome proliferator-activated receptor γ. In normal mice, oral administration of iso-α-acids led to a significant increase both in CD11b and CD206 double-positive anti-inflammatory type microglia (p < 0.05) and in microglial phagocytosis in the brain. In Alzheimer's model 5xFAD mice, oral administration of iso-α-acids resulted in a 21% reduction in amyloid β in the cerebral cortex as observed by immunohistochemical analysis, a significant reduction in inflammatory cytokines such as IL-1β and chemokines including macrophage inflammatory protein-1α in the cerebral cortex (p < 0.05) and a significant improvement in a novel object recognition test (p < 0.05), as compared with control-fed 5xFAD mice. The differences in iso-α-acid-fed mice were due to the induction of microglia to an anti-inflammatory phenotype. The present study is the first to report that amyloid β deposition and inflammation are suppressed in a mouse model of Alzheimer's disease by a single component, iso-α-acids, via the regulation of microglial activation. The suppression of neuroinflammation and improvement in cognitive function suggests that iso-α-acids contained in beer may be useful for the prevention of dementia.

Flavour-active volatile compounds in beer: production, regulation and control

Many classes of compounds have been shown to play an important role in the development of flavour characteristics of beer. This significantly influences its taste and sensory properties, thus affecting its market performance. Despite the intensive research aimed at unravelling the precise mechanism and regulation of flavour formation in beer, current knowledge remains far from complete. Several reviews are available on the general composition of beer and yeast metabolic pathways involved in the production of volatile compounds in beer. However, a limited amount of work has been reported concerning the influence of some of the beer constituents and other important parameters on beer flavour. This paper reviews the current knowledge of the biochemistry behind flavour formation in beer and discusses the different factors that influence its formation and how it can be controlled during brewery fermentation. Copyright © 2017 The Institute of Brewing & Distilling

Non-alcoholic compounds in beer have protective effects in Caco-2 cells by increasing the expression of genes in the Keap1–Nrf2 pathway

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Non-alcoholic beer compounds attenuates aluminium-induced neurotoxicity in rats

Non-alcoholic beer compounds attenuates aluminium-induced neurotoxicity in rats

Solvent-assisted stir bar sorptive extraction by using swollen polydimethylsiloxane for enhanced recovery of polar solutes in aqueous samples: Application to aroma compounds in beer and pesticides in wine

A novel solvent-assisted stir bar sorptive extraction (SA-SBSE) technique was developed for enhanced recovery of polar solutes in aqueous samples. A conventional PDMS stir bar was swollen in several solvents with log Kow ranging from 1.0 to 3.5 while stirring for 30min prior to extraction. After extraction, thermal desorption – gas chromatography – (tandem) mass spectrometry (TD-GC-(MS/)MS) or liquid desorption – large volume injection (LD-LVI)-GC–MS were performed. An initial study involved investigation of potential solvents for SA-SBSE by weighing of the residual solvent in the swollen PDMS stir bar before and after extraction. Compared to conventional SBSE, SA-SBSE using diethyl ether, methyl isobutyl ketone, dichloromethane, diisopropyl ether and toluene provided higher recoveries from water samples for test solutes with log Kow<2.5. For SA-SBSE using dichloromethane, recoveries were improved by factors of 1.4–4.1, while maintaining or even improving the recoveries for test solutes with log Kow>2.5. The performance of the SA-SBSE method using dichloromethane, diisopropyl ether, and cyclohexane is illustrated with analyses of aroma compounds in beer and of pesticides in wine.

Analysis of flavour compounds in beer with extruded sorghum as an adjunct using headspace solid-phase micro-extraction and gas chromatography-mass spectrometry

Sorghum is a widely used adjunct that is used in the production of beer and increasingly affects beer flavour as the amount added increases. The aim of this work was to establish a simple, solvent-free technique, without derivatization, to analyse flavours and typical volatile compounds present in extruded and unextruded sorghum beer, and to compare the flavour differences of the two types of beer. Headspace solid-phase micro-extraction gas chromatography–mass spectrometry was used to determine the flavours in the two beers and eight typical volatile compounds were quantified using GC. Forty-five flavour compounds were identified and quantified in extruded white sorghum beer, while 31 flavour compounds were identified in unextruded white sorghum beer. Extruded or unextruded white sorghum can be used to produce ale beer, but the primary flavour content in the extruded white sorghum beer was higher than in the unextruded white sorghum beer. Copyright © 2016 The Institute of Brewing & Distilling

Sulfites in beer: reviewing regulation, analysis and role

Beer is an extremely complex mixture of more than 3,000 different compounds in an aqueous environment. Thus, it is perhaps not surprising that the maintenance of beer quality throughout its lifetime has been a considerable challenge for brewers. Whilst it is inevitable that chemical changes will occur in beer with the passage of time, it is the formation of flavor-active components which is of immediate concern to an overview of beer shelf life stability. Sulfur dioxide has long been recognized by brewers as the most important factor in delaying flavor staling, and prolonging the shelf life of beer. However, nowadays, sulfur dioxide and sulfites are considered allergens and concerns about the safety of their use as food additives have been on the increase. The present review is structured into three main parts. Firstly, the chemical properties of sulfur dioxide are presented, along with the toxic effects and maximum legal levels permitted according to U.S. and EU legislation. As the accurate determination of the free, bound and total sulfur dioxide in beer is essential to ensuring regulatory compliance, several methods have been developed for analyzing sulfur dioxide in beer. Thus, secondly, various types of methods are reported and compared with the officially recommended ones. Finally, the crucial role of sulfite in the control of flavor instability of beer is discussed in light of the current data. Two courses of action have been proposed, which are elucidated in detail relating firstly to the fact that sulfite inhibits beer oxidation during storage by acting as an antioxidant and, secondly, sulfite reacts with the carbonyl staling compounds in beer, and thereby masks stale flavors.

Determination of benzoxazinoids in wheat and rye beers by HPLC-DAD and UPLC-QTOF MS

Phenolic compounds in beer have received considerable interest. Besides the more typical phenolic acids and flavonoids, beer contains also lesser-known compounds, such as hordatines, their agmatine precursors and other phenolamines. Current work shows that beers brewed from wheat or rye malts, in addition to barley malts, contain benzoxazinoids, a group of nitrogen containing secondary metabolites typical to wheat and rye. In this work, HPLC-DAD was used for the quantification of major benzoxazinoids in 32 wheat and four rye beers. Of the wheat beers 22 samples and all of the rye beers contained benzoxazinoids, or their breakdown products. Concentrations of DIBOA (2,4-dihydroxy-1,4-benzoxazin-3-one) (as aglycon) varied from 1.7 to 21.9mg/l in wheat beers and from 5.6 to 31.6mg/l in rye beers. Breakdown products BOA (benzoxazolin-2-one), found in 15 beers, and MBOA (6-methoxy-benzoxazolin-2-one), found in two beers, were measured at concentrations ranging from 2.4 to 10.7mg/l and 8.4 to 10.5mg/l, respectively.Identification of benzoxazinoids by UPLC-QTOF MS was done on selected beers. Benzoxazinoid profiles varied greatly between different wheat beers, and compared to rye beers the chemical diversity of benzoxazinoids was higher. As far as the authors know, this is the first time that other benzoxazinoids, rather than just the decomposition products BOA or MBOA, have been reported in beer. The results also show that benzoxazinoids can be present in beer glycosylated with three or four hexose units.

Evaluation of non-volatile metabolites in beer stored at high temperature and utility as an accelerated method to predict flavour stability

Flavour stability is vital to the brewing industry as beer is often stored for an extended time under variable conditions. Developing an accelerated model to evaluate brewing techniques that affect flavour stability is an important area of research. Here, we performed metabolomics on non-volatile compounds in beer stored at 37°C between 1 and 14days for two beer types: an amber ale and an India pale ale. The experiment determined high temperature to influence non-volatile metabolites, including the purine 5-methylthioadenosine (5-MTA). In a second experiment, three brewing techniques were evaluated for improved flavour stability: use of antioxidant crowns, chelation of pro-oxidants, and varying plant content in hops. Sensory analysis determined the hop method was associated with improved flavour stability, and this was consistent with reduced 5-MTA at both regular and high temperature storage. Future studies are warranted to understand the influence of 5-MTA on flavour and aging within different beer types.

Beeromics: from quality control to identification of differentially expressed compounds in beer

A rigorous quality control platform was developed to monitor short- and long-term retention time reproducibility, instrument response and mass accuracy for untargeted differential analysis of beer. The optimized workflow utilized a QC beer and external calibration standards to yield LC retention time variation <3 s, average interday response RSDs <15 % and average mass errors <10 ppm on a quadrupole time of flight mass spectrometer. QC statistics guided data processing, including molecule feature (MF) extraction, MF alignment across samples and recursion, prior to differential analysis of single-hop India Pale Ales produced in two different production years (2010 vs. 2011). Differential analysis and significance testing revealed that the year of production (vs. hop used) accounted for the greatest compositional difference between samples. Negative and positive ion ESI data collectively revealed a minimum 3× fold change (p < 0.05) for ~4000 MFs. Since identification of ~4000 MFs was untenable, focus turned to the identification of ~150 high-abundance MFs. Targeted MS/MS, Metlin database searching and the use of ChemSpider with automated MS/MS spectral prediction and correlation, identified candidate compounds that were confirmed by authentic standards. Most interestingly, the 2010 beers, which were stored longer at room temperature prior to analysis, provided additional evidence for the use of purines, specifically 5-methylthioadenosine with methionine, as nonvolatile molecular indicators of beer oxidation during storage. While this untargeted metabolomics platform was developed with beer in mind, the workflow described here could be applied to any food metabolomics application.

Development of stable isotope dilution assays for the quantitation of free phenolic acids in wheat and barley and malts produced thereof

Free phenolic acids present in cereal malts serve as precursors of different volatile compounds in beer. To study their generation from wheat and barley on the way to the respective malts, stable isotope dilution assays (SIDAs) were developed using high-performance liquid chromatography–tandem mass spectrometry to quantitate the free phenolic acids caffeic, cinnamic, p-coumaric, ferulic, sinapic, and vanillic acid in the grain as well as in the malts produced thereof. An optimised extraction procedure using methanol instead of water in combination with the newly developed SIDAs enabled their selective and sensitive quantitation with low limits of detection and limits of quantitation as well as good recoveries. In kiln-dried wheat malt, the most abundant free phenolic acid was sinapic acid with 2.30 mg/kg dry mass, while in kiln-dried barley malt ferulic acid predominated with 2.76 mg/kg dry mass. The concentration of the latter in kiln-dried malt is of special interest, because this acid is a well-known precursor of the important wheat beer aroma compound 2-methoxy-4-vinylphenol. The concentration of cinnamic acid, the precursor of the toxicologically relevant vinylbenzene (styrene), in kiln-dried wheat and barley malt were 0.56 and 0.97 mg/kg dry mass, respectively. Generally, kiln-dried barley malt showed higher concentrations of most phenolic acids in comparison to kiln-dried wheat malt.

The effect of pitching rate on fermentation, maturation and flavour compounds of beer produced on an industrial scale

The aim of the study was to determine the effect of the initial number of yeast cells in the wort on the process of fermentation, maturation and the content of the volatile components of beer, as well as the viability and vitality of the yeast biomass. The experiments were performed on an industrial scale, with fermentation and maturation in cylindro-conical fermentation tanks with a capacity of 3800 hL. Yeast for pitching was collected after secondary fermentation (third passage) and wort pitching levels were 5 × 106, 7 × 106 and 9 × 106 cells/mL. During fermentation and maturation, the changes in the content of the extract, yeast growth, yeast vitality and selected volatile components were investigated. Experiments showed that the yeast inoculum had a significant impact on the course of the fermentation and metabolic changes. With increasing numbers of cells introduced into the wort, the content of the esters and fusel alcohols increased, while the acetaldehyde concentration decreased. These changes affected the final quality of the beer. Copyright © 2015 The Institute of Brewing & Distilling

Determination of flavour compounds in beer using stir-bar sorptive extraction and solid-phase microextraction

The analysis of volatile compounds in beer is important for quality control in the brewing industry. In this study, stir-bar sorptive extraction (SBSE) and solid-phase microextraction (SPME), two solvent-less enrichment techniques, were applied in combination with gas chromatography flame ionization detection (GC/FID) for the determination of four flavour compounds (isoamyl acetate, ethyl hexanoate, benzaldehyde, myrcene) in beer. Limits of detection, linearity and repeatability of both methods were determined using standard ethanol solutions, while accuracy was determined by conducting recovery tests on commercial beer samples. Both methods were characterized by high linearity (r > 0.996) and repeatability (RSD = 1.76–10.66%). When both methods were compared, higher recoveries were obtained by SBSE, with limits of detection 1.8–2.8 times lower compared with SPME. In the analysis of commercial beer samples using both methods, SBSE analysis resulted in higher recoveries, therefore demonstrating promise for the analysis of beer volatiles. Copyright © 2015 The Institute of Brewing & Distilling

Profiling of thiol-containing compounds by stable isotope labeling double precursor ion scan mass spectrometry.

Here we developed a novel strategy of isotope labeling in combination with high-performance liquid chromatography-double precursor ion scan mass spectrometry (IL-LC-DPIS-MS) analysis for nontargeted profiling of thiol-containing compounds. In this strategy, we synthesized a pair of isotope labeling reagents (ω-bromoacetonylquinolinium bromide, BQB; ω-bromoacetonylquinolinium-d7 bromide, BQB-d7) that contain a reactive group, an isotopically labeled moiety, and an ionizable group to selectively label thiol-containing compounds. The BQB and BQB-d7 labeled compounds can generate two characteristic product ions m/z 218 and 225, which contain an isotope tag and therefore were used for double precursor ion scans in mass spectrometry analysis. The peak pairs with characteristic mass differences can be readily extracted from the two precursor ion scan (PIS) spectra and assigned as potential thiol-containing candidates, which facilitates the identification of analytes. BQB and BQB-d7 labeled thiol-containing compounds can be clearly distinguished by generating two individual ion chromatograms. Thus, thiol-containing compounds from two samples labeled with different isotope reagents are ionized at the same time but recorded separately by mass spectrometry, offering good identification and accurate quantification by eliminating the MS response fluctuation and mutual interference from the two labeled samples. Using the IL-LC-DPIS-MS strategy, we profiled the thiol-containing compounds in beer and human urine, and 21 and 103 thiol candidates were discovered in beer and human urine, respectively. In addition, 9 and 17 thiol candidates in beer and human urine were successfully identified by further comparison with thiol standards or tandem mass spectrometry analysis. Taken together, the IL-LC-DPIS-MS method is demonstrated to be a promising strategy in the profiling of compounds with identical groups in metabolomics study.