A Method to Detect Anti‐metabolic Factors in Fermentations

Premature yeast flocculation (PYF) has been described as the rapid settling of yeast cells during fermentation despite the presence of sufficient nutrients. PYF can cause negative impacts on beer quality and thus can be quite costly to brewers and maltsters. To investigate the causative agent of PYF, small‐scale fermentations were undertaken in both test tubes and cuvettes (15 and 3.5 mL respectively) using worts prepared from PYF‐positive and PYF‐negative malt samples. Fermentations were carried out using six malts, for up to seven days. Turbidity and extract values were monitored for all samples. The small scale (test tube) assay exhibited clear yeast cell flocculation differences between malts. In the cuvette assay the wort fermented, but the yeast cells settled out of suspension rapidly. While this property made the cuvette assay unsuitable for detecting PYF malt, it did allow for measurement of impaired sugar uptake by the yeast independent of yeast in suspension effects. All wort samples fermented in the cuvette assay showed a similar decline in apparent extract (p > 0.05), indicating that (at least in the samples studied) premature yeast flocculation was not caused by a decline in yeast activity. We believe the simple cuvette assay reported here could have application in the measurement of anti‐metabolic factors in fermenting media.     

Screening for new brewing yeasts in the non‐Saccharomyces sector with Torulaspora delbrueckii as model

This study describes a screening system for future brewing yeasts focusing on non‐Saccharomyces yeasts. The aim was to find new yeast strains that can ferment beer wort into a respectable beer. Ten Torulaspora delbrueckii strains were put through the screening system, which included sugar utilization tests, hop resistance tests, ethanol resistance tests, polymerase chain reaction fingerprinting, propagation tests, amino acid catabolism and anabolism, phenolic off‐flavour tests and trial fermentations. Trial fermentations were analysed for extract reduction, pH drop, yeast concentration in bulk fluid and fermentation by‐products. All investigated strains were able to partly ferment wort sugars and showed high tolerance to hop compounds and ethanol. One of the investigated yeast strains fermented all the wort sugars and produced a respectable fruity flavour and a beer of average ethanol content with a high volatile flavour compound concentration. Two other strains could possibly be used for pre‐fermentation as a bio‐flavouring agent for beers that have been post‐fermented by Saccharomyces strains as a consequence of their low sugar utilization but good flavour‐forming properties. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of the fermentative potential of Candida zemplinina yeasts for craft beer fermentation

The fermentative potential of Candida zemplinina Y.01667 and Y.01670 was evaluated to explore the potential use of these yeasts for craft beer fermentations. Fermentation experiments were carried out at different temperatures and soluble solid concentrations, using synthetic media with glucose syrup as a sugar source and with a laboratory malt wort plus different adjuncts. Results showed that both strains fermented well at 14 °C and had improved fermentative activity at 20 °C. The fermentative kinetics of C. zemplinina Y.01667 and Y.01670 were not affected when experiments at higher concentrations of soluble solids were conducted. Furthermore, C. zemplinina strains had better growth, higher viable cells counts, less free amino nitrogen consumption, lower sedimentation rates and slighter changes in pH values, when compared with results of the lager beer yeast Saccharomyces cerevisiae S‐23 in the synthetic medium tested. Fermentations in a malt wort with different adjuncts indicated that C. zemplinina Y.01670 could possibly be used as a yeast in craft beer production. Copyright © 2016 The Institute of Brewing & Distilling     

Application of Plackett–Burman experimental design for investigating the effect of wort amino acids on flavour‐active compounds production during lager yeast fermentation

Aroma‐active higher alcohols and esters are produced intracellularly in the cytosol by fermenting lager yeast cells, which are of major industrial interest because they determine aroma and taste characteristics of the fermented beer. Wort amino acid composition and their utilization by yeast during brewer's wort fermentation influence both the yeast fermentation performance and the flavour profile of the finished product. To better understand the relationship between the yeast cell and wort amino acid composition, Plackett–Burman screening design was applied to measure the changes in nitrogen composition associated with yeast amino acids uptake and flavour formation during fermentation. Here, using an industrial lager brewing strain of Saccharomyces pastorianus , we investigated the effect of amino acid composition on the accumulation of higher alcohols and volatile esters. The objective of this study was to identify the significant amino acids involved in the flavour production during beer fermentation. Our results showed that even though different flavour substances were produced with different amino acid composition in the fermentation experiments, the discrepancies were not related to the total amount of amino acids in the synthetic medium. The most significant effect on higher alcohol production was exercised by the content of glutamic acid, aromatic amino acids and branch chain amino acids. Leucine, valine, glutamic acid, phenylalanine, serine and lysine were identified as important determinants for the formation of esters. The future applications of this information could drastically improve the current regime of selecting malt and adjunct or their formula with desired amino acids in wort. Copyright © 2017 The Institute of Brewing & Distilling     

THE INFLUENCE OF FREE ALPHA-AMINO NITROGEN IN SORGHUM BEER FERMENTATIONS

The interactions of wort free α-amino nitrogen (FAN) and sugar in sorghum beer fermentations were quantified and a simple equation derived. This equation describes the wort FAN demand as a function of the sugar concentration necessary to produce a fully fermented beer within 48 hours. The influence of wort FAN on sorghum beer fermentations had not been quantified so research was undertaken to define sorghum beer yeasts' requirement for wort FAN and the interactions that occur between wort FAN and sugar. Laboratory, sorghum malt and adjunct, worts mashed to cover a wide range of FAN and wort sugar concentrations, were fermented and analysed. The initial wort FAN affects the ethanol production rate, FAN uptake and sugar utilisation rates.     

The Impact of a Xanthohumol‐Enriched Hop Product on the Behavior of Xanthohumol and Isoxanthohumol in Pale and Dark Beers: A Pilot Scale Approach

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

西瓜啤酒制作工艺的研究

以西瓜汁和大麦芽为主要原料,采用啤酒独特的低温发酵工艺酿制西瓜啤酒。通过单因素试验和响应面分析试验,以感官评分为评价标准,结合理化指标研究了西瓜汁添加量、西瓜汁添加时间和原麦汁浓度对西瓜啤酒品质的影响。确定了西瓜啤酒的最佳发酵工艺条件为：西瓜汁添加量14.0%,在发酵的第4.5天添加西瓜汁,原麦汁浓度11.2°P。在此条件下,进行了400 L发酵罐的验证试验,获得了一种具有西瓜清爽口感和啤酒典型口感的西瓜果味啤酒。     

Impact of the Long‐Term Maintenance Method of Brewer's Yeast on Fermentation Course,Yeast Vitality and Beer Characteristics

The effect of the long‐term maintenance method used with a brewer's yeast on its technological properties was determined in laboratory fermentation trials with a 12°P all‐malt wort. The trials were performed at a constant temperature and under conditions of constant substrate concentration. Two cultures of a bottom fermenting yeast, Saccharomyces pastorianus RIBM 95, were tested — one culture was maintained by subculturing on wort agar slopes at 4°C and the other culture underwent a three year storage in liquid nitrogen at minus 196°C. Parameters under investigation included yeast vitality measured as acidification power (AP), fermentation time needed to reach an alcohol level of 4%, the yeast cell count, sedimentation of the yeast during the fermentation, and the production of beer flavour compounds in green beer. The yeast culture stored for three years in liquid nitrogen displayed a higher count of suspended cells, required a shorter time to attenuate the wort to produce 4% alcohol and produced a 1.5 to 2.5‐fold higher concentration of a number of flavour compounds. The long‐term storage method did not affect the sedimentation ability and vitality of the yeast strain tested.     

Brewing with 100% Oat Malt

Oats are a cereal with beneficial nutritional properties and also unrealized brewing potential. Furthermore, oats can be tolerated by the majority of people who suffer from celiac disease. Malting of oats produced a malt, which was found suitable for brewing a 100% oat malt beer. The mashing regime, designed by using mathematical modelling, was successfully transferred to a pilot scale plant. The improved lautering performance of oat malt was due to its higher husk content, which also led to a lower extract content in oat wort when compared to barley wort. The protein profile of oat wort, as measured by using Lab‐on‐a‐Chip analysis, revealed that there was no significant difference in the protein profile between oat and barley wort. The fermentation of oat and barley worts followed the same trend; differences could only be seen in the higher pH and lower alcohol content of the oat beer. The flavour analysis of oat beer revealed some special characteristics such as a strong berry flavour and a lower amount of staling compounds when forced aged. This study revealed that it was possible to brew a 100% oat malt beer and that the produced beer was comparable to a barley malt beer.     

The influence of LOX‐less barley malt on the flavour stability of wort and beer

The aim of this study was to investigate the influence of lipoxygenase‐less (LOX‐less) barley malt on the quality of wort and beer, with the main focus on beer flavour stability. In the current study, pilot‐scale (1000 L) brewing trials were conducted with a control barley malt AC Metcalfe and a LOX‐less barley malt, PolarStar. The results clearly indicated that the LOX‐less barley malt showed less nonenal potential than the control, although LOX activities in both barley malts were relatively low. The beer brewed from the LOX‐less barley malt contained much lower concentrations of trans‐2‐nonenal (T2N) and gamma‐nonalactone, especially after the (forced or natural) aging of the beer, compared with the beer brewed under the same conditions using the control malt. The sensory panel evaluation indicated similar results in the general flavour profile. The freshness scores of beer brewed from the LOX‐less malt were higher than those from the control malt, and this was more pronounced after forced aging. In addition, the beer brewed from LOX‐less malt had a much better foam stability, almost 30 s (NIBEM test). These results confirm that the use of the LOX‐less barley malt was beneficial to beer flavour stability and foam stability. Copyright © 2014 The Institute of Brewing & Distilling     

小麦麦芽在低度啤酒生产中的应用

在低度啤酒生产中，酿造时添加30％小麦麦芽，30％大麦麦芽，40％大米，采用添加复合酶补充酶活，增加可发酵糖含量，降低麦汁粘度，提高原料利用率；过滤时添加硅胶，提高啤酒非生物稳定性；酵母接种量为原料的0．6％，采用低温发酵；可减少副产物，改善啤酒风味特征；提高社会效益。     

啤酒中戊聚糖检测方法的比较

为了能够准确测定麦芽、麦汁和啤酒中的戊聚糖,通过比较地衣酚-盐酸法和间苯三酚法在测定不同样品时的精密度和回收率得出:间苯三酚测定麦芽中戊聚糖较为准确,通过测定几种麦芽,发现不同品种的麦芽之间戊聚糖存在较大的差异;麦汁不能直接采用两种方法测定,经过酵母发酵处理之后的麦汁采用地衣酚-盐酸法测定时结果较为准确;地衣酚-盐酸法测定啤酒的戊聚糖较为准确,通过测定几种啤酒,发现不同啤酒中戊聚糖存在明显差异。     

The Evolution of Dextrins During the Mashing and Fermentation of All‐malt Whisky Production

The production of malt whisky involves the mashing of barley malt, followed by the fermentation of the resulting wort without further treatment. While this process has many parallels to the production of an all‐malt beer, one of the main differentiating steps during substrate preparation is the inclusion of a boiling step for the wort in the production of beer. Other than the destructive action of the boiling process on microorganisms, the boiling also destroys all malt enzyme activity. Since a typical whisky wash is not boiled it carries through a certain proportion of microbial activity associated with the malt, but more importantly it retains some enzyme activity that has been activated during the malting and mashing processes. The changes in sugars and dextrins during both mashing and fermentation of the resulting wash were investigated. Evidence of the continuous amylolytic activity during an unboiled, all‐malt wash fermentation is shown; while no ongoing amylolytic activity could be deduced during the fermentation of a boiled all‐malt wort. Furthermore, the data suggests that the amylolytic activity during mashing and fermentation are different with regards to α‐amylase action linked to its multiple‐attack action pattern as a function of substrate conformation, temperature, and effectiveness of potential hydrolytic events.     

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     

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     

Comparison of beer quality attributes between beers brewed with 100% barley malt and 100% barley raw material

BACKGROUND: Brewing with 100% barley using the Ondea^® Pro exogenous brewing enzyme product was compared to brewing with 100% barley. The use of barley, rather than malt, in the brewing process and the consequences for selected beer quality attributes (foam formation, colloidal stability and filterability, sensory differences, protein content and composition) was considered. RESULTS: The quality attributes of barley, malt, kettle‐full‐wort, cold wort, unfiltered beer and filtered beer were assessed. A particular focus was given to monitoring changes in the barley protein composition during the brewing process and how the exogenous OndeaPro^® enzymes influenced wort protein composition. All analyses were based on standard brewing methods described in ASBC, EBC or MEBAK. To monitor the protein changes two‐dimensional polyacrylamide gel electrophoresis was used. CONCLUSION: It was shown that by brewing beer with 100% barley and an appropriate addition of exogenous Ondea^® Pro enzymes it was possible to efficiently brew beer of a satisfactory quality. The production of beers brewed with 100% barley resulted in good process efficiency (lautering and filtration) and to a final product whose sensory quality was described as light, with little body and mouthfeel, very good foam stability and similar organoleptic qualities compared to conventional malt beer. In spite of the sensory evaluation differences could still be seen in protein content and composition. Copyright © 2011 Society of Chemical Industry     

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     

Impact of Dark Specialty Malts on Extract Composition and Wort Fermentation

Dark specialty malts are important ingredients for the production of several beer styles. These malts not only impart colour, flavour and antioxidative activity to wort and beer, they also affect the course of wort fermentations and the production of flavour‐active yeast metabolites. The application of considerable levels of dark malt was found to lower the attenuation, mainly as a result of lower levels of fermentable sugars and amino acids in dark wort samples. In fact, from the darkest caramel malts and from roasted malts, practically no fermentable material can be hydrolysed by pilsner malt enzymes during mashing. Compared to wort brewed with 50% pilsner malt and 50% dark caramel malt or roasted malt, wort brewed with 100% pilsner malt contained nearly twice as much fermentable sugars and amino acids. Reduced levels of yeast nutrients also lowered the fermentation rate, ranging from 1.7°P/day for the reference pilsner wort of 9 EBC to 1.1°P/day for the darkest wort (890 EBC units), brewed with 50% roasted malt. This additionally indicates that lower attenuation values for dark wort are partially due to the inhibitory effects of Maillard compounds on yeast metabolism. The application of dark caramel or roasted malts further led to elevated levels of the vicinal diketones diacetyl and 2,3‐pentanedione. Only large levels of roasted malt gave rise to two significant diacetyl peaks during fermentation. The level of ethyl acetate in beer was inversely related to colour, whereas the level of isoamyl acetate appeared to be affected by the use of roasted malt. With large levels of this malt type, negligible isoamyl acetate was generated during fermentation.     

Effect of wheat malt on the concentration of metal ions in wort and brewhouse by‐products

The ionic composition of brewer's wort depends on the raw materials and processing employed. The macroelement content is usually sufficient for yeast, but some of the microelements (mainly zinc) often need to be supplemented to the wort. Wheat malt is used as an adjunct in the production of beer, replacing up to 60% of barley malt. In this study, the effect of replacing barley malt with wheat malt on the concentration of magnesium, manganese, iron and zinc ions in brewer's wort was investigated. The ionic content of both the raw materials and by‐products were analysed. Similar amounts of magnesium ions were found in wheat malt and barley malt, whereas, manganese, zinc and iron were more abundant in the wheat malt. Nevertheless, wheat malt did not cause a significant change in ion concentration in the first wort (except for magnesium; its content decreased). The ionic content in the spent grains increased owing to wheat malt addition; the concentration of ions in the wort decreased after wort boiling (Mn²⁺ and Fe) or remained unaffected (Mg²⁺ and Zn²⁺). It was concluded that the ionic composition of the wort depends mainly on the removal rate of ions from the wort during mash filtration and hot trub separation, rather than on the actual amount of ions in the raw materials. Copyright © 2015 The Institute of Brewing & Distilling     

Exploration of high‐gravity fermentation to improve lactic acid bacteria performance and consumer's acceptance of malt wort‐fermented beverages

Lactic acid bacteria (LAB) fermentation performance is essential for aroma metabolites formation and product flavour quality. Hence, this study appraises high‐gravity malt wort fermentation (HGF) by three LAB strains to improve the fermentation performance and consumer's acceptance of lactic acid‐fermented malt‐based beverages (LAFMB). HGF at 20% (w/w) provided higher amino acid content and buffering capacity that allowed greater cell development, viable cell count and sugar utilisation. Moreover, the pH change was lesser although marked lactic acid accumulation. It is noteworthy that HGF significantly incremented the content of higher alcohols (+0 – 161%), 2‐phenylethanol (+11–147%), acetaldehyde (+27–44%) and β‐damascenone (+25 – 66%) comparing to low‐gravity malt wort at 12%. Thus, HG‐fermented beverages were significantly preferred with greater hedonic scores (4.6 ± 2.1). Our results indicate that HGF is a valuable strategy for improving LAB fermentation performance in malt wort, which in turn increases key aroma compound content resulting in enhanced acceptance of LAFMB.