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PubMed2003

Radicaloid-type oxidative decomposition of beer bittering agents revealed.

trans-Isohumulones, dihydroisohumulones, tetrahydroisohumulones, and humulinones, which are important hop-derived flavor components of beer, were found, by using electrolysis of organic solutions, to be stable against oxidation, like weak acids; however, they are readily oxidized in their anionic forms as present in beer. Oxygen- and carbon-centered radicals were formed by oxidation and identified by using spin trapping under aerobic and anaerobic conditions, followed by EPR (electron paramagnetic resonance) spectroscopy. Generated radicals were reactive, most likely degrading into products lacking the tricarbonyl chromophore; this is typical of five-membered-ring hop derivatives. Thus, flavor-active beer constituents may degrade oxidatively in the absence of oxygen, thereby leading to reaction products that escape UV detection.

Beer↗

PubMed2004

Optimisation of gradient HPLC analysis of phenolic compounds and flavonoids in beer using a coularray detector.

A method was developed for simultaneous analysis of natural antioxidants in beer using multichannel electrochemical detection with a CoulArray detector, which enables selective and sensitive antioxidant detection in gradient HPLC and facilitates the identification of analytes based on the ratios of signals recorded at different potentials applied to the detection cells arranged in series. The separation conditions were optimised for 27 phenolic compounds including derivatives of benzoic and cinnamic acids, flavones, and a few related glycosides identified in beer samples. Separation selectivities of 11 columns with different stationary phase chemistries were compared, and the pH and gradient programs were optimised for the individual columns to provide best resolution and high number of resolved peaks, using the window-diagram approach. The effects of pH on the sensitivity of electrochemical coulometric detection were considered in the optimisation approach. The optimised conditions were applied to the analysis of real beer samples.

Antioxidants↗

PubMed2002

Analysis of saccharides in beer samples by flow injection with electrospray mass spectrometry.

Saccharides in foods play important roles, as they are essential substrates for fermentation processes. In brewing, the concentration of maltooligosaccharides influences the characteristics of beers and therefore their determination is of great practical interest. Electrospray ionization mass spectrometry (ESI-MS) was applied to identify and characterise maltooligosaccharides in beer samples. The effects due to different cation concentrations and dilution of samples were studied. Furthermore, quantitative analyses of maltooligosaccharides by means of flow-injection ESI-MS (FI/ESI-MS) of 1-microL beer samples (diluted 1000-fold) are described.

Beer↗

PubMed1996

The cocoyam, Xanthosoma sagittifollium, as a potential raw material source for beer brewing.

A widely cultivated cocoyam variety, Xanthosoma sagittifollium, was assessed for its suitability for lager beer production, using malted Sorghum vulgare (white variety) for saccharification of the substrate. The three-mash decoction method was used. Results showed that the cocoyam was superior to barley and sorghum as a substrate because of its potentially higher carbohydrate content (71-78%) compared to barley (65%) and sorghum (70-73%). The percentage wort extract was 13.3-14.5 degrees plato compared to 7-12 for barley and 13 degrees for the tuber crop, cassava. The kiln dried Xanthosoma sagittifollium gave a dark bager beer with good aroma (68%) and very good flavour (73%) when compared with a commercial lager beer (Monarch) as standard (100%). The alcohol content (4.16% w/v) and the specific gravity (1013) were within the range (4.0-6.4%) and (1011-1019), respectively, specified by the Standard Organization of Nigeria. Although the bitterness value 40 EBU, was higher than the typical range 16-30 EBU, the taste panel indicated this was acceptable. The pH was 4.68 compared with the standard 4.36, while the acidity (as % lactic acid) was 0.36 compared to 0.24 for some commercial products.

Beer↗

PubMed1991

Volatile and nonvolatile nitrosamines in beer.

The occurrence of N-nitroso compounds was investigated at different stages in the production of four different beer types and in 14 retail beer samples. Only two N-nitroso compounds, namely N-nitrosodimethylamine (0.17 +/- 0.18 microgram/kg; not detected to 0.60 microgram/kg) and N-nitrosoproline (1.51 +/- 1.01 micrograms/kg; range 0.5-3.60 micrograms/kg) were detected. For moderate beer drinkers, the N-nitrosodimethylamine exposure levels are unlikely to present a significant health risk while the presence of noncarcinogenic N-nitrosoproline does not pose any hazard to human health.

Beer↗

PubMed1985

Neither dietary ethanol nor beer augments experimental colon carcinogenesis in rats.

There is an epidemiologic association between beer consumption and rectal cancer. Beer and ethanol were tested in the rat-dimethylhydrazine (DMH) experimental carcinogenesis model in order to verify this observation. Ethanol was found not to affect the number of colonic tumors induced by DMH (86 vs. 77 controls, P = 0.764). In rats fed beer and treated with DMH, there was a decrease in gastrointestinal tumor induction (P = 0.043). This instance then becomes one of many in which conclusions drawn from epidemiologic studies have been contradicted when subjected to analysis in an experimental colon carcinogenesis model.

1,2-Dimethylhydrazine↗

PubMed2001

Molecular cloning of a putative divalent-cation transporter gene as a new genetic marker for the identification of Lactobacillus brevis strains capable of growing in beer.

Random amplified polymorphic DNA (RAPD) PCR analysis of Lactobacillus brevis isolates from breweries revealed that one of the random primers could distinguish beer-spoilage strains of L. brevis from nonspoilage strains. The 1.1-kb DNA fragment amplified from all beer-spoilers included one open reading frame, termed hitA (hop-inducible cation transporter), which encodes an integral membrane protein with 11 putative trans-membrane domains and a binding protein-dependent transport signature of a non-ATP binding membrane transporter common to several prokaryotic and eukaryotic transporters. The hitA polypeptide is homologous to the natural resistance-associated macrophage protein (Nramp) family characterized as divalent-cation transport proteins in many prokaryotic and eukaryotic organisms. Northern blot analysis indicated that the hitA transcripts are expressed in cells cultivated in MRS broth supplemented with hop bitter compounds, which act as mobile-carrier ionophores, dissipating the trans-membrane pH gradient in bacteria sensitive to the hop bitter compounds by exchanging H+ for cellular divalent cations such as Mn2+. This suggests that the hitA gene products may play an important role in making the bacteria resistant to hop bitter compounds in beer by transporting metal ions such as Mn2+ into cells that no longer maintain the proton gradient.

Amino Acid Sequence↗

PubMed1990

Detection and estimation of the barley prolamin content of beer and malt to assess their suitability for patients with coeliac disease.

Malt, lager, brown ale, bitter and stout were assessed for their barley prolamin (hordein) content. Monoclonal antibody immunoperoxidase staining of electrophoretically separated samples of beer revealed the presence of immunoreactive hordein. Polyclonal antibody based enzyme linked immunosorbant assays (ELISAs) revealed 1.6 mg of hordein per gram of malt and 1.5 mg per pint in the beers. Patients with coeliac disease should avoid ingestion of beer and foods that contain malt since they contain quantifiable amounts of hordein that is known to exacerbate the condition.

Alkaline Phosphatase↗

PubMed1996

N-nitrosodimethylamine in Spanish beers.

A survey of 21 beers produced in Spain during 1994 was conducted to assess contamination with volatile N-nitrosamines. N-Nitrosodimethylamine (NDMA), the only volatile N-nitrosamine detected, was found in 52% of Spanish beers at or above the detection level (0.05 microgram/kg). The mean NDMA level for all samples was 0.11 microgram/kg, and the range was from not detected to 0.55 microgram/kg. No differences in the NDMA content were observed between the different beer types. Individual daily intake of NDMA may reach up to 0.021 microgram/person/day for Spanish people.

Beer↗

PubMed2004

Analysis of iso-alpha-acids and reduced iso-alpha-acids in beer by direct injection and liquid chromatography with ultraviolet absorbance detection or with mass spectrometry.

A liquid chromatography (LC) method is described for the simultaneous analysis of iso-alpha-acids and reduced iso-alpha-acids in beer. Volatile mobile phase additives were selected to enable hyphenation to mass spectrometric (MS) operated in the atmospheric pressure chemical ionization (APCI) mode. Contrary to other recent LC optimization procedures for the same compounds, an alkaline pH was selected hereby improving peak shape and selectivity. Both UV and MS detection are sensitive enough to analyze beers without sample pre-concentration. All major bitter acids are separated within 65 min with exception of cis-dihydroisoadhumulone, which co-elutes with trans-isocohumulone. Due to the selectivity of the MS, these compounds could be differentiated according to their m/z value. The performance in terms of quantification of bitter acids by LC-UV and LC-MS are compared for standard solutions and a selection of 14 beers.

Acids↗

PubMed2004

Development of a rapid method based on solid-phase extraction and liquid chromatography with ultraviolet absorbance detection for the determination of polyphenols in alcohol-free beers.

An analytical method based on solid-phase extraction (SPE) and followed by liquid chromatographic separation and ultraviolet detection (HPLC-UV) is proposed for the determination of 10 phenolic compounds which participate on beer stability and sensory properties in alcohol-free beers. Acetonitrile was found to be the most appropriate solvent for the elution of polyphenolic compounds adsorbed on C18 cartridges. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (generally higher than 60%), repeatability (lower than 10%), linearity (r2 higher than 0.993) and limits of quantitation (ranging from 1 to 37 microg/L); no matrix effects were observed. The polyphenol content of different Spanish alcohol-free beers is presented. Five phenolic compounds such as protocatechuic, p-coumaric, ferulic, caffeic acids, and (+)-catechin were identified at levels lower than 10 mg/L.

Beer↗

PubMed2005

Determination of ochratoxin A in beer marketed in Spain by liquid chromatography with fluorescence detection using lead hydroxyacetate as a clean-up agent.

A new sample treatment for liquid chromatographic analysis of ochratoxin A (OTA) in beer is proposed. Degassed beer is mixed with lead hydroxyacetate, which precipitates some bulk components but does not remove OTA. The precipitate is separated and the acidified liquid is extracted with chloroform. The solvent is evaporated and the residue is dissolved in mobile phase (acetonitrile-water, 40:60, v/v; acidified at pH 3.0 with phosphoric acid) and separated by liquid chromatography using fluorescence detection. The limit of detection was 0.005 ng/ml. The average recovery rate and the average RSD of recovery in the spiking level range 0.01-0.5 ng/ml were 95.5% and about 5%, respectively. The method is cheaper that other alternative ones using immunoaffinity columns or other solid-phase extraction cleanup:The separation was optimised with regard to composition and flow of the mobile phase and no interference from the matrix was found. The method was applied to 88 samples of beer (domestic and imported) marketed in Spain. OTA was detected in 82.9% of them. The range for positive samples was 0.007-0.204 ng of OTA/ml.

Acetates↗

PubMed2006

Method optimization by solid-phase microextraction in combination with gas chromatography with mass spectrometry for analysis of beer volatile fraction.

A simple and sensitive method for the analysis of beer volatile compounds was optimised using headspace solid-phase microextraction (SPME) and gas chromatography with mass detection. Headspace SPME using a 75 microm Carboxen-polydimethylsiloxane (CAR-PDMS) fiber provided effective sample enrichment and enabled extraction of a wide variety of compounds. The reproducibility depended on the compounds, with a mean value of 1.4% for alcohols, 3.3% for ethers, 6.7% for aldehydes, 3.4% for acids, 1.7% for aromatic compounds, 2.4% for esters, 7.4% for hydrocarbons, 1.8% for alicyclic compounds, and 3.4% for heterocyclic compounds. The optimised methodology can be used to compare volatile profile from different types of beers and eventually to study the evolution of a particular beer during aging.

Beer↗

PubMed2006

New method for determination of ochratoxin A in beer using zinc acetate and solid-phase extraction silica cartridges.

A new method for the determination of ochratoxin A (OTA) in beer has been developed. The new method has been compared with a reference method currently accepted as AOAC official first action. The limits of detection and quantification of the proposed method were 0.0008 and 0.0025 ng/ml, respectively, while they were 0.0025 and 0.0075 ng/ml, respectively, in the AOAC method used as reference. The recovery levels in the 0.025-0.40 ng OTA/ml spiking range for the proposed and the reference methods were 80.6-87.6% and 78.2-83.8%, respectively. The relative standard deviations of recoveries were 2.6-7.5% for the proposed method and 0.7-6.1% for the reference method. Passing and Bablok regression analysis of recovery data obtained by the proposed method versus data obtained by the reference method on an OTA-spiked beer sample showed good correlation (r2 = 0.9993), while the slope and intercept were 1.049 and -0.0013, respectively. The advantage of the proposed method is the low cost of the materials used in sample preparation because expensive immunoaffinity columns are not needed to clean-up samples while it maintains or even increases the good performance of the reference method. The proposed method was applied to 69 beer samples from different geographic origins (national and imported) but purchased in the Spanish market. They were found to be contaminated with OTA in the range from 0.008 to 0.498 ng/ml (average: 0.070 ng/ml). Five samples surpassed the limit recommended by the European Union (0.2 ng OTA/g).

Beer↗

PubMed2004

Overall alcohol intake, beer, wine, and systemic markers of inflammation in western Europe: results from three MONICA samples (Augsburg, Glasgow, Lille).

AIM: Anti-inflammatory effects of moderate alcohol consumption have been proposed to explain why moderate alcohol intake lowers coronary heart disease risk. We investigated the relationship between overall alcohol, beer or wine consumption and markers of systemic inflammation in three different geographical areas in Europe. METHODS AND RESULTS: Cross-sectional samples, each representative of the general population from Germany, Scotland, and France (MONICA Augsburg 1994/95, 2275 men and 2186 women, 25-74 years; Glasgow MONICA 1994/95, 561/616, 25-74 years, and MONICA Lille 1994/95, 581/574, 35-64 years) were studied. Alcohol intake was assessed by standardized interview. Adjusted means of C-reactive protein (CRP), fibrinogen, white blood cell (WBC) count, plasma viscosity (PV), and albumin were calculated among categories of alcohol intake, and separately for beer or wine consumption, by multiple linear regression. Self-reported moderate daily alcohol intake up to 40 g was associated with lower concentrations of CRP, fibrinogen, PV and WBC count, compared to non-drinking and heavy drinking, even after adjustment for various potential confounders. CONCLUSIONS: Moderate consumption of either wine or beer is associated with lower levels of systemic inflammatory markers in three different European areas, suggesting that ethanol itself might be largely responsible for the potential anti-inflammatory effects of these beverages.

Adult↗

PubMed2005

Beer constituents as potential cancer chemopreventive agents.

Beer is a complex alcoholic beverage made from barley (malt), hop, water and yeast. Phenolic constituents of beer are derived from malt (70-80%) and hop (20-30%). Structural classes include simple phenols, benzoic- and cinnamic acid derivatives, coumarins, catechins, di-, tri- and oligomeric proanthocyanidins, (prenylated) chalcones and flavonoids as well as alpha- and iso-alpha-acids derived from hop. Compounds belonging to different structural classes have distinct profiles of biological activity in in vitro test systems, and in combination might lead to enhanced effects. Scientific evidence has accumulated over the past 10 years pointing to the cancer preventive potential of selected hop-derived beer constituents, i.e., prenylflavonoids including xanthohumol and isoxanthohumol, and hop bitter acids. Chemopreventive activities observed with these compounds relevant to inhibition of carcinogenesis at the initiation, promotion and progression phases, as well as results from in vivo studies on metabolism, bioavailability and efficacy are summarised in this review.

Angiogenesis Inhibitors↗

PubMed2005

Rapid detection and counting of viable beer-spoilage lactic acid bacteria using a monoclonal chemiluminescence enzyme immunoassay and a CCD camera.

A chemiluminescence enzyme immunoassay carried out with a monoclonal antibody (MAb) and a charge-coupled device (CCD) camera was developed for rapid enumeration of viable beer-spoilage lactic acid bacteria. LA-4 MAb, which recognizes a broad spectrum of lactic acid bacteria isolated from several breweries across Spain, was produced and characterized. Test samples were filtered through polycarbonate membranes, and the membranes with retained bacteria were incubated at 31 degrees C for 2 days. They were then subjected to a two-step chemiluminescence enzyme immunoassay with MAb LA-4, and light-emitting points were detected and counted with a CCD camera. Eighteen out of 19 beer-spoilage lactic acid bacteria analysed produced luminous spots that could be enumerated. Results provided by the immunochemiluminescence assay correlated very well with those obtained by visual plate counting within a range of 3-100 CFU/100 ml. Correlation coefficients were 0.994 for four strains in sterile saline solution and 0.984 for 14 strains in artificially contaminated beer. The excellent agreement suggests that luminous spots detected within 2 days of culture are produced only by viable cells.

Animals↗

PubMed2005

Accurate caloric compensation in rats for electively consumed ethanol-beer or ethanol-polycose mixtures.

High elective intake of ethanol was achieved in rats by presenting ethanol in palatable vehicles. We simultaneously measured intake of food (chow) to assess the accuracy of caloric compensation for the energy in the alcoholic commodity. In the first study, we used beer; nonalcoholic beer was consumed in large amounts, and when 5% or 10% ethanol was added, intake amounted to approximately 10% of daily calories. In the second study, Polycose in either solution or a gel matrix was used as the palatable vehicle for ethanol. The intake of ethanol was even higher than in the beer study, particularly in the gel preparation. In all cases, both male and female rats showed accurate caloric compensation by a reduction in chow intake. In a final study, we showed that restricted time access to the Polycose-alcohol gel produced high elective intakes and substantial blood alcohol levels. Over 24 h, caloric compensation was again accurate. Thus, unlike some reports in humans, rats seem able to compensate accurately for alcohol calories and in particular when, as with most alcohol consumption by humans, these are presented in palatable vehicles.

Animals↗