Pavel Dostalek

Abstract: JELINEK L., DOLECKOVA M., KARABIN M., HUDCOVA T., KOTLIKOVA B., DOSTALEK P. (2012): Influence of growing area, plant age, and virus infection on the contents of hop secondary metabolites. Czech J. Food Sci., 30: 541-547. Hops and hop products (pellets and extracts) belong to the major raw materials employed in brewing industry. Many effects such as the growing area, hop plant age, and virus infection influence the contents of the brewing-important hop secondary metabolites (alpha- and beta-bitter acids, essential oils, and polyphenols). The clones of the Czech cultivars Saaz and German cv. Taurus were used in this work and compared with the aim to investigate the influence of the effects mentioned on the contents of hop secondary metabolites.

Abstract: (Department of Biotechnology, Institute of Chemical Technology, Prague): The Importance of Hop Prenylflavonids for Human Health In recent years, a growing interest in health-promoting effects of hop constituents has been observesd. Xanthohumol is a hop prenylated chalcone, which shows a wide range of biological activities such as antioxidant, anticancerogenic, antimicrobial and estrogenic. Most interesting findings obtained with xanthohumol and other prenylated hop flavonoids in preclinical and clinical studies are summarized. The review is primarily focused on the effects on human health. Biosynthesis of prenylated flavonoids in plants and their biotransformations in humans are also mentioned.

Abstract: In order to understand how xanthohumol affects a brewing yeast's metabolism, yeast viability and vitality were studied during the production of a xanthohumol enriched beer (10 mg/L xanthohumol) on a 50 L pilot plant scale. The results showed that yeast viability was not significantly affected, but yeast vitality in the xanthohumol enriched brewing trials was slightly better. The content of higher alcohols, esters and organic acids was similar to the control in all the xanthohumol enriched brewing trials, however the content of sulphur dioxide, acetaldehyde and saturated fatty acids was lower in the xanthohumol enriched brewing trials. To the authors' knowledge, this is the first time brewing trials have been carried out showing that xanthohumol has a positive effect on a yeast's physiological condition.

Abstract: The contents of resins, essential oils and polyphenols in eight Czech hop varieties were detd. The typical values (markers) chosen were used for a compilation of variety profiles and a diagram which can be used for the identification of Czech hop varieties.

Abstract: The aim of this study was to summarize the findings about the best known beer stabilizers. Their operational principals and processing sections of their application are described. The attention was given also to the new polyamide sorbent BEERPAP. It was developed some years ago and tested in several breweries in full scale conditions. This sorbent has the same sorbent capacity for polyphenols which cause beer turbidity (haze) as the same amt. of polyvinylpolypyrrolidone (PVPP) when recalcd. to the same polymer wt. This sorbent also has a sorption activity for nitrogen compds., excellent flow characteristics, low filtration resistance, is completely insol. in beer and is instantly useable in the prodn. without previous soaking.

Abstract: Alcs., esters and acids are substances which create specific flavor of beer. The aim of this work is to describe a no. of methods, which are used for their detn. in beer, with emphasis on modem methods developed in recent years. A comparison of these methods is also given.

Abstract: In this work, a recently developed extn. technique for sample prepn. aiming the anal. of volatile and semi-volatile compds. named gas-diffusion microextn. (GDME) is applied in the chromatog. anal. of aldehydes in beer. Aldehydes-namely acetaldehyde (AA), methylpropanal (MA) and furfural (FA)-were simultaneously extd. and derivatized with 2,4-dinitrophenylhydrazine (DNPH), then the derivs. were sepd. and analyzed by high-performance liq. chromatog. with spectrophotometric detection (HPLC-UV). The identity of the eluted compds. was confirmed by high-performance liq. chromatog.-atm. pressure chem. ionization-mass-spectrometry detection in the neg. ion mode (HPLC-APCI-MS). The developed methodol. showed good repeatability (ca. 5%) and linearity as well as good limits of detection (AA-12.3, FA-1.5 and MA 5.4 μg L-1) and quantification (AA-41, FA-4.9 and MA 18 μg L-1); it also appears to be competitive in terms of speed and cost of anal. [on SciFinder(R)]

Abstract: A review. Compared to most other alc. beverages, beer is unique due to its instability in the final packaged form. The rate of beer deterioration depends on prodn. batch and storage time and temp. The most important parameter is the colloidal stability of beer during its shelf-life as beer should not become hazy/turbid. There are 2 principal methods for assessing the colloidal stability of beer: the accelerated aging of packaged beer involving heating for several days followed by measuring turbidity at a low temp. and the measurement of protein or polyphenol contents to predict the beer shelf-life. Specific methods used for the prediction of colloidal stability of beer and its shelf-life in practice are examd. The methods include pptn. reactions (ammonium sulfate, Mg sulfate, trichloroacetic acid, picric acid), turbidity-prone proteins detn., tannoids detn., gliadin/catechin turbidity test, formaldehyde test, cold alc. test, redox status detn., immunochem. methods, etc. [on SciFinder(R)]

Abstract: Allergens in beer were investigated in relation to content of SO2 and gluten in beer samples collected from the Czech retail market. SO2 content was determined using chronopotentiometry. None of the beers analysed contained more than 20 mg/l of SO2. In samples of Czech beer, concentration of SO2 was Link to the Ovid Full Text or citation: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&NEWS=N&PAGE=fulltext&D=fsta2&AN=2010-Hc4558

Abstract: Seven Czech hop varieties (dry hop cones) coming from the harvest of 2008 (Agnus, Bor, Harmonie, Premiant, Rubin, Sladek, and Saaz) were compared for their compn. depending on their varietal differentiation. These cultivars were analyzed for the contents of α- and β-bitter acids analogs, essential oils, and polyphenols. Hop essential oil constituents significantly contribute to the individual hop varieties. The dichotomous key for the authentication of Czech hop varieties was established based on some characteristic varietal markers. [on SciFinder(R)]

Abstract: Ten different barley cultivars and their corresponding malts were analyzed for monomeric and oligomeric flavan-3-ols content by using high-performance liq. chromatog. UV detection-electrospray ion trap mass spectrometry. The Folin-Ciocalteau and the vanillin spectrophotometric assays were used for the assessment of the total polyphenol and total flavan-3-ol content resp., and the antioxidant activity was detd. by DPPH and FRPR Catechin and prodelphinidin B3 were resp. the major monomeric and dimeric flavan-3-ols. Moreover, prodelphinidin B3 was shown to be the main contributor for the radical scavenging activity both for barley and malt. The same samples were used to obtain different fractions. The contribution of bound phenolics to the total polyphenol content was significantly higher than that of free and esterified fractions. Catechin and ferulic acid, quantified by HPLC-DAD, were the most abundant phenolics in the free and bound fractions, resp. The antioxidant activities of phenolic fractions were investigated using the radical scavenging assay (DPPH) and the ferricyanide reducing power (FRP). Further the hot water exts. of barley cultivars and corresponding malts were analyzed. The ferric reducing antioxidant power (FRAP) and radical scavenging activity (ABTS) and indicator time test (ITT) were compared. The total polyphenol content, as measured according to Folin-Ciocalteu's method, was pos. correlated with all antioxidant methods used. Free phenolic compds. were measured by HPLC with CoulArray detector. The dominant phenolic compd. was ferulic acid. [on SciFinder(R)]

Abstract: The gluten content in various glucose syrups was determined by two sandwich ELISA methods and one competitive ELISA. Different extraction solutions were used for ELISA methods. MALDI-TOF mass spectrometry and SDS-PAGE were also carried out as a complementary technique to ELISA methods. The analysis proved that glucose syrups analyzed in this work and used in many food products and gluten-free food products are safe for patients suffering from celiac disease. Four food products containing glucose syrup were analyzed with satisfactory results as well. One sample of chocolate bar has gluten content lower than the current limit for gluten-free foods. Gluten content above this limit was found in this chocolate bar after cocktail-gelatine extraction. This product is not labelled as gluten-free food. This fact shows that the analyses of gluten-free products are not simple and need more work and attention. (C) 2009 Elsevier Inc. All rights reserved.

Abstract: Barley primarily serves as a major animal feed crop; smaller amounts of barley are used in health foods and in the malting process. Detailed geometric parameters of kernels are very important for the design of food engineering processes, such as the air transport, drying, milling, and malting. Image analysis was used to determine the size parameters of one hundred kernels of selected varieties of Hordeum vulgare L. The data for every kernel captured were stored for further use, together with the mean, standard deviation (SD), coefficient of variation (01), and images themselves. The measured data were then used to compute the volume and surface area of each of the five kernel models (Models 0-4), the results being subsequently verified by pycnometric measurement. Model 0 represents the general ellipsoid, models 1-3 various combinations of two parts of a general ellipsoid with one or two cone frustums. The best fitted model 4 was a combination of two cone frustums. Based on the results of image analysis measurements and on the presented model 4, a simplified method for the specific surface estimation of barley grains from the weight of 1000 kernels is recommended.

Abstract: Iso-alpha-acids or isohumulones are hop-derived beer constituents formed in the brewing process. Iso-alpha-acids are light-sensitive; they play a key role in the origin of the well-known light-struck off-flavour of beer. To prevent the negative effect of light, beers are generally stored in light-proof cans or dark bottles. Alternatively, reduced iso-alpha-acids, resistant to light-induced degradation, can be added to beer. These substances also show a positive effect on foam stability. This paper describes the impact of iso-alpha-acids, reduced iso-alpha-acids, tetrahydro-iso-alpha-acids, and hexahydro-iso-alpha-acids on brewing; their food legislation frame is also mentioned. Chemical and physical methods of analysis of the substances are also reviewed.

Abstract: High performance liquid chromatography (HPLC) method with the pre-column derivatisation by AccQ.Tag agent and following determination of these derivates after their separation in reverse phase column followed by fluorescent detection was used for the determination of amino acids in cheeses. The contents of sixteen free amino acids in twenty five cheeses commercially available in the Czech Republic were measured. The total content of free amino acids in the studied cheeses varied in the range from 27 g/kg to 160 g/kg. Among individual amino acids, seven amino acids were more concentrated in all cheese samples and came from three distinctive taste groups: bitter tasting amino acids (leucine, lysine, and phenylalanine), bitter sweet amino acids (proline and valine), and salty-umami amino acids (glutamic acid and aspartic acid). The differences in the contents of the total and individual free amino acids were influenced by the kind of cheese and mainly by the duration and intensity of proteolysis.

Abstract: A review. The prolamin protein fraction from wheat, barley, and rye can have adverse effects when ingested by people with celiac disease (sprue). It is one of the most common food allergies affecting ∼1 in 300 people in Europe. The current treatment of celiac sprue is based on strict diet free of toxic cereal proteins even in trace amts. There is still a need for reliable and specific methods for the detn. of gluten and prolamins in foods. Electrophoresis and chromatog. are widely used for fractionation of a complex mixt. of hordeins, but immunochem. techniques are used for sensitive and specific detn. of hordein and its derivs. ELISA systems have been produced, mainly for wheat gliadin detection. The immunol. systems are usually based on monoclonal antibodies. The immunochem. anal. systems used for prolamin detection in foods are reviewed. [on SciFinder(R)]

Abstract: The pattern of the monomeric and oligomeric flavan-3-ols for 10 barley varieties and the corresponding malts were identified and quantified using HPLC-UV detection-electrospray ion trap MS. The Folin-Ciocalteau and the vanillin spectrophotometric assays were used for the assessment of the total polyphenol and total flavan-3-ol content, resp., and the antioxidant activity was detd. as the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and the ferricyanide reducing power. Catechin and prodelphinidin B3 were resp. the major monomeric and dimeric flavan-3-ols. Moreover, prodelphinidin B3 was shown to be the main contributor for the radical scavenging activity both for barley and malt. [on SciFinder(R)]

Abstract: A review. Flow cytometry as a rapid anal. technique can be used for monitoring yeast (Saccharomyces cerevisiae) growth in biotechnol. processes. The method allows anal. of single cells in suspensions and to est. cell size distribution, granularity, intracellular contents of DNA, proteins and sterols, viability, cell cycle, intracellular pH, and enzyme activities. Flow cytometry can also be used for cell sorting. Despite the anal. advantages of flow cytometry, its use in biotechnol. labs. is still limited. [on SciFinder(R)]

Abstract: A review. The attractive prospect of a continuous beer fermn. system consists mostly of the accelerated transformation of wort into beer. Although continuous beer fermn. has been studied as a promising technol. for several decades, the no. of industrial applications is still limited. The major obstacle hindering the extensive industrial exploitation of this technol. is the difficulty in achieving the correct balance of sensory compds. in the short time typical for continuous systems. This paper offers an integral view on the particularities of continuous systems, which may impart beer a sensorial character distinct from conventionally fermented counterparts. The main groups of flavor active compds. are discussed from the perspective of possible control strategies by means of process parameters and strain selection. [on SciFinder(R)]

Abstract: In this article the effect of yeast brewing strains and technol. conditions on the prodn. of sulfur dioxide are studied. The decrease of sulfur dioxide during the storage, its influence on the improvement of the oxidative and the stale flavor of beer and also the correlation between its concn. in beer and redox capacity of beer are monitored in this study. [on SciFinder(R)]

Abstract: Ten different barley cultivars and their corresponding malts were used to obtain different fractions. Phenolics extd. belonged to free, sol. esters and insol.-bound fractions. Total phenolic content (TPC) of the free fraction, as measured according to the Folin-Ciocalteu method, ranged from 37.7 to 167.2 mg gallic acid equiv/kg of dried material (GAE/kgdw) for barley and between 34.1 and 72.3 mg GAE/kgdw for malt. The bound phenolic content ranged from 210.3 to 320.5 and between 81.1 and 234.9 mg GAE/kgdw for barley and malt, resp. The contribution of bound phenolics to the TPC was significantly higher than that of free and esterified fractions. Catechin and ferulic acid, quantified by high performance liq. chromatog. with diode array detector (HPLC-DAD), were the most abundant phenolics in the free and bound fractions, resp. The p-coumaric acid content was lower in hulless genotypes, as compared to hulled genotypes, showing that it is mainly concd. in the hull. The antioxidant activities of the phenolic fractions were investigated using the radical scavenging assay (DPPH) and ferricyanide reducing power. The bound phenolics demonstrated a significantly higher antioxidant capacity compared to the free and esterified phenolics. During the malting process, a significant decrease of the bound phenolics was obsd. with a corresponding increase of the esterified fraction. [on SciFinder(R)]

Abstract: The content of 16 free amino acids in 35 beers com. available in Czech Republic was measured using high-performance liq. chromatog. method with pre-column derivatization by AccQ·Tag agent and sepn. in reverse phase column followed by fluorescent detection. Content of proline, which was the amino acid most commonly found, varied in range from 40 to 250 mg/L. Czech beers were characterized by a significantly higher amino acid content in comparison to imported global brands (450.41±27.66 vs. 257.53±46.46 mg/L). Among individual amino acids, nine amino acids were significantly (p<0.01) more concd. in the Czech beer brands than in the studied foreign brands, and those amino acids were from three distinctive taste groups: bitter tasting amino acid (isoleucine, leucine, lysine, phenylalanine and histidine), bitter sweet amino acids (valine and proline) and salty-umami amino acids (glutamic acid and aspartic acid). [on SciFinder(R)]

Abstract: Hot water (45°C) exts. of ten barley varieties and their corresponding malts were analyzed in terms of antioxidant activity. The ferric reducing antioxidant power (FRAP) and radical scavenging activity (ABTS), ranged from 0.23-0.45 mg GAE/gdw for malt and 0.12-0.25 mg GAE/gdw for barley. The hull-less malt KM 1910 was the variety with the best antioxidant properties, whereas the highest antioxidant capacity for barley was detected for the variety Merlin. A significant pos. correlation between the methods FRAP, ABTS and ITT was found (p < 0.01). The influence of fertilization (20 kg N/ha) on barley antioxidant capacity was studied. The results obtained suggest that the impact of fertilization was not evident and that it depends significantly on barley genotype. The total polyphenol content, as measured according to Folin-Ciocalteu's method, ranged from 0.6-2.9 mg GAE/gdw and correlated pos. with all the antioxidant methods used (p < 0.01). Free phenolic compds. were measured by HPLC with a CoulArray detector. The dominant phenolic compd. was ferulic acid and its content ranged from 12.5-21.9 and 7.8-56.1 μg/gdw for barley and malt, resp. The content of catechin ranged from 11.0-17.0 μg/gdw in barley and 0.9-12.1 μg/gdw in malt. [on SciFinder(R)]

Abstract: The fate of five Fusarium toxins - deoxynivalenol (DON), sum of 15- and 3-acetyl-deoxynivalenol (ADONs), HT-2 toxin (HT-2) representing the main trichothecenes and zearalenone (ZON) during the malting and brewing processes - was investigated. In addn. to these 'free' mycotoxins, the occurrence of deoxynivalenol-3-glucoside (DON-3-Glc) was monitored for the first time in a beer prodn. chain (currently, only DON and ZON are regulated). Two batches of barley, naturally infected and artificially inoculated with Fusarium spp. during the time of flowering, were used as a raw material for processing expts. A highly sensitive procedure employing high-performance liq. chromatog. coupled with tandem mass spectrometry (LC-MS/MS) was validated for the anal. of 'free' Fusarium mycotoxins and DON-conjugate in all types of matrixes. The method was also able to detect nivalenol (NIV), fusarenon-X (FUS-X) and T-2 toxin (T-2); nevertheless, none of these toxins was found in any of the samples. While steeping of barley grains (the first step in the malting process) apparently reduced Fusarium mycotoxin levels to below their quantification limits (5-10 μg kg-1), their successive accumulation occurred during germination. In malt, the content of monitored mycotoxins was higher compared with the original barley. The most significant increase was found for DON-3-Glc. During the brewing process, significant further increases in levels occurred. Concns. of this 'masked' DON in final beers exceeded 'free' DON, while in malt grists this trichothecene was the most abundant, with the DON/DON-3-Glc ratio being approx. 5:1 in both sample series. When calcg. mass balance, no significant changes were obsd. during brewing for ADONs. The content of DON and ZON slightly decreased by a max. of 30%. Only traces of HT-2 were detected in some processing intermediates (wort after trub removal and green beer). [on SciFinder(R)]

Abstract: Based on the health-promoting properties of xanthohumol (XN), the prodn. of an enriched beer in this substance would be of interest to the brewing industry, from the perspective of pointing out the benefits that beer could bring consumer health. For that purpose, in this work efforts were applied to produce a beer enriched in XN. Also investigated was the influence of a XN-enriched hop product on the content of XN and isoxanthohumol (IXN) in pale and dark beers. It was verified that XN was largely converted into IXN during wort boiling. However, the use of dark malts revealed a pos. effect on the thermal isomerization of XN. These results are indicative of the isomerisation-inhibiting effect of the stout prodn. process, which resulted in high levels of XN in the beer. Further losses of XN were due to incomplete extn. from the hops into the wort, adsorption to insol. malt proteins and adsorption to yeast cells during fermn. It was possible to produce a dark beer enriched in XN (3.5 mg/L) by using colored malt (caramel malt, roasted malt and roasted malt ext.) and a special XN hop ext. combined with late hop usage during wort boiling. [on SciFinder(R)]

Abstract: Carbonyl compds., esp. aldehydes, notably affect the taste of beer. Although the concns. of carbonyls in beer are very low, most of them also have very low threshold concns. for the taste reception; thus the carbonyls are among the most closely monitored substances in brewing. The use of HPLC in combination with solid-phase extn. and derivatization with 2,4-dinitrophenylhydrazine (DNPH) was studied. The analytes were purged from the samples by N2 for 3 h and adsorbed on SPE column, from which they were eluted with acetonitrile and analyzed by HPLC with Novapak C18 column and PAD detector (Waters 2226). The levels of acetaldehyde, diacetyl, furfural, 2-methylbutanal, 3-methylbutanal, 2-methylpropanal, pentanal, hexanal, and (E)-2-nonenal were measured. The levels of individual carbonyl hydrazones were detd. in 4 brands of com. beer. The contents of individual substances were consistent with previously reported concns. detd. by other anal. methods. [on SciFinder(R)]

Abstract: A clear evidence of impact of hop polyphenols and antioxidant properties of wort on the formation of carbonyl compds. during boiling process as well as during storage of beer was discovered. Data collected by both methods for detn. of antioxidant properties (ABTS and DPPH) correlate well (correlation coeff. = 0.8988). Brews prepd. with a reduced content of hop polyphenols showed higher increment of carbonyl compds. content during wort boiling and beer storage in comparison with brews prepd. with a higher content of hop polyphenols.

Abstract: The content of cis and trans isomers of iso-α-bitter acids was studied during beer storage at 8, 20, and 30°C for 4 mo. Stereoisomers of iso-α-bitter acids were detd. by optimized HPLC method based on Harms and Nietzsche method. The HPLC with photodiode array detection (PDA; 275 nm) system could resolve 6 stereoisomers of iso-α-bitter acids without identification. The contents of trans isomers decreased during beer storage, while the contents of cis isomers remained almost const. The lag time and T150 values were measured by ESR spectroscopy in fresh beer and beer after storage. [on SciFinder(R)]

Abstract: Excellent liq. chromatog. (LC) sepn. of cis/trans stereoisomers of iso-α-acids has been achieved with reversed-phase sorbent XTerra MS C18. An isocratic alk. mobile phase, consisting of a mixt. of 5 mmol l-1 ammonium acetate (pH 8)-acetonitrile-methanol, 62:21:17 (vol./vol./v), was used. In the DCHA-Iso international calibration std. trans-isoposthumulone was identified combining photo diode array (PDA) spectra and electrospray high-accuracy mass spectrometric (MS) data. Moreover, the mol. mass of two degrdn. products resulting from the in-soln. storage of the DCHA-Iso std. was detd. The presence of trans and cis isomers of isoposthumulone, isocohumulone, isoadhumulone and iso-n-humulone in beer samples was confirmed. The trans isomers of iso-α-acids showed characteristic and reproducibly slightly different UV absorbance spectra with respect to cis isomers. [on SciFinder(R)]

Abstract: The detn. of polyphenols by spectrophotometric detection is complicated due to their low concns. in beer. The beer samples have to be pre-concd. before using the spectrophotometric detection for their quantification. An anal. method based on solid-phase extn. (SPE) and followed by high performance liq. chromatog. sepn. with diode-array detection is used for the detn. of free gallic, protocatechuic, caffeic, p-coumaric, ferulic and salicylic acids, of (+)-catechin, (-)-epicatechin, and quercetin. These phenolic compds. participate in colloidal and sensory stability of beer. Six different SPE cartridges were tested and three different types of elution with the most appropriate solvents (acetonitrile, acetone and methanol) were used. The performance of the HPLC method was assessed by the evaluation of parameters such as abs. recovery, relative std. deviation (RSD - lower than 10%), the limit of quantification (LOQ), and the limit of detection (LOD). The polyphenol content in various types of Czech beer is presented. [on SciFinder(R)]

Abstract: A review. The article provides a summary about various types of methods for the detn. of sulfur dioxide in beer, with the emphasis on the electrochem. methods. In this article a new electrochem. method for the detn. of free and total sulfur dioxide-flow chronopotentiometry is described. This new method was optimized, compared with std. EBC methods and introduced to the practice. [on SciFinder(R)]

Abstract: The possibilities of immunochem. detection of barley hordein protein fractions and their cleavage products were examd. by characterization of monoclonal antibodies prepd. for rapid, specific, and sensitive detn. of hordein proteins in food industry, esp. in beer prodn. An indirect competitive ELISA method for barley prolamins (hordein fraction) was developed and the working concns. of all immune agent solns. were detd. Cross-reactivity of the monoclonal antibodies with proteins from other cereals (rye, wheat, oat, rice, corn) was tested. The detection limit of the method was 2 ppm. The calibration curve linear range was 1-100 ppm. The method was used for the anal. of barley grain (flour), malt, and lager beer. [on SciFinder(R)]

Abstract: A review. Data on the effects of stress conditions on properties of the brewing yeast (Saccharomyces cerevisiae) during propagation, fermn., and storage are discussed. Effects of temp., ethanol presence, anaerobic and aerobic culture, storage conditions are examd. The most frequently used optical fluorescence anal. methods for monitoring these changes are presented. [on SciFinder(R)]

Abstract: This article describes the role of sulfur dioxide in beer in relation to its activity as an antioxidant, an antimicrobial agent and a substance disguising stale beer flavour. Forms in which it occurrs in beer, concn. commonly occurring in beer and legislation relating to its use in beer are presented. Mechanisms and factors influencing sulfur dioxide formation during fermentation are described and decrease in concn. during storage is discussed

Abstract: A review. Many methods for the detn. of antioxidant activity in malting and brewing industry have been recently described. Raw brewing materials (barley, malt, hop products, wort) are complex in their compn. and types and amts. of antioxidants. The main chem. and phys. anal. methods for the detn. of antioxidants in these raw materials are examd. [on SciFinder(R)]

Abstract: Despite extensive research carried out in the last few decades, continuous beer fermn. has not yet managed to outperform the traditional batch technol. An industrial breakthrough in favor of continuous brewing using immobilized yeast could be expected only on achievement of the following process characteristics: simple design, low investment costs, flexible operation, effective process control and good product quality. The application of cheap carrier materials of byproduct origin could significantly lower the investment costs of continuous fermn. systems. This work deals with a complete continuous beer fermn. system consisting of a main fermn. reactor (gas-lift) and a maturation reactor (packed-bed) contg. yeast immobilized on spent grains and corncobs, resp. The suitability of cheap carrier materials for long-term continuous brewing was proved. It was found that by fine tuning of process parameters (residence time, aeration) it was possible to adjust the flavor profile of the final product. Consumers considered the continuously fermented beer to be of a regular quality. Anal. and sensorial profiles of both continuously and batch fermented beers were compared. [on SciFinder(R)]

Abstract: The gluten content in different varieties of barley and malts, and in different types of beers, was detd. by a 'sandwich' enzyme immunoassay (RIDASCREEN Gliadin kit). The gluten levels in barley wheat, rye and spelt malts ranged 18.8-45.0, 44.0-68.0, 41.6, and 21.2 g/kg-1, resp. When various types of beer were compared, the gluten concn. increased as follows: alc.-free beer (<3.0), lager beers (<3.0-8.7 mg/l-1), stouts (9.0-15.2 mg/l-1), and wheat beers (10.6-41.2 mg/l-1). When 10 Czech lager beers were analyzed, using both sandwich and competitive ELISA, the results showed that the latter method provided values several times higher than the former. Gluten balance was carried out during the brewing process, starting from the raw materials and terminating at the final beer. Gluten levels decreased due to pptn. during the mashing process, primary and secondary fermn. and, lastly, as a result of adsorption during beer stabilization. The gluten content in beer is, thus, approx. three orders of magnitude lower than in the raw malt. [on SciFinder(R)]

Abstract: A review. A rich, dense, and long-lasting foam head on tap beer is one of the first favorable perceptions among beer drinkers. The most important factors influencing the stability of beer foam include the quality of hop substances, carbohydrates, carbon dioxide and proteins (esp. hydrophobic proteins). The beer foam functional properties, foam structural models, impact of brewing technologies, proteins involved (protein Z, lipid transfer protein I - LTPI, lipid-binding proteins, hordeins), non-protein foam components supporting foam formation and stability, and components with neg. effects on beer foam are discussed. [on SciFinder(R)]

Abstract: A chronopotentiometric method for the detn. of total sulfur dioxide in beer is described. Free and bound sulphites were converted to sulphite anions on alkalising the sample solns. On acidifying the soln., the released sulfur dioxide was online sepd. through a semipermeable membrane and transported by an electrolyte into the measuring cell and measured by stripping chronopotentiometry. The proposed method was validated and compared with the three EBC methods. The RSD of repeatability was 8.6% for the normal SO2 level in the beer (3.4 mg/L). The results corresponded well with those obtained with the alternative EBC methods. The elaborated method was much faster and simpler than the EBC methods. [on SciFinder(R)]

Abstract: A review. Anal. methods for the detn. of polyphenols (total and individual) in brewing industry are discussed. The group methods include detn. of anthocyanogens, tannins, and flavonoids. For the detn. of individuals polyphenols, the most widespread method is HPLC (reversed-phase) with different modes of detection. Less used is GC with MS detection because of need for analyte derivatization. Procedures for sample prepn. for the different methods are also oxamined. [on SciFinder(R)]

Abstract: Use of waste brewery yeasts for isolation of beta-glucans and properties and use of the final product are discussed. Methods for isolation of glucans or cell walls from yeasts are presented comprising cell disintegration, use of enzymes, autolysis and acid or alkali hydrolysis. Influence of temp. and pH on release of soluble compounds during autolysis are discussed.

Abstract: The importance of amino acids in brewing industry with respect to suitable compn. of N compds. of hopped wort ext. and optimal course of fermn. is reviewed. The roles of free amino acids in the prodn. of metabolites important for beer sensory properties and of compds. adversely affecting the beer during storage are emphasized. The initial overview provides a brief chem. characterization of amino acids and their anal. by spectrophotometric, HPLC, gas chromatog., gel permeation chromatog., and hydrophobic interaction chromatog. methods. An example of free amino acids detn. in beer using derivatization with the Waters AccQ.Fluor Reagent (6-aminoquinolyl-N-hydroxysuccinimidyl carbamate) HPLC anal. on Waters AccQ.bul.Tag reverses-phase column NovaPak C18 at 37°C with fluorescence detection (250/395 nm, excitation/emission) is provided. The anal. conditions of amino acid isolation and quantification for anal. of real pale lager beer samples are given. [on SciFinder(R)]

Abstract: A review discusses the perspectives of the continuous brewing in regard to the major obstacles posed to the commercialization of this technol. and to their potential solns. [on SciFinder(R)]

Abstract: This work focused on the possibility of using PCR (polymerase chain reaction) to detect Lactobacillus. PCR was compared with several other methods, including FISH (fluorescence in situ hybridization). Thirteen Lactobacillus species from collection were chosen. Their identities were confirmed by API CH50 tests. While biochem. features of all chosen Lactobacillus species are known, the complete genomic DNA sequence is known only for some of them. Several com. available kits based on PCR were used for their identification. Primers specific for the 16S-23S rDNA intergenic spacer region (ISR) were used. These primers were used for non-specific PCR reaction with lower annealing temp. Such amplified DNA fragments were cloned into pCR4 vector by TOPO TA kit and afterwards sequenced. The amplified DNA sequences obtained were analyzed and species-specific primers were designed. The same region for amplification was used also for real-time PCR. Real-time PCR is an advanced and highly specific method so we expected to obtain lot of important data. We expect to use these data for detg. individual Lactobacillus species. Another method used for Lactobacillus species detn. was FISH, based on detection of specific DNA probe labeled with fluorescent dye. We have used fluorescent probes from com. available kit Vermicon. [on SciFinder(R)]

Abstract: Beer is a beverage with important nutritional aspects and with a low content of proteins, of which the main source is malt. Malt contains prolamins that are assocd. with coeliac disease. The concn. of prolamins in beer depends on the type of malt, the mashing technol., and the fermn. and stabilization processes. The sandwich ELISA RIDASCREEN gliadin kit, which uses R5 antibody detection approach, and the gliadin ELISA kit have been used for the detn. of prolamins in some types of malts and in some beers from the Czech market. The content of prolamins in the beers varied, but was always less than 10 mg l-1. Also, the prolamin content and balance at various stages in the malting and brewing processes was estd. [on SciFinder(R)]

Abstract: Although traditional batch overwhelmingly prevails over continuous fermn., a breakthrough in quality and savings could be achieved by a simple, flexible and cheap fermn. system. This work deals with a complete continuous beer fermn. consisting of an airlift and a packed-bed reactor contg. yeast immobilized on spent grains and corncobs, resp. The goal was to study the influence of process parameters on bioreactor performance and flavor profile of beer. Consumers considered the continuously fermented beer to be of a regular quality. The possibility of flavor adjustments by changing the process parameters was proved by a panel of experienced tasters. [on SciFinder(R)]

Abstract: This review surveys rapid bioluminescent detection techniques applied in food industry and discusses the historical development of the rapid methods. These techniques are divided into two groups: methods based on bioluminescent ATP (ATP) assay, and on bacterial bioluminescence. The advantages and disadvantages of these methods are described. The article provides the bibliog. of fluorescent method applications in food samples. [on SciFinder(R)]

Abstract: A review of hop substances with estrogenic effects, their structures, biosynthesis, and fate during brewing processes. Main attention is given to 8-prenylnaringenin and its precursor desmethylxanthohumol. Detn. of these 2 substances in beer and hops and of their estrogenic effects is discussed. Health implications of hop phytoestrogens and prepn. of food additive/supplements based on hop are examd. [on SciFinder(R)]

Abstract: The existing and new findings on xanthohumol and other prenylated hop flavonoids are reviewed. First, synthesis of flavonoids and prenylated flavonoids in plants is described. The contents of major prenylflavonoids in hops in general and the xanthohumol contents in Czech cultivars in the last year are listed. Formulae of all the known hop prenylflavonoids and their chemical, physical and biochemical properties are given. Their effect on human health and their current and potential future utilization are discussed. Biotransformations of xanthohumol in microorganisms, mammals and humans are also mentioned. The balance of xanthohumol and isoxanthohumol in the production of beer is given.

Abstract: In the continuous systems, such as continuous beer fermentation, immobilized cells are kept inside the bioreactor for long periods of time. Thus an important factor in the design and performance of the immobilized yeast reactor is immobilized cell viability and physiology. Both the decreasing specific glucose consumption rate (q(im)) and intracellular redox potential of the cells immobilized to spent grains during continuous cultivation in bubble-column reactor implied alterations in cell physiology. It was hypothesized that the changes of the physiological state of the immobilized brewing yeast were due to the aging process to which the immobilized yeast are exposed in the continuous reactor. The amount of an actively growing fraction (X-im(act)) of the total immobilized biomass (Xi,,) was subsequently estimated at approximately m 0.12 g(IB) g(C)(-1) (IB = dry immobilized biomass, C = dry carrier). A mathematical model of the immobilized yeast biofilm growth on the surface of spent grain particles based on cell deposition (cell-to-carrier adhesion and cell-to-cell attachment), immobilized cell growth, and immobilized biomass detachment (cell outgrowth, biofilm abrasion) was formulated. The concept of the active fraction of immobilized biomass (X-im(act)) and the maximum attainable biomass load (X-im(act)) was included into the model. Since the average biofilm thickness was estimated at ca. 10 mum, the limitation of the diffusion of substrates inside the yeast biofilm could be neglected. The model successfully predicted the dynamics of the immobilized cell growth, maximum biomass load, free cell growth, and glucose consumption under constant hydrodynamic conditions in a bubble-column reactor. Good agreement between model simulations and experimental data was achieved.

Abstract: Metabolic activity of 3 strains of lager yeasts (No. 2, 7 and 95 obtained from the Culture Collection of Brewing Yeasts, Research Institute of Brewing & Malting in Prague, Czech Republic) was studied in relation to utilisation of the main wort sugars, glucose, maltose and fructose. The trial was conducted in a pilot scale fermentor at 13 degrees C using worts of original gravity 12% with grist partly substituted by unmalted barley. Sequential utilisation of sugars was observed, glucose being utilised as the 1st followed by fructose and maltose. Strain no. 2 and 95 exhibited lower sensitivity to glucose; exponential phase of maltose utilisation started at 45% (strain no. 2) and 55.7% (strain no. 95) of residual glucose level in worts. Strain no. 7 showed the shortest and the fastest and strain no. 95 the longest linear phase of maltose utilisation. Results indicated that fructose was fermented slower and to a lower degree than glucose and maltose. Fructose probably contributed considerably to the parameter 'sweetness' in beer and unfermented malt.

Abstract: In the process of preparation of a non-toxic metal biosorbent by entrapment of yeast cells in silica matrix by sol-gel technique, the homogeneity of yeast cell dispersion and prevention of precipitation during tetraethoxysilane pre-polymerization were found to be the 21 parameters substantially influencing the sorption capacity for Cd2+. Ultrasonic treatment of cell walls increased the sorption capacity by 25% as a result of the suppression of their agglomeration. Precipitation during tetraethoxysi lane (TEOS) pre-polymerization was tracked by measurement of light absorbance at lambda = 600 nm. The biosorbent formed from pre-polymer with a light absorbance of 0.3 had 50% less sorption capacity than that with an absorbance of 0.05. Modification of the TEOS: methanol: water ratio in the range from 1: 10: 8 to 1: 10:40 and specific surface between 210 and 390 m(2) g(-1) influenced the sorption capacity of biosorbents only within the limits of experimental error. The sorption capacity per unit weight of biosorbent was proportional to the yeast cell wall content. The content could be increased up to a cell walls: SiO2 ratio congruent to 1.5 (w/w). Biosorbent with higher cell wall content was fragile and friable. Biosorbents were shaped by crushing and regular particles were prepared by moulding into millimetre-scate cylindrical moulds. In this shaping process, the loss of biosorbent mixture was small and the process could easily be scaled up. Using a mathematical model of a packed-bed adsorber, taking into account axial dispersion and mass transfer resistance the break-through curve for crushed and moulded biosorbent was predicted with high fidelity. (C) 2004 Elsevier Ltd. All rights reserved.

Abstract: Biosorption of Cd2+ Cu2+ and Ag+ ions by C-, N-, P-, S-, Mg- and K-limited cells of Saccharomyces cerevisiae was examined. Raman spectroscopy and analysis of elemental composition were used to identify differences between individual yeast cultures. K-, Mgand C-limited cells accumulated the greatest amounts of Cd2+ ions. The greatest amount of Cd2+ ions was bound by biomass grown in K-limited medium. P-limited cells bound the greatest amount of Ag+ ions, but in contrast they had the lowest sorption capacity for Cd2+ ions. The smallest amounts of Cu2+ and Ag+ ions was bound by biomass grown in S-limited medium. (C) 2004 Elsevier Ltd. All rights reserved.

Abstract: PCR method was used for the identity confirmation of 14 isolates of lactic acid bacteria, the most frequent bacterial contaminants in brewing industry. The isolates were biochem. characterized as Lactobacillus plantarum. Detailed procedures for genomic DNA sepn. by the NucleoSpin Tissue Kit and amplification by the BrewSave Kit are described. All isolates were confirmed as Lactobacillus by the BrewSave PCR. It was not possible to distinguish sep. species since the BrewSave kit was designed for lactic acid bacteria genus identification rather than species differentiation. [on SciFinder(R)]

Abstract: Beer samples (n=200) were analyzed for the contents of zinc, copper, lead, and cadmium by galvanostatic stripping chronopotentiometry (GSCP). The av. contents per L were 55.4 μg Zn, 0.2 μg Cd, 32.6 μg Cu, and 6.5 μg Pb. The GSCP method was confirmed by MS with inductively coupled plasma. As the lead content was relatively high, 50 samples of non-alc. beverages and wine were also analyzed for the Pb content. The av. lead content was 7.5 μg and 41.8 μg/L in non-alc. beverages and wines, resp. Thus, beer is the purest beverage with respect to lead and other heavy metal contents. The brewing raw materials and intermediate products were analyzed during in brewing process. Only traces of the metals (1% zinc and cadmium, 9% copper, 2% lead) passed from raw materials into beer. The brewing process is a self-cleaning process with respect to heavy metal contents. [on SciFinder(R)]

Abstract: The Zn content of different types wines from Znojmo region was detd. by DPASV without sample pre-treatment. Forty-five different wines were analyzed. Almost all samples of wine contained less than 1.5 mg/L of Zn (from 0.05 to 3.71 mg/L). The mean Zn concns. were 1.01 and 1.17 mg/L for white and red wines, resp. The av. of Zn level in sparkling and fortified wines were 1.44 and 1.21 mg/L, resp. [on SciFinder(R)]

Abstract: Milled-sieved and epichlorhydrin-immobilized Azolla biosorbed ca. 363 and 320 μmol Cu2+ g-1 from a 100 mg L-1 soln. Efficiency of Cu2+ removal by columns was in the order epichlorohydrin-immobilized Azolla>milled-sieved Azolla>untreated Azolla. The 2.5 g epichlorohydrin-immobilized Azolla column demonstrated complete metal sequestration from ca. 12 L of influent 5 mg Cu2+ L-1 and was still at less than 75% satn. even after ca. 22 L had passed through the column. EDTA effectively desorbed Cu2+ with a ca. 55-fold decrease in vol. [on SciFinder(R)]

Abstract: In this work we compared biosorbents obtained by encapsulation of polysaccharides, isolated from waste brewing biomass, in sol-gel derived silicates and an organic polymer. Biosorbents were prepared by mixing cross-linking-agents-organic or siliceous-with dried cells envelopes. Siliceous prepolymers were synthesized via transesterification and hydrolysis from tetraethoxysilane (TEOS) and methanol. Sorption of Cd2+, Cu2+ and Ag+ by biosorbent granules (0.25-0.6 mm) was examined in batch and in a packed column. The biosorbent prepared by interesterification of TEOS showed a 2-3 times higher intensity of sorption than the biosorbent cross-linked with epichlorohydrin (the most effective cross-linking organic agent) while the sorption capacity of both biosorbents was equal. The specific surface area of the silica matrix was 597 m(2)/g but only traces of metals were sequestered from solution with a concentration of Cd2+ of 50 mg/l. The biosorbent with a silica matrix is a heterogeneous material containing microporous matrix inclusions of thin cell walls. Its high sorption intensity and good mechanical strength will be useful in continuous metal uptake of low concentrations of metals.

Abstract: Two types of magnetic biosorbent were prepared by novel protocols from epichlorhydrin-cross-linked Saccharomyces cerevisiae cell walls and their biosorption characteristics were compared to those of non-magnetic cell walls. The magnetic biosorbents I and II were capable of binding Cu2+ maximally to 225 and 50 mu mol/g, Cd2+ to 90 and 25 mu mol/g and Ag+ to 80 and 45 mu mol/g respectively. These values compare with 400, 125 and 75 mu mol/g, respectively, for non-magnetic cell walls.

Abstract: Extn. methods used for volatile substances isolation from beer are described and compared. Extns. into N-pentane and dichloromethane mixt. in ratio 2:1 with varying extn. time (eg. 24 h, 16 h, 8 h and 2 h performed in a continual extn. app.) as well as distillate batch extn. into dichloromethane were verified. A 12% beer was used as a sample. The highest concn. of higher alcs. was measured during 24 h extn. time; the highest ester and fatty acids levels were found during 16 h extn. time. The ratio of higher alcs. and esters attained the highest level (3.02) during 24 h extn., the lowest (2.38) during 16 h extn. Steam distn. followed by batch extn. into dichloromethane resulted in lower yields of volatile substances, however, seen from the viewpoint of time and extn. solvent saving, this method appears suitable for practice because it provides reproducible results. [on SciFinder(R)]

Abstract:

Abstract: The lead content of different types of Czech and Moravian wines was detd. by differential pulse anodic stripping voltammetry without sample pretreatment. Fifty-four different wines were analyzed. Almost all samples of wine contained <200 μg/L of lead. The mean lead concns. were 41 and 49 μg/L for white and red wines, resp. Lead level is generally higher in red wines, except wines from the Znojmo-Mikulov area. The samples originating from this region also show the widest range of lead content. The lowest lead contents were found in wine samples from Bzenec-Straznice (white 11 μg/L, red 27 μg/L). The lead concns. in wines from the Czech central region are comparable with wines from Hustopece-Hodonin (white 25 μg/L, red 62 μg/L). [on SciFinder(R)]

Abstract: A review with 8 refs., emphasizing the authors' studies of infusion and decoction mashing and fermn. of wort, employing different proportions of nonmalted barley meal. [on SciFinder(R)]

Abstract: Biosorbents are materials derived from specific kind of biomass which are cheaper and more effective alternatives for the removal of metal ions from aqueous solution. In this chapter, based on the literatures and our research results, the biosorbents widely used for heavy metal removal were reviewed, mainly focusing on their pretreatment, modification, immobilisation, regeneration, modelling of column bioadsorber and potential applications. Part or chapter is dedicated to application of biosorbents in reactors for removal of metals from aqueous solutions and some large scale applications of biosorbents were reviewed too.

Abstract: Production of pale barley malt consists from three basic operations: steeping, germination and kilning. During germination the grain undergoes modification. Heat is produced by the respiration during germination of the barley and is removed by cold air with high relative humidity. The optimal temperatures in modern malting during germination are between 14 and 18 degrees C. During grain germination, cooling is provided by the passage of humid air. Air is cooled by water adiabatic evaporation and mostly by refrigeration plant. This solution provides us optimal germination process in relatively hot year period and keeps quality of barley malt. Cooling by refrigeration plant provides malts without high loses of extracts (malting loses) by very intensive respiration and growth. Paper describes the process and results of the refrigeration technology with capacity 1.4 MW of cold corresponding to the malt production 27 000 t per year.

Abstract: In the present invention, there is disclosed a polymer-based compd. material comprising nanoparticles and contg. 95 to 99.99 percent by wt. of polymeric matrix and 0.01 to 5 percent by wt. of nanoparticles preferably within a range of 0.02 to 1 percent by wt., wherein the nanoparticles are planar of layered materials (minerals) and are homogeneously distributed within the polymeric matrix. The planar particles of a layered material can be preferably of graphite, mica or kaolin and the polymeric matrix can be preferably of poly(ethyleneterephthalate) or polycaprolactam-6. There is also disclosed a process for prepg. the above-described compd. material, said prepn. process comprising delaminating of a layered material by ultrasound waves with frequency within the range of 20 to 100 kHz either in a polymer starting component and the obtained mixt., contg. planar particles, is then subjected to polymn. or copolymn., or directly in a polymer soln., wherein solvent being present in the polymer soln. is subsequently distd. off or evapd., or in an auxiliary liq. phase contg. delaminated nanoparticles, which auxiliary liq. phase is then mixed with a corresponding starting component of the polymer or said polymer starting component is dissolved therein and the auxiliary phase is subsequently removed from the mixt. The resulting mixt. is then subjected to polymn. or copolymn. The compd. materials of the present invention can be used in the first instance in the manuf. of barrier wrappers for beverages or foodstuffs.

Abstract: Brewers yeast are decompd. with alk. at pH 7.0-7.7 and 90-95° and filtered, the filtrate is neutralized by acetic acid, the ppt. is removed, the retentate is acidified to pH < 3.0, supplemented with 10-30% ethanol, and RNA is isolated from the sediment by Et alc., acetone, or ether. Thus, 1 L of liq. brewers yeast kept at 4° is mixed with 1 L a NaOH soln. of 7.5 pH; 0.7 g NaOH is dissolved in 50 mL water, brought to 250 mL, warmed to 90°, added to the brewers yeast mixt., the mixt. is warmed to 95°, held at this temp. for 30 min., and filtered out. The filtrate is neutralized with a 50% acetic acid soln., cooled to 0°, acidified to pH <3.0 by HCl, supplemented with 100 mL ethanol, and held for several hours. After filtering the ppt., RNA is isolated with 25 mL acetone, washed out with 25 mL ether, and dried, yielding a powd. prepn. contg. 60-70% RNA. [on SciFinder(R)]

Abstract: A 50-68.3% sucrose soln. is incubated with alginate-gel immobilized brewer's yeast at 30°. In a 6 h 3-step process, the inversion was 95%. [on SciFinder(R)]