Abstracts BrewingScience articles 2011

W.S. Veraverbeke, J. De Cock, G. De Rouck, J.A. Delcour, H. Van Mellaert, G. Aerts and W.F. Broekaert
Partial Substitution of Barley Malt by Wheat Bran in the Grist Results in Lager Beer with Better Taste Profile and Higher Content in Arabinoxylan-Oligosaccharides (AXOS)
The use of wheat bran as a new adjunct in brewing at 25 % of total grist in combination with the use of a xylanase in the mashing step was tested by brewing control and bran-brewed lager beers. Sensory analysis revealed marked improvements in taste profile due to bran-brewing, with statistically significant increase in body, smoothness and warming notes, and a decrease in acetaldehyde, after-bitterness, drying and grainy attributes. A detailed physico-chemical analysis of the beers was performed. Key parameters on which a significant impact was demonstrated include increased content of arabinoxylan-oligosaccharides (AXOS), ferulic acid, and soluble protein, and lowered content of aldehydes, the latter indicative of reduced oxidation during brewing. Traditional but long forgotten use of wheat bran for brewing of small beers holds potential to make innovative beers with an interesting taste profile.
Descriptors: body, sensory analysis, wheat bran, xylanases
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (November/December 2011), pp. 168-174

K. Müller, S. Sängerlaub, A. Kramer, C. Huber and K. Fritsch
Temperature-dependent Oxygen Permeation through PET/MXD6-Barrier Blend Bottles with and without Oxygen Absorber
The oxygen permeability of PET bottles has a significant influence on the shelf-life of beverages that are sensitive to oxygen. To reduce the permeability, PET is blended with barrier materials like MXD6 (MXD6 is a mainly aliphatic polyamide resin which contains meta-xylylene groups). The aim of this study was to investigate the temperature dependence of oxygen permeation through PET/MXD6 blends. The oxygen content inside water-filled PET/MXD6-blend bottles with 2, 5 and 8 % wt. of MXD6 was determined at 5, 23, 38, and 55 °C. The MXD6 was applied both purely and with a catalyst that is enabling it to work as an oxygen absorber. The results were compared to PET bottles not containing MXD6. The oxygen partial pressure inside the bottles was measured as gaseous oxygen using an optical-chemical sensor. The activation energy of oxygen permeation was calculated to be in the range from 32.8 kJ/mol for PET bottles without MXD6 and up to 43.4 kJ/mol for PET bottles with 8 wt-% for the passive barrier of MXD6. In the barrier PET bottles with MXD6 in combination with a catalyst, the oxygen content in the water-filled PET bottles remained up to 0.2 mg O2/L dissolved oxygen for a period of 6 months, depending mainly on the MXD6 concentration. This range was consistent for all applied temperatures. These data serve as a basis for the prediction/calculation of oxygen permeability of PET barrier materials at different temperatures and further for developing a standardization of oxygen absorber characterization concerning absorber kinetics and oxygen barrier.
Descriptors: PET bottle, Oxygen absorber, Oxygen permeation, Activation energy, MXD6
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (November/December 2011), pp. 161-167

K. Schwarz and F.-J. Methner
Styrene Concentrations during Wheat Beer Production
The screening of styrene concentrations during different stages of wheat beer production shows that in opposite to thermal processes like mashing and wort boiling the primary and secondary fermentation contribute most to the styrene content in final beers. Therefore, the enzymatic decarboxylation of cinnamic acid by brewers' yeast is the predominant kind of reaction. Styrene concentrations in bottled beer were up to 25 ppb. In addition, the results of the screening were compared with the precursor concentration of cinnamic acid in the corresponding pitching wort. A linear correlation could not be found. Moreover, the influence of various manufacturing considerations like the kind of fermentation or the ratio of wheat grist load is shown. For example, the cinnamic acid content in wort decreases with an increasing amount of wheat malt.
Descriptors: styrene, wheat beer, aroma, cinnamic acid, 4-vinylguaiacol
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (November/December 2011), pp. 156-160

J. Matoušek, J. Patzak, T. Kocábek, Z. Füssy, J. Stehlík, L. Orctová and G.S. Duraisamy
Functional Analyses of Lupulin Gland-Specific Regulatory Factors from WD40, bHLH and Myb Families of Hop (Humulus lupulus L.) show Formation of Crucial Complexes Activating chs_H1 Genes
Complex lupulin gland-specific cDNA library from Osvald's clone 72 hop was constructed to dissect regulation of biosynthetic pathway(s) leading to the accumulation of hop bitter acids and prenylflavonoids with promising health-beneficial activities. From this cDNA library we isolated first hop-specific allelic isoforms of transcription factors (TF) bHLH (HlbHLH2, GeneBank AC:FR751553) and WD40 (HlWD40_1, AC:NM_122360) which are involved in combinatorial control of light-responsive and tissue-specific activation of phenylpropanoid pathway. HlbHLH2 and HlWD40_1 are quite lupulin gland-specific and, according to our transient expression experiments, they form specific complexes with another novel hop TF HlMyb2 (AC:FN646081) and previously isolated lupulin gland-specific HlMyb3 (AC:AM501509). The complex formation leads to strong activation of chalconsynthase gene (chs_H1) promoter. The interplay and regulation of expression of these crucial TF complexes could co-determine the rate of accumulation of valuable metabolites of lupulin.
Descriptors: Humulus lupulus L., N. benthamiana, lupulin metabolome, transcription factors, protein complexes, transient expression assay
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (November/December 2011), pp. 151-155

L.-A. Garbe and N. Rettberg
The Power of Stable Isotope Dilution Assays in Brewing
The quantification of trace substances in raw materials, mash, wort and beer is becoming more frequently required by brewers. Stable isotope dilution assay (SIDA) coupled to gas chromatography mass spectrometry or liquid chromatography mass spectrometry instrumentation is a sensitive and highly specific technique for precise quantification of trace substances from complex matrices. The current paper elucidates the basic principles of stable isotope dilution assays and presents practical applications related to brewing. It emphasizes the importance of isotope standards in multi-step sample clean-up procedures and answers the question why SIDA is (so far) not widely used in brewery quality control.
Descriptors: mass spectrometry, stable isotope dilution analysis, SIDA, beer staling, contamination
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (November/December 2011), pp. 140-150

B. Jaskula-Goiris, B. De Causmaecker, G. De Rouck, L. De Cooman and G. Aerts
Detailed Multivariate Modeling of Beer Staling in Commercial Pale Lagers
It is generally recognized that flavour quality and flavour(in)stability cannot be grasped by one parameter, since the multitude of flavour chemicals involved. To identify beer chemistry changes during staling in commercial pilsner beer, an integrated analytical-sensorial methodology using multivariate statistical analysis was applied on samples subjected to ageing at 30 °C. Application of this technique to model the taste(in)stability in an objective way, offers the opportunity to more thoroughly investigate the influence of raw materials, brewing methods and applied technologies on flavour stability. The models obtained showed differences in aging behaviour of six commercial pale lager beers. Furthermore, detailed multivariate analysis allowed us to identify chemical compounds related to beer staling and facilitates a better understanding of beer flavour (in)stability by pinpointing the impact of process parameters and applied technologies.
Descriptors: Beer ageing, flavour stability, pale lager, multivariate statistical analysis
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (November/December 2011), pp. 119-139

K. Müller-Auffermann, M. Hutzler, H. Schneiderbanger and F. Jacob
Scientific Evaluation of Different Methods for the Determination of Yeast Vitality
In this paper, two non standard methods are introduced and described precisely for measuring the vitality of yeast. Both are simple and produce results in a very short time. For the purpose of demonstrating these methods, brewing yeasts were placed under specific types of stress in various situations and compared to yeast not under stress. Their capacity for producing CO2 was measured, and the condition of their cell walls was determined parallel through potentiometric titration. The results show that both of the methods demonstrated in this paper are effective for determining the physiological condition of yeast. Relative to the untreated yeast, the yeast placed under stress produced less CO2 in controlled small-scale fermentation trials. Also, the condition of their cell walls changed, which was made apparent by the volume titrant required in the potentiometric titration. It should also be mentioned, that the trials described here were in fact preliminary trials for establishing the methodology for the respective tests. In a future paper, a further test designed for practical application in the industry includes a measurement of the intracellular pH and fermentation pressure in addition to the other measurements performed here.
Descriptors: yeast, brewing yeast, vitality, viability, physiological condition, CO2, CO2 production, pressure, temperature, potentiometric titration, cell wall surface area, surface charge
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (September/October 2011), pp. 107-118

A. Schmelzle, B. Lindemann and F.-J. Methner
Sensory Descriptive Analysis and Investigation of Consumer Acceptance of German Pilsner
To derive differences between German pilsner beers which have effects on acceptance, sensory description is linked to consumer acceptance. The sensory perception of pilsner beer is described by sensorily-trained consumers. For the pilsner type of beer, an appropriate number of representative and characteristic attributes are compiled for the precise description of sensory perceptions. By investigating acceptance by untrained consumers (n=142) in blind and open product tests, estimations of pilsner beers are measured. The results can highlight promising pilsner varieties and identify those which are sensorily unconvincing. In addition, split analyses are performed concerning consumers' objectives and sensory expectations. In the blind test, it was confirmed that consumers' acceptance of bitter pilsner (> 34 Bitterness Units, BU), leaving a coating mouthfeel, is lower than that of pilsner which is less bitter. If the brand name is known to consumers, they rate bitter pilsner (> 34 BU) with high acceptance. Additionally, pilsner varieties with an intense hop aroma and bitter pilsners (> 34 BU) are rated significantly better by consumers who drink beer for enjoyment. Consumers who state that they enjoy drinking a more bitter pilsner rate mild pilsners (< 20 BU) significantly lower. If consumers expect a hop aromatic pilsner, they also prefer these pilsner beers in blind taste tests.
Descriptors: pilsner, sensory evaluation, descriptive analysis, acceptance testing, bitter taste, hop aroma
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (September/October 2011), pp. 95-106

C. Schmidt, A. Lagemann, A. Stephan and G. Stettner
Impact of the Use of Inline Pre-isomerized Hop Products on Analytical and Sensory Markers for Beer Ageing
The main quality challenge of beer is the change of its chemical composition during storage. It is known that the typical bitterness of fresh beer declines in the intensity and changes in the quality with an increasing age of the beverage. The bitter tasting compounds trans-iso-α-acids converse into lingering and harsh bitter tasting tri- and tetracyclic degradation products. In order to investigate the evaluation of beer flavour stability, the behaviour of trans-iso-α-acids, the trans/cis ratio of bitter acids, and the formation of tricyclocohumol and tricyclohumol as representatives of acidic-catalyzed degradation products of trans-iso-α-acids were chosen as analytical markers in wort, fresh beer as well as in 2 and 4 months aged beer samples with and without inline pre-isomerization. The characteristics of these analytical parameters were determined using HPLC-DAD and HPLC-MS/MS analysis. Supplementary to quantitative data, fresh beer as well as 2 and 4 months stored beer samples with or rather without the use of pre-isomerization were evaluated for the attributes aroma, taste, and beer ageing by a trained sensory panel. The performed experiments with a hop yield enhancer in comparison to conventional hopping showed no effect on the flavour stability of Pilsener beer. Nevertheless, the tricyclic degradation products tricyclocohumol and tricyclohumol were suitable as solid analytical parameters to estimate the flavour stability during storage.
Descriptors: iso-α-acids, pre-isomerization, beer ageing, tricyclic degradation products, HPLC-MS/MS analysis, sensory evaluation
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (September/October 2011), pp. 89-94

C. Heim, M. Ureña de Vivanco, M. Rajab, K. Glas, H. Horn, B. Helmreich and T. Letzel
Ozone II: Characterization of In Situ Ozone Generation Using Diamond Electrodes
Ozone can be widely used for oxidation of diverse water constituents and mineralization of organic compounds and therefore for their elimination in drinking and process water as explained before in the review Ozone I: Characteristics/Generation/Possible Applications by Heim C. and Glas K., BrewingScience 2011 [1]. Electrolytic ozone generation in situ using boron-doped diamond electrodes is a relatively new and promising technology. The current article describes the formation of ozone directly from water with a DIACHEM® electrode. Ozone concentrations in water depend on the applied current on the one hand and on the water matrix on the other hand. The influence of organic and inorganic components on residual ozone concentrations in several water matrices was also investigated. The results form the basis to find reasonable applications of the described technology in the food and beverage industry.
Descriptors: ozone, oxidation, diamond electrode, water quality
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (September/October 2011), pp. 83-88

T. Kunz, H. Woest, E.-J. Lee, C. Müller, F.-J. Methner
Improvement of the Oxidative Wort and Beer Stability by Increased Unmalted Barley Proportion
The influence of unmalted barley on the brewing process and the quality of the resulting beer-like beverages was investigated with the main focus on the oxidative stability by using traditional beer analyses and EPR-Spectroscopy (EAP-, T450-value). Although all analytical values of the final beverages were within the normal range according to MEBAK, a slight decrease in total polyphenol and FAN content caused by an increased barley proportion in the grist was measured. In direct correlation an increase of higher molecular proteins and ß-glucan were detectable. Based on these results, it can be said that beers with a barley proportion up to 75 % will achieve comparable or higher final attenuation of the "beer" due to a combined effectiveness of malt and technical enzymes. The missing heat exposure and oxidative stress by the malting process resulted in lower values of TBI and wort respectively beer colour with increasing barley proportions in the grist. Furthermore, it was observable that an increase of barley content leads to higher oxidative stability (EAP-value) and a lower EPR signal intensity (T450 value) as an indicator for the radical generation in the wort and final beverage. In comparison to beer produced with 100 % of malt, the beers brewed with up to 50 % barley proportion were slightly preferred and up to 75 % comparable in sensory analyses. Only the brew with a barley proportion of 90 % showed a more astringent bitter taste.
Descriptors: unmalted barley, flavour stability, barley proportion, oxidative beer stability, brewing, Electron Spin Resonance Spectroscopy (EPR)
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (July/August 2011), pp. 75-82

C. Schwarz, M. Zarnkow, W. Back, T. Becker
Predicting Haze Stability in Wheat Beer using Light Scattering Analysis Techniques
Visible and intense turbidity is seen as a defining characteristic of German and Belgian wheat beers. To date, no reliable method has been established for predicting the haze stability of wheat beer. It would be very beneficial for breweries to be able to predict haze stability so as to ensure that the beer retained a satisfactory level of haze during its shelf life. To predict wheat beer haze, trials were undertaken, in which light scattering analysis techniques and particle size distribution measurements were made, for the purpose of characterizing the haze stability of wheat beer. The wheat beer samples assessed had substantial differences in haze stability durability, from 19 days up to more than 160 days, as judged by when 90° scatter light intensity drops bellow 30 EBC units. Interestingly, the classification of all samples by the 90°:25° ratio of scatter light intensity showed values from 0.5 up to 1.0 and it was observed that as haze stability increases, the ratio expressing the intensity of light scattering at 90°:25° also increases. Particle size distribution measurements showed for samples with high 90°:25° ratios of scatter light intensity (> 0.9) had monomodal distributions with high ratios of particles < 1 µm which was favourable indicator of beer haze durability.
Descriptors: wheat beer, haze, haze measurement
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (July/August 2011), pp. 68-74

T. Kunz, E. J. Lee, V. Schiwek, T. Seewald, F.-J. Methner
Glucose - a Reducing Sugar? Reducing Properties of Sugars in Beverages and Food
The properties of reducing sugars are interesting for the shelf life of beverages, particularly beer, and for human nutrition. For the brewing process the different reducing potentials and the mode of action of fermentable sugars are vitally important, especially during wort boiling where the reactions of sugars are accelerated. Additionally, several breweries use non-fermentable sugars in the brewing process to imbue the beer with unique flavour, body and mouthfeel. An optimised method to ascertain the reduction potential of sugars against Fe3+ at low pH was developed in this work.
Sugars behave differently at low pH compared to the generally known behaviour described by Fehling when using NaOH. At low pH conditions, the formation of the open chain aldehyde structure of glucose is inhibited. Fructose has a higher ability to generate the open structure, resulting in stronger reducing properties. The results show at pH 4.3 the strongest reduction potential results from isomaltulose (PalatinoseTM), followed by fructose, Vitalose® and maltotriose. The higher reduction potential of the "non-reducing" sucrose compared to glucose can be explained by the invert sugar's acid hydrolysation. Additional investigations give further evidence about the behaviour of fermentable sugars during the brewing process. Thereby is beside the described mode of action of glucose, fructose and sucrose, the detected stronger reduction potential of maltotriose versus maltose remarkable.
The optimised Chapon method can be used to support the investigation of the complex reaction mechanism of the different sugars in beverages like juice, wine and beer as well as during the brewing process and during storage.
Descriptors: reduction potential, reducing sugars, Chapon, Fehling, beverages, beer
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (July/August 2011), pp. 61-67

R. Folz, R. Hofmann and U. Stahl
Impact of Permeation of O2 and CO2 on the Growth Behaviour of Saccharomyces diastaticus in Beer
Different bottle types had been tested on their permeation characteristics (including oxygen ingress and carbonation retention) and the microbiological stability of the bottled beer. The microbiological stability was assessed by measuring the turbidity and the concentration of colony forming units (CFU). Measurement of the CO2 content and the turbidity was done in beer; evaluation of the oxygen ingress had to be done in especially prepared distilled water since beer itself is oxygen-consuming. In case of microbiological growth the colonies were checked with macroscopic and microscopic methods for exclusion of unwanted microorganisms leading to an erroneous positive result.
The results of the study showed the combined influence of oxygen uptake and loss of carbon dioxide on the microbiological stability of beer. With the help of oxygen consuming and passive barrier materials the turbidity in the test beer with and without inoculated microorganisms could be kept at a lower level. Especially the inoculation with Saccharomyces diastaticus showed increasing turbidity and concentrations of colony forming units over time. For contamination with Saccharomyces diastaticus glass bottles and plastic bottles with combined passive gas and oxygen quenching barrier enhancement showed significantly lower turbidity and concentrations of colony forming units than the other tested bottle formulations.
Descriptors: PET, permeation, microbiological stability, oxygen, turbidity
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (May/June 2011), pp. 52-60

H. G. J. Welten and F. R. Sharpe
Report by the EBC Analysis Committee on the Determination of NDMA in Beer by GC-TEA or GC-MS Detection (2009 Collaborative Trial)
Approved by the Analysis Committee for inclusion in the EBC Analytica
The determination of NDMA in beer by the method of GC-TEA or GC-MS was collaboratively tested by the EBC Analysis Committee according to ISO standard 5725-2: 1994. Repeatability (r95) and reproducibility (R95) values are presented. There is statistically significant evidence (Spearman rho = 0.83, p = 0.008) of dependence of repeatability on the mean value (repeatability is worse for bigger mean), there is also statistically significant evidence (Spearman rho = 0.94, p = 0.001) of dependence of reproducibility on the mean value (reproducibility is worse for bigger mean). This relationship between s and m can be represented by a straight line s = a + bm. Final repeatability standard deviation = sr = 0.022 + 0.034 m. Final reproducibility standard deviation = sr = 0.054 + 0.117 m. Note that the precision becomes poor at concentrations below 0.5 µ/l.
Descriptors: NDMA in beer, Analytics, EBC Analytica, GC-TEA-Analysis, GC-MS-Analysis
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (May/June 2011), pp. 46-51

M. Verhülsdonk, K.-L. Rieck and K. Glas
Introduction to the Growth and Modelling of Biofilms in Ultrafiltration and Reverse Osmosis Plants
In the environment, there is actually no surface without the potential for adhesion of biofilms. Especially in membrane processes, biofilms have a negative effect on the performance, resulting in higher energy costs, higher efforts for cleaning and a lower durability of membranes. Within a research project, the possibilities of a process water production from brewery waste water will be explored. A part of this research project is the examination of biofouling for the purpose of process optimization. This essay gives an overview about biofilms and their effects on membrane processes as well as an introduction to biofilm modeling. In the next part of this article series, first results of the research project will be presented.
Descriptors: membranes, biofilm, biofouling, biofilm modelling, wastewater treatment
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (May/June 2011), pp. 41-45

A. Dammann, K. Schwarzer, U. Müller and J. Schneider
Flash Pasteurization of Beer - a Critical Review
The pasteurization of beer and in particular the flash pasteurization is a widely used technique for the biological product stabilization. In spite of the large extend of experience with the pasteurization the way how it is used in practice is a comparably rough method of low precision. In order to precisely adjust the two core process parameters temperature and exposition time detailed knowledge about the individual microbiological inactivation kinetics as well as about specific process and equipment characteristics is required. The article first considers the questions of the biologically demanded thermal load in terms of "required Pasteurization Units (PU)". The assumed underlying thermal death kinetics and the determination of the necessary logarithmic cell count reduction are discussed. Every claim demanding for a particular target PU for specific kinds of beers (or other beverages) base naturally upon simplifications and assumptions concerning the initial and target cell counts and the D-values of present microorganism. The necessity of both species/strain and matrix specific D-values are pointed out. In the second step the recalculation of the actually applied thermal load in terms of "effective PU" is critically reviewed. The origin of the questionable so called beer formula is revealed indicating the evident deviations to realistic calculations. In contrast to the assumption in the beer formula the z-value, describing the heat dependency of the D-value, is constant 7°C, it varies in a wide range with species and matrix. This leads to miscalculation of the "effective PU". Furthermore the both parameters of the pasteurization process time and temperature are commonly simplified to average sizes. Investigations on residence time distributions (RTD) are evaluated and combined with thermal death kinetics of microorganism in order to show the relevance of RTD for the effectively applied thermal load and the "effective PU" respectively. Since the common way to determine the actual thermal effect (effective PU) are microbiological count reduction tests with a comparably low accuracy alternative approaches for an correct determination of the inactivation effect are proposed.
Descriptors: flash pasteurization/HTST, Pasteurization Units (PU), D and z-values, residence time distribution
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (March/April 2011), pp. 32-40

A. Justé, S. Malfliet, M. Lenaerts, L. de Cooman, G. Aerts, K. A. Willems and B. Lievens
Microflora during Malting of Barley: Overview and Impact on Malt Quality
Due to its high oxidative potential, ozone is a highly reactive molecule that is able to oxidize and mineralize inorganic and organic materials. In water, ozone decomposes into oxygen for which reason it seems to be an ideal candidate for removal of persistent substances and microbes during water treatment. Today, ozone is widely applied in water processing of drinking and process water. Other possible applications for treatment and disinfection of surfaces in medical areas and food processing are currently under development and will be further described in the next part of this article series. This review gives an overview over the current state-of-the art in ozone production and possible operational areas.
Descriptors: ozone, ozone generation, oxidation, disinfection
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (March/April 2011), pp. 22-31

J. Tippmann, J. Voigt, K. Sommer
Measuring Particle Size Distribution of Mash with Laser Diffraction to Evaluate the Process Success
The coherence of particle size distribution and reaction behaviour is well-known in process engineering as well as in the brewing industry [15, 17, 21]. Additionally, the particle size distribution can give precious information about the status quo of several processes. Usually, in the brewhouse, only the particle size distribution of the malt grist is measured by sieving [4]. But, the particle size distribution changes during the mashing process. To measure these changes, wet sieving methods are possible but too complex to get fast and authentic results. Thus a fast and reproducible method is missing for mash. Therefore, an analysis method with laser diffraction was developed, which give brewers now the possibility to analyse the status of the mashing process. Against the background, this analysis is not applicable in every brewhouse, a method was investigated to freeze the samples and analyse them in the laboratory. With this new knowledge, now it possible to find out correlations between the particle size distributions, mash conversion, viscosity and filtration performance.
Descriptors: particle measurement, milling, mashing, lautering, brewhouse
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (March/April 2011), pp. 13-21

C. Heim and K. Glas
Ozone I: Characteristics/Generation/Possible Applications
Due to its high oxidative potential, ozone is a highly reactive molecule that is able to oxidize and mineralize inorganic and organic materials. In water, ozone decomposes into oxygen for which reason it seems to be an ideal candidate for removal of persistent substances and microbes during water treatment. Today, ozone is widely applied in water processing of drinking and process water. Other possible applications for treatment and disinfection of surfaces in medical areas and food processing are currently under development and will be further described in the next part of this article series. This review gives an overview over the current state-of-the art in ozone production and possible operational areas.
Descriptors: ozone, ozone generation, oxidation, disinfection
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (January/February 2011), pp. 8-12

V. Psota, L. Sachambula and K. Kosar
Collection of Malting Barley Varieties in the Czech Republic in 2010
The present study reviews changes in the requirements for malting quality and collection of malting barley varieties in the Czech Republic in 2010. It gives micromalting results and results of malt and wort analyses of 22 most widespread and new malting barley varieties registered in the Czech Republic. Varieties causing haze were withdrawn from the collection. The actual collection includes two groups of malting barley varieties. The varieties with high activity of hydrolytic enzymes and high attenuation and the varieties recommended for production of beer with the Protected Geographical Indication Czech Beer, i.e. varieties with lower degree of final attenuation, lower values of Kolbach index, friability, etc.
Descriptors: barley, variety, malting quality
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 64 (January/February 2011), pp. 1-7

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Abstracts BrewingScience articles 2010 S. Malfliet, L. De Cooman and G. Aerts
Application of Thermostable Xylanases at Mashing and During Germination
For the evaluation of the intrinsic lautering performance of malt an in-house test, predictive for both lauter tun and mash filter operations, has been used. Commercial thermostable endoxylanases added during mashing differ in their ability to increase the filtration rate. Especially the addition of a family 10 endoxylanase at mashing-in can be very efficient in view of wort filtration. Family 10 endoxylanases degrade barley arabinoxylans in an effective way and are not inhibited by the Hordeum vulgare L. xylanase inhibitor (HVXI) purified from barley. Moreover, the addition of this family 10 endoxylanase during germination has a positive effect on the filtration capacity of the kilned malt because the added endoxylanase activity is only partly destroyed during kilning. Furthermore, addition of endoxylanases during germination appears to have no effect on standard malt quality characteristics.
Descriptors: endoxylanase activity, exogenous xylanases, filtration performance
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (November/December 2010), pp. 133-141

H. Scheuren, J. Menze and K. Sommer
A New Approach to Sensory Evaluation
Flavour is the significant criterion of evaluation in beer tasting, which depends on many primary and secondary causes. This includes desirable and un-desirable aromatic compounds, but also haptic and physical issues like viscosity, the CO₂-level and colour. A beverage for example with a nontypical colour presented in a wrong drinking vessel is always evaluated differently to the "correct" form without any modifications.
Next to these problems taste in general is a subjective matter and is valued individually quite different. Furthermore the influences of process changes on taste are difficult to evaluate. In order to get representative and fast results in the brewing and beverage technology, a sensory test developed by Sommer was used [1]. The test consists of a dual testing, therefore one sample is the product with the original taste and the second one is the product with a changed aromatic profile. The proband has to detect the changed sample. For the case he is not able to determine it, he has to guess. This test is repeated several times with a changing taste difference of both samples. New about this procedural is the interpretation of the testing results by using a probabilistic evaluation form. Thereby an intensity curve is given which indicates the relation between rising taste difference and consumer taste perception.
The needed requirements are the same as for every taste test. The relative number of test persons, who can detect a difference in change, remains almost constant in a group and more or less independent from external influences. Individual errors follow statistic behaviour and can be assessed if the number of tasters is big enough. The significance of results from a smaller group of experienced tasters in a sensory panel can be improved by increasing the number of test persons even if they are less experienced.
The results of this work are based on differentiation trials with beer of different concentrations of Benzaldehyde as a typical off-flavour compound [2]. The usage of this compound is caused by its concentration depended nontoxity and the well known marzipan taste. In a group of inexperienced tasters, mainly young food technology students, qualified differentiation showed high conformance and significance. This test indicates that the method with the incorporation of statistical methods can be used efficiently for the evaluation of process changes and their effect on beer taste. For the performed Benzaldehyde beer mixing process the developed functional coherence can be applied for economic process optimisation. So for the possibility of creating a new and atypical marzipan beer which can taste 99 % of the consumers the needed dosage of Benzaldehyde could be calculated.
Descriptors: sensory evaluation, taste, flavour, Benzaldehyde
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (November/December 2010), pp. 128-132

L.-A. Garbe, K. Neumann and N. Rettberg
Bisphenol A - A problem for consumers of canned beer?
Potential risks and analysis of debatable plastics used in canned beer coatings
The precise determination of Bisphenol A (BPA) amounts in complex matrix like beer is presented. A practical, rapid and reliable sample preparation procedure for BPA determination is shown. The application of stable isotope dilution assay (SIDA) utilizing labmade deuterated BPA standards made it possible to obtain accurate analytical data. BPA concentrations in seven randomly chosen canned beers ranged from 1 µg BPA/L to 6.5 µg BPA/L. Compared to other canned foodstuff these amounts are low and presumably safe.
Descriptors: Bisphenol A, stable isotope dilution assay, GC-MS, canned beer
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (September/October 2010), pp. 122-127

G. Wenk, I. Weber and R. Pahl
New Methods to determine the come-off time of paper labels
In the beverage industry labels are removed from returnable bottles in bottle cleaning machines. For a successful cleaning process the labels come-off time is crucial. If the labels detach too late in this process, they can block rinsing nozzles and affect the cleaning effectiveness of the machine. The term "come-off time" is defined by DIN 16524-6 as the time a tested label needs, to fully separate from a Petri dish when immersed in a caustic bath. However, the method according to DIN 165246 does not account for any double bonding of neck-ring labels, used on so called long-neck or ale bottles. Furthermore, many procedure steps of DIN 16524-6 are executed manually by the examiner, are not defined precisely or are impractical. Tests performed at the VLB Berlin showed that results between different examiners can differ significantly. In this paper the results of the IGF research project 15343 N are presented. Within this project the come-off behaviour of different paper labels was tested against various influencing factors. It was found that the amount of labelling glue is of particular importance in combination with metallised paper labels. Deriving from that knowledge, an existing model for the come-off behaviour was extended, allowing to develop a Modified Method and an Extended Method to overcome existing limitations and inaccuracies of DIN 16524-6.
Descriptors: paper labels, metallised paper labels, come-off time, bottle cleaning machine
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (September/October 2010), pp. 112-121

S. Kappler, Ch. Schönberger, M. Krottenthaler and T. Becker
Isohumulones - a Review
Isohumulones, an isomerisation product from hop (humulus lupulus sp.) derived humulones are the main bittering substance in beer. They contribute to more than 85 % of the allover bitterness of beer [65]. Hops and its constituents as well as its application in the brewery is subject of investigations for more than a century already. Hops as an ingredient in beer has been used since the early Middle Ages. The objective back than was to save beer from microbiological spoilage and to use the hops as a flavouring ingredient [6]. Today we know that hops and its constituents also improve foam stability and contributes to the flavour stability of beer in various ways [71]. This paper gives a short overview about the most important literature which was published throughout the last decades.
Descriptors: hops, humulones, isohumulones, isomerisation, beer flavor, beer quality, bitterness
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (July/August 2010), pp. 105-111

P. Hughes
Novel Approaches to the Measurement of flavour-related Properties: A Brief Overview and Future Prospects
The challenges of relating analytical data to sensory evaluation are well-known, and may be attributed to recognised sensory biases and interactions (matrix-effects) that influence the sensory activity of flavour attributes. One approach to obviating these difficulties is to attempt to mimic sensory detection mechanisms to determine the activity of flavour attributes. In this short paper, two examples are given. Firstly, the feasibility of determining beer bitterness by exploiting the lipophilicity of hop bitter acids and measuring changes in pH across a model membrane. Secondly, the derivation of a measure of astringency by observing the binding of beer polyphenol complements to an appropriate protein. Whilst such an approach needs much fine-tuning and benchmarking against existing analytical and sensory tests, it nonetheless offers an alternative strategy for enhancing the predictiveness of beer flavour based on analytical measures.
Descriptors: hops, bitterness, astringency, iso-α-acids, polyphenols, lipophilicity
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (July/August 2010), pp. 100-104

S. Hanke, V. Ditz, M. Herrmann, W. Back, T. Becker and M. Krottenthaler
Influence of Ethyl Acetate, Isoamyl Acetate and Linalool on off-flavour Perception in Beer
Beer flavour is a very complex flavour created by interaction off several hundred aroma compounds. Obvious off-flavours which can be detected by the consumer decrease the drinkability and acceptance of a beverage. The image of a brand can be damaged. It is known that undesired flavours, like stale flavour, can be masked by positive ones like certain hop flavours. Therefore it is of interest to find out if other off-flavours can also be masked by positive aroma compounds. Positive flavour impressions are e.g. linalool and some esters among others. Whether these compounds can suppress the perception of dimethyl sulphide (DMS), diacetyl and isovaleric acid in beer is unknown until today. In this study the influence of ethyl acetate, isoamyl acetate and linalool on flavour thresholds of DMS, isovaleric acid and diacetyl was investigated. The obtained results show that linalool decreases the perceived intensity of off-flavours at low concentrations but increases at higher concentrations. Esters also showed suppressing and synergistic effects. The flavour composition is an important factor for flavour perception and must be taken into account when comparing flavour thresholds of flavour compounds determined in different beers types.
Descriptors: off-flavour perception, dimethyl sulfide, diacetyl, esters, flavour threshold, linalool
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (July/August 2010), pp. 94-99

M. Biendl
New International Calibration Standard (ICE-3) for HPLC Analysis of alpha-and ß-acids
Submitted on behalf of the International Hop Standards Committee
The International Hop Standards Committee (IHSC), announces the release of a new calibration standard, ICE-3, for the HPLC analysis of alpha- and ß-acids. This standard replaces ICE-2, which is now withdrawn.
Descriptors: Iso-alpha-acids, Rho-iso-alpha-acids, Tetrahydroiso-alpha-acids, Hexahydroiso-alpha-acids, calibration standard, HPLC analysis, methodology
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (May/June 2010), pp. 92-93

A. Sorgatz, F. Gabler and I. Voigt
A New Stepless Control Concept for Multi-Lane Bottle Conveyors
Multi-lane bottle conveyors are in use at almost all bottling plants. They are not only needed for the transportation of bottles but also for decoupling the failure sensitive machines of the plant by storing and providing bottles. This increases the overall efficiency of a plant by bridging short downtimes. These buffer conveying systems have to be controlled with regard to their filling level. State of the art is the stepwise detection of the filling level by mechanical switches, which are actuated by accumulating bottles. This leads to a stepwise control.
In this paper a new control concept is presented which allows controlling multi-lane conveyors stepless by monitoring the infeed and the output of the conveyor. This enables a more precise control of the conveyor sections velocities and outputs of the up- and downstream machines. No mechanical jam switches are necessary.
The developed control algorithm was successfully implemented and tested at an industrial scale pilot plant. Test runs showed an equal flow of bottles due to the continuous adaption of the machine outputs and conveyor sections velocities and the minimization of the conveyors dead time.
Descriptors: conveyor control, bottling plant, buffer system
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (May/June 2010), pp. 80-91

M. Christian, J. Titze, V. Ilberg and F. Jacob
Combined Particle Analysis as a New Tool to Predict Gushing Shown with Alcohol-Free Beverage Products
Combined particle analysis was applied as a tool to predict gushing in alcohol-free beverage products. Gushing is known as spontaneous overfoaming of carbonated beverages that is an intermittent problem for brewers and the beverage industry. Therefore, preventive tests to examine raw materials for their gushing risk are of interest for the industry. Previously, the focus of gushing tests was on the overfoaming of carbonated samples in specifically shaken bottles, after which the amount of overfoaming was recorded as the measure of gushing. As these tests require a number of days to be performed, it often happens that the raw materials have already been processed before the results are available. Here the combined particle analysis is presented as a "real time" alternative to such tests. This testing methodology was applied in beverage products (for producing spritzers) where it was shown that this analysis was successful in predicting gushing. In the test samples for producing apple spritzers putative gushing causing particles with sizes of only 1-2 nm were identified. Significantly higher stray light intensities for these particles with sizes of 1-2 nm were detected for the gushing-positive compared to gushing-negative samples. The particle charge titration method revealed higher titrated volumes for the gushing-positive samples (to neutralize the entire particle surface charge) than for the gushing-negative ones. Therefore, the higher titrated volumes were associated with significantly higher amounts of 1-2 nm-particles. Accordingly the titrated volume for charge-neutralization was proposed as measurement parameter to "quantify" gushing-relevant 1-2 nm-particles in order to estimate the gushing propensity. In further beverage products (for producing apple-cherry-spritzers) small particles were not detected, which explains why considerably lower titrated volumes were used and no gushing was observed. The results demonstrate that the particle size and the particle surface charge are promising analytical parameters to predict the gushing propensity of beverage products.
Descriptors: beverage, combined particle analysis, fruit spritzer, gushing, particle charge analyzer, particle size measurement
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (May/June 2010), pp. 72-79

J. Titze, M. Christian, V. Ilberg and F. Jacob
Particle Analysis - A Combined Method to Analyze the Colloidal Characteristics of Particles
Particle analysis and its potential in describing the physico-chemical characteristics of particles in beer were investigated. It was the aim to figure out the feasibility for its application in brewing and beverage science. To describe existing problems in the beverage industry caused by insufficient physico-chemical stability of the beverages a rule of great generality according to the particle characteristics was also defined as follows: Beverages are liquids, in which colloids, also called particles, exist in disperged (e.g. beer) or emulsified (e.g. milk) form. One main particle characteristic is the surface. This can be seen in many interfacial phenomena, like the surface potential. Mathematically it was shown, that especially for small particles the ratio between surface and volume increases. Surfaces carry electric charges, which terminate or change the physico-chemical characteristics of the particles. By combining (1) the particle charge detection with polyelectrolyte titration for determining the surface charge, the surface potential and charge density of particles with (2) the particle size analysis by dynamic stray light to analyze the particle size and particle size distribution, the particles could be characterized.
The results, conducted with the help of a Forcier test, revealed that with the increased aging of beer the particle charge, measured by the titrated volume, as well as the surface potential decrease. Both dimensions are in a linear relation with a coefficient of determination of R² = 0.9611. The results could not explain if the decrease has been caused by the reduction of particle surfaces due to agglomeration or by a significant loss of surface charges of the particles. However, using a particle size measurement, it was found out that small particles (sizes < 50 nm) disappeared and larger particles with sizes from 700 nm to 2000 nm occurred. So it could be demonstrated that the coarsening of particles was caused by agglomeration.
In addition to that, the mechanism of forming a 1:1 stoichiometrical charge complex was graphically displayed by the particle size measurement. The highest coefficients of determination (R² = 0.9997) were found for the titrated volume and the concentration of beer in a dilution series by mixing beer and water, which shows the use of particle charge titration for quantitative determination. In contrast to that, it could be illustrated by nearly identical particle size distribution curves at different concentration levels that it is not possible to "quantify" the detected particles by using only particle size measurement. Therefore, the particle analysis was introduced as a combined method. Due to the statistically good results of this particle analysis, future experiments should involve impacts on the colloidal stability of filtration or flash pasteurization in the beverage industry to get more information in the area of physico-chemical stability of beverages. Besides further experiments, interlaboratory tests should be conducted additionally to utilize the presented particle analysis for the brewing and beverage industry.
Descriptors: beverage, charge titration method, combined particle analysis, particle charge analyzer, particle size measurement
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (May/June 2010), pp. 62-71

S. M. Deckers, K. Gebruers, G. Baggerman, Y. Lorgouilloux, J. A. Delcour, C. Michiels, G. Derdelinckx, J. Martens and H. Neven
CO₂-Hydrophobin Structures Acting as Nanobombs in Beer
Part 1: A critical review of hypotheses and mechanisms
Primary beer gushing is defined as the wild and uncontrolled overfoaming of packaged beer induced by contaminated raw materials as barley and malt. It is generally admitted that most probably amphipathic molecules such as hydrophobins and non-specific lipid transfer proteins (ns-LTPs) are responsible for this phenomenon. These molecules are synthesized by moulds and by vegetal tissues respectively in order to modify the polarity of surfaces and the solubility of molecules. At present, hydrophobins are extensively studied as they are considered as the major responsible molecules involved in primary gushing. Although a strong reduction (more than 85 %) of the initial concentration of hydrophobins present in malt occurs during the brewing process, the residualquantity remaining in finished beer is sufficient to provoke the gushing of packaged beer and the subsequent dramatic commercial damages to a particular beer brand. This review compiles the relevant fundamental physical and chemical properties of CO₂ and experimental observations at laboratory and pilot scale. A plausible mechanism of primary gushing is presented. It is based on the effective role of hydrophobins association to CO₂ nanobubbles, acting as "nanobombs" and perhaps as "nucleation sites" causing effects from overfoaming to strong gushing depending on the concentration and the carbonation rate. In beer formation of CO₂ bubbles proceeds through heterogeneous nucleation. The rapid heterogeneous nucleation initiated at the opening of the container in excessively gushing beer suggests the the presence of catalysts to overcome the energy barriers. Since hydrophobin molecules are able to bind to carbonic acid, they prevent part of the CO₂ from dissolution. These structures will aggregate in timeframes of days or even weeks depending on the beer by forming nanobubbles of a typical critical radius. The internal pressure of these nanobubbles is proportional to the carbonation pressure of gaseous CO₂ in the container at filling (about 3.0 till 4.0 ATU of CO₂ ). At the opening of the container, the difference of partial pressure of carbonic acid in the bottle and in the atmosphere provokes the explosion of these nanobubbles and results in a strong gushing effect.
Descriptors: Hydrophobin, carbonic acid, primary gushing, mechanism, beer, barley
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (March/April 2010), pp. 54-61

Saison, D., Vanbeneden, N., De Schutter, D. P., Daenen, L., Mertens, T., Delvaux, F. and Delvaux, F. R.
Characterisation of the Flavour and the Chemical Composition of Lager Beer after Ageing in Varying Conditions
Aged beer flavour was studied by ageing a lager beer in different conditions (varying temperature-time profiles, different oxidative conditions and varying pH and ethanol concentrations). This led to beers with a varying aged flavour, which could be explained by differences in the reaction rate of ageing reactions. High temperatures, oxidative conditions and to a lesser extent, a lower pH, accelerated beer ageing. Enhanced (E)-2-nonenal formation probably led to the greater perception of cardboard flavour after ageing at high temperatures. Madeira flavour was only perceived after ageing at 20 °C and ribes flavour was mainly perceived in oxidatively aged beer. In beers with these flavour notes, high concentrations of acetal-dehyde, Strecker aldehydes and diacetyl were found and in the Madeira flavoured beer, also of 2-furfuryl ethyl ether and 5-hydroxymethylfurfural. In the end, this study provides an overview of the different aged flavours that can develop in different ageing conditions and the corresponding flavour compounds that make up the chemical composition of these flavours.
Descriptors: beer, flavour, ageing, carbonyl compounds, flavour stability
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (March/April 2010), pp. 41-53

G. De Rouck, A. G. Flores-Gonzáles, J. De Clippeleer, J. De Cock, L. De Cooman and G. Aerts
Sufficient Formation and Removal of Dimethyl Sulfide (DMS) without Classic Wort Boiling
The formation and removal of dimethyl sulfide (DMS) was studied during a new method for wort production, without classic wort boiling. This was compared with classic brewing trials comprising one hour of wort boiling. The new wort production method consists of fine milling of malt under water to minimize LOX reactions, mashing-off at 95 °C, membrane assisted thin bed filtration, in-line injection of clean steam in the filtered wort and stripping of the wort while entering the combination vessel ('boiling' kettle/decantor), optional clean steam injection during filling of the combination vessel, and finally decantation of the hot trub in the same combination vessel. Oversized chimneys with condensate traps are installed on both the mash vessel and the combination vessel to promote removal and prevent re-entrance of unwanted volatiles, including DMS. Like in classic wort production, the contents of DMS precursor and DMS were sufficiently reduced when applying the new brewing method and DMS presented no flavour problem in the finished beer. The processing time of the innovative wort production method until the end of filling of the combination vessel and optional stripping of the wort was only 2.5 hours as compared to at least 3.5 hours for classic brewing using the same brewing line. Therefore, application of the proposed innovative wort production method allows for preparation of significantly more brews per day with sufficient removal of unwanted volatiles.
Descriptors: wort production, DMS, wort boiling
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (January/February 2010), pp. 31-40

R. F. Vogel, P. Preissler and J. Behr
Towards an Understanding of Hop Tolerance in Beer Spoiling Lactobacillus brevis
Lactobacillus brevis comprises strains with diverse metabolic capabilities. Some specialized strains can grow even in highly hopped pilsner beers without the need of long term adaptation. Other strains develop tolerance upon prolonged hop exposition or remain sensitive. In this communication genetic analyses, proteomics and physiological tests in beer as well as studies in membrane physiology and cell wall composition are reviewed, which are useful to differentiate L. brevis strains along their beer spoiling potential and to elucidate decisive marker traits for categorizing beer spoiling L. brevis along their relevance for the brewer. Hop adaptation in L. brevis TMW 1.465 is a multifactorial process, which results in changes in metabolism, protein profile, membrane and cell wall composition and intracellular manganese levels. It involves mechanisms to cope with intracellular acidification and divalent cation limitation, redox imbalance and oxidative damage and mechanisms for energy generation and economy, genetic information fidelity and enzyme functionality, and as a result enables beer spoilage. Differentiation along the beer spoiling capacity is possible by comparative proteomics, or by physiological tests employing manganese efflux or reduction of tetrazolium to formazan upon growth in lager beer. A simple test for mangenese efflux provides a useful tool for categorization of beer spoiling L. brevis. On the other hand, genetic determinants potentially useful for PCR detection systems were widely spread in all strains with no reference to high hop tolerance. The further understanding of hop tolerance requires comparative genomic studies revealing critical strain differences and thus multiple (PCR) markers.
Desriptors: Lactobacillus brevis, beer spoilage, hop tolerance, redox potential
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (January/February 2010), pp. 23-30

H. Withouck, A. Boeykens, B. Jaskula, K. Goiris, G. De Rouck, C. Hugelier and G. Aerts
Upstream Beer Stabilisation during Wort Boiling by Addition of Gallotannins and/or PVPP
Addition of stabilisation products in the upstream brewing process is a very convenient way of physico-chemical stabilisation without the need for extra filtration or the risk of beer losses. Therefore, in this study the use of appropriate stabilisation products upstream the brewing process, more specifically at the end of wort boiling, have been evaluated in relation to improved colloidal stability. Applications of PVPP (Polyclar 10, ISP) and gallotannins (Beerotan Q, BFTI) have been investigated. The lowest gallotannin levels (wort boiling: 5 g/hL; contact time in boiling kettle: 3 minutes) are already sufficient to obtain enhanced stability due to adequate removal of haze- sensitive proteins. Furthermore, the addition of 10 g/hL PVPP has an explicit effect on the amounts of polyphenols, which results in an improved colloidal stability. Lowering pH at mashing-in also results in improved physico-chemical properties and flavour stability.
Descriptors: colloidal stability, haze, wort boiling, gallotannins, PVPP
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (January/February 2010), pp. 14-22

L. Strack and U. Stahl
Brewer's Yeast Modification: Effects Both on Diacetyl Production and Alcohol Formation^*
New industrial brewing yeasts^*1 have been generated by introduction of two genes involved in valine biosynthetic pathway in order to clarify their roles for the reduction of diacetyl content in beer. The Saccharomyces cerevisiae genes as well as lager^*2 genes both BAT1 (encoding branched-chain amino acid aminotransferase) and BAT2 (encoding branched-chain amino acid aminotransaminase) have been transferred into brewer's yeast. Within this approach it was possible to decrease diacetyl levels at the end of main fermentation without affecting the by-product profile of the beer negatively. Furthermore, our results pointed to the regulation of these genes concerning diacetyl formation.
Descriptors: brewer's yeast, metabolic engineering, diacetyl, maturation
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (January/February 2010), pp. 6-13

L. van Hoyweghen, M. Biendl and A. Heyerick
Radical Scavenging Capacity of Hop-derived Products
Dietary antioxidants are believed to be effective in the prevention of oxidative stress related diseases (eg. cancer and cardiovascular diseases). Polyphenols are widely recognized as potent antioxidants as they can scavenge reactive oxygen species (ROS). The hop plant (Humulus lupulus L.), used in a variety of health applications and indispensible as a beer ingredient, is an interesting source of polyphenolic antioxidants including tannins, flavonol glycosides and prenylated flavonoids. In addition, also hop oil and hop acids (including downstream products) have been reported as potent antioxidants. In this investigation, the radical scavenging activity of hop products (including different extracts and downstream products) was investigated using two different antioxidant assays: the ORAC to study the peroxyl radical scavenging capacity and HORAC to investigate the hydroxyl radical scavenging capacity. Quercetin and a grape extract containing oligomeric proanthocyanidins (OPC) were used for comparison. The peroxyl radical scavenging capacities of prenylated flavonoids were highly analogous to quercetin and OPC equaling 5-10 Trolox equivalents. The hydroxyl radical scavenging capacities of Xantho-FlavTM products correlated with the concentration of xanthohumol and pure xanthohumol (> 95 %) corresponded to about 60 Trolox equivalents, which is 10-20 times higher than that of quercetin and OPC. Consistently, ethanol extracts showed a higher radical scavenging activity than CO₂-extracts. Furthermore, tannin extract proved an efficient peroxyl radical scavenger. Thus it can be concluded that xanthohumol-containing products show high radical scavenging capacities, which partly may be mediated by its metal ion chelating properties. Apart from their possible health benefits, these products might also contribute antioxidant power during the brewing process and during storage.
Descriptors: antioxidant, xanthohumol, health, hops
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 63 (January/February 2010), pp. 1-5

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Abstracts BrewingScience articles 2009

L. Strack and U. Stahl
Brewer's Yeast and "Omics" Technologies
"Omics" technologies comprise genomics, transcriptomics, proteomics and metabolomics; the last three fields are pooled within the notion "functional genomics". In this review, these techniques which concentrate on aspects of the "course from gene to metabolites" are surveyed especially with regard to bottom-fermenting brewer's yeasts. With the aid of these global methods it is possible to combine a collective knowledge of an investigated organism which is necessary to understand the details of its metabolic system. Hence, the challenge is to introduce the above mentioned studies for the determination of targets and approaches for the improvement of yeast organisms. Herein, brewing yeasts are reviewed with concern to the determination of their "ome" levels. But because of the hybrid nature of the brewer's yeast's genome problems emerged regarding the "omics"-applicability which are depicted in this paper furthermore. This Minireview is the first section of a two-part publication. The second part with the title "Reduction of diacetyl production by brewer's yeast" will be published in the next issue of Brewing Science in February 2010.
Descriptors: brewer's yeast, hybrid genome, omics technologies, genetics
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (November/December 2009), pp. 187-190

S. Hanke, M. Kern, M. Herrmann, W. Back, Th. Becker and M. Krottenthaler
Suppression of Gushing by Hop Constituents
Gushing is one of the most unsolved problems in brewing. This is a very severe quality defect. Efforts are being made to reveal the identity of gushing components. The beer defect of gushing is a temporary brewery problem that is primarily caused by fungi derived factors. In this work the influence of humulones, pure linalool and hop oils on natural occurring gushing and an activated carbon (AC) induced gushing of commercial brews was tested. The experiments proved that linalool significantly reduces the gushing volume. Hop oils (linalool) decreased the gushing tendency of beer. Gushing, induced by activated carbon, is suppressed by the addition of linalool and humulones. These results suggest that some of the properties of the hop constituents, humulones and linalool, prevent beer from gushing especially when hops are added at late stages of wort boiling.
Descriptors: Gushing, beer, hops, linalool, humulones, hop oils, Humulus lupulus L.
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (November/December 2009), pp. 181-186

H. Murakami, T. Fujii, and N. Hayashi
Loop-mediated Isothermal Amplification to Detect and Identify Beer Spoilage Lactobacillus spp. Bacteria
Primers for a loop-mediated isothermal amplification (LAMP) method to specifically identify beer spoilage caused by Lactobacillus spp. including Lactobacillus brevis, Lactobacillus lindneri, Lactobacillus backi and Lactobacillus paracollinoides were developed. These LAMP primer sets were designed from target sequences in the 16S rRNA gene or the spacer region. To identify beer spoilage strains in the species, we also developed a LAMP primer set to detect highly specific genetic markers. The LAMP primer sets in this study distinguished the target species or beer spoilage strains from other lactic acid bacteria in 40-60 min. Moreover, using these primer sets in conjunction with the LAMP method enabled detection of approximately 1 × 102 cfu/ml lactic acid bacteria from suspensions in distilled water, beer and beer that contained large amounts of bottom-fermenting yeast cells. Thus, the LAMP method may be useful for direct detection and identification of Lactobacillus spp. in samples taken during the fermentation process and from final products.
Descriptors: Lactic acid bacteria, beer-spoilage bacteria, rapid detection, loop-mediated isothermal amplification, LAMP, DNA amplification
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (November/December 2009), pp. 172-180

M. Christian, V. Ilberg, J. Titze, H. Parlar and F. Jacob
New Ideas for Quantifying the Gushing Potential of Malt
In this work it was first shown how to quantify the gushing potential of malt with a modification of a common gushing test. Today there exist two acknowledged gushing tests for the brewing industry (Modified Carlsberg Test and Weihenstephaner Test). Both analytical methods use the overfoaming amount of a test-specific produced carbonated wort to determine the gushing potential of malt. Unfortunately the overfoaming amount can vary statistically in a way that this parameter can "only" be used for qualitative information if the malt has a potential for gushing or not and if one malt has a higher or lower gushing potential than another one; but a precise quantitative comparison for example between two malts which both have a gushing potential is difficult. This was the focus of this investigation. With two gushing-positive samples (malt A and B) it could be shown that with an increase of the concentration of malt solutes a certain point is reached where gushing appears the first time determined by the overfoaming amount applied the Modified Carlsberg Test. For malt A a frequently higher gushing potential (f ≥ 5) than for malt B was identified. These results were verified by determining the amount of a gushing suppressing hop product that led gushing to zero by having a constant concentration of malt solutes. The results demonstrated enhanced gushing analyses to quantify the gushing potential reproducibly, not by the overfoaming amount but by the "zero point" where gushing begins (concentration of malt solutes) or is neutralized (amount of hop product). The introduced methods enable the chance for the first time to quantify the gushing potential of malt more precisely.
Descriptors: gushing analysis, Modified Carlsberg Test, Weihenstephaner Test, quantification, gushing potential
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (November/December 2009), pp. 164-171

J. Savel, P. Kosin and A. Broz
New oxidation destructive analysis (NODA)
Beer pigments compose of caramels, melanoidins and polyphenols pigments, which can be prepared by heating or boiling of mild colored or colorless precursors, such as sugar or (-)-epicatechin. The natural pigments behave as natural pH and redox indicators. During preparation of caramels by sugar heating at 175 °C in oven, various sugars came into slight yellow (maltose), brown (glucose, mannose, ribose, xylose), or dark brown (arabinose, fructose) products. At heating, reductones were formed prior to caramel pigments. Redox indicators were added to beer and the absorbances (at 666 nm for methylene blue, 520 nm for methyl red and 610 nm for indigocarmine) were recorded before and after illumination with visible light (5 min) under aerobic and anaerobic condition. Natural or synthetic indicators can change their color reversibly or irreversibly. Reducing compounds can initialize oxygen free radical formation as well as their scavenging. 1,2-diaminobenzene addition supported the oxygen consumption in beer.
Descriptors: reductone, caramel, antioxidant, prooxidant, 1,2-diaminobenzene, indigocarmine
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (September/October 2009), pp. 155-163

L. A. Hazelwood, J.-M. Daran, A. J. A.van Maris, J. T. Pronk and J. R. Dickinson
A Review on Fusel Alcohol Formation by Yeast
Based on a lecture given at the 32nd European Brewery Convention Congress in Hamburg, 10-14 May 2009
Fusel alcohols and the esters derived therefrom are important flavour and aroma constituents in beers. Consistent batch-to-batch maintenance of the desired concentrations of these compounds is essential. The formation of fusel alcohols is one of the longest-studied biochemical processes: investigations having been begun by Ehrlich in 1907. The aims have been (i) to define the steps of the biochemical pathway (the 'Ehrlich pathway'), (ii) to identify the enzymes involved and the genes which encode them, and (iii) to understand the biochemical and genetic regulation associated with changes in yeast's growth and environmental conditions. The methods included the use of amino acids specifically labelled with ¹³C followed by ¹³C NMR spectroscopy to identify the metabolic sequences, specific mutants suspected or known to encode particular enzymes/isoenzymes, overexpression of structural genes and transcriptome profiling.
Leucine, isoleucine, valine, phenylalanine, tyrosine, tryptophan and methionine that are present in wort serve as the starting materials for the formation of isoamyl alcohol, 'active' amyl alcohol, isobutanol, 2-phenylethanol, tyrosol, tryptophol and methionol (respectively). The steps of the Ehrlich pathway are transamination in which the amino acid is converted into an α-keto acid, then decarboxylation in which the α-keto acid is converted to an aldehyde. The aldehyde is then reduced resulting in formation of the appropriate fusel alcohol. In aerobic conditions (not found in beer production), the aldehyde could be oxidized to the corresponding fusel acid. Four transaminases, 5 TPP-dependent decarboxylases, 16 alcohol dehydrogenases, 6 aldehyde dehydrogenases and 2 broad-spectrum reductases have roles in the pathway depending mainly upon the amino acid, growth phase of the yeast and other cultivation conditions. Transcriptional regulation of the structural genes explains most, but not all of the regulation observed. Posttranslational modification(s) of enzymes remain to be discovered. Timely use of the Ehrlich Pathway likely offers both metabolic and developmental advantages to a yeast.
Recent work has led to a far more complete understanding of fusel alcohol formation and its regulation. Consequently, the development of elite strains dedicated to specific processes and with greatly-improved consistency of performance is now a realistic possibility.
Descriptors: Amino acid, fusel alcohol, genetics, physiology
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (September/October 2009), pp. 147-154

S. Wunderlich, M. Biendl, A. Zürcher and W. Back
Reduced Xanthohumol Recovery after Solid Phase Extraction of Dark Beers
In wort and beer the hop polyphenol xanthohumol (XN) is often determined after solid phase extraction (SPE). Recently researchers described substances in roasted malts that help to enrich XN in dark beers. The carrier effect that reduces losses during beer production may influence the SPE as well. We investigated the XN recovery in dark beer samples with and without SPE sample preparation. In SPE eluates the XN recovery significantly decreased with increasing XN content compared to directly injected samples. Experiments on XN recovery in SPE passes repeatedly treated by SPE showed that this is not due to an overload of the sorbent. The use of SPE prior to XN determination in samples containing roasted substances proved to be inefficient compared to direct injection.
Descriptors: hops, polyphenol, roasted malt, SPE, HPLC-DAD
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (July/August 2009), pp. 95-99

M. Christian, V. Ilberg, A. A. Aydin, J. Titze, A. Friess, F. Jacob and H. Parlar
New Gushing Mechanism Proposed by Applying Particle Size Analysis and Several Surfactants
The complex phenomenon of gushing occurring in carbonized beverages has been investigated in order to better understand the mechanism and to give input for further research to introduce preventive measures for the industry. The knowledge that microbubbles are stabilized through surface active substances, and in this form can induce gushing, was used to examine a selection of representative surfactants. For the analysis, a particle size distribution method was used which enabled to detect particles at nanometer level, starting from 0.8 nm onwards. The experiments using pure aliphatic surfactants (DTAC, TTAC, CTAC, ODTABr, CPC, SDS, and Tween 20) revealed that only CTAC, solved in CO₂ containing table water at 2 g/l (above the critical micellar concentration), induced gushing. CTAC therefore was characterized as gushing typical by its structure (length of hydrophobic part and kind of head group). Gushing caused by CTAC was not only observed through shaking of the bottles, but also without any shaking at all. The latter observed fact was not explainable by the mechanical incorporation of CO₂ bubbles stabilized by CTAC monomers, but generally through stabilized microbubbles formed by a mechanism that is yet unknown. The particle size analysis revealed that particles grow, starting from ca. 10 nm to reach several 100 nm, if sufficient amounts of CO₂ molecules are present. The growth was accelerated by a mild shaking of the bottles. The results pointed out that CTAC micelles grow by diffusion of CO₂ molecules into the hydrophobic core. Thereby, microbubbles are formed and stabilized through CTAC monomers at the interface gas/liquid, and can grow to gushing-relevant sizes of several 100 nm.
Descriptors: gushing, particle size distribution, surfactant, hexadecyltrimethylammonium chloride (CTAC), micelle growth, carbon dioxide diffusion, stabilized microbubbles
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (July/August 2009), pp. 100-107

Takoi, K., Degueil, M., Shinkaruk, S., Thibon, C., Kurihara, T., Toyoshima, K., Ito, K., Bennetau, B., Dubourdieu, D. and Tominaga, T.
Specific Flavor Compounds Derived from Nelson Sauvin Hop and Synergy of these Compounds
Based on a poster presented at the 32nd Congress of the European Brewery Convention, Hamburg, Germany, May 2009
Nelson Sauvin (NS) is a unique hop cultivar that gives a specific flavor (exotic fruit-like, Sauvignon Blanc wine-like) to finished beers. We have attempted to identify the specific flavor compounds derived from NS. First, isobutyric esters, including 2-methylbutyl isobutyrate (2MIB), have been found in the beers used with NS (NS product). These compounds had a green apple-like and/or apricot-like flavor. We next focused on certain volatile thiols that are well known to contribute to wine flavors, especially Sauvignon Blanc, and identified two new volatile thiols, 3-sulfanyl-4-methylpentan-1-ol (3S4MP) and 3-sulfanyl-4-methylpentyl acetate (3S4MPA), having a grapefruit-like and/or rhubarb odor, similar to that of Sauvignon Blanc. Among these compounds, 3S4MP was contained twice of its thresholds and 3S4MPA and 2MIB were contained below their threshold, in the NS product. However, it was confirmed that 3S4MP enhanced the flavors of 3S4MPA and 2MIB by synergy. In addition, we also confirmed that 3S4MP enhanced the flavors of terpene alcohols (linalool and geraniol). Therefore, we concluded that 3S4MP might contribute to the specific flavor of the NS product as a key compound having two roles, its own characteristic flavor and its function as a flavor enhancer.
Descriptors: beer aroma, hop, Nelson Sauvin, flavor, isobutyric esters, thiols, synergy
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (July/August 2009), pp. 108-118

Zarnkow, M., Mauch, A., Burberg, F., Back, W., Arendt, E. A., Kreisz, S. and Gastl, M.
Proso Millet (Panicum miliaceum L.) a Sustainable Raw Material for the Malting and Brewing Process: A Review
On going research further substantiate that consumption of whole grains and grain-based products is associated with health benefits and risk reduction of chronic diseases. Epidemiological studies on these cereals continue to generate an increasing interest on cereal products. This attention also concerns the beverage industry and in the present study, more specifically, malt and beer production, connected with an expansion of the market for gluten free beers. A declaration as an ecological and natural produced good is willingly carried out by the producers. Malted cereals will be appropriate for that kind of declaration because, for brewing purposes, suited malt will offer a good fermented product derived from a simple and well-known technology. More importantly, easy availability is an essential advantage.
Proso millet (Panicum miliaceum L.) has a high potential as an alternative food ingredient especially in regions, where the appropriate growing conditions for cereals like wheat, barley, among others, are not met. This paper reviews publications and technical literature on P. miliaceum. By doing so, it provides an overview of the cereal composition and, if found, of its structures' behaviour when used for malt, wort and beer production. Many of the verified publications deal with the study of the use of proso millet for foodstuffs. Nevertheless, the compiled data show a good correlation to those cereals that are well known to be good raw brewing material and are therefore used for malting and brewing purposes.
Descriptors: proso millet, alternative cereal, gluten-free, malting, brewing
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (July/August 2009), pp. 119-140

Jerkovic, V. and Collin, S.
The cis-resveratrol Concentration is Proposed as a New Indicator of the Hop Freshness
trans-Piceid, cis-piceid and trans-resveratrol contents of hop cones and hop pellets from six American varieties (harvest 2004) were monitored by RP-HPLC-APCI(+)-MS/MS over 12 months of storage. trans-Resveratrol, cis-piceid and trans-piceid were found in all samples. After 8 months of storage, the overall stilbene content was decreased in the same range whatever the conditioning. Absent in fresh hop cones or pellets, cis-resveratrol was released from cis-piceid in all stored samples. cis-Resveratrol concentration revealed very interesting for assessing hop freshness.
Descriptors: resveratrol, stilbene, polyphenols, hop conditioning, hop storage, resveratrol stability
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (July/August 2009), pp. 140-146

H. Evers, A. Schmitt and J. Bechtluft
Tests on Rinsing Methods for Non-refillable PET Bottles
Preliminary tests were conducted in order to develop a standard contamination, which can be used to analyse the mechanical effects of rinsing. These showed that a 70 % mustard ethanol suspension, dried slightly, is suitable to fulfil this task. In a systematic decision-making process, the conductivity measurement was selected as the method to determine the residual contamination. The performed measurement systems analysis confirmed the suitability of the used Conductometer for this measuring task. The design of the experimental plan as well as the evaluation and graphical display of the results was realized with the software Visual X-Sel^® 10.0 in order to attain a large amount of information with a minor effort.
The process of rinsing is used to remove dust particles. Due to the nature and quantity of the dirt, the mustard suspension does not represent a realistic contamination. That is why the rinsing procedure rather resembles a cleaning process than a pure rinsing out process. Therefore an additional test series with the powdered dye Allurared AC as standard contamination was conducted. The percentage of rinsed-out material is calculated based on the original and residual contamination in order to obtain a meaningful value for the effectiveness of rinsing. The target size for mustard as standard contamination is the cleaning rate and for Allurared AC it is the rinsing rate.
The previously reported worse performance of the germ reduction tests of ribbed bottles was confirmed. The maximum cleaning and rinsing rate is reached by the lower setting of the number of ribs (0 ribs) and the lowest tenside concentration as well as the upper setting of air and water pressure. During the experiment with Allurared AC a direct relation between the remaining quantity of water and the rinsing rate was assumed. This could not be confirmed since no correlation between these two parameters was observed.
In conclusion mustard as standard contamination is suitable for the investigation of the mechanical effects of rinsing and for spray shadow tests. Allurared AC can be used in case fast results are demanded or to estimate real rinse programmes or bottle shapes.
Descriptors: rinsing, PET bottles, conductivity measurement, contamination
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (May/June 2009), pp. 44-53

M. Zarnkow, B. Schultze, F. Burberg, W. Back, E. K. Arendt, S. Kreisz, M. Krahl and M. Gastl
Triticale Malt (xTriticosecale Wittmack) a Raw Material for Brewing - Using Response Surface Methodology to Optimise Malting Conditions
Response surface methodology was used to investigate the influence of three malting parameters, degree of steeping, germination time and temperature, on the quality of triticale malt. Each predictor variable was tested at three levels. Germination times were set to 5, 6, and 7 d, degrees of steeping to 42, 45, and 48 %, and germination temperatures were 15, 18 and 21 °C. The initial kilning temperature for all malts was set to 50 °C and gradually increased to 80 °C. A series of malt quality attributes were investigated including extract, viscosity, arabinoxylan, apparent attenuation limit, α- and β-amylase activity, limit dextrinase activity, α-amino nitrogen (FAN), Kolbach index, soluble N and dimethyl sulfide precursor (DMS-P). The optimum malting programme was determined with 5 d germination time, 45 % degree of steeping, 15 °C steeping and germination temperature. The amylolytic and proteolytic activity obtained, were 84.8 % extract, 78.3 % AAL, 264 U/kg limit dextrinase activity, 1055 U/g β-amylase activity, 254 U/g α-amylase activity, 155 mg/L FAN, 1.7 mg/kg dimethyl sulfide precursor (DMS-P) and 2.305 mPa × s viscosity.
Descriptors: triticale, malt, response surface methodology, alternative cereal
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (May/June 2009), pp. 54-66

T. Schleicher, Q. Smejkal, A. Martin, W. Russ and M. Faulstich
Influences of the Type of Fluxing Agent during Fluxcalcination of Kieselguhr on Formation of Crystalline Phases, Permeability and Colour
Commercial fluxcalcined kieselguhr or coarse kieselguhr is produced using sodium carbonate as fluxing agent. This coarse kieselguhr contains crystalline structures of silicon dioxide, mainly cristobalite and opal-CT. These crystalline structures are, in respirable form, classified as carcinogenic material and thereby cause concern in occupational health and disposal of spent material. In this paper the influence of the formation of crystalline material during fluxcalcination of kieselguhr using various fluxing agents is described. Additionally characteristics of the kieselguhr samples, concerning the suitability as filter aid have been investigated. Samples were heat treated from 900 °C to 1050 °C for 1h to 4h in a muffle kiln. These samples were analysed via X-ray diffractometry, in order to determine type and content of crystalline material. Based upon these experiments, it was proven that the fluxcalcination of kieselguhr can be accomplished using fluxing agents containing potassium ions. These fluxing agents lead to a coarse kieselguhr which is significantly lowered in crystalline matter, has suitable permeability and wet density and equal colour values compared to commercial fluxcalcined kieselguhr.
Descriptors: kieselguhr, fluxing agent, fluxcalcination, filtration, X-ray diffractometry, cristobalite
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (May/June 2009), pp. 67-82

M. Christian, V. Ilberg, J. Titze, A. Friess, F. Jacob and H. Parlar
Gushing Laboratory Tests as Successful Methods for Obtaining New Cognitions on Gushing
This work investigated the gushing phenomenon in wort samples by applying commonly used gushing tests (Weihenstephaner and modified Carlsberg test) in order to identify conditions for the development of gushing. The mashing and boiling procedures were modified (Weihenstephaner test), and the amount of wort and time of shaking of the bottle were increased (modified Carlsberg test). For the experiments one malt sample was applied that was identified as gushing-positive (Weihenstephaner test). A changing pattern of the mashing process revealed that gushing was induced after heating up to 97 °C while no gushing was observed until 80 °C. Heating up the mash from 80 °C to 100 °C and boiling it for 5 min afterwards sufficed for gushing to be induced in the wort sample. From the applied malt sample it was possible to produce not only a gushing-positive wort but also a gushing-negative one. By mixing these wort samples, gushing could be reduced, or even entirely suppressed, applying a volume of only 10 % v/v of the gushing-negative sample. The gushing-positive wort could only induce gushing in amounts of above a critical level. Gushing started to develop after a mild shaking for 10 h (modified Carlsberg test) and increased significantly after 20 h of shaking. The results demonstrated that the temperature of the mash is a decisive parameter for the development of gushing.
Descriptors: gushing, beer, Weihenstephaner test, modified Carlsberg test, mashing and boiling procedure, wort concentration, shaking duration
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (May/June 2009), pp. 83-89

E. Steiner and W. Back
A Critical Review of Protein Assays and Further Aspects of New Methods in BrewingScience
Total nitrogen content of barley, malt and beer was usually measured by Kjeldahl method. In brewing science this method has been used for many years to measure total protein (N x 6.25 = protein concentration) in beer, but it measures nitrogen rather than proteins. Kjeldahl method determines total nitrogen but is prone to interference from non-protein and nitrogen-containing compounds, and fails to detect subtle changes in the protein content of wort and beer.
Many quality attributes (e.g. turbidity, mouthfeel, foam stability) and processability (parameters such as filterability, are affected by the protein composition and content in beer. For example protein Z (MR 40 kDa) [12] is claimed to be responsible for haze formation and LTP1 [25] (MR 10 kDa) for foam stability. Siebert [23] suggests that a higher amount of proline results in a higher turbidity.
Therefore, for brewers its is important to quantitatively measure the protein content and also to qualitative evaluate the protein composition in beer.
The aim of this review is to describe and compare different methods of protein quantification and qualification. For that reason six different methods have been evaluated.
Descriptors: protein assays, Kjeldahl method, Bradford method, lab-on-a-chip analysis, 2D-PAGE, mass spectrometry
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (May/June 2009), pp. 90-94

F. Braun, W. Back and M. Krottenthaler
Beer Filtration using Cellulose Fibres - a Review
Presently, kieselguhr filtration of beer is the most commonly used technology worldwide. Due to the growing problems with this filter aid, mainly concerning worker health and kieselguhr disposal, many alternatives have been investigated. Especially small and medium-sized breweries need solutions that allow existing equipment to be retrofitted. In the last decades, occasional articles treating the filtration of beer using cellulose fibres have been published. The properties of filter aids consisting exclusively of cellulose have been investigated as well as the properties of mixtures of cellulose and other filter aids. A lot of knowledge has thus been acquired. As a result of a systematic analysis of the existing literature on the topic, the important properties of cellulose-based filter aids are presented. Pre-coat filtration of beer by cellulose is possible. The beer has to be well pre-clarified. An economic technology, which would have to include a multiple regeneration of the filter aid, could not yet be found. Possible starting points for future investigations are named.
Descriptors: cake filtration, cellulose, regeneration, beer
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 62 (March/April 2009), pp. 33-43

M. Munzert, M. Baumer, U. Blum, A. Wurzinger, G. Henkelmann, M. Herz and H. Holland-Moritz
Mineral Nutrients and Malt Quality of Spring Barley (Hordeum vulgare L.)
Samples of barley grains from 10 varieties and 8 locations were analysed on 48 mineral nutrients and 13 malt quality parameters. The article presents means, ranges of variation and (expanded) measurement uncertainties. For many elements a significant influence of varieties could be found. The statistical analysis includes the calculation of coefficients of correlation between the element content and the quality parameters using a covariance analysis in order to eliminate the variety effects (partial coefficent rp). The closest positve rp (adjusted by varieties) to malt quality have been found for K, Pb, Mo and Na. Most of minerals correlate negatively to the malt quality index, especially Zn (rp = -0,67), Mg (rp = -0,47) and Fe (rp = -0,43). The opposite behaviour of zinc in malt and yeast is discussed, as well as the physiological background of the minerals with relation to the malt quality and the practical relevance of the results for farming and breeding.
Descriptors: mineral elements, malt quality, mineral content, correlation, spring barley
Source: BrewingScience – Monatsschrift für Brauwissenschaft 62 (January/February 2009), pp. 1-13

M. Biendl
New International Calibration Standard (ICS-I3) for HPLC Analysis of Iso-α-acids
Submitted on behalf of the International Subcommittee for Isomerized Hop α-Acids Standards
Descriptors: methodology, calibration standard, HPLG-analyisis, iso-α-acids
Source: BrewingScience – Monatsschrift für Brauwissenschaft 62 (January/February 2009), pp. 25

Schmelzle, A.
The Beer Aroma Wheel
Aroma wheels provide a terminology for the sensory description of products. They were developed to help people responsible for quality control and product development to communicate using unambiguous terminology.
30 years ago, Meilgaard [14] developed the beer flavour wheel. Its development was an important milestone in establishing an accepted terminology for the sensory science of beer. It still serves as the basis for the selection of terms in descriptive profiling tests today. Sensory science has since come a long way in terms of accumulating knowledge and developing sensory standards. In order to guarantee a consistent use of language, the existing beer terminology therefore needs to be reviewed. In Meilgaard's flavour wheel, olfactory, gustatory and haptic sensory perceptions overlap and several terms are not clearly matched with sensory perceptions.
Furthermore it is important for the communication with customers that they, too, understand the terminology. In some cases, it can be difficult to assign terms to the individual classes. This assumes that tasters come equipped with the knowledge of a beer connoisseur.
This article presents a beer aroma wheel that is structured according to sensory standards. Even people who have no knowledge of the way flavours in beer develop can use it to describe sensory perceptions. Alongside this, a beer aroma
wheel is shown that supports assessors in the description of positive and desirable characteristics of beers. Initially an overview of the sensory language in accordance with European standards is provided.
Descriptors: sensory, aroma wheel, mouthfeel, trigeminal perceptions, flavour wheel, reference materials
Source: BrewingScience – Monatsschrift für Brauwissenschaft 62 (January/February 2009), pp. 26-32

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Abstracts BrewingScience articles 2008

Garbe, L.-A.
γ-Nonalactone in Beer: Biosynthesis by Yeast
γ-Nonalactone is known as an aroma active and chiral compound in beer and other fermented products. Labeling experiments with tetra deuterated (9,10,12,13-²H₄)-linoleic acid, single deuterated 13- and 9- hydroxyoctadecadienoic acids (HODE) and its corresponding oxygen-18 labeled oxidation product [¹⁸O₁]- 13- and 9- HODE elucidated two different biosynthetic routes from linoleic oxidation products (HODE) to γ-nonalactone in brewers yeast Saccharomyces cerevisiae and a model yeast Sporobolomyces odorus. I) 13-Peroxidation of linoleic acid into 13-HODE in barley or during malting and ß-oxidation followed by one a-oxidation type step finally resulting in γ-nonalactone with (S)-stereospecificity ( (S) ~ 60 % e.e.). II) 9-Peroxidation of linoleic acid into 9-HODE in barley or during malting and Baeyer-Villiger type oxidation resulting in 2E,4E-nonadien-1-ol and azelaic acid. 2E,4E-nonadien-1-ol was further transformed to γ-nonalactone with (R)-stereo-specificity( (R) ~ 46 % e.e.).
Descriptors: gamma Nonalactone, enantiomers, chiral analysis, yeast metabolism, isotope labeling, lipoxygenase
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (September/October 2008), pp. 175-180

M. Krahl, C. Hagel, M. Zarnkow, W. Back and S. Kreisz
Changes of the Content of Water-soluble Bioactive Compounds during the Malting Process of Spelt Wheat (Triticum aestivum var. spelta)
Spelt wheat (Triticum aestivum var. spelta), a hexaploid variety of the genus Triticum is a cereal closely related to common wheat (Triticum aestivum). The major non-starchy carbohydrates in spelt wheat are arabinoxylans and fructans. Furthermore spelt wheat is known to contain relatively high levels of thiamine and riboflavin, two vitamins from the B-group. In this work the influence of a standard malting process on the content of these four bioactive compounds was studied. The amount of water-extractable arabinoxylan increased significantly during the malting process, as well as the water-extractable riboflavin content. The fructan concentration in the analysed samples showed a slight increase and thiamine levels staid stable.
Descriptors: spelt wheat, Arabinoxylan, malting, Thiamine, Riboflavin, Fructan, dietary fibre
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (September/October 2008), pp. 170-174

H. Scheuren, K. Sommer and M. Hertel
Vaporisation of Aromatic Components during the Beer Production
In a lot of processes and production steps in the Life-Science-Industry liquid semi-finished products are in contact with high temperatures and associated pressures. As a result steaming operations occur which have to be seen as thermodynamic separation processes. Concerning the exhaustion of aromatic components these steps influence intentionally or unintentionally the quality of the final product. The purport of this article is an overview of the thermodynamical basics concerning the steaming of aromatic components. Therefore the process of vaporisation by vaporescence and the vaporisation by boiling are both explained and defined. Furthermore this theoretical background and the corresponding formulas are tested and proofed by two samples of the sum of all existing experiments.
Descriptors: wort boiling, mashing, vaporisation, boiling, vaporescence, flavours, Dimethylsulphide (DMS)
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (September/October 2008), pp. 162-169

F. Thiele, A. Hartwig and W. Back
Yeast Quality Distribution in the Cone of Cylindro Conical Tanks
Yeast cropping from cylindro-conical tanks and repitching of the yeast is a key procedure in the brewing industry. In general it is assumed that the yeast collected from the cone of a tank is a homogenous culture. However results from studies investigating this aspect indicate that yeast quality as well as the environmental conditions within the cone can vary extensively. Results from different studies have been contradictory in various aspects. In order to add more information to this topic several yeast crops in two industrial breweries were followed obtaining samples in certain intervals. Each sample was analyzed for the physiological conditions of the yeast and various characteristics of the recoverable beer were investigated. In addition for some trials the replicative age and the fermentation performance in EBC Tall tubes have been examined. It was found that yeast vitality and viability did not vary considerably throughout the individual crops but large differences were found in-between several crops. Similar results were found for the characteristics of the recoverable beer. Regarding the replicative cell age a gradient throughout the crop was found. But the fermentation performance of the individual samples could not be related to the cell age.
Descriptors: yeast, cropping, viability, vitality, fermentation performance
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (July/August 2008), pp. 148-161

S. Hanke, M. Herrmann, J. Rückerl, C. Schönberger and W. Back
Hop Volatile Compounds (Part II): Transfer Rates of Hop Compounds from Hop Pellets to Wort and Beer
Several hundred aroma compounds are known in hops but only a few have great impact to hop aroma of beer. Adding hops at late stages of boiling gives a pleasant hoppy flavour to the final beer. Linalool is known to be a good indicator for such a hoppy flavour. In this study it could be shown that different hop varieties have different transfer rates of linalool and other aroma compounds. The behaviour of the aroma compounds is different and compound specific. Linalool increases during fermentation and there were differences between beers fermented at 8 °C and 12 °C. The 12 °C samples showed lower concentrations of linalool but higher scores in aroma intensity. Possible explanation are additive interactions between fermentation-by-products and hop aroma compounds.
Descriptors: hop aroma, linalool, geraniol, hop flavour, hops, Humulus Lupulus L.
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (July/August 2008), pp. 140-147

M. Herrmann, S. Hanke, D. Kaltner and W. Back
Hop Volatile Compounds (Part I): Analysis of Hop Pellets and Seasonal Variations
The measurement of the hop volatiles targets the flavour-active components, mainly terpene and sesquiterpene alcohols, that are able to create the typical hoppy flavour in beer. These substances are both indicator substances as well as key components of the flavour. This paper presents the method of analysis via aqueous extraction, water steam distillation and detection by GC-FID. Furthermore data is provided, describing the relationship between alpha acids content and oil content compared to actual flavour component levels. Neither alpha acids content nor oil content show a reliable correlation to the actual content of flavour compounds. It is therefore proposed to dose hop pellets according to the actual level of hop flavours and not according to the currently used dosage based on alpha-acids content. Part 2 of this paper presents data on transfer rates.
Descriptors: hop, hopping, beer flavour, hop aroma, analysis, gaschromatography, analytical method, volatile compounds
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (July/August 2008), pp. 135-139

D. P. De Schutter, M.-R. De Meester, D. Saison, F. Delvaux, G. Derdelinckx, J.-M. Rock, H. Neven and F. R. Delvaux
Characterization and Quantification of Thermal Load during Wort Boiling
Thermal load is often considered as a vague and obscure burden for brewers. In order to clarify the concept of thermal load, this paper aimed to characterize and quantify thermal load during wort boiling. Thermal processing of wort was found to cause the accumulation of Maillard intermediates, which might lead to the generation of off-flavours during beer ageing. The amount of intermediates could be quantified in terms of HMF-equivalents. A part of these intermediates was reduced by yeast during fermentation. The remaining non-reducible intermediates in beer can therefore be considered as the chemical memory of thermal load on wort. In order to quantify thermal load in wort, the kinetic behaviour was examined and a pseudo 0th order kinetics was established. The quantification of thermal load was then captured in a formula, which consisted of two terms. The first is a specific wort term, which evaluates the susceptibility of a particular wort to applied thermal load. This tool could be used by every brewer to predict the effect of boiling process changes on the wort. In addition, a boiling system term was created. Although the latter term is highly theoretical, it provides insights in the impact of differences in boiling intensity on thermal load of wort.
Descriptors: wort boiling, thermal load, TBA, HMF, Maillard reaction, Maillard intermediates
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (July/August 2008), pp. 121-134

C. Zufall, K. Wackerbauer and C. Brandt
The Influence of Hop Products on Beer Flavour Stability
The use of reduced iso-alpha-acids in brewing has become more widespread in past years, although their characteristics during beer ageing are not completely known. During our investigations, important differences in ageing characteristics were detected not only between the categories of reduced and non-reduced hop extracts, but also within the group of beers containing reduced hop products. Forced ageing in the absence of light had the strongest impact on beers hopped with CO₂-extract, followed by iso-alpha-extracts. Rho, Tetra and Hexa showed a significantly better stability with the tendency to improve from Rho- over Tetra- to Hexahydro-isohumulone. Under light exposure, besides showing lightstruck flavour, beers hopped with CO₂-extract were the first to show cardboardy oxidation aroma, while beers containing only reduced hop products were virtually unaffected. Extended periods of light exposure, however, led to the formation of methyl-furfuryl-disulphide (MFDS) off-flavour, also in light-stable beers, as previously reported [1]. The findings from sensory analysis could be confirmed by instrumental analysis of chemiluminescence behaviour. The results indicate clearly that the choice of hop products has a decisive influence on beer flavour stability.
Descriptors: flavour stability, light-stable beer, reduced iso-alpha-acids, sensory analysis, flavour descriptors
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (May/Juni 2008), pp. 113-120

J. Schneider, I. Weber and R. Pahl
Measurement of Water Vapour Ingress in PET Bottles and Correlation with Oxygen and Carbon Dioxide Permeation
The beer and beverage industry is using ever more barrier enhanced plastic bottles for the filling of its products. The quality of the products can be considerably affected by the permeation of oxygen into the bottle and carbon dioxide out of it. The quality control of the bottles with particular emphasis on the gas barrier is thus of great importance. However, the conventional gas permeation measuring method needs too much time. In order to respond effectively and quickly to barrier defects, bottle production or incoming goods inspection measuring time must be shortened, for example by 2 hours. A physical problem of a quick measurement of oxygen is the comparably long unsteady state of permeation due to desorption of oxygen into the bottle after filling. In order to overbear this difficulty methods are tested which use other gases or as in this instance water vapour. Instead of a complete permeation only the migration of water from PET into the bottle inner is measured. The ruggedness of the method meets the requirements of the practical measurement conditions. The correlation of the water vapour migration rate with the permeation of carbon dioxide and oxygen measured with a real-time method is linear. Active barriers employing scavenger material can not be detected by the water vapour ingress measurement.
Descriptors: multilayer, oxygen, PET bottle, permeation, quick test, water vapour
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (May/Juni 2008), pp. 105-112

M. Zarnkow, C. Almaguer, F. Burberg, W. Back, E. K. Arendt, S. Kreisz and M. Gastl
The Use of Response Surface Methodology to Optimise Malting Conditions of Tef (Eragrostis tef (Zucc.) Trotter) as a Raw Material for Gluten-free Foods and Beverages
Celiac disease is a condition, in which case the person’s body reacts to the prolamins of wheat, rye, barley, and oats. The only way to treat CD is a total lifelong avoidance of gluten consumption. In this study Tef (Eragrostis tef L.), which belongs to the family poaceae that is regarded as gluten free, was used as raw material. The objective of this study was to optimize the malting conditions to produce a gluten free malt of high quality for gluten free foods. Tef, with a thousand kernel weight of 0.3–0.4 g, needed special arrangements like small sieves etc. Tef has a remarkable agronomical advantage that the water requirement is probably the lowest of any major cereal. Response surface methodology was used to investigate the influence of the three malting parameters, vegetation time, degree of steeping and temperature on the quality of tef malt. Each predictor variable was tested at three levels. Vegetation times were 4, 5 and 6 days, degrees of steeping were 46, 50 and 54 % and vegetation temperatures were 16, 20 and 24 °C. Kilning temperatures of 65 °C were used. The used analyses were based on methods outlined in EBC or by MEBAK. The raw material was yielded 2006 in Utah, USA. A range of malt quality parameters was determined including extract, apparent attenuation limit, gelatinisation temperature, a-amylase activity, ß-amylase activity, limitdextrinase activity, Kolbachindex, alpha amino nitrogen, viscosity, and colour. The achieved values slightly deviate from the calculated ones. The obtained attributes were 52.1 % extract, 69.1 % AAL, 84 U/g a-amylase activity, and 187 U/g ß-amylase activity, 1062 U/kg limit dextrinase activity, 5.9 EBC colour, 285 mg/100 g FAN and 2.782 mPa x s viscosity. This publication shows clearly that on the one hand RSM is a prove method for testing the malting conditions of unknown cereals and on the other hand Eragrostis tef is a crop with a potential as a raw material for malting purposes.
Descriptors: tef, malt, response surface technology, gluten-free, cereal
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (May/Juni 2008), pp. 94-104

M. Schmidt, C. Eder and A. Delgado
Design of a Pilot Setup to sort Damaged Returned Empty Beverage Crates in an Automatic Filling Line
The inspection of returned beverage crates as well as bottles in industrial automatic filling lines is mainly performed by imaging systems. These systems are not able to detect invisible damages or embrittlement. A powerful novel system based on the principle of mechanical vibration analysis for the detection of small and concealed damages is presented. The selection of individual crates is performed automatically by a pre-trained artificial neural network (ANN). Numerical finite element simulations form a basic insight into the vibration behaviour of the crates and help to plan a pilot setup. This leads to a final recognition rate of more than 99 % over all checked crates in a prototype for industrial use.
Descriptors: damage recognition, artificial neural network, vibration analysis, finite element simulation
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (May/Juni 2008), pp. 81-93

J. Titze, H. Walter, F. Jacob, A. Friess and H. Parlar
Evaluation of a new Optical Sensor for Measuring dissolved Oxygen by Comparison with Standard Analytical Methods
The determination of the concentration of dissolved oxygen (O₂) plays an important role in different stages of beer production. Only precise, stable and fast measurement procedures for determining the oxygen content in beer are therefore suitable for the use in breweries. A research project was carried out in order to evaluate the newly developed oxygen measurement system built in the CO₂/O₂ Gehaltemeter type c-DGM of Haffmans BV by comparison with other standard analytical references such as the Orbisphere 3650 from Hach Ultra Analytics GmbH and the DIGOX 6 from Dr. Thiedig & Co. The purpose of this study was to determine the precision and accuracy as two main criteria for the evaluation of a suitable oxygen measurement in the brewing industries, since the precision describes the quality of a measurement procedure and the accuracy the level of agreement between the indicated and real value. The measurement system of the c-DGM was compared with the certified reference systems during a series of tests. The measurement methods of the reference systems are specified in Brautechnische Analysenmethoden, volume II of the Mitteleuropäische Brautechnische Analysenkommission (MEBAK) and are considered to be the recognized procedure for oxygen regulation in the brewing industry. It was observed that in comparison to the reference systems, the oxygen measurement system built in the c-DGM exhibited an effective work performance regarding precision and accuracy, and moreover signalized a fast response and low calibration efforts.
Descriptors: oxygen measurement, dissolved oxygen (O₂), oxygen content in beer
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (March/April 2008), pp. 66-80

Ch. Klose, B. D. Schehl and E. K. Arendt
Protein Changes during Malting of Barley using Novel Lab-on-a-Chip Technology in Comparison to two-dimensional Gel Electrophoresis
During the malting process storage proteins are degraded by proteolytic enzymes into small peptides and amino acids. The activity of these enzymes was measured at various stages during malting of barley and was found to be increased. To visualize proteolytic degradation, proteins of unmalted, germinating and malted grains were fractionated. After extracting the proteins on the basis of their solubility (Osborne fractionation) protein fractions were analysed using a Lab-on-a-Chip technique, which separates the proteins, based on their molecular weight, by capillary electrophoresis. This new technique for the analysis of proteins was supported by using two-dimensional gel electrophoresis. In addition, amino acid analysis on barley and barley malt was carried out. In general a degradation of the proteins to small peptides and amino acids could be observed in all fractions. In the albumin and globulin fraction also a protein increase was observed, which is due to the fact that these fractions contain the majority of the metabolically active proteins. The Lab-on-a-Chip analysis technique was found to be appropriate for analysis of degrading or increasing proteins, as it revealed rapid, repeatable and reliable results, which could be validated by using common protein analysis techniques such as two-dimensional gel electrophoresis and amino acid analysis.
Descriptors: barley, Lab-on-a-Chip analysis, malting, protein changes, protein fractions, two-dimensional gel electrophoresis
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (March/April 2008), pp. 56-65

R. Pahl, F.-J. Methner, J. Schneider, J. Kowalczyk, S. Hausmanns and A. Radowski
Study on the Applicability of Isomaltulose (Palatinose™ ) in Beer and Beer Specialties, and its remarkable Results
The functional disaccharide isomaltulose (Palatinose™) was tested to determine its suitability as an ingredient in beer and beer specialties, and its potential fermentability by typical beer contaminants, and typical beer production yeasts. It was shown that all tested beer contaminants were in the majority of the cases completely unable to ferment isomaltulose. The same was true for most of the tested brewing yeasts. As a result of the non-fermentability, promising results were obtained with respect to the microbiological stability, and to the sensorial profile and taste of beer and beer specialties.
Descriptors: microbiological stability, sensorial profile, functional, isomaltulose
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (March/April 2008), pp. 49-55

S. Loch-Ahring, F. Decker, S. Robbert and J. T. Andersson
Chill-haze – Identification and Determination of Haze-active Constituents by HPLC and Mass Spectrometry
Part I: The role of polyphenols and the astonishing impact of hop components on chill haze formation
The formation of haze is a serious problem of bright beers because it limits the storage life of the bottled or barrelled product. The problem is particularly evident in the bottle. Haze (chill haze) is said to be caused by different substances and mechanisms. The most commonly held opinion makes a protein polyphenol interaction responsible for its formation. Therefore efforts of the brewing industry are targeted towards a minimization of one or both of these components by filtration through PVPP (polyvinylpolypyrrolidone) and diatomite (Celite). The objective of this study was to trace the influence of polyphenols as well as other phenolic substances on the colloidal stability of beer and to lay the foundation for tracing them throughout the brewing process. In regard to chill haze performance and brewing stabilisation, the repeated reference to polyphenols led us to examine the polyphenol content of isolated chill haze in detail. Based on an existing method normally used to determine the polyphenol composition of beer and wort, a modified approach was developed to examine polyphenols in chill haze. To examine the possible influence of polyphenols on chemo-physical endurance, beer samples taken throughout the brewing process, isolated chill haze and permanent beer turbidity were determined by HPLC-DAD-QTOF-MS, UPLC-DAD-QTOF-MS and nano ESI chip-QTOF-MS. This is the first part of our work and only discusses the polyphenol analysis in wort, beer and isolated haze performed by HPLC-DAD-QTOF-MS and nano ESI chip-QTOF-MS. Haze properties were not studied using kinetics but analytical methods with the aim to identify single components. The influence of some polyphenols on the formation of haze clouding was observed. The strong influence of hop substances on the colloidal stability could be demonstrated
Descriptors: chill haze, colloidal stability, polyphenols, catechin, xanthohumol, hop components, PVPP stabilisation
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (March/April 2008), pp. 32-48

L. Gabel, K. Glas, F. Jacob, A. Friess and H. Parlar
Efficient Formation of Iso-Humulones in Aqueous Hop Solutions at Low Temperatures
In this work, new cognitions on the influence of common parameters for the isomerization of humulones, such as the temperature, pH, storage time, the concentration of humulones, microbial growth and pressure in especially prepared aqueous hop solutions were observed. The results provided an important background for future works regarding the enrichment of humulones and iso-humulones from aqueous solutions by using foam fractionation, in order to produce isomerized and non-isomerized marketable hop products. At low pHs between 2 and 3, higher isomerization rates were observed. Isomerization took place already at low temperatures between 8 and 10 °C, which previously has not been observed. At higher pHs, sufficient isomerization was also induced, but after a duration of ca. 72 hours. Higher isomerization rates occurred at longer storage duration of up to, e.g., 240 hours. Regarding the concentration of humulones in the hop solutions, it was found that the ratio of solved humulones to the formation of iso-humulones remained nearly the same (mostly 50 %, but at least 25 %). The ratio observed over a period of 240 hours continued almost unchanged, except for 144 hours (more than 75 %). Isomerization under the applied conditions took place at normal pressure. A relationship between the concentration of humulones and iso-humulones towards microbial growth could not be established, because microorganisms grew in aqueous hop solutions spiked with a disinfectant, as well as in those without disinfectant.
Descriptors: isomerization parameters, humulones, iso-humulones, aqueous hop solution, extraction
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (January/February 2008), pp. 25-31

M. Yano, W. Back and M. Krottenthaler
The Impact of Liquid Adjunct and Barley on Wort and Beer Quality
The use of adjunct is one of the most important factors in the beer industry, since adjunct not only influences production variables such as quality and cost, but also has an influence on market sales strategy, such as pricing strategy in Japan where liquor tax is assessed according to malt usage. Although a great deal of knowledge has been accumulated regarding adjuncts such as liquid adjunct (L. A.) and barley, not many reports have been published regarding special quality characteristics derived from these adjuncts, such as beer flavor stability. In this study, we have performed exhaustive research to elucidate the impact of L. A. and barley on process and quality, specifically with regard to taste and flavor stability, by comparing wort and beer made from 100 % malt, 75 % malt with 25 % adjunct, and 60 % malt with 40 % adjunct, using a pilot plant capable of making 60 L of cold wort. No exogenous enzymes were used in the brews. As a result of our experiments, we discovered a tendency toward improved flavor stability when 40% of malt was substituted for L. A. We also found a tendency that flavor stability decreased when 40 % of malt was substituted for barley. Other process and quality characteristics of adjunct beers are also discussed as well. Descriptors: adjunct, barley, brewing, flavor stability, foam, liquid adjunct
Source: BrewingScience – Monatsschrift für Brauwissenschaft, 61 (January/February 2008), pp. 10-24

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