Brewing with 100% green malt – process development and key quality indicators

Brewing with undried, germinated (green) malt has the potential to lower energy and water usage in the malting and brewing chain. However, doing so introduces technical and biochemical (flavour) challenges. Beers were brewed using 100% green malt (n = 3) or kilned pilsner malt (n = 3), prepared from the same batch in each case, utilising the pilot brewery at KU Leuven (2.5 hL). Three further pairs of beers were brewed whereby the green malt was pre-steeped under deaerated water for 1 hour; this procedure was previously shown to lower LOX activity in green malt. Six green malt beers were brewed with acceptable specifications in terms of pH, alcohol content, foam stability and colour. No significant taints or obvious defects were detected in green malt beers. Increased S-methyl methionine levels were measured in worts and beers made from green malt, however DMS concentrations in the finished beers did not differ significantly from the reference beers. Furthermore, the results demonstrated promising indicators for flavour stability, such as reduced TBI, lower residual FAN and trihydroxy fatty acid (THFA) levels in brews using untreated green malt. Using re-steep water in green malt brewing (for reasons of water economy), however, increased THFA levels, possibly because oxygen uptake was not adequately controlled at this step. Whilst further process optimisations are undoubtedly required, it is shown that an acceptable lager style beer could be brewed to a specification not dissimilar to that of a kilned malt control beer, using 100% green malt with intact rootlets. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling     

CONTROL OF FERULIC ACID AND 4-VINYL GUAIACOL IN BREWING

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. Pof^δ). 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.     

Biological acidification and beer quality: addition of lactic acid bacteria isolated from malt

Two lactic acid bacteria, Pediococcus acidilactici HW01 and Leuconostoc citreum isolated from Pilsner malt, were added during mashing and the impact on fermentation examined. The pH of lactic acid bacteria supplemented (bioacidified) wort and finished beer were lower than that of the control. Bioacidified worts resulted in higher levels of free amino nitrogen, reducing sugars and alcohol in the corresponding beers. Foam stability of beers from P. acidilactici and L. citreum worts were increased by 19% and 26%, respectively. The filtration time was reduced in P. acidilactici treated beers but increased with L. citreum. The use of P. acidilactici and L. citreum as bioacidification agents resulted in beers with higher sensory quality. © 2020 The Institute of Brewing & Distilling     

以黑小麦为辅料酿造啤酒的初步研究

以黑小麦为辅料进行啤酒酿造研究,并与使用大米作为辅料和全麦酿造的啤酒进行对照,结果显示以黑小麦为辅料制得的麦汁可溶性氮含量高、多酚含量明显下降,并且其成品啤酒泡持性好,酯香突出,所以选用黑小麦为啤酒辅料具有良好的应用前景。     

Volatile compounds isolated from rice beers brewed with three medicinal plants

The volatile compounds and physicochemical properties of rice beers brewed with three medicinal plants, namely Acanthopanax senticosus (Siberian ginseng), Scutellaria baicalensis (baikal skullcap) and Cornus officinalis (Japanese cornel) were analysed. The rice beers were produced and fermented from unhulled ground rice, malt, and medicinal plant extracts. The medicinal plant extracts, used at 5 and 10 % (v/v) were blended with wort before fermentation. Compared with a draft beer fermented without rice, the rice beers had lower levels of pH, acidity, amino acid content and reducing sugars. Of the rice beers, the beer with the addition of 10% Japanese cornel had the highest colour value and foam stability. The volatile compounds of the rice beers were extracted using a solvent‐assisted flavour evaporation apparatus and analysed by gas chromatography–mass spectrometry. The rice beer with 10% Siberian ginseng showed the most diverse volatile profile, in that 54 kinds of volatile compounds were detected. The rice beer with 10% Japanese cornel had the highest relative amount of volatile chemicals of all of the rice beers. Lactones such as γ‐hexalactone, γ‐nonalactone and γ‐decalactone were detected in all of the rice beers. Copyright © 2013 The Institute of Brewing & Distilling     

Corn grist adjunct – application and influence on the brewing process and beer quality

In the brewing industry, barley malt is often partially replaced with adjuncts (unmalted barley, wheat, rice, sorghum and corn in different forms). It is crucial, however, to preserve constant quality in the beer to meet the expectations of consumers. In this work, how the addition of corn grist (10 and 20%) influences the quality of wort and beer was examined. The following parameters were analysed: wort colour, dimethyl sulphide (DMS) and protein content, non‐fermentable extract, extract drop during fermentation, alcohol content and the attenuation level of the beer, together with filtration performance. The samples (all‐malt, and adjunct at 10 and 20% corn grist) were industrial worts and the beers produced in a commercial brewery (3000 hL fermentation tanks). The application of 10 and 20% corn grist had an effect on the wort colour, making it slightly lighter (11.1 and 10.5°EBC, respectively) than the reference barley malt wort (12.2°EBC). The free amino nitrogen level, DMS and non‐fermentable extract were significantly lower in the worts produced with the adjunct; the alcohol content and attenuation levels were higher in the beers produced with adjunct. The use of corn grist, at the level of up to 20% of total load, appears to affect some of the technological aspects of wort and beer production, but it does not significantly influence the final product characteristics. Copyright © 2014 The Institute of Brewing & Distilling     

MALTING CHARACTERISTICS OF FINGER MILLET,SORGHUM AND BARLEY*

The malting characteristics of the finger millet variety Imele (FI), sorghum varieties Andivo (SA) and Ingumba (SI) and the barley variety Research (BR) were compared in relation to the brewing of traditional African opaque beer as well as conventional lager beer. The investigations include (a) the effect of steeping and germination conditions, (b) the influence of gibberellic acid and kilning temperature on the activity of important brewing enzymes and (c) an appraisal of the brewing potential of the worts obtained. FI, SA and SI malts were considered unsuitable as barley malt extenders for conventional lager beers, but FI and possibly SI malts would be suitable for tropical lager beer manufacture.     

The Role of Malt and Hop Polyphenols in Beer Quality,Flavour and Haze Stability

Pilot‐scale brewing trials of a 12°P pale lager beer were conducted to look at the effect of a modified dose of hop and malt polyphenols on haze, flavour quality, and stability. Results confirmed that malt polyphenols, and particularly hop polyphenols, in the course of wort boiling, improved reducing activity values and the carbonyl content in fresh and stored beers. Hop polyphenols significantly increased reducing activity and decreased the formation of carbonyls (TBA value) in fresh and stored beer. Reduced content of malt polyphenols, combined with the use of hop CO₂ extract, caused an increase in the TBA value in beer. PVPP stabilized beers tended to be lower in reducing activity. Both malt and hop polyphenols affected the intensity of “harsh taste” in fresh beers and a significant influence from PVPP stabilization of beer was not observed. The staling degree of forced‐aged beers depended on the polyphenol content in the brewhouse. Both hop and malt polyphenols had a positive impact on flavour stability. PVPP treatment of beer had a positive effect on the flavour stability of heat‐aged beers. Polyphenols, especially hop polyphenols, slowed down flavour deterioration during the nine month storage period, but the primary effect was seen during the first four months of storage. Storage trials did not show any unambiguous effects for PVPP stabilization on beer flavour stability. Results confirmed the negative impact of malt and hop polyphenols on haze stability, and PVPP stabilization minimized differences in shelf life prediction values between beers prepared with the modified dose of polyphenols.     

Chemical characterization and antioxidant capacity in blue corn (Zea mays L.) malt beers

Corn has been widely used in traditionally fermented Mexican beverages. We recently developed a process to prepare beers using 100% pigmented corn varieties that provide polyphenols and anthocyanins with antioxidant properties. Moreover, new styles could be created when modifying the process conditions and ingredients. Thus, we explored the effect of caramel malt addition and different amounts of hops and guajillo chili, generating several styles of blue corn malt beers (BCMB). The objective was to evaluate these effects on selected chemical parameters and antioxidant properties at three different stages of the brewing process. To achieve this, base and caramel malts were obtained and used to develop eight styles of BCMB, using different concentrations of chili and hops, using an ale fermentation process. Eleven chemical properties were determined in the wort, green and mature beer of the eight styles of BCMB. Low‐alcohol beers were obtained and the values of total reducing sugars, alcohol, pH, total acidity, bitterness units and iso‐α ‐acids during the stages of the process were similar to barley beers. Additionally, anthocyanin concentration, polyphenols and antioxidant capacity decreased through the process stages. The interaction of the ingredients produced effects on the chemical composition and antioxidant activity in mature beers. After statistical analysis, by both univariate ANOVA and multivariate methods (hierarchical cluster analysis and principal component analysis), a higher concentration of anthocyanins and ABTS antioxidant capacity was founds in two beer styles that were formulated with 85% base malt and 15% caramel malt. Copyright © 2017 The Institute of Brewing & Distilling     

The influence of unmalted barley on the oxidative stability of wort and beer

The aim of this study was to investigate the influences of unmalted barley on the brewing process and the quality of the resulting beer‐like beverages, with the main focus on the oxidative stability, using traditional beer analyses, GC‐MS for the determination of aging compounds and electron paramagnetic resonance spectroscopy to determine free radical activity. For the investigation, brews with different barley proportions and 75% barley brews with a colour malt addition, to compensate for a lower colour using barley, were produced. In general, it can be said that beers with a proportion of up to 50% barley achieved a comparable or higher extract yield and final attenuation owing to the combined effectiveness of the malt and microbial enzymes. Although all analytical values were within the normal range according to Methodensammlung der Mitteleuropäischen Brautechnischen Analysenkommission (MEBAK), a slight decrease in total polyphenols and free amino nitrogen content was observed. Also in response to higher barley portions, an increase of higher molecular weight proteins and β‐glucan was detected. Barley is not exposed to heat and oxidative stress in the malting plant, which explains the lower values of the thiobarbituric acid index and colour as an indicator of Maillard reaction products in the resulting wort and beer. Additionally, the results demonstrate a slower increase of aging compounds during beer storage with increasing barley proportions. Furthermore, it was observed that higher barley proportions led to a better oxidative stability indicated by a lower radical generation (T₄₅₀‐value) in wort and an increasing beverage antioxidant index/endogenous antioxidative potential (BAX/EAP value) in the final beverage. The case of ‘barley beers’ showed that the positive effect of barley on the oxidative beer stability was greater than the negative effect of the addition of colour malt, to adjust the colour of a 100% malt beer. In sensory comparison with beer produced with 100% malt, the beers brewed with a barley proportion up to 50% showed a slight flavour preference and up to a 75% equivalent evaluation. Copyright © 2012 The Institute of Brewing & Distilling     

125th Anniversary Review: The science of the tropical cereals sorghum,maize and rice in relation to lager beer brewing

Mainstream lager beer brewing using the tropical cereals sorghum, maize and rice, either as malt or as raw grain plus commercial enzymes, is becoming widespread. This review examines the differences in composition between these tropical cereals and barley and their impact on brewing processes and beer quality. All of these cereals have a starch gelatinization temperature some 10 °C higher than barley. The sorghum prolamin proteins are particularly resistant to proteolysis owing to disulphide cross‐linking involving γ‐kafirin. Unlike barley, the major endosperm cell wall components in sorghum and maize are arabinoxylans, which persist during malting. The rice cell walls also seem to contain pectic substances. Notably, certain sorghum varieties, the tannin‐type sorghums, contain considerable levels of condensed tannins (proanthocyanidins), which can substantially inhibit amylases, and probably also other brewing enzymes. Tropical cereal malts exhibit a similar complement of enzymic activities to barley malt, with the notable exception of β‐amylase, which is much lower and essentially is absent in their raw grain. Concerning beer flavour, it is probable that condensed tannins, where present in sorghum, could contribute to bitterness and astringency. The compound 2‐acetyl‐1‐pyrroline, responsible for the popcorn aroma of maize and also the major aroma compound in rice, presumably affects beer flavour. However, much more research is needed into tropical cereals and beer flavour. Other future directions should include improving hydrolysis of prolamins into free amino nitrogen, possibly using prolyl carboxypeptidases and investigating tropical cereal lines with useful novel traits such as high amylopectin, high protein digestibility and low phytate. Copyright © 2013 The Institute of Brewing & Distilling     

THE USE OF EXTRUDED BARLEY,WHEAT AND MAIZE AS ADJUNCTS IN MASHING

The principles of extrusion cooking are summarised. In small scale trials good extracts were obtained from extruded barley when it was mashed with industrial enzymes, using a programmed temperature cycle. Extruded barley, wheat and maize and wheat flour yielded acceptable levels of extract when mashed with lager malt (70%) using a programme with 1 hour rests at 50°C and 65°C. The extracts obtained from these grists were increased above those obtained from grists of lager malt alone and the viscosities of the worts were reduced when the mashes were supplemented by preparations of bacterial enzymes. Enzyme additions also improved extract recoveries from all-malt mashes and reduced the viscosities of the derived worts. Using a temperature programmed mashing cycle and supplementary enzymes beers were prepared from a lager malt grist and grists in which the lager malt was partly replaced, by 30%, with extruded barley or extruded wheat, or extruded maize or wheat flour pellets. In every case wort was recovered relatively easily, the worts fermented normally and the beers were all fully acceptable, although their flavours did differ. However, in contrast to results of preliminary brewing trials, the head retentions of the beers made with adjuncts were unusually low, possibly because of particular enzyme additions.     

Differences in protein content and foaming properties of cloudy beers based on wheat malt content

To investigate differences in protein content, all barley malt beer, wheat/barley malt beer and all wheat malt beer were brewed, and the protein during mashing, wort, fermentation and beer determined. It was shown that protein was mainly extracted during mashing and the protein rest phase, decreased in the early stages of fermentation and remained almost steady during wort boiling and cooling, in the middle and late stages of fermentation. By separating beer foam from beer, similar protein bands of 51.7, 40.0, 27.3, 14.8, 6.5 and < 6.5 kDa appeared in the three beers, defoamed beers and beer foams using the sodium dodecyl sulphate polyacrylamide gel electrophoresis. Quantitatively, protein bands of 6.5–14.8 and <6.5 kDa had the highest contents in the three beers. Unique bands at 34, 29.2, 23.0, 19.7 and 17.7 kDa were found in beer, defoamed beer and beer foam from wheat beer and all‐wheat malt beer, respectively. Wheat beer foam showed the best foam stability and the protein in all barley malt beer showed the best migration to the foam. The beer foam properties were influenced by not only protein content but also protein characteristics and/or origin. It is suggested that the barley malt contributed the beer foam ‘skeleton protein’ while protein components from wheat malt kept the foam stable. © 2018 The Institute of Brewing & Distilling     

Determination of Prolamins in Beers by ELISA and SDS‐PAGE

Coeliac disease is triggered by exposure to the prolamin protein fraction of wheat, barley, or rye. The prolamin content of five lager beers and one wheat beer were analyzed by sodium dodecyl sulfate—polyacrylamide gel electrophoresis (SDS‐PAGE) and immunoblotting and seven lager beers and three wheat beers were analyzed by enzyme‐linked immunosorbent assay (ELISA). Most of the lager beers were made from barley and some had varying amounts of rice or corn as adjuncts. One of the beers was “gluten‐free”, having been produced from corn and buckwheat without barley. The lager beer samples were gel‐filtered before ELISA or SDS‐PAGE analysis. Prolamin proteins were found in all but one beer which was made of corn, rice and barley and which was not the “gluten‐free” beer. ELISA analysis was done using a commercially available gluten assay kit. For lager beers, a barley prolamin standard for ELISA was propanol‐extracted from barley malt instead of using the prolamin standard of the gluten assay kit. As expected, the wheat beers contained much higher amounts of prolamins than the lager beers. The samples were studied by SDS‐PAGE to identify different prolamin fractions. Proteins having a relative molecular mass in the range of 8000–17,000 and 38,000 and above were detected in immunoblotting by the prolamin sensitive antibody in the lager beers.     

原麦汁浓度与发酵度对低浓啤酒风味的影响

将啤酒酵母(S.uvarum)BY-2分别接入6.0、6.5、7.0、7.5、8.0°P麦汁中,10℃发酵。酒液澄清后进行理化指标分析和感官品评。啤酒发酵度高于70%时,随着原麦汁浓度的降低,啤酒的香气和滋味依次变得淡薄。根据原麦汁浓度的高低,分别选取4个发酵度水平进行发酵实验:6.0°P啤酒的发酵度分别控制在50%、56%、60%、70%左右;6.5、7.0、7.5、8.0°P啤酒的发酵度分别控制在55%、60%、65%、70%左右。感官品评表明:酿造6.0°P、6.5°P、7.0°P、7.5°P、8.0°P啤酒时,发酵度分别为50.6%、61.8%、59.45、59.1%、65.5%时风味最佳。     

Assessment of endogenous antioxidative compounds and antioxidant activities of lager beers

BACKGROUND: Flavour stability is increasingly becoming the limiting factor in the shelf life of beer. Increasing the antioxidant activity of beer itself could suppress the rate of oxidative reaction and improve the flavour stability of beer. This report describes the levels of phenolic compounds, melanoidins and sulfur dioxide, and antioxidant activities of 40 lager beers. The relationships between antioxidative compounds and antioxidant activity were elucidated by multivariate analysis techniques. RESULTS: The results showed that the total phenolic content and the melanoidins content correlated well (P < 0.05) with antioxidant activity, while there was no significant correlation (P > 0.05) between total sulfur dioxide content and antioxidant activity. Satisfactory discrimination among beer samples with significantly different antioxidant activity was achieved by principal component analysis. Results from stepwise linear regression further demonstrated that different antioxidative components responsible for antioxidant activity were dependent on the assay used. The phenolic compound group is by far the most antioxidative compounds in beer and total phenolic content, melanoidins and sulfur dioxide together made a 22–68% contribution to the antioxidant activities of beers. CONCLUSION: Therefore, it might be an efficient means for brewers to increase total phenolic content during brewing for improvement in flavour stability of the final beer. © 2012 Society of Chemical Industry     

New approach to the production of xanthohumol‐enriched beers

Xanthohumol is a hop polyphenol with proven positive effects on human health. The aim of this work was to use special malts (roasted malt and melanoidin malt) for the preparation of high‐gravity sweet worts with an extremely high xanthohumol content. The solubility of xanthohumol was higher in sweet worts prepared from roasted malts than from Pilsen or melanoidin malts. This sweet wort (xanthohumol ~20 mg L^?1) was used for the preparation of xanthohumol‐rich beer. The importance of melanoidins in xanthohumol solubility was also examined. Isomerization reactions occurring at increased temperatures is one of the main reasons for the loss of xanthohumol in the brewing process and therefore the most appropriate temperature for addition of xanthohumol products to sweet worts was determined. The influence of filtration and stabilization materials (diatomaceous earth, polyamide sorbents and tannic acid) on the concentration of xanthohumol in enriched beer was also examined. Only a small effect of these materials was shown in xanthohumol‐rich dark beers, with the exception of tannic acid, which removed a significant amount of this polyphenol. Copyright © 2013 The Institute of Brewing & Distilling.     

Suitability of unmalted quinoa for beer production

BACKGROUND

This study provides the first detailed investigation into the effect of partially substituting barley malt with quinoa (Chenopodium quinoa Willd.) on the characteristics of wort and beer. Quinoa seeds and flakes were compared in terms of their suitability for brewing. The benefits of applying a commercial enzyme mixture during beer production with quinoa were also investigated.

RESULTS

These findings show that quinoa is a good starchy raw material for brewing. Even without exogenous enzymes, it is possible to substitute barley malt with up to 30% quinoa. The form in which quinoa is used has a negligible influence on the quality of the wort and beer. The foam stability of beer made with quinoa was better than that of all‐malt beer, despite there being a lower level of soluble nitrogen in quinoa beer in comparison with all‐malt beer and more than twice the amount of fat in quinoa in comparison to barley malt.

CONCLUSION

The addition of unmalted quinoa does not give unpleasant characteristics to the beer and was even found to have a positive effect on its overall sensory quality. This offers brewers an opportunity to develop good beers with new sensory characteristics. © 2018 Society of Chemical Industry     

The Influence of Hopping on Formation of Carbonyl Compounds During Storage of Beer

Improving beer flavour stability is an important brewing goal. Pilot scale brewing trials (50 L) were performed that focused on the determination of the influence of hop pellet dosage and dosage timing on carbonyl compounds in stored beer. The reducing activity of experimental worts, beers and stored beers appeared to depend on the hop pellet dose. Brews with lower amounts of hop antioxidants showed an enhanced formation of carbonyl compounds over the course of beer storage. A correlation between DPPH reducing activity and the content of some carbonyls, including the important markers 2‐furfural and (E)‐2‐nonenal, was found. Fresh and aged beers hopped by different amounts of hop pellet doses were clearly distinguishable according to their carbonyl content using Cluster analysis. Results of the sensorial analysis corresponded to the analytical criteria values. Results of this study bring further evidence of the indispensable impact of hop antioxidants on the suppression of undesirable carbonyl compound formation in the course of beer staling, which can be significant in beers hopped by aroma hops. However, hop antioxidants are only one of many factors affecting beer staling.     

Brewing Beer with Sorghum

Research reports on extracts, proteins, total nitrogen and free amino nitrogen content of sorghum malt and worts obtained from mashes indicate that sorghum is potentially an alternative substrate for conventional beer brewing in the tropics. Remarkable variations in biochemical characteristics among different sorghum cultivars affect their optimal malting conditions. Factors such as temperature and time of steeping and germinating of grains with their intrinsic enzymic activities, and kilning temperature determine the quality of malt. Further works on mashing, viscosity and fermentability of worts as well as the character of the resulting beers, such as alcoholic content, colour, taste and specific gravity tend to confirm the status of sorghum as a credible substitute for barley in beer brewing. This review reports on progress made in the use of sorghum for brewing beer.