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Physicochemical characterization of sahti, an ‘ancient’ beer style indigenous to Finland
Abstract
Sahti, a strong, unhopped farmhouse beer flavoured with juniper, is still actively brewed in rural areas in Finland. Presented here is the first comprehensive analysis of the physical and chemical properties of this unique beer style. Twelve sahti samples from the southwest of Finland were analysed and, while properties varied, the beers generally had high levels of alcohol (mean = 7.9% ABV) and high residual extract (mean = 9.5°P). Foam stability was negligible, as is typical for the style, and glycerol concentrations at 3.1 – 4.7 g L−1 were higher than in reference beers (commercial lager, wheat beer and porter). These features may be attributed to the very high gravity conditions employed in brewing sahti beers. Bitterness levels were relatively low (3–13 IBU) owing to the absence or moderate use of hops. All samples contained detectable levels of the clove-like compound 4-vinylguaiacol owing to the use of baker's rather than brewer's yeast for brewing. Concentrations of higher alcohols and esters were high, with many individual aroma compounds being above the normal flavour thresholds. Results have highlighted the uniqueness of this style of beer in comparison to commercially available beers and have contributed to our understanding of the reasons for the particular sensorial properties of this traditional beer style. Copyright © 2015 The Institute of Brewing & Distilling
... In recent years, several studies highlighted the potential of feral S. cerevisiae strains isolated from spontaneously fermented beers or alternative food matrices, to produce beers with novel flavor profiles and other desirable properties [98][99][100][101][102][103][104]. Yeast isolation represents one of the most interesting solutions for brewers, since it takes advantage of the natural biodiversity of the microorganisms adapted to grow in their habitats. ...
... Although S. cerevisiae yeasts from various alcoholic beverages, such as Cachaça spirits [98], wine [99][100][101], pulche, tequila, or sake [102], were proposed for brewing, only baker yeasts were experimentally demonstrated to be truly exploitable in wort fermentation. This is historically proven by old-style beers such as the Russian Kvass or Finland's sahti beers, which are still brewed by natural fermentation of bread or by using baker's yeasts, respectively [103,104]. Remarkably, beer and baker's yeasts are phylogenetically closed [21] and grow on maltotriose as carbon source even under anaerobic conditions [105]. Several S. cerevisiae sourdough strains were able to ferment glucose, maltose, and trehalose. ...
Beer is a fermented beverage with a history as old as human civilization. Ales and lagers are by far the most common beers; however, diversification is becoming increasingly important in the brewing market and the brewers are continuously interested in improving and extending the range of products, especially in the craft brewery sector. Fermentation is one of the widest spaces for innovation in the brewing process. Besides Saccharomyces cerevisiae ale and Saccharomyces pastorianus lager strains conventionally used in macro-breweries, there is an increasing demand for novel yeast starter cultures tailored for producing beer styles with diversified aroma profiles. Recently, four genetic engineering-free approaches expanded the genetic background and the phenotypic biodiversity of brewing yeasts and allowed novel costumed-designed starter cultures to be developed: (1) the research for new performant S. cerevisiae yeasts from fermented foods alternative to beer; (2) the creation of synthetic hybrids between S. cerevisiae and Saccharomyces non-cerevisiae in order to mimic lager yeasts; (3) the exploitation of evolutionary engineering approaches; (4) the usage of non-Saccharomyces yeasts. Here, we summarized the pro and contra of these approaches and provided an overview on the most recent advances on how brewing yeast genome evolved and domestication took place. The resulting correlation maps between genotypes and relevant brewing phenotypes can assist and further improve the search for novel craft beer starter yeasts, enhancing the portfolio of diversified products offered to the final customer.
... In brewing, it mainly serves as an adjunct, that is to say, a source of fermentable extract at a reduced cost [22]. It is the key ingredient of traditional drinks such as kvass, a Russian fermented beverage made of rye bread [23], and historical beers including the Bavarian Roggenbier and the Finnish sahti, a farmhouse ale flavored with juniper branches and fermented with baker's yeast [24]. Moreover, rye enters the grist of beer styles such as Belgian Pale Ale [25], Saison and Specialty India Pale Ale (Rye IPA), sought after for its spicy and pungent aroma as a complementary ingredient to barley malt [26]. ...
Rye is used in some applications in the food and beverage industry and for the preparation of functional foods. It is an interesting raw material in malting and brewing due to its characteristic contribution to the beer’s color, turbidity, foam and aroma. The aim of this work was to optimize the micro-malting process of a rye landrace. The response surface methodology (RSM) was applied to study the influence of three malting parameters (germination time, germination temperature and degree of steeping) on the quality traits of malted rye. Long germination times at high temperatures resulted in an increase in the extract and Kolbach index. The model for the apparent attenuation limit showed a particular pattern, whereby time and temperature inversely influenced the response. The lowest viscosities were determined in the worts produced from highly modified malts. Optimization of the variables under study was achieved by means of a desirability function and a genetic algorithm. The two methodologies provided similar results. The best combination of parameters to optimize the malting process on the rye landrace under study was achieved at 6 days, 12 °C and 44 g/100 g.
... The decrease in pH and increase in titratable acidity observed in this research work is supported by Obi and Ugwu (2019). This is in conformity with the works of Lyumugabe et al. (2010), Bhuyan et al. (2014) and Ekberg et al. (2015). The decrease in values of TSS revealed progressive increase in the chemical reactions that consumed the sugars or reduced the concentration of sugars (Braide and Nwaoguikpe, 2011;Ocloo and Ayernor, 2008). ...
The search for local alternatives to barley for brewing has been a major concern to stakeholders in the beer industry in Nigeria and Africa. One of such alternative and which can be sustained is the use of Sorghum and cassava as raw materials. This research work was aimed at investigating the possibility of producing lager beer using a blend of sorghum and hybrid yellow cassava (IBA 070593 and IBA 070539). The two yellow cassava varieties were blended with the sorghum malt at ratio 0:100 (control), 20:80, 30:70, 40:60 and 50:50. Fermentation was carried out for duration of 10 days and samples analyzed every 2 days interval. Parameters analyzed were yeast count, pH, total soluble sugars, alcohol content and sensory evaluation using standard procedures. The results showed that the formulation ratio of 20:80 had the highest yeast count and alcohol content of 286.7 ± 2.60 × 10 12 cfu/ml and 6.78 ± 0.41 % respectively, while the least values of 247.3 ± 1.76 × 10 12 cfu/ml and 3.63 ± 0.49 % were from 50:50 ration.Sensory evaluation showed that overall acceptability of 8.00 ± 0.05 was from 20:80 ration while the least of 7.30 ± 0.13 was from 40:60. The study revealed that the hybrid of yellow cassava blended with sorghum can be a favourable raw material for beer production.
... Chętnie stosowana jest też lawenda o właściwościach uspokajających, przeciwlękowych oraz przeciwbakteryjnych, przeciwgrzybiczych i przeciwutleniających [2]. Może stanowić substytut chmielu, podobnie jak jałowiec będący podstawą piw gruit oraz tradycyjnego fińskiego piwa sahti [16].] Jałowiec ma działanie grzybobójcze, bakteriobójcze i moczopędne. ...
Beer is a popular and the most preferred alcoholic beverage among consumers around the world. In Poland its annual consumption amounts to nearly 100 litres per capita, thus our country is among the world leaders in this field. The perception of beer has been significantly reoriented over the last twenty years. The beer revolution and the related changes in the brewing industry contributed this beverage to achieve a status of prestigious drink. The market of innovative craft beers develops very dynamically for they are, in terms of flavour and quality, an interesting diversified alternative to mass brands. Among them "beer specials" dominate. This term is usually used to describe all the top and bottom fermentation beers other than traditional lagers and pils. A trend of premiumisation has emerged; the expectations of consumers continue to grow regarding the quality of beer, its composition, sensory properties and health-promoting potential. On the market there are more and more offers of beers containing bioactive additives, minerals or gluten-free. In this paper there was characterised the current situation on the Polish beer market, including its over-all structure and that of the speciality and functional beers. In details were discussed raw material and technological aspects of producing functional beers, such as: non-and low-alcoholic, gluten-free, isotonic, probiotic, xanthohumol-fortified beers and also gruit beers containing herbal additives. According to the literature data analysis, the segment of functional beers clearly stands out and the interest in beers for special nutritional uses continues to grow. Low-and non-alcoholic beers are and presumably will be the fastest growing category on the market. © 2021, Polskie Towarzystwo Technologow Zywnosci Wydawnictwo Naukowe PTTZ. All rights reserved.
... Uncontrolled fermentation, no addition of hops, and subsequent low carbonation resulted in a foam-less beverage. Research conducted by [1] on ancient Finnish beer Sahti showed that the investigated ancient beverage had no foam and showed a distinctive difference between today's beers, especially regarding flavor and aroma. Today's brewing industries are far from the ancient manufacturers, and stable and retentive foam head is one of the main indicators of beer freshness and quality. ...
Foam stability and retention is an important indicator of beer quality and freshness. A full, white head of foam with nicely distributed small bubbles of CO2 is appealing to the consumers and the crown of the production process. However, raw materials, production process, packaging, transportation, and storage have a big impact on foam stability, which marks foam stability monitoring during all these stages, from production to consumer, as very important. Beer foam stability is expressed as a change of foam height over a certain period. This research aimed to monitor the foam stability of lager beers using image analysis methods on two different types of recordings: RGB and depth videos. Sixteen different commercially available lager beers were subjected to analysis. The automated image analysis method based only on the analysis of RGB video images proved to be inapplicable in real conditions due to problems such as reflection of light through glass, autofocus, and beer lacing/clinging, which make it impossible to accurately detect the actual height of the foam. A solution to this problem, representing a unique contribution, was found by introducing the use of a 3D camera in estimating foam stability. According to the results, automated analysis of depth images obtained from a 3D camera proved to be a suitable, objective, repeatable, reliable, and sufficiently sensitive method for measuring foam stability of lager beers. The applied model proved to be suitable for predicting changes in foam retention of lager beers.
... Only in recent years have people started to look into the beer brewing potential of yeasts from traditional fermentations, such as cachaça spirits (Araújo et al., 2018), pulque, tequila (Cubillos et al., 2019), or sub-Saharan alcoholic beverages (Johansen et al., 2019). However, only the historically proven old-style beers such as Finnish sahti and the traditional Norwegian kveik beer, both using juniper instead of or in addition to hops, or the bread based Russian kvass have shown promising results so far (Dlusskaya et al., 2008;Ekberg et al., 2015;Preiss et al., 2018). There are still many traditional beverages left to explore such as traditional European low alcoholic beverages (Baschali et al., 2017) or fermented drinks produced by the Aboriginal people in Australia even before European arrival (Mangaitch, Way-a-linah, and Kambuda; Brady, 2008). ...
Fermented foods and particularly beer have accompanied the development of human civilization for thousands of years. Saccharomyces cerevisiae, the dominant yeast in the production of alcoholic beverages, probably co-evolved with human activity. Considering that alcoholic fermentations emerged worldwide, the number of strains used in beer production nowadays is surprisingly low. Thus, the genetic diversity is often limited. This is among others related to the switch from a household brewing style to a more artisan brewing regime during the sixteenth century and latterly the development of single yeast isolation techniques at the Carlsberg Research Laboratory in 1883, resulting in process optimizations in the brewing industry. However, due to fierce competition within the beer market and the increasing demand for novel beer styles, diversification is becoming increasingly important. Moreover, the emergence of craft brewing has influenced big breweries to rediscover yeast as a significant contributor to a beer's aroma profile and realize that there is still room for innovation in the fermentation process. Here, we aim at giving a brief overview on how currently used S. cerevisiae brewing yeasts emerged and comment on the rationale behind replacing them with novel strains. We will present potential sources of yeasts that have not only been used in beer brewing before, including natural sources and sources linked to human activity but also an overlooked source, such as yeast culture collections. We will briefly comment on common yeast isolation techniques and finally touch on additional challenges for the brewing industry in replacing their current brewer's yeasts.
... Strains of S. cerevisiae from environments other than commericial brewing have also been utilized for beer production. These strains have been sourced, for example, from cachaça fermentations (Araújo et al., 2018), from traditional Andean chichas (Grijalva-Vallejos, 2020), Beninese sorghum beer (Tokpohozin et al., 2019), Norwegian farmhouse ales (Preiss et al., 2018), grape must, apple and wine (Rossi et al., 2018), a probiotic supplement (Senkarcinova et al., 2019), and from baking/sourdough cultures (Ekberg et al., 2015;Marongiu et al., 2015;Mascia et al., 2015Mascia et al., , 2016Ripari et al., 2018;Rossi et al., 2018;Catallo et al., 2020). ...
... However, much greater variation was observed for the concentrations of volatile flavour compounds. These were, as expected, quite high in most beers (10), but there were clear strainspecific differences. Two sourdough strains in particular (C117 and C118) produced relatively low levels of flavour volatiles, and may be suitable for production of beers with a more prominent malt or juniper flavour. ...
The Finnish farmhouse ale sahti is unique in that it is fermented with baking, rather than brewing strains of Saccharomyces cerevisae. The custom of maintaining farmhouse yeast cultures is however no longer practiced in Finland, and much yeast derived diversity in sahti beers has presumably been lost as a consequence. Here, the brewing potential of a number of sourdough derived strains was tested with respect to a number of different fermentation traits. Seven strains originally isolated from Finnish or Italian sourdough cultures were used to ferment high gravity sahti wort (20°P), and fermentation performance together with production of volatile compounds were assessed and compared with a reference baking yeast. Strains differed in terms of fermentation rate, yield, yeast viability and beer flavour profile. All were maltotriose positive, but utilisation varied so that alcohol yield could be greater or lower than that of the reference strain, with values ranging from 6.6 to 7.9% (v/v). Production of aroma compounds was also variable so that it was possible to identify strains producing high levels of esters and those with lower production, which could be used to emphasise flavours originating from raw materials. All strains generated 4‐vinyl guaiacol and so would be suitable for other beers where this is a part of the normal flavour profile. Results suggest that sourdough isolates of S. cerevisiae are suitable for sahti production, but could also be applied to other beer styles as a way to differentiate products. © 2020 The Authors. Journal of the Institute of Brewing published byJohn Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling
... Although S. cerevisiae yeasts from various alcoholic beverages, such as pulche, tequila or sake, were proposed to have brewing potential [102], only baker yeasts were experimentally demonstrated to be truly exploitable in wort fermentation. This is historically proven by old style beers such as the Russian Kvass or the Finland's sahti beers which are still brewed by natural fermentation of bread or by using baker's yeasts, respectively [103,104]. Remarkably, beer and baker's yeasts are phylogenetically closed [21] and grow on maltotriose as carbon source even under anaerobic conditions [105]. Most of the S. cerevisiae strains isolated from sourdough were able to ferment glucose, maltose and trehalose. ...
Beer is a fermented beverage with a history as old as human civilization and its productive process has been spread all around the world becoming unique in every country and iconic of entire populations. Ales and lagers are by far the most common beers; however, the combination of raw materials, manufacture techniques and aroma profiles are almost infinite, so it is not surprising to notice that there is a large amount of different beer styles, each of them with unique characteristics. Nowadays, diversification is becoming increasingly important in the brewing market and the brewers are continuously interested in improving and extending the already wide range of products, especially in craft brewery. One of the major components that can have a deep impact on the final product is yeast, since it is able to convert carbohydrates in wort, especially maltose and maltotriose, into ethanol, carbon dioxide and other minor aroma-active compounds. Saccharomyces cerevisiae (top‐fermenting yeasts used to produce ales) and Saccharomyces pastorianus (cryotolerant bottom‐fermenting hybrids between S. cerevisiae and Saccharomyces eubayanus responsible for the fermentation of lagers) are most used in breweries. However, an increasing number of different yeast starter cultures are commercially available, to improve the production efficiency also at relative low temperatures and to obtain desirable and diversified aroma profiles avoiding undesired compounds. Four main genetic engineering-free trends are becoming popular in craft brewing yeast development: 1) the research for novel reservoirs as source of new performant S. cerevisiae yeasts; 2) the creation of synthetic hybrids between S. cerevisiae and Saccharomyces non-cerevisiae in order to mimic lager yeasts by expanding their genetic background; 3) the exploitation of evolutionary engineering approaches; 4) the usage of non-Saccharomyces yeasts either in co-coculture or in sequential fermentation with S. cerevisiae. In the present work we summarized pro and contra of these approaches and provided an overview on the most recent advances on how brewing yeast genome evolved and domestication took place. Finally, we delineated how the correlations maps between genotypes and relevant brewing phenotypes can assist and further improve the search for novel craft beer starter yeasts.
In the food and beverage industries, implementing novel methods using digital technologies such as artificial intelligence (AI), sensors, robotics, computer vision, machine learning (ML), and sensory analysis using augmented reality (AR) has become critical to maintaining and increasing the products’ quality traits and international competitiveness, especially within the past five years. Fermented beverages have been one of the most researched industries to implement these technologies to assess product composition and improve production processes and product quality. This Special Issue (SI) focused on the latest research on the application of digital technologies on beverage fermentation monitoring and the improvement of processing performance, product quality and sensory acceptability.
Various adjuncts, including fruits, are added for flavoring beer, one of the most famous beverages in the world. The influence of persimmon fruit on antioxidant activities and quality characteristics of beer was investigated in this study. The antioxidant activities measured through DPPH and superoxide and hydroxyl anions scavenging potentials as well as total polyphenol contents of the persimmon-treated beer were significantly (p < 0.05) high compared to the control. The mineral elements Mg, K, and Ca were also significantly (p < 0.05) increased, however toxic heavy metals were not detected in the persimmon beer. Among the persimmon beer samples, the overall acceptance value was significantly (p < 0.05) high when the beer was prepared by adding 150 g of the fruit in 10 L of water. The results suggested that an addition of 150 g of persimmon fruit per 10 L of water could better enrich the nutritional, organoleptic, and antioxidant potentials of beer.
This article presents a model of beer fermentation in terms of flavor component content. It describes the production of two higher alcohols (isoamyl alcohol and phenyl ethanol) and three esters (isoamyl acetate, ethyl acetate, and ethyl hexanoate) selected according to their organoleptic threshold values in beer, as well as the effects of operating conditions on their formation. A step-by-step modeling approach was used, which exploited prior biological information coupled with analysis of experimental data. These data resulted from a two-level full-factorial experimental design for three factors: temperature (10-16°C), top pressure (50-800 mbar), and yeast inoculum (0.5 x 107-2 x 107 cells per milliliter). Experiments were carried out in a 15-L reactor. Because CO2 emission, which represented the only on-line measurement in this process, is directly associated with primary yeast activity, the aroma dynamics were predicted from those for CO2, with yield coefficients depending only on operating conditions (temperature, dissolved CO2, yeast inoculum size). Model parameters were identified from experimental data. An initial experimental validation gives a successful prediction of most of the aroma compounds when compared with their measured values. The model quantifies the effects of operating conditions on the production kinetics and final concentrations of aroma compounds. These results suggest that this model could be successfully used for both prediction and control of some aroma compounds under industrial conditions.
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Effects of mashing on total phenolic contents (TPC), radical-scavenging activity, reducing power and metal chelating activity of malts and corresponding worts were clarified in this study. Results showed that there were significant variations in TPC and antioxidant activity across malts and worts. An 8.8% of increase in TPC was observed during the early stage of mashing, accompanied by an increase in antioxidant activity. However, 2.6% of decrease in TPC and inconsistent changes in antioxidant activity were found during the mashing at higher temperature. Overall, mashing resulted in 6.0% and >10.0% of increases in TPC and antioxidant activity, respectively. Moreover, Pearson correlation analysis revealed that there were good correlations (ranging from 0.622 to 0.735, P < 0.01) between TPC and antioxidant activity of malts and worts. Additionally, mashing resulted in more positive correlations between TPC and antioxidant activity, emphasising the key role of malt phenolic compounds for wort antioxidant activity.
The effect of ethanol on the foaming properties of beer protein fractions was studied using a microconductivity method and nitrogen gas to generate the foam. Increasing the ethanol concentration resulted in a decrease in foam stability. Interfacial studies including thin film drainage and dilational elasticity measurements indicated that ethanol reduced the rigidity of the adsorbed protein layer resulting in accelerated drainage from the foam lamellae and increased probability of film rupture. These results conflict with data from the Rudin method (using nitrogen gas to generate the foam) which indicate that, at low concentration, ethanol improves foam stability. These apparently conflicting results may be explained by the foam positive effects of a decline in bubble size and increase in bulk viscosity observed for the Rudin method, contrasted with the negative influence of a reduction in surface viscosity observed for the microconductivity foam assessment method.
Formation of ethyl acetate and isoamyl acetate by seven wine yeast strains in a model grape juice was examined during fermentation. The amounts in which the two esters are produced during fermentation were found to depend on the particular yeast strain, its specific production rate and its rate of survival in the wine.Kloeckera apiculata exhibited the highest ability for acetate formation. Hansenula subpelliculosa, Kluyveromyces marxianus, Torulaspora delbrueckii and Saccharomyces cerevisiae produced intermediate levels and Pichia membranaefaciens and Candida guilliermondii very low levels of the two esters measured in this study.
The aim of this study is to demonstrate the influence of production strains (bottom-fermenting Saccharomyces pastorianus and S. cerevisiae with disruption in the KGD2 gene), carrier materials (spent grains and corncobs), reactor arrangements (packed-bed and gas-lift reactors), and mixing regimes (ideally mixed and plug flow) on the formation of flavor-active compounds during alcohol-free beer production. In addition, the composition of alcohol-free beer produced on a laboratory scale was compared with those of commercial products. The results confirmed the influence of each component of the production system (yeast strain, reactor, and carrier) on flavor formation, but their individual importance was case specific. The results indicate that the interplay between the appropriate production strain, carrier material, and bioreactor design is very important in continuous immobilized cell reactors and that suitable combinations could be used to improve both system performance and product quality.
Volatile esters are responsible for the fruity character of fermented beverages and thus constitute a vital group of aromatic compounds in beer and wine. Many fermentation parameters are known to affect volatile ester production. In order to obtain insight into the production of ethyl esters during fermentation, we investigated the influence of several fermentation variables. A higher level of unsaturated fatty acids in the fermentation medium resulted in a general decrease in ethyl ester production. On the other hand, a higher fermentation temperature resulted in greater ethyl octanoate and decanoate production, while a higher carbon or nitrogen content of the fermentation medium resulted in only moderate changes in ethyl ester production. Analysis of the expression of the ethyl ester biosynthesis genes EEB1 and EHT1 after addition of medium-chain fatty acid precursors suggested that the expression level is not the limiting factor for ethyl ester production, as opposed to acetate ester production. Together with the previous demonstration that provision of medium-chain fatty acids, which are the substrates for ethyl ester formation, to the fermentation medium causes a strong increase in the formation of the corresponding ethyl esters, this result further supports the hypothesis that precursor availability has an important role in ethyl ester production. We concluded that, at least in our fermentation conditions and with our yeast strain, the fatty acid precursor level rather than the activity of the biosynthetic enzymes is the major limiting factor for ethyl ester production. The expression level and activity of the fatty acid biosynthetic enzymes therefore appear to be prime targets for flavor modification by alteration of process parameters or through strain selection.
Brewing bacteriology was born when microorganisms responsible for the spoilage of beer were investigated by Louis Pasteur in his classic nineteenth century study. He was called upon to determine why French beer was inferior to German beer. He isolated a number of bacterial contaminants from French beer and malt wort and in 1876 published his famous book Études sur la Bière, ses Maladies, Causes qui les Provoquent. Procédés pour la Rendre Inaltérable, avec une Théorie Nouvelle de la Fermentation (Studies of Beer, its Diseases and the Causes That Provoke Them. Procedures for Making it Unalterable, with a New Theory of Fermentation). Today, it is generally believed that the presence of bacteria in the beer brewing process is undesirable.
Brewing bacteriology was born when microorganisms responsible for the spoilage of beer were investigated by Lotus Pasteur in his classic nineteenth- century study. He was called upon to determine why French beer was inferior to German beer. He isolated a number of bacterial contaminants from French beer and malt wort and in 1876 published his famous book Études sur la Bière, ses Maladies, Causes qui les Provoquent. Procéè;s pour la Rendre Inaltdérable, avec une Théorie Nouvelle de la Fermentation (Studies of Beer, its Diseases and the Causes That Provoke Them. Procedures for Making it Unalterable, with a New Theory of Fermentation). Today, it is generally believed that the presence of bacteria in the beer-brewing process is undesirable.
Brewing is one of the oldest and most complex technologies in food and beverage processing. Its success depends on blending a sound understanding of the science involved with an equally clear grasp of the practicalities of production. Brewing: science and practice provides a comprehensive and authoritative guide to both of these aspects of the subject. After an initial overview of the brewing process, malts, adjuncts and enzymes are reviewed. A chapter is then devoted to water, effluents and wastes. There follows a group of chapters on the science and technology of mashing, including grist preparation. The next two chapters discuss hops, and are followed by chapters on wort boiling, clarification and aeration. Three chapters are devoted to the important topics of yeast biology, metabolism and growth. Fermentation, fermentation technologies and beer maturation are then reviewed, followed by a consideration of native African beers. After a discussion of brewhouses, the authors consider a number of safety and quality issues, including beer microbiology and the chemical and physical properties of beer, which contribute to qualities such as flavour. A final group of chapters cover packaging, storage, distribution and the retail handling of beer. Based on the authorsâ? unrivalled experience in the field, Brewing: science and practice is a standard work for the industry. © 2004 Dennis E. Briggs, Chris A. Boulton, Peter A. Brookes and Roger Stevens. All rights reserved.
The aim of this study is to demonstrate the influence of production strains (bottom-fermenting Saccharomyces pastorianus and S. cerevisiae with disruption in the KGD2 gene), carrier materials (spent grains and corncobs), reactor arrangements (packed-bed and gas-lift reactors), and mixing regimes (ideally mixed and plug flow) on the formation of flavor-active compounds during alcohol-free beer production. In addition, the composition of alcohol-free beer produced on a laboratory scale was compared with those of commercial products. The results confirmed the influence of each component of the production system (yeast strain, reactor, and carrier) on flavor formation, but their individual importance was case specific. The results indicate that the interplay between the appropriate production strain, carrier material, and bioreactor design is very important in continuous immobilized cell reactors and that suitable combinations could be used to improve both system performance and product quality. Keywords: Alcohol-free beer, Beer flavor, Continuous reactor, Immobilization, Reactor arrangement, Strain selection
The aim was to discover the effect of high gravity brewing on yeast protease activity during fermentation, on the loss of hydrophobic polypeptides from wort during fermentation, and on the foam stability of stored beer. The hydrophobic polypeptide content of low (10° Plato) gravity worts showed a steady decline throughout fermentation, but for the 20° Plato wort there was a rapid decline over the first 8 days of fermentation, followed by little change over the remaining period. The decrease in hydrophobic polypeptides was greater in the high gravity fermentation. Proteinase A increased during fermentations with the highest levels being present at the end of fermentations. High gravity fermentations exhibited levels of yeast protease that from the 3rd to 11th day of fermentation were at least twice the values of the low gravity fermentations. The high gravity brewed beer contained significantly higher levels of proteinase A activity than the low gravity brewed beer. The inclusion of FERMCAP™, an antifoam, in high gravity wort did not affect either the hydrophobic polypeptide levels or foam stability of the resultant beer. This suggests that proteinase A, rather than fermenter foaming, must be the major contributor to the lack of foam stability of high gravity brewed beer. Head retention measurements conducted on the high and low gravity brewed bottled beers, over a five month period, demonstrated a steady decline in foam stability for both beers. The declines in head retention did not occur in high and low gravity beers that had been pasteurised.
Influences on foam stability and cling were compared by brewing trials investigating beer hopping rate, hopping type and modification of beer protein composition by the inclusion of a proline specific protease (PSEP). The comparison of the NIBEM, Rudin and lacing foam assessment methods with the level of hopping demonstrated the superiority of hydrogenated hop α-acids with respect to foam stability and particularly lacing. In addition, the NIBEM and Rudin foam analysis tests appear to respond relatively similarly with respect to hopping rate and hop type, with the NIBEM being somewhat more responsive in terms of foam stability measurments. The PSEP trials suggested that protein composition may only have a subtle effect on foam stability. Although more specific to haze active proteins, PSEP treatment in the small and pilot scale trials generally, but not always, resulted in a minor reduction in foam stability. This effect was not observed in 20 hL pilot and industrial scale beer productions. It was verified that both NIBEM and Rudin were positively influenced by increased levels of foam positive proteins. Although both foam tests were responsive to hopping rate and type, it is suggested that the Rudin foam test is somewhat biased towards foam positive proteins, particularly albuminous foam positive proteins (LTP1 and protein Z4), while in comparison the NIBEM foam test appears somewhat biased towards hordein foam positive proteins.
In this work, fermentable sugar, total protein, phenolics and ferulic acid content were estimated in sweet worts at different points of lautering. Transfer of these selected malt compounds into worts was analyzed in relation to the method of malt milling (wet milling of malt — the “test worts” or dry milling of malt — the “reference worts”). Glucose, maltose and maltotriose were more rapidly transferred into sweet worts at the early stages of lautering (40 hL and/or 80 hL of wort) after wet milling in comparison to dry milling. Total protein content in the test worts was significantly higher than in the corresponding reference worts at each stage of lautering. Transfer of phenolic compounds and ferulic acid (in the free as well as in the ester form) from the mash into sweet worts was significantly improved by dry milling, but not by wet milling. No difference in the total antioxidant activity was observed between the two types of worts. In conclusion, it can be stated that wet conditioning of malt before milling enhances the fast transfer of fermentable sugars and proteins from the mash into the sweet wort during lautering. Lautering is a time-consuming process, and time reduction without the loss of wort quality should be a priority. Therefore, wet milling can be of interest to professionals in the field as an interesting alternative method to improve the mashing process.
Wort, to which was added various amounts of solutions of glucose, fructose, sucrose or maltose, was fermented, and in the resulting beers the concentrations of the following flavour components were determined by gas chromatography: ethyl acetate, isobutyl acetate, iso-amyl acetate, 2-phenyl ethyl acetate, ethyl caproate, ethyl caprylate, n-propanol, isobutanol, amyl alcohols, 2-phenyl ethanol, caprylic acid and capric acid. The concentrations of these compounds were affected in different ways by the various amounts of sugar added, and some differences were observed etween the different carbohydrates.
Intensification of the industrial brewing process, particularly the use of higher gravity worts, has been driven by increasing competition within the industry as well as the need to maximise the use of raw materials and minimise energy expenditure. These developments have, however, placed greater demands on brewing yeast strains, whose evolutionary history has not prepared them for the extreme conditions associated with higher gravity brewing. Various yeast nutrient supplements have been used or proposed to maintain yeast performance under stressful conditions. These have included specific metal ions, lipids and lipid components such as fatty acids and sterols and free amino nitrogen, usually supplied in the form of a complex yeast food. Correction of wort nutritional deficiencies may reduce stress sensitivity of yeast and improve fermentation performance. Potential negative consequences of altering wort composition must however be considered, as important beer quality attributes such as taste, stability and foam can be affected. Here, the various options for nutrient supplementation and their influence on yeast physiology and performance, as well as beer characteristics are considered.
The ability of beer to produce good foam is influenced by the level of foam-active polypeptides. Specific polypeptides with hydrophobic domains, such as Lipid Transfer Protein (LTP1), are important components of beer foam. Although, high gravity brewing is a commercially viable technique, it has the disadvantage of producing beer with less foam stability compared to lower gravity brewed counterparts. It is thought that proteinase A plays a key role in the degradation of these hydrophobic polypeptides responsible the beer foam stability. The object of this study was to compare and quantify the loss of hydrophobic polypeptides and specifically foam-LTP1 during high gravity (20°Plato) and low gravity (12°Plato) wort fermentations and to evaluate the effect of proteinase A on these polypeptides. The losses of hydrophobic polypeptides and foam-LTP1 were generally greater in high gravity brews. Furthermore, the results obtained suggest that proteinase A alters the hydrophobicity of these polypeptides rather than their molecular size. Approximately 20% of hydrophobic polypeptides and approximately 57% of foam-LTP1 appeared to be proteinase A resistant. These differential losses of hydrophobic polypeptide and foam-LTP1 could have implications for the foam stability of the finished product.
Some effects have been studied of fermenting wort of unusually high specific gravity, followed by dilution with water to give beer of normal original gravity. This procedure permits increased overall rates of beer production, but matching of flavours requires control of the level of flavour determinants. If not controlled, the concentration of volatile esters may be disproportionately increased so that, after dilution, beer flavour is markedly different. Higher alcohol production is not affected in this way. The concentration of esters can be adjusted to appropriate levels by increasing the production of yeast mass during fermentation. Unsaturated fatty acids, which increase yeast dry matter production without altering the rate of fermentation, are particularly effective in reducing the extent of ester synthesis.
Phenolic acids in beer are important because they can be decarboxylated to phenols, which usually impart off-flavours. An improved high performance liquid chromatographic system was used to monitor phenolic acids and phenols during the brewing process. Ferulic acid was the most significant phenolic acid found in beers prepared from malted barley. Extraction of ferulic acid from malt involved an enzymatic release mechanism with an optimum temperature about 45°C. Mashing-in at 65°C significantly decreased the release of free ferulic acid into the wort. Wort boiling produced 4-vinyl guaiacol by thermal decarboxylation, in amounts (0.3 mg/L) close to its taste threshold, from worts that contained high contents of free ferulic acid (> 6 mg/L). The capacity of yeasts to decarboxylate phenolic acids (Pof+ phenotype) was strong in wild strains of Saccharomyces and absent in all lager brewing yeast and most ale brewing yeasts. Some top-fermenting strains, especially those used in wheat beer production, possessed a weak decarboxylating activity (i.e. Pofδ). During storage of beers there were appreciable temperature-dependent losses of 4-vinyl guaiacol. These results indicated that the production of 4-vinyl guaiacol is amenable to close technological control.
One way to naturally inhibit the oxidative deterioration of beer would involve protecting the antioxidants present in barley (mainly polyphenols) during the malting process. Depending on the variety, the antioxidant activity of barley is not negligible. Its relationship with the content of the three main phenolic groups (flavan-3-ols, hydroxycinnamic derivatives and flavonols), determined by a new ultraviolet spectrophotometric method, is proposed. It increases during malting probably not only by the modification or releasing of phenolic compounds, but also by the formation of new antioxidants, such as Maillard reaction products.
Esters are secondary products produced by brewing yeasts during the anaerobic metabolism of sugars and constitute one of the largest and most important groups of compounds affecting beer flavour. Many esters can be formed, the most important being ethyl acetate, isoamyl acetate, isobutyl acetate, 2-phenylethyl acetate and ethyl hexanoate. The odour threshold levels for ester detection are very low. Esters are especially important in high gravity brewing, where over production occurs causing unwanted solvent-like flavours. They are also important in low alcohol beer production due to the low levels produced, which can result in beers with little flavour. The factors influencing ester production are reviewed, together with the ways in which they can be used to control ester synthesis. It is believed that acetate esters are synthesized by an enzyme called alcohol acetyl transferase (AAT) which uses as substrates an alcohol and acetyl co-enzyme A; the latter plays a central role in many intracellular reactions. However, esters can also be synthesized by esterase enzymes working in reverse. Several attempts have been made to locate theAAT enzyme and recent work suggests that it is located in either the yeast cell plasma membrane or in intracellular organelles called "vacuomes".
a b s t r a c t This review focuses on the considerable amount of research directed at defining the accumulation of esters during fermentation and their contribution to aromas in foods and beverages. From this research it is clear that esters are extremely important for the aroma profile of fermented beverages and various dairy products. A large amount of this research is focused on wine and has yielded the genes involved in ester synthesis and hydrolysis in organisms such as Saccharomyces sp. It is also clear from recent research in both the fermented beverage and dairy context that lactic acid bacteria possess an extensive collection of ester synthesising and hydrolysing activities. This review describes the major esters reported in wine and the enzymes responsible for their hydrolysis and synthesis. Ester impact on wine aroma and forma-tion during primary and malolactic fermentation is also evaluated. Finally the potential applications of current knowledge are outlined.
J. Inst. Brew. 115(3), 243–252, 2009 Phenolic acids are widely distributed in foods and raw materials. They are easily absorbed by humans due to their simplicity. Once they enter the blood plasma, they act as antioxidants. Beer can be a rich source of phenolic acids in the diet. The aim of this study was to determine the concentrations of phenolic acids in two experimental worts and beers as well as in nine market beers (using HPLC-UV). An examination of the total antiradical activ-ities of phenolic acids with in vitro model systems (using ABTS and DPPH free radicals), at the concentrations comparable to those detected in beers, was performed. Only low fractions of the main phenolic acids present in barley malt (ferulic, vanillic and p-coumaric acid) were detected in the experimental worts. Moreover, the concentrations of phenolic acids significantly de-creased until the last steps of beer production. The main beer phenolic acids (vanillic and ferulic acid) exerted a lower share of total antiradical activity against both free radicals (calculated as the sum of the individual activities of all acids detected in beer) than the minor phenolic acids (caffeic, chlorogenic, o-coumaric, sinapic or syringic acid). The synergies, between individual phe-nolic acids in pairs, were also studied with in vitro model solu-tions using free radicals. The total antiradical activity of the compounds studied in pairs, was at the most as high as the sum of the antiradical activity of the individual phenolic acids, but in most cases it was considerably lower (i.e. no synergy was de-tected). Abbreviations: ABTS: 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid), DPPH: 2,2-diphenyl-1-picrylhydrazyl radical, TAA: total antiradical activity.
J. Inst. Brew. 111(2), 112–117, 2005 The degradation of a major protein component in beer, the lipid transfer protein (LTP1), by the yeast proteinase A was deter-mined. Another major protein fraction in beer, the protein Z-fraction, was not degraded by this enzyme. Protein preparations from beer and barley containing LTP1 were examined for degra-dation by proteinase A using SDS-PAGE, immunoblotting and RP-HPLC. LTP1 from barley was completely resistant to pro-teinase A, whereas LTP1 concentrated from beer was cleaved. We conclude that LTP1 was modified during the brewing pro-cess, thus rendering it more susceptible to proteinase A degra-dation.
Two brewer's yeasts and one baker's yeast grew with 95% (w/w) pure maltotriose as carbon source in the presence of antimycin A to block respiration. Biomass yields (0.15 and 0.24 g dry yeast g–1 sugar, respectively, with and without antimycin A) were similar for growth on maltose and maltotriose, and yields of ethanol were 80% of stoichiometric. Yeasts harvested during growth on glucose and containing low maltose transport activity did not begin to use maltotriose in the presence of antimycin A until after a long lag phase (up to 50 h), but yeast harvested during growth on maltose, and containing high maltose transport activity, began to use maltotriose after about 25 h. Much shorter lags were observed before growth started in the absence of antimycin A.
Beer contains a wide range of polyphenolic compounds originating mainly from malt and hops. In this work newly modified on-line
coupled HPLC–photodiode-array (PDA)–MS methods were used for analysis of characteristic phenolic compounds in several Czech
lager beers, in comparison with some foreign lager beers. After optimization of column type, elution mode, and gradient steepness,
chromatography was performed with a Restek Ultra Aqueous, C18 (5μm, 250mm×4.6mm) column at 30°C and gradient elution using an optimized linear gradient of aqueous acetonitrile acidified
with 1% acetic acid, at a flow rate 0.4mLmin−1. In total, 49 compounds were identified. Eleven individual compounds, predominantly malt phenolics (gallic acid, (−)-catechin,
epicatechin, ferulic acid, chlorogenic acid, morin, rutin, quercetin, caempherol, naringenin, and luteolin) were quantified
by use of two detection techniques: MS with electrospray ionization and UV detection. Compared with foreign beers, Czech beers
contained higher levels of most of the phenolic compounds; specific distributions of individual compounds were also observed.
Experimental PDA results for individual polyphenols were evaluated statistically by modified cluster analysis. Because of
very tight covariance of the data a new procedure was devised for correlation analysis. The set of beers analyzed can be divided
into four clusters closely related to the origin of the and the technology used. It seems that some of the flavonoids have
potential use in beer authenticity analysis.
KeywordsHPLC–PDA–MS–Beer–Lager–Czech beer–Phenolics–Flavonoids
Fourteen typical malting barley varieties from China were evaluated for their DPPH radical, ABTS radical cation and superoxide anion radical scavenging activities, reducing power, metal chelating activities, and total phenolic contents (TPC). All barley samples exhibited significant antioxidant activities determined by different assays, and contained significant levels of phenolic compounds. Gan4 and Wupi1 barley exhibited the highest DPPH radical scavenging activity, ABTS radical cation scavenging activity and reducing power. Gan4 and Humai16 barley showed the highest TPC, whereas the highest superoxide anion radical scavenging activity and metal chelating activity were found in Huaimai19 and Ken3 barley, respectively. The Pearson correlation analysis revealed that the TPC showed strong correlations with DPPH radical scavenging activity, ABTS radical cation scavenging activity, and reducing power (P < 0.01), whereas its correlations with superoxide anion radical scavenging activity and metal chelating activity were poor (P > 0.05). Moreover, DPPH radical scavenging activity, ABTS radical cation scavenging activity and reducing power were well positively correlated with each other (P < 0.01). Principal component analysis (PCA) was applied to understand the interrelationships among the measured antioxidant activity evaluation indices, and to gain an overview of the similarities and differences among the 14 barley varieties.
This work represents a survey of the occurrence of hydroxycinnamic acids and volatile phenols in a variety of beer styles. The contribution of 4-vinylguaiacol to the overall flavour perception of top-fermented specialty beers was shown. Significant differences in hydroxycinnamic acids (both free and ester-bound) and volatile phenol content between different beers were observed. The variability in volatile phenol content between different beers and beer styles can be explained by the high incidence of Pad1+ phenotype and the variability of Pad1 activity observed among top-fermenting brewing yeast strains. The relative importance of thermal versus enzymatic decarboxylation can account for the differences found between bottom and top-fermented beers. Concerning the optimisation of volatile phenol levels in beer, the selection of a suitable brewing yeast strain is the most important means of creating a phenolic taste profile in beer. Given that a considerable amount of hydroxycinnamic acids in beer still occurs in ester-bound form, enhancing the enzymatic release of these phenolic flavour precursors during mashing can greatly enhance the phenolic aroma potential of wort.
In this study, the effects of mashing variables such as mashing-in temperature, time and pH, mash thickness, grist coarseness and composition, and stirring regime on the release of ferulic acid were examined. Ferulic acid is a precursor for the formation of flavour-active volatile phenols and a potent natural antioxidant in beer. Given one barley malt variety, the multitude of choice in setting various process parameters and adding brewery adjuncts during brewhouse operations can give rise to worts with widely varying ferulic acid levels. A clear difference in temperature- and pH-dependence between the release of the water-extracted and the enzymatically hydrolyzed fraction was found. The T,t-dependencies of arabinoxylan-degrading enzyme activities were correlated with ferulic acid release during mashing. Results from laboratory-scale mashing experiments were validated with those from a pilot-scale (5 h) wort production process. Enhancing the enzymatic release of phenolic flavour precursors from bound forms during mashing can greatly enhance the phenolic aroma potential of wort. Optimising this precursor release during mashing may be a means for controlling final volatile phenol levels in beer.
Normal gravity wort and high gravity wort with different nitrogen levels were used to examine their effects on the fermentation performance of brewer's yeast and the formation of flavor volatiles. Results showed that both the wort gravity and nitrogen level had significant impacts on the growth rate, viability, flocculation, and gene expression of brewer's yeast and the levels of flavor volatiles. The sugar (glucose, maltose, and maltotriose) consumption rates and net cell growth decreased when high gravity worts were used, while these increased with increasing nitrogen level. Moreover, high gravity resulted in lower expression levels of ATF1, BAP2, BAT1, HSP12, and TDH, whereas the higher nitrogen level caused higher expression levels for these genes. Furthermore, the lower nitrogen level resulted in increases in the levels of higher alcohols and esters at high wort gravity. All these results demonstrated that yeast physiology and flavor balance during beer brewing were significantly affected by the wort gravity and nitrogen level.
Phenolic acids were repeatedly pointed out as powerful antioxidants. The studies in the past prove the differences in the phenolic acids content in malts and worts. In this work, the influence of wort boiling and whirlpool separation on the phenolic acid content was studied.
Worts were produced in the local brewery by the infusion method using pale pilsner-type barley malt. Samples were analysed at the beginning of the boil, after the boil and after whirlpool separation (5 and 30 min). Free and total alkali extractable phenolic acids contents were analysed using HPLC-DAD.
The main phenolic acid in all worts was ferulic acid in the free (35.47 ±3.28-117.51 ±4.40 mg·dm(-3)) as well as total alkali extractable form (193.49 ±4.84-294.72 ±2.65 mg·dm(-3)). With both forms no decrease was seen after boiling of wort (80 min at 100-100.5°C) followed by wort separation in the whirlpool. Similarly, no significant changes in the free and total form of p-coumaric acid content were seen.
It can be concluded that an elevated temperature during wort boiling and separation in whirlpool had no significant influence on the content of phenolic acids (at least in the case of the specific mashing program applied in this brewery: equipment, enzyme preparations, mashing, time-temperature parameters etc.). The differences in the phenolic acids levels could be rather attributed to different supplies of malt used for the production.
The impact of mixed cultures of Hanseniaspora osmophila and Saccharomyces cerevisiae with different initial yeast ratios on wine composition has been examined. The mixed culture significantly affected sugar consumption, the main enological parameters and ester concentrations, with the exception of glycerol, isoamyl acetate and diethyl succinate levels. Remarkably, in wines obtained with mixed cultures the concentration of 2-phenylethyl acetate was approximately 3- to 9-fold greater than that produced by S. cerevisiae pure culture. Moreover sensory evaluation revealed a stronger fruity character in wines fermented with mixed cultures than in control wines. Independently of the mixed culture used, all wines showed concentrations of acetic acid and ethyl acetate within the ranges described for wines. Our data suggest that a mixed culture of H. osmophila and S. cerevisiae can be used as a tool to increase 2-phenylethyl acetate in wine and that its concentration can be controlled by modulating the initial yeast ratio in the culture.
The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e., higher inoculum size). However, the decreased yeast net growth observed in these high cell density fermentations can have a negative impact on the physiological stability throughout subsequent yeast generations. The use of different oxygen conditions (wort aeration, wort oxygenation, yeast preoxygenation) was investigated to improve the growth yield during high cell density fermentations and yeast metabolic and physiological parameters were assessed systematically. Together with a higher extent of growth (dependent on the applied oxygen conditions), the fermentation power and the formation of unsaturated fatty acids were also affected. Wort oxygenation had a significant decreasing effect on the formation of esters, which was caused by a decreased expression of the alcohol acetyl transferase gene ATF1, compared with the other conditions. Lower glycogen and trehalose levels at the end of fermentation were observed in case of the high cell density fermentations with oxygenated wort and the reference fermentation. The expression levels of BAP2 (encoding the branched chain amino acid permease), ERG1 (encoding squalene epoxidase), and the stress responsive gene HSP12 were predominantly influenced by the high cell concentrations, while OLE1 (encoding the fatty acid desaturase) and the oxidative stress responsive genes SOD1 and CTT1 were mainly affected by the oxygen availability per cell. These results demonstrate that optimisation of high cell density fermentations could be achieved by improving the oxygen conditions, without drastically affecting the physiological condition of the yeast and beer quality.
During fermentation, the yeast Saccharomyces cerevisiae produces a broad range of aroma-active substances, which are vital for the complex flavour of beer. In order to obtain insight into the influence of high-gravity brewing and fermentation temperature on flavour formation, we analysed flavour production and the expression level of ten genes (ADH1, BAP2, BAT1, BAT2, ILV5, ATF1, ATF2, IAH1, EHT1 and EEB1) during fermentation of a lager and an ale yeast. Higher initial wort gravity increased acetate ester production, while the influence of higher fermentation temperature on aroma compound production was rather limited. In addition, there is a good correlation between flavour production and the expression level of specific genes involved in the biosynthesis of aroma compounds. We conclude that yeasts with desired amounts of esters and higher alcohols, in accordance with specific consumer preferences, may be identified based on the expression level of flavour biosynthesis genes. Moreover, these results demonstrate that the initial wort density can determine the final concentration of important volatile aroma compounds, thereby allowing beneficial adaptation of the flavour of beer.
We have found that proteases A, B and C of are localized in the vacuole. The corresponding inhibitors of these three proteases are present in the extravacuolar cytosol. The compartmentation of the yeast proteases suggests that their function is primarily the intravacuolar digestion of proteins. Yearst cells were grown under various conlitions, and it was found that culture conditions which either induce biochemical differentiation of cells or which do not allow growth result in the enhancement of proteolytic activities.
In the prokaryotic two-component signal transduction systems, recognition of an environmental stimulus by a sensor molecule results in the activation of its histidine kinase domain and phosphorylation of a histidine residue within that domain. This phosphate group is then transferred to an aspartate residue in the receiver domain of a cognate response regulator molecule, resulting in the activation of its output function. Although a few eukaryotic proteins were identified recently that show sequence similarity to the prokaryotic sensors or response regulators, it has not been clear whether they constituted a part of a 'two-component' system. Here we describe a two-component system in Saccharomyces cerevisiae that regulates an osmosensing MAP kinase cascade.
Two non-Saccharomyces wine yeast strains, Hanseniaspora guilliermondii 11104 and Pichia anomala 10590, selected as good producers of acetate esters when grown on synthetic microbiological medium, have been tested in wine fermentations as mixed cultures together with Saccharomyces cerevisiae. Wines produced using mixed cultures showed levels of acetaldehyde, acetic acid, glycerol and total higher alcohols within the ranges described for wine, whereas an increase in acetate ester concentrations was found. Ethyl acetate was the main ester produced, and isoamyl acetate and 2-phenylethyl acetate made up the next largest group of ester compounds in the wines analysed. H. guilliermondii 11104 was found to be a strong producer of 2-phenylethyl acetate in both pure and mixed cultures whereas S. cerevisiae was the best producer of ethyl esters. Mixed cultures did not influence ethyl ester levels at all.
The release of ferulic acid and the subsequent thermal or enzymatic decarboxylation to 4-vinylguaiacol are inherent to the beer production process. Phenolic, medicinal, or clove-like flavors originating from 4-vinylguaiacol frequently occur in beer made with wheat or wheat malt. To evaluate the release of ferulic acid and the transformation to 4-vinylguaiacol, beer was brewed with different proportions of barley malt, wheat, and wheat malt. Ferulic acid as well as 4-vinylguaiacol levels were determined by HPLC at several stages of the beer production process. During brewing, ferulic acid was released at the initial mashing phase, whereas moderate levels of 4-vinylguaiacol were formed by wort boiling. Higher levels of the phenolic flavor compound were produced during fermentations with brewery yeast strains of the Pof(+) phenotype. In beer made with barley malt, ferulic acid was mainly released during the brewing process. Conversely, 60-90% of ferulic acid in wheat or wheat malt beer was hydrolyzed during fermentation, causing higher 4-vinylguaiacol levels in these beers. As cereal enzymes are most likely inactivated during wort boiling, the additional release of ferulic acid during fermentation suggests the activity of feruloyl esterases produced by brewer's yeast.
As they are responsible for the fruity character of fermented beverages, volatile esters constitute an important group of aromatic compounds in beer. In modern high-gravity fermentations, which are performed in tall cylindroconical vessels, the beer ester balance is often sub-optimal, resulting in a clear decrease in beer quality. Despite the intensive research aimed at unravelling the precise mechanism and regulation of ester synthesis, our current knowledge remains far from complete. However, a number of factors that influence flavor-active ester production have already been described, including wort composition, wort aeration and fermentor design. A thoughtful adaptation of these parameters allows brewers to steer ester concentrations and thus to control the fruity character of their beers. This paper reviews the current knowledge of the biochemistry behind yeast ester synthesis and discusses the different factors that allow ester formation to be controlled during brewery fermentation.
In spite of the wide literature describing the biological effects of phenolic compounds, scarce data are available on their absorption from diet. In the present work, we studied the absorption in humans of phenolic acids from beer, a common beverage rich in different phenolic acids with related chemical structures. Beer was analyzed for free and total (free+bound) phenolic acids. Ferulic, caffeic and sinapic acids were present in beer mainly as bound forms, while 4-hydroxyphenylacetic acid and p-coumaric acid were present mainly as free forms. Vanillic acid was present equally in the free and bound forms. Plasma samples were collected before and 30 and 60 min after beer administration and analyzed for free and conjugated phenolic acid content. A significant two- to fourfold increase in plasma levels of phenolic acids was detected with peak concentrations at 30 min after beer ingestion. 4-Hydroxyphenylacetic acid was present in plasma mainly as nonconjugated forms while p-coumaric acid was present equally as nonconjugated and conjugated forms. Ferulic, vanillic and caffeic acids were present in plasma predominantly as conjugated forms, with a slight prevalence of sulfates with respect to glucuronates. Our results indicate that phenolic acids from beer are absorbed from the gastrointestinal tract and are present in blood after being largely metabolized to the form of glucuronide and sulfate conjugates. The extent of conjugation is related to the chemical structure of phenolic acids: the monohydroxy derivatives showing the lowest conjugation degree and the dihydroxy derivatives showing the highest one.
During brewery handling, production strains of yeast must respond to fluctuations in dissolved oxygen concentration, pH, osmolarity, ethanol concentration, nutrient supply and temperature. Fermentation performance of brewing yeast strains is dependent on their ability to adapt to these changes, particularly during batch brewery fermentation which involves the recycling (repitching) of a single yeast culture (slurry) over a number of fermentations (generations). Modern practices, such as the use of high-gravity worts and preparation of dried yeast for use as an inoculum, have increased the magnitude of the stresses to which the cell is subjected. The ability of yeast to respond effectively to these conditions is essential not only for beer production but also for maintaining the fermentation fitness of yeast for use in subsequent fermentations. During brewery handling, cells inhabit a complex environment and our understanding of stress responses under such conditions is limited. The advent of techniques capable of determining genomic and proteomic changes within the cell is likely vastly to improve our knowledge of yeast stress responses during industrial brewery handling.
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Foam, American Society of Brewing Chemists
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Review on comparative analyses of different phenolic acids content in different beers
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Throughout the brewing process barley lipid transfer protein 1 (LTP1) is transformed into a more foam-promoting form
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