Beer Aroma Research Articles

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

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

Part III: the influence of serial repitching ofSaccharomyces pastorianuson the production dynamics of some important aroma compounds during the fermentation of barley and gluten-free buckwheat and quinoa wort

The present paper is the last report of a comprehensive study regarding the influence of the serial repitching of Saccharomyces pastorianus TUM 34/70 on the composition of a barley, buckwheat or quinoa fermentation medium. In particular, it focuses on the production dynamics of important volatile compounds typically associated with the aroma of beer. Samples were taken every 24 h after 11 serial repitchings of a single starter culture, analysed for the particular aroma compound content by distillation followed by gas chromatography with flame ionization detection. The term ‘serial repitching factor’ is used for the first time to support the visual evaluation of the influence of serial repitching. Results showed that the levels of methanol in the quinoa wort fermentation were only slightly higher than in barley and in practical terms independent of successive fermentation. The behaviour of acetaldehyde in quinoa was similar to that in barley. However, there was a final 2-fold lower production of some important aroma compounds compared with barley and buckwheat and for this reason quinoa cannot be recommended as a gluten-free substitute to produce a bottom-fermented beer. Regarding the buckwheat wort fermentation, a 2- to 3-times lower final acetaldehyde content than in barley is desirable, whereas a relatively high methanol content is not desirable. Barley and buckwheat showed comparable sum concentrations and similar overall profiles of some important aroma compounds. From this perspective, buckwheat appears to be a promising substitute for barley as a brewing raw material. The overall conclusions of our comprehensive study (Parts I–III) are that buckwheat shows adequate brewing properties to substitute for barley in the commercial preparation of a bottom-fermented gluten-free beer-like beverage, and yeast can be repitched at least 11 times. In contrast, quinoa in practical terms shows no substitutional potential for barley in beer; however, it has many nutritious advantages, thus the commercial preparation of a unique, bottom-fermented gluten-free ‘non-beer-like’ beverage – where the yeast could be repitched six times at most – appears feasible. Copyright © 2015 The Institute of Brewing & Distilling

Characterization of Volatile Components from Hüller Bitterer Hop Variety Using In-Tube Extraction GC-MS Analysis

The composition of hop oil contributes to the aroma of beer and the essential oil profile of hop samples contains valuable information for brewers. The aim of this study was to characterize the HA¼ller Bitterer hop variety, during the development of hop cones, by analysis the composition of volatile oil using in-tube extraction gas chromatography-mass spectrometry (ITEX-GC-MS). The obtained results show that the ITEX-GC/MS method is suitable for the determination of volatile compounds from hop samples. A number of 60 compounds were separated and 50 of them were identified. The most important volatile compounds found in HA¼ller Bitterer hop variety belonging to the monoterpenes and sesquiterpenes classes are represented by: I²-myrcene, I²-caryophyllene and I±-humulene. Â

Insights on beer volatile profile: Optimization of solid-phase microextraction procedure taking advantage of the comprehensive two-dimensional gas chromatography structured separation.

The aroma profile of beer is crucial for its quality and consumer acceptance, which is modu-lated by a network of variables. The main goal of this study was to optimize solid-phase microextraction experimental parameters (fiber coating, extraction temperature, and time), taking advantage of the comprehensive two-dimensional gas chromatography structured separation. As far as we know, it is the first time that this approach was used to the untargeted and comprehensive study of the beer volatile profile. Decarbonation is a critical sample preparation step, and two conditions were tested: static and under ultrasonic treatment, and the static condition was selected. Considering the conditions that promoted the highest extraction efficiency, the following parameters were selected: poly(dimethylsiloxane)/divinylbenzene fiber coating, at 40ºC, using 10 min of pre-equilibrium followed by 30 min of extraction. Around 700-800 compounds per sample were detected, corresponding to the beer volatile profile. An exploratory application was performed with commercial beers, using a set of 32 compounds with reported impact on beer aroma, in which different patterns can be observed through the structured chromatogram. In summary, the obtained results emphasize the potential of this methodology to allow an in-depth study of volatile molecular composition of beer.

Chemometric analysis of the volatile fraction evolution of Portuguese beer under shelf storage conditions

In this work we present a multivariate statistical analysis of the evolution of the volatile fraction of Portuguese beer over an extended period of 1year under standard shelf storage conditions, using gas chromatography coupled with mass spectrometry (GC–MS). A systematic methodology is proposed for detecting the onset of meaningful changes in chemical composition during shelf storage and to monitor its evolution along time. We also put forward and discuss chemometric procedures for analyzing the contributions of different chemical components in the definition of dynamic ageing trends. In summary, the chemometric analysis reveals that the chemical composition of beer presents a statistically meaningful deviation from the reference scenario after a period of 7months, although the deviation trend has its onset during the 6th month. The analysis performed also underlines the limitations of current variable contribution methods, and an alternative procedure was proposed based on the analysis in the original domain which finally led to a consistent and interpretable clustering structure of the volatile fraction compounds. Esters and higher alcohol compounds stand up on a cluster arrangement suggesting that their strict control can effectively point out meaningful changes on beer aroma. Organic acids, namely caprylic, capric and acetic acids can also be very helpful in that sense.

Enhancing the levels of 4-vinylguaiacol and 4-vinylphenol in pilot-scale top-fermented wheat beers by response surface methodology

Top-fermented wheat beers are desired by consumers because of their distinctive clove-like and phenolic aroma, in which two characteristic flavour substances, 4-vinylguaiacol (4VG) and 4-vinylphenol (4VP), are of vital importance. In this paper, the levels of 4VG and 4VP were the subject of an intensive and detailed investigation. The influence of wheat malt proportion, mashing-in temperature, boiling time and fermentation temperature on 4VG and 4VP was studied by pilot-scale brewing experiments using a 10 hL mashing vessel and 20 hL fermentation tanks. Response surface methodology (RSM) was used to explore the possibilities for enhancing the concentration of 4VG and 4VP in top-fermented wheat beers. Statistical analysis of the results showed that for the ranges of wheat malt proportion studied, mashing-in temperature, boiling time and fermentation temperature all had a significant influence (p <0.05) on 4VG and 4VP production. Based on the response surface plots, the optimal brewing parameters that maximized 4VG and 4VP levels were as follows: (a) wheat malt proportion 40%; (b) mashing-in temperature 44°C; (c) boiling time 88 min; and (d) fermentation temperature 19.5°C, resulting in significantly increased levels of 4VG and 4VP (2.418 mg/L and 1.402 mg/L, respectively). These brewing and fermentation parameters were concluded to be the optimal conditions to highlight the typical flavour and aroma of top-fermented wheat beers. Copyright © 2015 The Institute of Brewing & Distilling

Humulus lupulus- a story that begs to be told. A review

The hop cones of the female plant of the common hop species Humulus lupulus L. are grown almost exclusively for the brewing industry. Only the cones of the female plants are able to secrete the fine yellow resinous powder (i.e. lupulin glands). It is in these lupulin glands that the main brewing principles of hops, the resins and essential oils, are synthesized and accumulated. Hops are of interest to the brewer since they impart the typical bitter taste and aroma to beer and are responsible for the perceived hop character. In addition to the comfortable bitterness and the refreshing hoppy aroma delivered by hops, the hop acids also contribute to the overall microbial stability of beer. Another benefit of the hop resins is that they help enhance and stabilize beer foam and promote foam lacing. In an attempt to understand these contributions, the very complex nature of the chemical composition of hops is reviewed. First, a general overview of the hop chemistry and nomenclature is presented. Then, the different hop resins found in the lupulin glands of the hop cones are discussed in detail. The major hop bitter acids (α- and β-acids) and the latest findings on the absolute configuration of the cis and trans iso-α-acids are discussed. Special attention is given to the hard resins; the known δ-resin is reviewed and the e-resin is introduced. Recent data on the bittering potential and the antimicrobial properties of both hard resin fractions are disclosed. Attention is also given to the numerous essential oil constituents as well as their contributions to beer aroma. In addition to the aroma contribution of the well-known essential oil compounds, a number of recently identified sulfur compounds and their impact on beer aroma are reviewed. The hop polyphenols and their potential health benefits are also addressed. Subsequently, the importance of hops in brewing is examined and the contributions of hops to beer quality are explained. Finally, the beer and hop market of the last century, as well as the new trends in brewing, are discussed in detail. Hop research is an ever growing field of central importance to the brewing industry, even in areas that are not traditionally associated with hops and brewing. This article attempts to give a general overview of the different areas of hop research while assessing the latest advances in hop science and their impact on brewing. Copyright © 2014 The Institute of Brewing & Distilling

Processing of bottom-fermented gluten-free beer-like beverages based on buckwheat and quinoa malt with chemical and sensory characterization

Typical beer contains significant amount of gluten, and being the third most popular beverage worldwide, the commercial production of its gluten-free form is of rising interest. This research aimed to prepare bottom-fermented beverages from buckwheat and quinoa and to explore their physical, chemical and sensory properties. Compared with barley, the analysis of brewing attributes of buckwheat and quinoa showed a lower malt extracts, longer saccharification times, higher total protein and fermentable amino nitrogen content and higher values of the iodine test and colour. Fermentability values, the wort pH and the soluble protein content were similar for barley and buckwheat, but different for quinoa, whereas only values of viscosity and beverage pH were similar between barley and quinoa. Both beverages, especially the quinoa beverage, contained a superior level of metal cations. The fermentable carbohydrate content in the buckwheat wort was comparable to barley but lower in quinoa; however, worts derived from both pseudocereals contained predominantly glucose. The amino acid content of the buckwheat wort was similar to barley, whereas the content in the quinoa beverage was almost twice as high. The content of volatile compounds commonly associated with beer aroma was comparable between the barley and buckwheat beverage but significantly lower in the quinoa; however, the latter contained some distinctive volatile substances not found in the other beverages. The organoleptic perception of the buckwheat beverage was better than that of the quinoa, although both showed a good general acceptance. In general, buckwheat appears quite similar to barley, whereas quinoa shows many unique properties. Copyright © 2014 The Institute of Brewing & Distilling

Quality of pilsner malt and roasted malt during storage

Malt is usually expected to be stable during 12 months of storage. However, in practice many brewers notice changes in malt aroma during storage. The oxidative stabilities of pilsner malt and roasted malt were evaluated during a 12 month storage at different temperatures (10 and 20 °C) and water activities (0.231 and 0.432). The radical content in malt kernels was measured by electron spin resonance spectroscopy and the volatile profile of the resulting sweet worts was measured by head-space analysis followed by GC-MS analysis. The storage of malt resulted in oxidative reactions and a large change of the volatile profile of the resulting worts. Roasted malt was much more unstable than pilsner malt, as illustrated by a higher initial radical intensity, larger radical decay during storage and a larger change in the volatile profile of the wort with increased amounts of lipid oxidation products. For both roasted malt and pilsner malt, good correlations were found between radical decay and changes in the volatile profile of the wort, where high temperature and high water activity resulted in the largest changes. During the 12 months of storage, the sugar extract of the wort made from the malts remained constant and was not affected by the chemical changes. This study suggests that chemical changes occurring in malts during less than 12 months of storage may potentially affect the aroma of beer, and that water activity and storage temperature should both be kept low in order to maintain a high malt quality. Copyright © 2014 The Institute of Brewing & Distilling

Wort composition and its impact on the flavour-active higher alcohol and ester formation of beer - a review

The most significant factors influencing beer quality are the variety of aroma flavours that stem from a complex system of interactions between many hundreds of compounds. With increasing demand for flavour control and enhanced productivity, the presence of consistent and balanced amounts of higher alcohols and esters are critical aspects of process control. Extensive research has focused on the formation of flavour compounds by the brewing yeast and the factors that influence their synthesis. Fermenting wort is a complex medium from which the brewing yeast utilizes nutrients for living and growth and to where it places its metabolic by-products. Thus, changes in wort composition will greatly influence final beer aroma. The current paper reviews up-to-date knowledge on the contribution of wort composition to the flavour quality of the final product, in particular higher alcohols and esters. Different wort constituents involved in the biosynthesis of these aromatic substances, and which therefore require control during brewery fermentations, are reviewed. Copyright © 2014 The Institute of Brewing & Distilling

Dimethyl Sulfide – Significance, Origins, and Control

Dimethyl sulfide (DMS) is a substantial contributor to the aroma of many lager-style beers. Opinion varies on its desirability. It can be derived in beer from two sources: the thermal decomposition of S-methyl-methionine (SMM) produced in the embryo of barley during germination, or the reduction of dimethyl sulfoxide (DMSO, derived from the breakdown of SMM during the curing of malt) by yeast. The enzyme that effects DMSO reduction is a reductase whose primary function is the reduction of methionine sulfoxide and which competes for reducing power with several other cellular systems. Control of DMS production from SMM is achieved by specifying precursor levels in malt, by attending to the vigor and duration of the boil, and by controlling the length of the whirlpool stand. Control of DMS production from yeast is achieved by specifying yeast strain, wort gravity, free amino nitrogen and pH, the type of fermenter (ergo the extent of volatilization), and the fermentation temperature.

Characterization of the Key Aroma Compounds in Two Bavarian Wheat Beers by Means of the Sensomics Approach

Application of aroma extract dilution analysis (AEDA) on the volatiles isolated from a commercial Bavarian wheat beer (WB A) eliciting its typical aroma profile, best described by a clove-like, phenolic odor quality, revealed 36 odorants in the flavor dilution (FD) factor range from 16 to 4096. Among them, 2-methoxy-4-vinylphenol (clove-like) and 2-phenylethanol (flowery) showed the highest FD factors. AEDA of a second wheat beer (WB B), somewhat lacking the typical wheat beer odor note, revealed 32 odor-active components in the FD factor range from 32 to 8192. Among them, 2-phenylethanol, (E)-β-damascenone (cooked apple-like) and 3-methylbutanol (malty) were detected with the highest FD factors. Next, all odorants evaluated with an FD factor ≥32 were quantitated by stable isotope dilution assays in both beers, and the odor activity values (OAVs; ratio of concentration to odor threshold) were calculated. Thereby, ethanol, (E)-β-damascenone, 3-methylbutyl acetate, ethyl methylpropanoate, and ethyl butanoate showed the highest OAVs in WB A, followed by acetaldehyde, 3-methylbutanol, and dimethyl sulfide. In WB B, ethanol, (E)-β-damascenone, ethyl methylpropanoate, ethyl butanoate, and 3-methylbutyl acetate showed the highest OAVs. Whereas most aroma compounds were present in the same order of magnitude in both beer samples, in particular, 2-methoxy-4-vinylphenol and 4-vinylphenol (smoky, leather-like) were by factors of 13 and 15, respectively, higher in WB A. For the first time, the overall aroma of wheat beer (WB A) was successfully simulated on the basis of 27 reference compounds in their natural concentrations using water/ethanol (95:5; v/v) as the matrix.

Effect of unmalted oats (Avena sativa L.) on the quality of high-gravity mashes and worts without or with exogenous enzyme addition

Barley malt is the preferred brewing material these days because of its high extract content and high enzyme activities. However, when substituting malted barley with oats to create a unique beer flavor and aroma, endogenous malt enzymes become the limiting factor. Therefore, the objectives of this study were to evaluate the effect of 10–40 % unmalted oats on the quality of high-gravity mashes/worts and to investigate the limitations of endogenous malt enzymes as well as the benefits of the application of industrial enzymes. The enzyme mix Ondea® Pro was found to be particularly suitable for mashing with unmalted oats and was therefore used in the present rheological tests and laboratory-scale mashing trials. In order to gain detailed information about the biochemical processes occurring during mashing, the quality of mashes was comprehensively analyzed after each mash rest using standard methods described by Mitteleuropaische Brautechnische Analysenkommission and Lab-on-a-Chip capillary electrophoresis. Mashing with up to 40 % oats resulted in increased mash consistencies, color/pH (20 °C) values, β-glucan concentrations, wort viscosities 12.0 %, and filtration times as well as decreased FAN and extract contents. The application of Ondea® Pro enormously increased the color of worts despite lower pH values but considerably improved the quality and processability of 30 or 40 % oat-containing mashes/worts. However, the substitution of up to 20 % barley malt with unmalted oats can easily be realized without the addition of exogenous enzymes.

Development of SNP markers for genes of the phenylpropanoid pathway and their association to kernel and malting traits in barley.

BackgroundFlavonoids are an important class of secondary compounds in angiosperms. Next to certain biological functions in plants, they play a role in the brewing process and have an effect on taste, color and aroma of beer. The aim of this study was to reveal the haplotype diversity of candidate genes involved in the phenylpropanoid biosynthesis pathway in cultivated barley varieties (Hordeum vulgare L.) and to determine associations to kernel and malting quality parameters.ResultsFive genes encoding phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), chalcone synthase (CHS), flavanone 3-hydroxylase (F3H) and dihydroflavonol reductase (DFR) of the phenylpropanoid biosynthesis pathway were partially resequenced in 16 diverse barley reference genotypes. Their localization in the barley genome, their genetic structure, and their genetic variation e.g. single nucleotide polymorphism (SNP) and Insertion/Deletion (InDel) patterns were revealed. In total, 130 SNPs and seven InDels were detected. Of these, 21 polymorphisms were converted into high-throughput pyrosequencing markers. The resulting SNP and haplotype patterns were used to calculate associations with kernel and malting quality parameters.ConclusionsSNP patterns were found to be highly variable for the investigated genes. The developed high-throughput markers are applicable for assessing the genetic variability and for the determination of haplotype patterns in a set of barley accessions. The candidate genes PAL, C4H and F3H were shown to be associated to several malting properties like glassiness (PAL), viscosity (C4H) or to final attenuation (F3H).

THE INFLUENCE OF THE AGE OF A HOP PLANT ON THE QUALITY OF HOP AROMAS IN BEER

Hops (Humulus lupulus L.) are one of the most important ingredients in beer in terms of taste and quality - providing bitterness, aroma and fullness. However, it is difficult to produce beer products with a consistent level of quality as hop quality may vary due to the climate, cultivation method, soil conditions, root condition, etc. The purpose of this study was to elucidate the influence of hop hop plant age on beer quality, especially on the aroma of beer. We examined differences in hop aroma by means of sensory evaluation and chemical analysis. In addition, in order to assess how the vegetative growth and reproductive growth of hops were dependent on hop plant age, the length of the vine and leaf size, stem diameter and flowering were monitored throughout the growing season. The hop samples used were selected from 8 hop gardens in the Saaz region during the 2010 and 2011 growing seasons. A comparison of vegetative growth, leaf size and stem diameter showed that hop plants that were younger (in terms of hop plant age) were larger and flowered later. In addition, the α-acid content was higher in the younger hops. As a result, significant differences in hop aroma characteristics were observed in beer made from the different hop samples. Based on these results, it was concluded that the more luxuriant vegetative growth and late flowering associated with the younger roots changed secondary metabolism, which also affected the generation of terpenes, thereby altering hop aroma quality in the beer produced. This information can help the brewers improve quality and design hop and beer products with a better aroma.

Enzymatic release of odourant polyfunctional thiols from cysteine conjugates in hop

Polyfunctional thiols are contributors to the hop varietal aroma of beer. Besides free thiols, a cysteine-S-conjugate has recently been shown to be an additional component of the thiol potential of hop. Such cysteine adducts investigated here in four hop cultivars and in different hop forms. Hop hydroalcoholic extracts were purified on a cation exchanger and subjected to apotryptophanase β-lyase activity. The Cascade hop variety exhibited the highest bound 3-sulphanylhexan-1-ol (grapefruit-like) potential, while both Tomahawk and Nelson Sauvin cultivars were confirmed to be important sources of bound 3-methyl-2-butene-1-thiol (skunky-like), 3-sulphanylpentan-1-ol and 4-sulphanyl-4-methylpentan-2-one (box-tree-like). Surprisingly, hop CO2 extracts proved to contain cysteine conjugates. Although related, the concentrations of cysteine-bound thiols in hop are not strictly correlated to the amounts of free volatiles found in the derived beers. Copyright © 2013 The Institute of Brewing & Distilling

English

&nbsp; Amgba is an African traditional maize sorghum based opaque beer mainly considered as food than beverage by Gbaya peoples in Adamaoua region of Cameroon. Despite Amgba&rsquo;s importance as food, physicochemical composition as well as its process production is still not well understood. To overcome these constraints, the process production of &ldquo;Amgba&rdquo; was carried out in order to identify critical points and eventually standardize the production process. To do this, a cross-sectional and descriptive study, including qualitative and quantitative survey, followed by laboratory scale production were conducted. Different products were given to a panel, for sensory analysis and were used to assess physicochemical characteristics. Results show that the main process production seems similar to most African opaque beer production technologies. Irrespective of the amount of added sorghum and maize, multiple regression analyses revealed an inverse significant (P &lt; 0.05) relationship between aroma, taste, visual examination, and overall acceptability of beers. Physicochemical analysis results showed high alcohol content (4.5 to 7%), total titratable acidity varied from 14.4 to 16.2 mg/L, residual sugars (g/L) were found to be in the range of 1.3 to 1.5 (g/L), and total polyphenols form 772 to 802 (mg/L). This data highlights the possibilities for improvement of &ldquo;Amgba&rdquo; quality for industrial production. &nbsp; Key words:&nbsp;Beer, sorghum, maize, fermentation.

The impact of different ale brewer’s yeast strains on the proteome of immature beer

BackgroundIt is well known that brewer’s yeast affects the taste and aroma of beer. However, the influence of brewer’s yeast on the protein composition of beer is currently unknown. In this study, changes of the proteome of immature beer, i.e. beer that has not been matured after fermentation, by ale brewer’s yeast strains with different abilities to degrade fermentable sugars were investigated.ResultsBeers were fermented from standard hopped wort (13° Plato) using two ale brewer’s yeast (Saccharomyces cerevisiae) strains with different attenuation degrees. Both immature beers had the same alcohol and protein concentrations. Immature beer and unfermented wort proteins were analysed by 2-DE and compared in order to determine protein changes arising from fermentation. Distinct protein spots in the beer and wort proteomes were identified using Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and MS/MS and revealed common beer proteins, such as lipid transfer proteins (LTP1 and LTP2), protein Z and amylase-protease inhibitors. During fermentation, two protein spots, corresponding to LTP2, disappeared, while three protein spots were exclusively found in beer. These three proteins, all derived from yeast, were identified as cell wall associated proteins, that is Exg1 (an exo-β-1,3-glucanase), Bgl2 (an endo-β-1,2-glucanase), and Uth1 (a cell wall biogenesis protein).ConclusionYeast strain dependent changes in the immature beer proteome were identified, i.e. Bgl2 was present in beer brewed with KVL011, while lacking in WLP001 beer.

Release of Phenolic Acids and Amino Acids during Mashing Dependent on Temperature, pH, Time, and Raw Materials

In this study the ideal mashing-in conditions for wheat beer were examined. The parameters concerning temperature, pH value, and time should guarantee an optimal activity of arabinoxylan- and protein-degrading enzymes and thus a high release of ferulic acid and p-coumaric acid as well as amino acids. These phenolic acids are precursors of the flavor-and aroma-active volatile phenols 4-vinylguiacol and 4-vinylphenol. Together with higher alcohols and esters, e.g., phenyl ethanol and isoamyl acetate, formed among others by amino acids, they make a decisive contribution to the typical aroma and taste profile of wheat beer. In addition to the maximized release of ferulic, p-coumaric acid, and amino acids, the investigated mashing-in conditions should reduce the amount of cinnamic acid. This phenolic acid, which is naturally prevalent in cereals, is converted by thermal and enzymatic decarboxylation into the harmful substance styrene during the brewing process. The studied parameters, especially the mashing-in pH, afford the realization of the set targets. Besides the determination of the effects of different mashing-in parameters, various colored malts and raw materials were investigated for their contents of phenolic acids and amino acids.

Discriminatory power assessment of the sensor array of an electronic nose system for the detection of non alcoholic beer aging

Many chemical changes in beer aroma occur during storage (aging), and monitoring these changes could give guidelines to the brewers how to manage and control the brewing process to obtain the final product with a high stability in flavour after packaging. In this regard, our laboratory aimed at a research into the application of an electronic nose in order to get the fingerprint of the change of non alcoholic beer aroma during aging. Th discriminatory power of the sensor array of this system was evaluated. Principal Component Analysis (PCA) and Soft Independent Modelling of Class Analogy (SIMCA) techniques were used for this purpose. The results obtained can direct us to performing other parts of our project. Considering the discriminatory power of the sensor array used, we can develop the application of a specific electronic nose system by picking up the most effective sensors or ignoring the redundant sensors.