EBC Units Research Articles

Assessment of source material for malting barley breeding

Background. The objective of the research was to identify promising genotypes of malting barley in the source material developed at Omsk Agricultural Scientific Center.Material and methods. The studies were carried out from 2017 to 2020. in the southern forest-steppe of Western Siberia. The target material included 13 lines: Sasha × Getman (2 lines), Sasha × Margret, Podarok Sibiri × Getman (3 lines), Omsky 95 × Beatrice (3 lines), Omsky 95 × Despina, Omsky 95 × Viva, Omsky 100 × Margret, and Omsky 90 × Margret. Biochemical assessment of grain quality for brewing qualities was carried out jointly with Nemchinovka Federal Research Center according to GOST 5060-86 (Bаrley for brewing. Specifications).Results and discussion. The most promising were the lines demonstrating increased yield (5.39–6.21 t/ha) and reduced mass fraction of protein (11.39–11.92%): Sasha × Getman (1), Sasha × Getman (2), Omsky 90 × Margret, Omsky 95 × Beatrice (2), Omsky 95 × Beatrice (3), and Omsky 95 × Despina. Besides, these lines had a set of the following brewing characteristics: grain evenness (98.7–99.95); grain filminess (9.3–9.9%), 1000 grain weight (55.6–57.0 g), grain extractivity (78.1 and 78.9%), mass fraction of starch (55,35–56.83%), color (0.15–0.30 EBC units), and malt vitreousness (0.0–3.0%).Conclusion., The lines Sasha × Getman (1) and (2), Omsky 90 × Margret, Omsky 95 × Beatrice (2) and (3), Omsky 95 × Despina are recommended for further research.

Assessment of Staling Aldehydes in Lager Beer under Maritime Transport and Storage Conditions.

Beer flavor stability is greatly influenced by external temperature, vibrations, and longer delivery times. The present study assessed the impact of transport and storage conditions on staling aldehyde evolution in lager beers across five sample groups (fresh, transport, and storage simulation, and their controls), which differed in their bottle opening system (either crown cap or ring pull cap). Maritime transport conditions (45 days of travel, vibrations of 1.7 Hz, and warm temperatures (21–30 °C)) were simulated, together with storage time in a distributor’s warehouse (up to 75 days). The results revealed that the concentration of Strecker aldehydes increased more quickly after transport and storage simulation in beer bottles with the ring pull cap opening system, and the contents of 2-methylpropanal and 3-methylbutanal, in particular, were up to three times higher. Benzaldehyde content also increased significantly, by 33% on average, in these samples. Hexanal was only found in beers with a ring pull cap that underwent transport simulation. Further storage after transport simulation significantly reduced the content of 2-methylpropanal, 3-methylbutanal, and hexanal, by 73%, 57%, and 43%, respectively, suggesting the formation of a bound state. 5-hydroxymethylfurfural was continuously increased by 78.5% and 40.5% after the Transport and Transport & Storage simulations, respectively. Transport conditions lead to a slight increase, of 0.6 EBC units, in beer color.

Covalent Protein-Polyphenol Bonding as Initial Steps of Haze Formation in Beer

Beer subjected to forced aging by five (Medium) or ten (High) heat/chill cycles (60 °C 48 h/0 °C 24 h) showed increased turbidity from 5.4 ± 0.4 EBC units without forced aging to 12.9 ± 0.7 and 48 ± 2 EBC units for Medium and High forced aged beers, respectively. The particle size diameter increased from 100–200 nm to 10–30 µm. The colloidal changes were associated with modifications of the low molecular weight fraction (∼1 kDa), which were found to increase in the soluble part of the beer as identified by size exclusion chromatography. Polyphenol analyses by liquid chromatography and mass spectrometry showed significant losses of gallic acid, hydroxyphenyllactic acid, salicylic acid, chlorogenic acid, vanillic acid, epicatechin, pyrocatechuic acid, ferulic acid, and luteolin during the forced aging, indicating that these phenolic compounds took part in the colloidal changes, proposedly upon polymerization into tannins. Gel electrophoresis coupled with staining by nitroblue tetrazolium indicated polyphenol modification of all proteins and especially LTP1 (lipid transfer protein 1). It is proposed that the di- and tri-hydroxyl phenolic compounds upon oxidation to quinones react with protein nucleophiles of especially LTP1 to generate the initial covalent bonds, which eventually leads to larger insoluble permanent haze particles.

Screening of durum wheat landraces (Triticum turgidum subsp. durum) for the malting suitability

Durum (T. turgidum subsp. durum) wheat production worldwide is substantially less than that of common wheat (Triticum aestivum) mainly due to the relatively limited end-users. In order to evaluate malting and brewing suitability, sixteen old durum wheat landraces were malted at micro scale. Results show malt quality parameters in the range 78.2–85.9% for the extract, 72.9–80.9% for the fermentability, 3–5 EBC units for the colour, 0.49–0.79% dm for water-extractable arabinoxylans and 0.043–0.059% dm for the β-glucans. Regarding wort viscosity (1.53–1.92 mPa s), we found negative correlation with endo-1,4-β-D-xylanase, positive correlation with endo-β-glucanases and soluble proteins, while no correlations were found with arabinoxylan and betaglucan wort content. These results showed that some durum wheats, such as Trentino, Martinella, Gioia, Inglesa, Francesa, Giustalisa and Bidì have suitable characteristics for malting and brewing. The improvement of the malting process is required for the other durum wheats.

Effect of crossflow microfiltration on the clarification and stability of beer from 100% low-β-glucan barley or malt

The clarifying effect of crossflow microfiltration (CFMF) on two types of lager beers made of 100% low β-glucan barley (LBGB), as such using the commercial Ondea®Pro enzyme preparation or pre-malted, was assessed and compared to that obtained using a commercial Pils Malt beer. All rough beers resulted to be quite similar with some differences in viscosity, color, and β-glucan, arabinoxylan, and polyphenol contents. The use of malted LBGB grains gave rise to a beer with low β-glucan (13 ± 4 mg/L) and arabinoxylan (568 ± 40 mg/L) concentrations, but high and stable colloidal turbidity (43.9 ± 0.2 EBC unit), with a consequent reduction in both permeation flux [23 ± 2 L/(m2 h)] and clarified beer quality. The best results in terms of filterability and permeated beer quality were obtained using 100% LBGB beer. Despite its high β-glucan (233 ± 4 mg/L) and arabinoxylan (917 ± 39 mg/L) contents, the limiting permeation flux approached 147 ± 24 L/(m2 h), about three times higher than obtained with the conventional all malted beer. The commercial Ondea®Pro enzyme preparation and CFMF clarification of the resulting rough beer might represent a valid option to produce a 100% barley beer, even if the raw materials used are not well suited for malting.

Beer Clarification by Novel Ceramic Hollow-Fiber Membranes: Effect of Pore Size on Product Quality.

In this work, the crossflow microfiltration performance of rough beer samples was assessed using ceramic hollow-fiber (HF) membrane modules with a nominal pore size ranging from 0.2 to 1.4 μm. Under constant operating conditions (that is, transmembrane pressure difference, TMP = 2.35 bar; feed superficial velocity, vS = 2.5 m/s; temperature, T = 10°C), quite small steady-state permeation fluxes (J* ) of 32 or 37 L/m2 /h were achieved using the 0.2- or 0.5-μm symmetric membrane modules. Both permeates exhibited turbidity <1 EBC unit, but a significant reduction in density, viscosity, color, extract, and foam half-life with respect to their corresponding retentates. The 0.8-μm asymmetric membrane module might be selected, its corresponding permeate having quite a good turbidity and medium reduction in the aforementioned beer quality parameters. Moreover, it exhibited J* values of the same order of magnitude of those claimed for the polyethersulfone HF membrane modules currently commercialized. The 1.4-μm asymmetric membrane module yielded quite a high steady-state permeation flux (196 ± 38 L/m2 /h), and a minimum decline in permeate quality parameters, except for the high levels of turbidity at room temperature and chill haze. In the circumstances, such a membrane module might be regarded as a real valid alternative to conventional powder filters on condition that the resulting permeate were submitted to a final finishing step using 0.45- or 0.65-μm microbially rated membrane cartridges prior to aseptic bottling. A novel combined beer clarification process was thus outlined.

Dextrin as the main turbidity components in wort produced from major malting barley cultivars of Jiangsu province in China

As wort is the sweet starter liquid for beer, its quality needs to be strictly controlled. It is generally accepted that wort turbidity is of importance in terms of the brewing process and the resulting beer quality. This study investigated the major ingredients of wort turbidity using the malting barley cultivar Dan'er, grown in Jiangsu province, China. It was found that dextrins of low molecular weight constituted the vast majority of the polysaccharides causing wort turbidity. To solve the turbidity problem with the Dan'er malt, the present study supplemented 80 U g−1 of β-amylase, and as an activator, an extra 50 mg L−1 of Ca2+ to the malting process of Dan'er barley. The turbidity of the resulting congress wort of the Dan'er malt declined to <5.0 EBC units, which then met the quality guidelines of the brewery. The results of the present study may also help in developing new turbidity detection methods and yield breeding clues for quality improvement of the barley cultivars in the Jiangsu province of China. Copyright © 2016 The Institute of Brewing & Distilling

Development of oats syrup technology

Interest in the cultivation and using of naked oats has increased significantly in recent years in the most of countries. This is due to dietary and curative properties of the grain and its derived products such as syrups. Technological stages of syrup production are germinating of cereal, preparation of wort and its concentration. The article reviews an issue concerning the impact of wort concentration temperature on the physico-chemical indicators of syrup, as well as, considers an experimental data on the content of dietary fiber and vitamins in syrups, and illustrates carbohydrate content of end-products. It is found that with increasing of wort concentration temperature from 40 ° C to 70 ° C the time of the process reduces 3.7 times, and further it leads to lessening of the reducing substances from 53.9% to 45.7% and increases the colour of syrup from 61.7 EBC units to 68.5 EBC units. For obtaining of optimal physicochemical parameters of syrup and ensuring a minimum time of concentration recommended temperature of the process is 60 ° C. It is shown that the syrup produced from commercial malt contains 2.2 times more pentosans compared to the syrup produced from Vyatsky oat. In turn, syrup from Vyatsky oat contains 2.5 times more β-glucan - the most important physico-chemical component in a viewpoint of nutrition. The carbohydrate composition of syrups permits to recommend them for using in functional products as well as high content of dietary fiber and vitamins gives a perspective of their application in the food industry.

Novel cold sterilization and stabilization process applied to a pale lager

In this work, the crossflow microfiltration (CFMF) performance of different lots of a rough pale lager, produced in the industrial brewery Birra Peroni Srl (Rome, Italy), was assessed in a bench-top plant, equipped with a 0.8-μm ceramic tubular membrane module, under constant crossflow velocity (6ms−1), transmembrane pressure difference (3.74bar), temperature (10°C), and periodic CO2 backflushing. The average permeation flux increased from (86±8) to (252±21) Lm−2h−1, provided that the rough beer was fed as such or pre-centrifuged to minimize the fouling contribution of yeast cells and aggregates, respectively. In both cases, the permeate turbidity at 20°C fulfilled that recommended by the European Brewery Convention standards; but, as expected, the chill haze at 0°C was quite higher than 0.6 EBC unit. A preliminary stabilization of pre-centrifuged beer using 0.5gL−1 of regenerable polyvinylpolypyrrolidone (PVPP) at 0°C for 24h allowed the permeate chill haze to be reduced to (0.63±0.22) EBC unit; but the average permeation flux fell to (161±21)Lm−2h−1. By removing the residual PVPP particles from stabilized beer using a 2.7-μm filter before CFMF, it was possible not only to re-enhance the average permeation flux up to 337Lm−2h−1 (this value being in line with those achievable with conventional DE-filters), but also to obtain a chill haze-free permeate ready for aseptically packaging.By referring to an industrial plant capacity of 2×106hL of lager beer, the estimated overall operating costs and global warming potential for this novel combined pale lager clarification and PVPP stabilization procedure reduced to about the 30% of those associated with the current industrial DE-filtration and regenerable PVPP stabilization procedures.

The phenomenon of Czech beer: a review

The character and authenticity of the Czech beer, which has been accorded the protected geographical indication (PGI) Česk&amp;eacute; pivo by the EU, are based on specific technology and use of unique raw materials. A number of chemical and sensorial markers of the Czech beer differ from those of other lager or Pils-type beers. The majority of Czech beers contain residual (unfermented) extract. One of the most typical characteristics of Czech beers is the difference in attenuation; its long-term recorded limit value is 4.5%. Another important characteristic typical of the Czech beer is bitterness, which is mostly higher in comparison with other lagers, with the limit value at 29 EBC units. Also the colour, pH, and total polyphenol content are higher in the Czech-type beer. The limit parameters obtained by long-term monitoring were 11.8&amp;nbsp;EBC, 4.52 and 153 mg/l, respectively. Differences in amino acid and protein profiles and contents were also observed.

Novel Procedure for Lager Beer Clarification and Stabilization Using Sequential Enzymatic, Centrifugal, Regenerable PVPP and Crossflow Microfiltration Processing

In this work, the crossflow microfiltration (CFMF) performance of different lots of lager beer, produced in a pilot scale at the Italian Brewing Research Centre (CERB, Perugia, Italy), was assessed in a bench-top plant, equipped with a 0.8-μm ceramic tubular membrane module, under constant crossflow velocity of 6 m s−1, transmembrane pressure difference of 3.74 bar, temperature of ~10 °C, and periodic CO2 backflushing. By feeding different beer samples (i.e., as such, precentrifuged (C), or pretreated with a commercial enzyme preparation to degrade the original arabinoxylans and β-glucans and then centrifuged (EC) to minimize the fouling contribution of yeast cells, aggregates, and polysaccharides), it was possible to increase the average permeation flux (expressed as mean value ± standard deviation) from 112 ± 13 to 199 ± 17 or 330 ± 22 L m−2 h−1, respectively. Only when using the EC-pretreated beer specimens, the permeate turbidity at 20 °C approached the limiting one (<0.6 EBC unit) recommended by the European Brewery Convention standards. As expected, the permeate chill haze at 0 °C was generally higher than the above haze target. By submitting EC-pretreated beer seeded with 0.5 g L−1 of regenerable polyvinylpolypyrrolidone (PVPP) to CFMF, it was possible to reduce the initial total polyphenol content by 30 % and permeate chill haze to 0.60 ± 0.01 EBC unit, but the average permeation flux fell to 84 ± 4 L m−2 h−1. By performing sequentially EC pretreatments, PVPP stabilization, cartridge filtration, and CFMF, it was possible not only to re-enhance the average permeation flux at about 230 L m−2 h−1 near to those achievable with DE filters, but also to obtain a chill haze-free permeate ready for aseptic packaging.

Effect of teff (Eragrostis tef) variety and storage on malt quality attributes

Varieties of a cereal may have a considerable influence on malting qualities owing to variations in the physicochemical properties of the grains. This research was aimed at assessing the influence of five teff varieties on malt quality attributes. The teff samples were malted using previously optimized malting conditions and mashed with the congress mashing procedure. In this research, the Kuncho teff variety was malted in a one year period after harvesting, whereas the other four varieties were malted after three years of storage. Alpha- and β-amylase, and limit dextrinase activity, were in the ranges 14–68, 10–440 and 375–1072 U/kg, respectively. Extracts ranged from 54% for Dessie to 74% for Ivory teff. Free amino nitrogen, protein content, soluble nitrogen, Kolbach index, viscosity and wort colour were in the ranges 160–364 mg/L, 8.6–13.6%, 532–1048 mg/100 g, 24–50%, 1.441–1.629 mPa s and 5.9–9.0 EBC units, respectively. High-performance liquid chromatographic analysis for individual fermentable sugars revealed that the highest value in all varieties was recorded for glucose followed by maltose. The concentration of glucose ranged from 9.49 g/L in Brown teff, to 19.42 g/L in Ivory teff, whereas maltose ranged from 2.95 g/L in Dessie teff to 16.1 g/L in Kuncho teff. All of the malt quality attributes considered in this study were markedly influenced (p < 0.05) by the type of teff cultivar. It was concluded that the use of different teff varieties yielded malts with significantly different malt quality attributes. Copyright © 2013 The Institute of Brewing & Distilling

Physico-Chemical Characterization of Brew during the Brewing Corn Malt in the Production of Maize Beer in Congo

The study consists in the production of a traditional beer from maize in the Congo. The traditional method of brewing corn malt has three main stages: malting corn, brewing corn malt and fermentation. During the brewing corn malt, endogenous amylase activity is destroyed during the stiffening of the starch to about 80°C. A pre-cooking of the mash is necessitated to promote amylolyse at 50°C with an exogenous enzyme. The use of a preparation of α- amylase can liquefy the mash and produce a sweet wort (average density = 12.5° Balling) rich in dextrin corresponding to an apparent extract of 4° Balling in beer. The rising profile of the pH of the corn malt mash, from mashing to extract the wort does not affect the pH of the beer produced. This beer, slightly alcoholic (3.6% ethanol), is characterized by a nomal acid pH (pH = 4.15 on average) and a brown color (25 EBC units). Its slight bitterness (21 EBU) and the fine aroma of a beer closer barley produced industrially in the Congo.

Physicochemical characterization of starches from some Nigerian and Chinese roots and tubers

Chemical changes during germination and malting characteristics of six Nepalese finger millet varieties (GPU 0025, GE 5016, Dalle, Okhle, Kabre and Juwain) were studied. Millets were steeped in water at room temperature overnight, germinated for 48 h at 28±1°C, kilned at 50±2°C for 24 h and then, chemical characteristics of unmalted and malted millets were analyzed. Germination increased (p<0.05) total reducing sugar and glucose contents in all millet varieties. Starch, amylose and amylopectin contents in unmalted millets were between 71.32 to 79.86, 20.39 to 24.13, and 49.11 to 55.72% dry basis (db) respectively; whereas, those of malted millets were 63.74 to 67.12, 16.62 to 19.27 and 44.47 to 50.18% (db) respectively. Similarly, total phenolics (as gallic acid), total flavonoids (as rutin) and tannin (as tannic acid) contents in unmalted millets ranged from 60.9 to 229.2, 35.2 to 141.7 and 169.9 to 566.0 mg% (db) respectively; whereas, the values in malted millets were 123.1 to 247.8, 50.1 to 236.3 and 173.7 to 301.8 mg% (db) respectively. Except in GE 5016 and Juwainmillets, malting decreased (p<0.05) antioxidant activity in other varieties. Malt extract analysis revealed that all malt extracts possessed aromatic odor and showed negative starch-iodine test. Filtration rate of Juwain malt extract was slow but it was normal in other extracts. The color (EBC unit), free amino nitrogen (FAN) (mg% as glycine) and total reducing sugar (% m/v as maltose) contents in extracts were 2.77 to 5.78, 2.6 to 9.0 and 4.50 to 6.93, respectively. Glucose (%, m/v) and extract yield of malt (%, db) ranged from 1.22 to 2.51 and 80.20 to 88.83, respectively. Total soluble solids (TSS) (o Bx), pH, extract (%, m/m), FAN (mg% m/v) and total reducing sugar (% m/m as maltose) in worts derived from Dalle, Kabre and Juwain millet malts were in the range of 12.43 to 13.07, 5.44 to 5.66, 12.0 to 12.7, 19.5 to 20.3 and 7.64 to 10.45, respectively. Key words: Millet malt, amylose, polyphenols, free amino nitrogen (FAN), antioxidant activity, malt extract, wort.

유색보리의 제맥 및 양조 특성

유색보리를 맥주의 원료로 이용하기 위하여 맥아 및 양조 특성을 검정한 결과를 요약하면 다음과 같다. 1. 자색 겉보리, 자색 쌀보리 및 청색 쌀보리의 안토시아닌은 침맥 20시간 후 약 30%, 22% 및 80%가 잔존하였다. 2. 일반적인 제맥 조건으로 제조된 자색보리 맥아는 안토시아닌 성분이 거의 소실되었으나 청색보리는 58% 정도 잔존하였다. 3. 흑색보리는 일반적인 제맥 및 당화 조건에서 색소성분이 손실되지 않았으며, 맥즙의 색도는 종피색의 농담이 아니라 가용성 질소 함량이 많아짐에 따라 진해지는 경향을 나타내었다. 4. 자색과 청색보리 맥아로 제조된 맥주에는 안토시아닌 성분이 존재하지 않았으나, 호품보리 맥아로 만든 맥주보다 색도가 높았다. This study was carried out to investigate the suitability of colored barley in malting and brewing properties and the possibility of utilizing pigments in colored barley as functional components in malting and brewing products. Purple and blue barley grains contained anthocyanins. However, about 80% and 20% of anthocyanins in the purple and blue barley grains, respectively, were lost during the steeping process. In malts, only 0.4~4.2% and 58.3% of anthocyanin in purple and blue barley grains, respectively, were remained. Wort color value was not affected by lemma color of black barley. In wort made from black barley, the color value was higher as its soluble nitrogen content higher. Anthocyanins were not found in wort and beer brewed from malts of purple and blue barley. The color value (EBC unit) was higher in wort and beer made from malts of purple and blue barley than those made from malt of the control variety, Hopum.

Effect of milling softness on basic technological parameters of wort

Crushing the malted grain in the process of milling enables extractive substances of malt to become available for water which accelerates dissolving and other chemical and physical processes during the time of mashing. The aim of this work was at the basis of performed analyses to evaluate to what extent the grist composition with regard to different proportion of meal fraction affects the amount of extract and other technological parameters of malt. Analyzed malt was made from four varieties of malting barley as are Nitran, Ebson, Malz and Xanadu coming from the harvest year 2009. Composition of malt grist in great extent influenced the entire process of mashing, lautering and the amount of extract. The highest values of extract were measured by all varieties at the variant III. with the highest content (50%) of the softest fraction meal + powder meal. The difference between variant I. with 10% content of the softest fraction and variant III. with 50% content, was already 3%. The most significant increase of this parameter was found out by varieties Ebson and Malz. Mashing and lautering parameters have not been significantly influenced by the milling variants. More significant differences were found out with regard to wort turbidity. Only variety Malz showed out the turbidity up to 4 EBC units, measured by turbidity meter under the angle 90°. The highest turbidity was measured by variant I. with the lowest proportion of the fraction meal + powder meal.

Comparison of hazes in freshly bottled and aged beers by multiple angle turbidimetry

The hazes of freshly bottled and aged pale lager beers determined with the 12° and 90° dual angle laboratory hazemeters and 10° to 90° range photogoniometer were compared and evaluated. The instruments were standardised in EBC formazin units. In freshly bottled beer, the forward (12°–25°) haze values were smaller approximately by a factor of three than the nephelometric (90°) values which yielded 0.33 EBC units. In aged beer, the forward haze was greater than the nephelometric one. Whereas the aged beer showed the greatest and the fresh beer the lowest intensity of scattered light, the formazin suspension intensity was in between. Due to the standardisation of the beer scattered intensities by relation to that of formazin, the standardised nephelometric haze in non-aged beer was greater than the forward haze, and vice versa in aged beer. The greater forward than the nephelometric haze in aged beer was caused by the growth of haze particles above the mean size of formazin particles which was larger than 2 &amp;mu;m as confirmed by the particle size distribution measurement.

Identification of Biological Wort Turbidity Caused by Microbial Contamination of Gairdner Barley

This study investigated the wort turbidity caused by microbial contamination of barley. One microbial strain isolated from Gairdner barley increased wort turbidity up to 31.9% and prolonged wort filtration time 2.67 times longer than that of the control experiment. Using morphological observation and 26S rDNA sequence alignment, the strain was identified as Aspergillus flavus. From the strain, a remarkable wort turbidity-inducing protein (WTIP) was isolated by gel-exclusion chromatography (Sephadex G-25) and purified by ion-exchange chromatography (DEAE-52 cellulose). Purified WTIP enabled wort turbidity to increase 39% (in EBC units) with the addition of 0.2 mg/L; the relative molecular weight was estimated at 80 kDa using SDS-PAGE analysis.

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.

Laboratory-Scale Production of High-Gravity Wort Suitable for a Broad Variety of Research Applications

A laboratory-scale high-gravity wort production protocol was developed. Currently, wort production and consequently, much of brewing research, is confined to breweries and specialized research institutions that possess the specialized brewhouse equipment needed to produce wort. A wort production protocol was designed around the nonspecialized equipment found in a typical bioprocess-engineering laboratory. Malted barley was ground in a hammer mill to produce a grist suitable for a mash tun vessel. Mashing and filtration were performed in a stirred, temperature-controlled fermentation vessel fitted with a simple mesh filter. A mash with a liquor/grist ratio of 3.3:1 produced a wort with a specific gravity of at least 22.74°P with an extraction efficiency of 89.7% in less than 335 min. Furthermore, the wort was shown to be fermentable, having a 73% attenuation limit when fermented with Saccharomyces cerevisiae NCYC 1338. The worts produced contained high levels (303 mg/L) of free amino nitrogen, had an average pH of 5.01, a color of 33.85 EBC units, and bitterness of 19.7 BU. This protocol can be used for almost any research application, including the comparative study of fermentations on the basis of all-malt wort, high-gravity malt wort and high-gravity adjunct wort. Furthermore, the protocol will enable researchers outside of the brewing industry to bring their specialized skills to brewing research.