The influence of the brewing process on the formation of biogenic amines in beers

Biogenic amines, as dabsyl derivatives, were determined in beer samples, intermediate products, and raw materials (malt and maize) by HPLC. A procedure for the extraction of the amines from malt and maize with diluted hydrochloric acid was optimised by combining a Response Surface Methodology with a Simultaneous Decision Making Approach. The results of the analysis indicate that, in brewing, technology and hygiene are the decisive factors that determine the amine concentrations in the final product.     

Die Oktoberfest‐Umlagerung: Hopfen und Malz ...

Beer brewed according to the German “Reinheitsgebot” or purity law is regarded as the quintessence of an unadulterated food produced without any “chemistry”. What an error! Already when moistening the barley the beer chemistry begins and large quantities of enzymes for decomposing the cell walls, proteins and starch are produced. During malting (drying and roasting) of the germinated grains many compounds giving beer its wonderful aroma and colour are synthesized through complex reaction cascades. The chemical climax is the conversion of some hop constituents into bittering substances. In a single Munich Oktoberfest, about 10,000 kg of hops are converted via a breathtaking α‐ketol‐rearrangement into several 100 kg of these so well appreciated bittering compounds. This is just another proof that chemistry cannot only be exciting but can also taste good. Prost!     

Application of proteomics to hordein screening in the malting process

This study was undertaken to investigate the effect of the malting process on hordein composition. For this purpose, combination of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and the method of isotopic peptides labeling iTRAQ was used. Barley proteins are essential components determining the quality of both malt and beer. Since hordeins represent the most abundant proteins accounting for about 40-50% of total protein fraction of mature barley grain, our research was focused on them. In this respect, the proteins of interest were extracted from milled samples of barley grain, germinated barley grain (samples collected at different time intervals), green malt and malt, respectively. Particular hordein extracts were firstly fractionated via SDS- PAGE, which was used as a relatively rapid and reliable technique providing information about hordein profile of analyzed samples. Then, separated proteins were in-gel digested and resulting peptides were measured by mass spectrometry. In addition, the chosen proteins, after in-gel digestion, were subjected to the iTRAQ method and the screening of proteins during malting process was evaluated. Our results have revealed that most of the hordein components present in the barley grain can be found in all stages of the malting process as well as in the final malt. The amount of hordeins decreases during the malting process; in the case of C hordein, the protein decrease is approximately 65%. On the other hand, significant degradation of D hordein was detected. The suggested procedure can be used to follow the development of the hordein profile during germination, which is of great technological importance in beer production.     

Isolation and Identification of Prenylflavonoids from Humulus lupulus

The hop plant (Humulus lupulus L. Cannabinaceae ) is cultivated widely through the temperate zones of the world. The female inflorescences of the hop plant (hops) are used in the brewing industry to give bitterness and aroma of beer. In China, hops are used as stomachics, diuretic and tranquilizer. [1] A number of prenylflavonoids have been isolated from hops, [2,3] which caused attention because of their potential anti-cancer properties, [4] endocrine activities, [5] and diacylglycerol acyltransferase inhibition. [6]     

Decision trees in selection of featured determined food quality

The determination of food quality, authenticity and the detection of adulterations are problems of increasing importance in food chemistry. Recently, chemometric classification techniques and pattern recognition analysis methods for wine and other alcoholic beverages have received great attention and have been largely used. Beer is a complex mixture of components: on one hand a volatile fraction, which is responsible for its aroma, and on the other hand, a non-volatile fraction or extract consisting of a great variety of substances with distinct characteristics. The aim of this study was to consider parameters which contribute to beer differentiation according to the quality grade. Chemical (e.g. pH, acidity, dry extract, alcohol content, CO(2) content) and sensory features (e.g. bitter taste, color) were determined in 70 beer samples and used as variables in decision tree techniques. This pattern recognition techniques applied to the dataset were able to extract information useful in obtaining a satisfactory classification of beer samples according to their quality grade. Feature selection procedures indicated which features are the most discriminating for classification.     

Quantitative analysis of xanthohumol and related prenylflavonoids in hops and beer by liquid chromatography-tandem mass spectrometry

A method for quantitation of six prenylflavonoids (xanthohumol, isoxanthohumol, desmethylxanthohumol, 6- and 8-prenylnaringenins and 6-geranylnaringenin) in hops and beer by HPLC-tandem mass spectrometry has been developed. The method allows direct analysis of beer and crude methanolic extracts of hops. After HPLC separation, prenylflavonoids were detected by positive ion multiple-reaction monitoring using a triple-quadrupole mass spectrometer equipped with a heated nebulizer--atmospheric pressure chemical ionization interface. The accuracy and precision were evaluated by replicate analyses of (spiked) samples. Thirteen commercial beers were analysed with the method. Isoxanthohumol, formed by isomerization of xanthohumol during the brewing process, was the most abundant flavonoid in hopped beers, ranging from 0.04 to 3.44 mg/l.     

Antioxidant Capacity and Total Phenol Content in Hop and Malt Commercial Samples

The antioxidant properties of commercial hops and malted barley were evaluated by electroanalytical methods and compared with spectrophotometric methods. Hop group showed better antioxidant capacity and total phenols content (TPC) values than malt group. The highest electrochemical Index (EI) was observed for HCO hop sample. Electrochemical Index (EI) showed a good Pearson correlation with ABTS (2,2′‐azino‐bis (3‐ethylbenzothiazoline‐6‐sulphonic acid)), DPPH (2,2‐diphenyl‐1‐picrylhydrazyl), and TPC, being of 0.85, 0.77 and 0.86 respectively for hop samples. While for the malt samples were 0.96, 0.69 and 0.49, respectively. The samples were compared to each other within each group and statistical differences can be observed, p<0.05. Therefore, the electroanalytical tools showed to be practical and easy to evaluate the antioxidant properties of hop and malt samples. The results may contribute to the selection of raw material for brewing and therefore with the quality of one of beverage one most consumed around the world.     

Fractionation by SFE and microcolumn analysis of the essential oil and the bitter principles of hops.

Supercritical fluid extraction (SFE) is evaluated and optimized for the enrichment and fractionation of the essential oil and the bitter principles of hops (Humulus lupulus), both of which contribute to the flavor of beer. Profiles of the essential oil of different hop varieties are compared. The bitter principles, the humulones and lupulones, are analyzed by miniaturized liquid chromatography (micro-LC) and by micellar electrokinetic chromatography (MEKC).     

Banana as Adjunct in Beer Production: Applicability and Performance of Fermentative Parameters

Traditionally, the raw materials for beer production are barley, hops, water, and yeast, but most brewers use also different adjuncts. During the alcoholic fermentation, the contribution of aroma compounds from other ingredients to the final beer flavor depends on the wort composition, on the yeast strain, and mainly on the process conditions. In this context, banana can also be a raw material favorable to alcoholic fermentation being rich in carbohydrates and minerals and providing low acidity. In this work, the objective was to evaluate the performance of wort adjusted with banana juice in different concentrations. For this, static fermentations were conducted at 15 °C at pilot scale (140 L of medium). The addition of banana that changed the concentration of all-malt wort from 10 °P to 12 and 15 °P were evaluated (°P is the weight of the extract or the sugar equivalent in 100 g solution, at 20 °C). The results showed an increase in ethanol production, with approximately 0.4 g/g ethanol yield and 0.6 g/L h volumetric productivity after 84 h of processing when concentrated wort was used. Thus, it was concluded that banana can be used as an adjunct in brewing methods, helping in the development of new products as well as in obtaining concentrated worts.     

Gas chromatographic determination of pesticide residues in malt, spent grains, wort, and beer with electron capture detection and mass spectrometry

A method for the simultaneous determination of 9 pesticides (dinitroanilines, organophosphorus, triazoles, and pyrimidines) in several products (malt, spent grains, wort, and beer) of the beer industry is reported. Solid samples (malt and spent grains) are extracted by homogenization with a water-hexane mixture, and the pesticides are partitioned with dichloromethane. Liquid samples (wort and beer) are extracted by sonication with a hexane-dichloromethane mixture. Determination of pesticide residues was made by capillary gas chromatography with an electron capture detector (ECD). Confirmation of the compounds was performed by gas chromatography/ion trap mass spectrometry in the selected ion monitoring mode. Detection limits for GC-ECD varied from 0.2 to 5.5 pg for trifluralin and malathion, respectively. Recoveries of the pesticides from spiked samples ranged from 81.2 to 113.7% with a relative standard deviation between 3.4-7.5%. The method presents good linearity over the studied range (0.005-2 microg/mL). The proposed method is rapid and reliable and can be useful for routine monitoring during brewing.     

Characterization of the methanolic extract of hops using capillary electrophoresis-electrospray ionization-mass spectrometry

Hops are used almost exclusively for bitterness and flavor by brewers. We propose the first analytical application of CZE coupled to ESI-MS for the separation and structural elucidation of organic compounds in the methanolic extracts of hops, and different extraction procedures of the plant material have been carried out. The proposed method permits the identification of hop polyphenols (flavonoids glycosides and chalcones), bitter acids (alpha-acids and beta-acids), and their oxidation products. The optimization of CZE parameters (pH, concentration, and type of buffer) and ESI-MS parameters (nature and flow rate of the sheath liquid, nebulizer pressure, drying gas flow rate, temperature, and compound stability) have permitted the development of a rapid, simple, direct, and straightforward CZE-ESI-MS method for the identification of components of methanolic extracts from different hops used in the brewing process.     

Determination of Volatile Markers from Magnum Hops in Beer by In-Tube Extraction—Gas Chromatography—Mass Spectrometry

ABSTRACT

A chromatographic method was developed for the identification of volatile markers from Magnum hops in two types of beer. The study was initially performed with Magnum hop pellets and hop essential oil and subsequently with traditional and flavored beer during the primary fermentation. The volatile compounds were isolated employing the in-tube extraction (ITEX) technique followed by identification and quantification through gas-chromatography—mass spectrometry (GC-MS) operating in scan mode. The main authentication markers identified in traditional beer were from aromatic compounds, aldehydes and alcohol esters. The most predominant authentication marker compounds in beer flavored with Magnum hop essential oil were obtained from terpenoids, followed by acid esters, alcohol esters and alcohol classes. A unique feature of this study was represented by the discriminant markers for the authentication of Magnum hop variety, identified in hop pellets, hop essential oil and flavored beer. The application of this methodology can be used for optimization of brewing technology and process parameters in view of prolonging fruity hop flavor stability of Romanian beers.     

Studies in organic mass spectrometry—X: The fragmentation of substituted 1,3-cyclo-pentanediones and 1,2,4-cyclopentanetriones,related to hop bitter acids

The Mass spectra of some 1,3-cyclopentanediones and 1,2,4-cyclopentanetriones, related to compounds encountered in the chemistry of hops bitter constituents have been determined. Methyl substituted compounds mostly show ring degradation, while for longer alkyl groups and acyl groups, fragmentations in the side chain carry most of the total ionization. When both alkyl (> 2C) and acyl substituents are present, fragmentations in the alkyl group always occur before those in the acyl side chain. The observed degradation processes are useful for the interpretation of the spectra of hop bitter acids and derived products.     

Size characterization of barley starch granules by gravitational field-flow fractionation: a rapid,low-cost method to assess the brewing capability of different strains

Cereal starch occurs as two types of micrometer-sized granules, large and small. Large starch granules are more susceptible to enzymatic hydrolysis. When cereal starch is used for fermentation processes, as in brewing of barley malt, the barley strains with the highest content of large starch granules should be preferred. Gravitational field-flow fractionation (GFFF) is a separation method able to fractionate starch samples at low cost and short analysis time. In this work, the search for the best GFFF conditions for the analytical separation of barley starch within an inter-laboratory approach is presented. For different barley strains cultivated under monitored conditions the size distributions of starch granules is here quickly monitored and characterized by GFFF. As a consequence, dimensional characterization of barley starch can allow for the selection of the most suitable strains with the lowest content of non-degradable starch.     

Characterization of prenylflavonoids and hop bitter acids in various classes of Czech beers and hop extracts using high-performance liquid chromatography–mass spectrometry

Hops contain a wide range of polyphenolic compounds with antioxidant properties divided in various chemical classes. These compounds are detected in hop extracts and also in beer as its main product. Based on the careful optimization of column type, column packing, mobile phase composition and gradient steepness, two high-performance liquid chromatography–mass spectrometry (HPLC/MS) methods have been developed. The first method using Purospher Star RP-8e column and the gradient of aqueous acetonitrile containing 0.3% formic acid is optimized for the separation of low polar polyphenolic compounds, while the second one with Zorbax SB-CN column is used for more polar hops and beer components. In this work, more compounds are detected in comparison to previous reports. In total, 49 low polar and 37 polar compounds are detected in studied samples and their molecular weights are determined based on atmospheric pressure chemical ionization (APCI) mass spectra. Some compounds are identified based on the interpretation of their full scan and tandem APCI mass spectra, retention behavior and UV spectra, while the full structure elucidation of other species still requires further research. The quantitation of xanthohumol related prenylflavonoids and bitter acids is done with two detection techniques (APCI-MS and UV detection) providing comparable results. Both compound classes (i.e., prenylflavonoids and bitter acids) are separated and quantitated in a single HPLC run, where numerous other polyphenolics are detected as well.     

Determination of cadmium,aluminium, and copper in beer and products used in its manufacture by electrothermal atomic absorption spectrometry

Procedures were developed for determining cadmium, aluminium, and copper in beer and the products used in its manufacture by electrothermal atomic absorption spectrometry. Beer samples were injected into the furnace and solid samples were introduced as suspensions after preparation in a medium containing hydrogen peroxide, nitric acid, and ammonium dihydrogen phosphate for cadmium atomization. Calibration was performed with aqueous standards, and characteristic masses and detection limits were, respectively, 1 and 0.3 pg for cadmium, 18 and 5.4 pg for aluminium, and 5.6 and 6.8 pg for copper. Different samples of beer, wort, brewer's yeast, malt, raw grain, and hops were analyzed by the proposed procedures. Cadmium was found in low concentrations (0.001-0.08 microg/g and 0-1.3 ng/mL); copper (3-13 microg/g and 25-137 ng/mL) and aluminium (0.6-9 microg/g and 0.1-2 microg/mL) were found at higher levels. The reliability of the procedure was confirmed by comparing the results obtained with others based on microwave oven sample digestion, and by analyzing several certified reference materials.     

Partial least-squares regression and fuzzy clustering — A joint approach

Chemical and physical analyses of malt, the main ingredient of beer, have been used to predict the concentration of certain volatile compounds in the finished beer.The prediction was done by means of the partial least squares regression (PLS2) in SIMCA. The total data set as well as individual malt clusters were submitted to PLS analysis. Best prediction was obtained by separating the total object matrix in classes according to similarity found by fuzzy pattern recognition (FCV). FCV was also used to separate the beer variables in classes and to select the subset of variables to be predicted.A joint approach of fuzzy pattern recognition to identify groups of samples and SIMCA-PLS2 to predict several dependent variables is suggested as a powerful tool in process-analytical chemistry.     

Fluctuation in the ergosterol and deoxynivalenol content in barley and malt during malting process

This paper describes determination of the deoxynivalenol and ergosterol in samples from different varieties of barley and, consequently, malt produced from this barley. In total, 20 samples of barley and 20 samples of barley malt were analyzed. The alkaline hydrolysis with consequent extraction into hexane was applied to obtain the ergosterol from cereals. Extraction to acetonitrile/water and subsequent solid-phase extraction (SPE) were used for deoxynivalenol. The determination of the samples was performed on high-performance liquid chromatography using UV detection (ergosterol) and mass spectrometric detection (deoxynivalenol). The influence of the malting process on the production of two compounds of interest was assessed from obtained results. Ergosterol concentration ranged 0.88–15.87 mg/kg in barley and 2.63–34.96 mg/kg in malt, where its content increased to 95% compared to samples before malting. The malting process was observed as having a significant effect on ergosterol concentration (P = 0.07). The maximum concentration of deoxynivalenol was found to be 641 μg/kg in barley and 499 μg/kg in malt. Its concentration was lower than the legislative limit for unprocessed cereals (1,250 μg/kg). The statistic effect of the malting process on deoxynivalenol production was not found. Linear correlation between ergosterol and deoxynivalenol content was found to be very low (barley R = 0.02, malt R = 0.01). The results revealed that it is not possible to consider the ergosterol content as the indicator of deoxynivalenol contamination of naturally molded samples.     

Characterization of a β-glucanase produced by Rhizopus microsporus var. microsporus, and its potential for application in the brewing industry

Background  

In the barley malting process, partial hydrolysis of β-glucans begins with seed germination. However, the endogenous 1,3-1,4-β-glucanases are heat inactivated, and the remaining high molecular weight β-glucans may cause severe problems such as increased brewer mash viscosity and turbidity. Increased viscosity impairs pumping and filtration, resulting in lower efficiency, reduced yields of extracts, and lower filtration rates, as well as the appearance of gelatinous precipitates in the finished beer. Therefore, the use of exogenous β-glucanases to reduce the β-glucans already present in the malt barley is highly desirable.