Journal of the American Society of Brewing Chemists

J. Am. Soc. Brew. Chem. Vol.48 Nr.3, 92 - 95 An automated turbidometric technique was tested for rapid detection of contaminants in pitching yeast. The turbidometer detects changes in optical density caused by microbial growth in a liquid medium. Pitching yeast samples were contaminated with three different cell concentrations of Lactobacillus casei subsp. casei, Pediococcus damnosus, Enterobacter agglomerans, Pectinatus cerevisiiphilus, and Saccharomyces cerevisiae (ex diastaticus). Detection times for the contaminants were calculated from the growth curves obtained with the turbidometer. Enrichment of contaminated yeast samples in broth and plating on selective agars were used as reference methods. The results obtained with the turbidometer were in most cases available one day before the appearance of visual turbidity. The time saved with the turbidometer compared with selective agars was from two to four days depending on the contaminating organism. The detection time was dependent more on the specific growth rate of the test organism than on its initial concentration. The detection limit of the turbidometer was 106 cfu/ml and the initial contamination level detected was 100 cfu/ml of yeast slurry.
Alternatives to traditional methods of estimating the potential malting quality of barley lines were examined through their application to two regional barley nurseries, with the goal of identifying streamlined procedures suitable for making initial assessments of malting quality. Mashing malt using an isothermal hot water extract (HWE) procedure instead of the standard Congress mash generated distinct but closely related values for primary measures of malt modification, including malt extract, wort soluble protein, soluble/total malt protein, wort beta-glucan, and wort free amino nitrogen. Simple measurements of other wort properties, including refractive index and wort osmolyte concentration, also showed strong correlations between Congress and HWE worts. Analyses of small-scale (microcentrifuge tube) versions of isothermal HWE worts showed good correlations with the attributes of Congress worts. Although the key malting quality metrics for Congress and HWE worts were not equivalent, their close correlations suggest that they may be equally able to differentiate the malting quality of barley lines. The simple isothermal temperature profile of the HWE wort, in conjunction with implementation of methods that use simple laboratory instrumentation for wort analysis, could simplify initial malting quality analysis and make it more accessible to laboratories lacking dedicated mashing and wort analysis instruments.
In the current collaborative work, barley samples covering several crop years in Canada were investigated for germinative capacity during storage. The first set of samples was sent to China for storage under typical local conditions while the control samples were stored at 5°C in Canada. Subsamples were taken from the material stored in China at intervals during the summer season and returned to Canada for analysis. Germination and α-amylase tests were carried out on the control and stored samples. Some samples that appeared to be acceptable at harvest were found to suffer germination losses as much as 70% during the process. In addition, commercial pearling tests and a rapid paper test used to detect preharvest sprout damage in wheat were carried out on the control samples. Correlation of the results with α-amylase values and the germination change after storage was studied. Samples that showed deterioration during storage were also subjected to examination using magnetic resonance imaging and near-infrared hyperspectral imaging (NIHI). The majority of nongerminating kernels exhibited a sharp interface between the endosperm and embryo in the ratio images produced by NIHI. Differences in the kernel images between the samples of different germinative capacity were apparent. The presence of the endosperm/embryo interface in the absorbance ratio image is therefore likely to correlate with a kernel's inability to germinate. The observation provides significant insights into the understanding and prevention of loss in germinative capacity in storage and handling of malting barley.
Journal of the American Society of Brewing Chemists Vol.43 Nr.1 , 43 - 46
During brewery fermentations, individual yeast cells may be confronted with a variety of environmental stresses that impair yeast growth and fermentative metabolism. An understanding of the stress physiology of industrial yeasts is therefore important in order to counteract deleterious effects of stress on fermentation and, ultimately, product quality. The present study describes the influence of magnesium ions in preventing cell death caused by temperature shock and ethanol toxicity in Saccharomyces cerevisiae yeast strains employed in brewing, distilling, and wine fermentations. Results obtained show that, by increasing the extracellular availability of magnesium ions, physiological protection may be conferred on temperature- and ethanol-stressed yeast cells with respect to culture viability and growth. This practical approach is envisaged to offer benefits to alcoholic fermentation processes in terms of enhancing the viability of the yeasts employed. It is proposed that magnesium prevents stress-induced damage to yeast cells by protecting the structural and functional integrity of the plasma membrane.
The metal cations K(^+), Mg(^2+), Ca(^2+), and Zn(^2+) are known to directly influence fermentative metabolism in yeast, and therefore knowledge of their interactions is essential to manipulate their availability in industrial fermentations to optimal levels. Defined media experimental fermentations were designed to mimic high, intermediate, and low levels of K(^+), Mg(^2+), and Ca(^2+) previously reported in sugarcane molasses and Mg(^2+), Ca(^2+), and Zn(^2+) previously reported in malt wort. Subsequent analysis of fermentations revealed that the yeast (distillers strain of Saccharomyces cerevisiae) produced higher levels of ethanol in the presence of higher levels of Mg(^2+) in synthetic molasses and malt wort. Analysis of variance showed that yeast fermentation performance depended on complex interactions among the metal cations studied. For simulated molasses fermentations with fixed levels of Mg(^2+), ethanol production varied with changing levels of Ca(^2+) and K(^+) in a predictable way that was well fitted by the quadratic response surface model. Maximum predicted ethanol yields found from the quadratic response surface model were generally confirmed by authentic molasses fermentations. In simulated malt wort fermentations with fixed levels of Zn(^2+), ethanol production varied in a predictable way with changing levels of Ca(^2+) and Mg(^2+). However, quadratic response surface model predictions of ethanol yield failed to match results obtained from authentic malt wort fermentations, indicating significant effects of extraneous factors in wort. Although the results from defined media experiments suggest that statistical modeling could prove a useful tool in predicting yeast fermentation performance, further analysis is required of the influence of other components in industrial fermentation media, such as brewers' wort.
Upon beer storage, the levels of staling aldehydes increase, which coincides with the appearance of characteristic off-flavors. Bound-state aldehydes have been reported as potential sources of off-flavor appearance in aging beer. This study investigated the stability of cysteinylated aldehydes, also referred to as 2-substituted 1,3-thiazolidine-4-carboxylic acids, and the release of aldehyde compounds from cysteine adducts in model solutions at different pH values that are relevant in malting and brewing. The cysteinylated aldehydes were initially synthesized for their use as reference compounds in model solutions. Confirmation of their chemical structure was obtained by ¹H-NMR. The results from the stability tests showed that degradation of cysteine-bound aldehydes results in concomitant release of the free aldehydes. The rate of degradation is highly dependent on the 2-substitution pattern of the thiazolidine ring, as well as on the pH of the model solution. At malting and brewing relevant pH values (pH 4.4, 5.2, 6.0), degradation of cysteine-bound aldehydes is observed, in particular at pH 4.4, which is representative of the beer pH.
This study evaluates the influence of biological mash and wort acidification using a thermophilic proteolytic/amylolytic active Lactobacillus amylovorus on brews containing 20% (wt/wt) unmalted barley in laboratory-scale trials as well as 10-hL pilot-scale brews. The biologically acidified mash was compared with a chemically acidified mash, 100% malt mash unacidified, and 80% malt (wt/wt)/20% (wt/wt) barley unacidified mash. Characteristics such as pH. extract, color, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), apparent fermentability, β-glucan, sugar, and amino acid profiles of the resultant worts were determined. In the pilot-scale brews, foam stability, accelerated shelf life, and sensory evaluation of the beer was determined. It was clearly shown that biological acidification (BA) could compensate for a lower enzymatic activity level of grists containing 20% (wt/wt) barley. Increased levels of extract, fermentability, TSN, and FAN were observed in the laboratory-mash trials along with a sharp decrease in β-glucan levels when BA was applied. Cast-out wort showed a considerable increase in nitrogenous fractions. Viscosity was decreased by acidification of mashes but did not correlate with β-glucan levels. The final biologically acidified beer showed a lighter color, improved foam stability, and a more well-rounded taste with increased shelf life in comparison with the chemically and the nonacidified beer.
In brewing research, non-Saccharomyces yeasts have gained attention in recent years, owing to their potential to influence the characteristics and flavor of beer. The Lachancea genus possesses an uncommon trait, the production of significant amounts of lactic acid during alcoholic fermentation. This trait could potentially be harnessed for brewing purposes, particularly for the production of low alcohol beer. In this study, the potential of Lachancea fermentati strain KBI 12.1 was investigated for the production of low alcohol beer in low gravity wort. KBI 12.1 was characterized for sugar utilization, hop sensitivity, phenolic off-flavor (POF) production, and propagation performance. Lab scale fermentation trials in diluted wort (6.6°P) were conducted and compared to a brewers’ yeast, Saccharomyces cerevisiae WLP001. Fermentations were monitored for lactic acid and ethanol production, pH drop, and sugar consumption. In the final beers, amino acid and free amino nitrogen (FAN) content were determined and secondary metabolites were quantified. Lachancea fermentati KBI 12.1 showed to be unable to utilize maltotriose. The strain exhibited no POF production, minor hop sensitivity, and excellent propagation performance. Amino acid and FAN consumption were much lower compared to that of the brewers’ yeast. In the final beer fermented with KBI 12.1, the lactic acid concentration reached 1.3 g/L, giving the beer a sour taste. During sensory analysis, the beer was additionally described to have a fruity character. In conclusion, Lachancea fermentati KBI 12.1 proved to be a suitable strain for brewing purposes, with promising traits with regard to nonalcoholic and low alcohol beer brewing.
Development of a simple, accurate, and rapid method for identifying malting barley cultivars is important for the malting, brewing, and seedprocessing industries. Recently reported methods that have been developed for using DNA to 'fingerprint' barley utilize DNA that is extracted from leaf tissue. For this study, we used the polymerase chain reactionrandom amplified polymorphic DNA (PCR-RAPD) technique with a selected set of 10-mer primers and DNA that was extracted from mature imbibed embryos. We were able to differentiate 16 malting barley cultivars or breeding lines that are commonly grown in North America, including the two-rowed cultivars Crystal, Garnet, Galena, Harrington, and B1202 and the six-rowed cultivars Robust, Stander, Morex, Excel, Lacey, Foster, Drummond, Russell, 88Ab536-B, B2601, and B2978. This method is simple to use and can be accomplished in 12-16 hr, since it bypasses the time-consuming germination and seedling growth steps. PCR results using embryo DNA samples are comparable to those obtained with leaf tissue DNA. The rapid and simple procedure that we have developed can be adapted by industry to maintain cultivar purity and to check the integrity of purchased seed lots.
A polymerase chain reaction (PCR) method for the detection of Pectinatus cerevisiiphilus and P. frisingensis was developed. The 16S rRNA gene (rDNA) and the spacer regions between the 16S rDNA and the 23S rDNA genes were used for the PCR reaction. The species-specific sequences in the spacer region between the 16S rDNA and the 23S rDNA genes were selected for use as PCR primers. The method developed in this study was rapid and sensitive. Furthermore, this method allowed identification at the species level, even between very closely related species, such as P. cerevisiiphilus and P. frisingensis.
Described in the article is the territorial distribution of the area of cultivated hops and hop production by the countries of the world, including the development and the grounds for their distribution. In the monitored period, the world area of cultivated hops decreased significantly, by more than a quarter. However, world hop production has grown little due to a substantial increase in hop yields. The area of cultivated hops and hop production are currently highly concentrated in the nine main hop producing countries. Roughly two thirds of the current area and three quarters of current production worldwide is attributable to the USA and Germany. Production increased in New Zealand, the USA, and to a lesser extent in Germany and Poland, while Australia, Czechia, Slovenia and especially China and the United Kingdom reduced production. Hop growing is very important for the agriculture of Germany, Czechia, and in particular Slovenia. These countries have the highest values of monitored hop indicators per capita, including hop export. The development of hop production in the coming years will depend on the introduction of new high-yielding hop varieties and enlargement or reduction of the area of cultivated hops in connection with hop price changes, profitability of hop growing and demand of breweries.
A new gas chromatography/mass selective detector method for determination of diacetyl and 2,3-pentanedione was developed. Diacetyl and 2,3-pentanedione were derivatized with 1,2-diaminobenzene to form 2,3-dimethylquinoxaline and 2-ethyl-3-methylquinoxaline, respectively. The amounts of formed 2,3-dimethylquinoxaline and 2-ethyl-3-methylquinoxaline were proportional to the diacetyl and 2,3-pentanedione concentrations present in the sample. 2,3-Dimethylquinoxaline and 2-ethyl-3-methylquinoxaline were extracted using solid-phase extraction (SPE) columns and determined by gas chromatography using a mass selective detector. Extraction by SPE columns proved to be very rapid, simple, and precise. This method was applied for the determination of diacetyl and 2,3-pentanedione concentrations during beer fermentation (primary fermentation and maturation). During fermentation, diacetyl and 2,3-pentanedione were quantified to demonstrate the suitability of the method. Primary fermentations were carried out at different temperatures (8 and 14°C) and an industrial bottom-fermented yeast strain was used. Corn grits, beside malt, were used for wort production. The level of corn grits varied from 10-40%. Diacetyl and 2,3-pentanedione formation and reduction were strongly influenced by temperature and the rates for both increased with an increase in primary fermentation temperature. The highest diacetyl and 2,3-pentanedione concentrations (0.6365 mg/L and 0.8192 mg/L, respectively) were obtained during fermentation with 40% corn grits at 14°C.
The objective of this research was to compare pearling with other techniques for the assessment of preharvest sprouting (PHS). The 2002 Midwestern crop provided a unique opportunity to evaluate PHS methodology because a large amount of sprouted samples from a limited varietal and geographic base were available. Approximately 30% of the samples collected in Minnesota and northern districts of North Dakota were sprouted. All samples (N = 285) were evaluated by pearling and stirring number (SN), while smaller subsets were utilized for the other methodology. Falling number and SN were most sensitive for the detection of low levels of PHS. Pearling and staining with fluorescein dibutyrate were less sensitive to low levels of PHS. The measure of conductivity was found not strongly related to other measures of PHS. Samples were stored at ∼20°C for up to 11 months following harvest. A decline in the germinative energy (GE) of some samples was observed and, in general, this was most severe for sprouted samples. While significant correlations were observed between GE and measures of PHS, in no case was a correlation of a magnitude where a measure of preharvest sprouting alone could be used to predict seed storability with an acceptable degree of accuracy.
In this collaborative BCOJ study, the Alcolyzer method, after removing yeast by centrifugation, was found to be applicable to the analysis of alcohol concentration in pitching yeast slurries and yeast containing samples during fermentation. This method has been adopted for inclusion in the Methods of Analysis of the BCOJ, as the differences between the average alcohol concentrations measured by the Alcolyzer method and the distillation method were as small as 0.01 to 0.04% (v/v) and considered comparable. This method has been admitted as a reasonable and accurate method for the analysis of alcohol concentration in yeast-containing beer samples by the National Tax Agency Japan.
Southern blot analysis with beer-spoilage Lactobacillus lindneri DSM 20690T showed the presence of the homologue of horA, a hop-resistance gene originally identified in L. brevis ABBC45. The horA homologue found in L. lindneri DSM 20690T was carried by a plasmid designated pRH20690. This plasmid is similar in size to pRH45, a plasmid harboring horA gene in L. brevis ABBC45. The full sequencing analysis of pRH20690 revealed that this 13.0-kb plasmid is remarkably similar in the organization of the open reading frames (ORFs) to that of pRH45. The putative replication origin regions and the ORFs encoding a putative rep gene were found to be 99.0 and 100.0% identical, respectively, between the two beer-spoilage strains, indicating that these two plasmids share the same origin. It was further shown that the 6.9-kb DNA portions of the plasmids containing six putative ORFs are 99.4% identical in nucleotide sequence, suggesting that the hop-resistant Lactobacillus strains acquired horA by plasmid-mediated horizontal gene transfer. This hypothesis potentially provides brewers with a theoretical basis for applying transspecies genetic markers, such as horA, to complement the traditional species-specific approaches.
Simple and sensitive methods for the simultaneous analysis of pesticides in malt and beer were developed using liquid chromatography with tandem mass spectrometry (LC/MS/MS). The extraction from malt carried out with acetonitrile/water was followed by liquid-liquid extraction with ethyl acetate and was purified in a solid-phase cartridge. The extraction from beer was carried out with ethyl acetate and purified in the same solid-phase cartridge. The LC separation was performed with an octadecylated silica column (5 μm, 2.1 × 150 mm) with a flow rate of 0.2 mL/min using a mobile phase consisting of water and methanol including ammonium acetate. MS/MS was used in multiple reaction monitoring, employing electrospray ionization. Recovery of the 277 pesticides was between 79.5 and 120.3% from malt and between 45.0 and 114.4% from beer spiked at 0.02 mg/kg. The method was applied to the analysis of 10 malt samples. Twelve chemicals were detected, and all samples complied with the maximum residue limits for barley in Japan. This method may have applications in quality assurance.
A rapid and sensitive, indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) method has been developed to measure aflatoxin B1 (AFB 1) in corn, rice, and barley using a heavy-chain IgG 2b isotype monoclonal antibody (MAb). One MAb was isolated and characterized after fusion of myeloma cells with spleen cells isolated from BALB/c mice that had been immunized with AFB1 carboxymethyl oxime conjugated with bovine serum albumin. The antibody was IgG 2b with a λ light chain. The cross-reactivities of the anti-AFB1 MAb clone were 1.0% against aflatoxin M I and <1.0% against aflatoxin B2, aflatoxin G1, and deoxynivalenol. The limit of detection for AFB1 was 0.001 ng/mL, and the AFB1 concentration required for 50% inhibition of binding was 0.01 ng/mL. The linear range for the developed IC-ELISA was 0.001―10.0 ng of AFB1 per mL. Assays of cereal extract samples mixed with AFB1 ranging in concentration from 0.1 to 10 ng/mL resulted in a mean ELISA recovery of 93.7%. In total, 53 samples of corn, rice, and barley were collected from farms in northeastern China. The concentration of AFB1 in all samples collected was <1 ng/g. The average AFB1 contamination rates were 66% in corn, 42% in rice, and 58% in barley. The results indicate that necessary precautions will have to be taken to minimize AFB1 contamination in corn, rice, and barley.
Limit dextrinase extracted from three sorghum cultivar malts (Safrari, S.35, and Madjeru) used for the production of bili-bili, a traditional beer in the northern part of Cameroon, was subjected to comparison using dextrin as a substrate. A four-factor Doehlert experimental design was used to build a model in order to optimize the impact of factors (temperature, pH, buffer concentration, and incubation time) involved in the extraction of free limit dextrinase from sorghum. The response surface methodology revealed that the action of those factors was different for each sorghum cultivar, with closer behavior between Safrari and S.35. Madjeru was revealed to be completely different. Optimizing the concerted actions of the factors for limit dextrinase specific activity gave the following combinations: For Safrari, 43°C, pH 4, 135 mM, and 300 min, with maximal specific activity of 3.10 U/μg; for Madjeru, 35°C, pH 5.77, 50 mM, and 60 min, with maximal specific activity of 1.51 U/μg; and for S.35, 50°C, pH 4, 191 mM, and 205 min, with maximal specific activity of 3.05 U/μg.
Mosaic (brand HBC 369) is a new flavor hop variety having unique and highly favored flavor characteristics. Mosaic was developed and released by the Hop Breeding Company LLC (HBC) and is protected by a U.S. plant patent ("Hop Plant Named 'HBC 369'"). Mosaic's maternal parent, YCR 14 (Simcoe), is a commercial cultivar with a unique aroma but with relatively low yield and susceptibility to powdery mildew. YCR 14 was crossed to a male plant with powdery mildew resistance and high yield in its genetic background, with the ultimate goal of creating a commercial cultivar with unique aromatic/flavoring characteristics, resistance to powdery mildew, and good yield. HBC 369 (Mosaic) was selected from this cross on that basis. Mosaic has a unique aroma combined with high α-acid content, powdery mildew tolerance, and exceptional yield. To date, flavor testing of beer brewed with Mosaic, both at pilot and commercial scale, has brought about an enthusiastic response from brewers and tasters, and the future of this new hop variety looks promising. The aroma/flavor descriptors used commonly include fruity (blueberry), citrus (tangerine, grapefruit), tropical (mango, guava), floral, and earthy. The combination of these aroma/flavor descriptors with the relatively high α-acid levels allows this hop to serve a dual purpose, as both a bittering and flavor/aroma hop in the brewing process. Ultimately, Mosaic provides flavor and aroma profiles in beer that cannot be accomplished with other hop cultivars.
1 BIOGRAPHICAL REVIEW 3 Enzymes, Egg White and Eccentrics 4 Memories from 37 years of research in the brewing industry 6 Charles W. Bamforth, 1 Department of Food Science and Technology, University of California, Davis, CA 8 1 Corresponding author. E-mail:; phone: +1-530-752-9476; fax: +1-530-752-
This study investigates the effects of lactic acid bacteria (LAB) added concomitantly to barley infected with fungal spores or mycelia of Fusarium culmorum TMW 4.0754. The trials were performed in a micromalting plant simulating an industrial malting program. Malt samples were compared with those of nonacidified barley, disinfected nonacidified barley, chemically acidified barley, and barley with additional modified DeMan-Rogosa-Sharpe 4 medium. All control samples had fungal spores and fungal mycelia added. Bacterial cultures were chosen as a result of their enzymatic (proteolytic/amylolytic) activity level or their good acidification properties. The effects of the LAB and Fusarium-infected malts on wort characteristics were investigated. Characteristics such as pH, extract, color, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), apparent fermentability, and lautering performance of the resultant worts were determined. Results showed that spores of F. culmorum TMW 4.0754 do not affect the quality of malt or wort. The quality of wort was reduced when mycelia of F. culmorum were applied in the presence of LAB or chemical lactic acid leading to slower filtration rates, lower extract, fermentability, TSN, and FAN yields along with higher viscosity levels. These effects seemed to depend mainly on the presence of mycelia together with the content of lactic acid present.
A key biochemical process in brewing is the hydrolysis of starch by diastatic power (DP) enzymes into fermentable sugars during the mashing stage of brewing. Efficient starch hydrolysis during mashing requires initially starch gelatinization at approximately 59–64°C and then sufficient DP enzyme activity to achieve starch hydrolysis. This investigation compared the persistence of DP enzyme activity during modified Institute of Brewing (MIoB, 1:3 grist/water ratio + Ca²⁺) mash with the conventional Congress (1:4 grist/water ratio) small-scale mash, using malt from three current Australian barley varieties. Traditionally, with the thermostability of DP enzymes, it is understood that a-amylase is relatively thermostable, whereas ß-amylase and limit dextrinase (LD) are relatively thermolabile at conventional mashing temperatures. In addition, it is also known that ß-amylase and in particular LD have bound and latent fractions that require release from binding proteins or inhibitors, respectively, before they are able to contribute to starch hydrolysis. One mechanism observed empirically was that heat applied during mashing at temperatures of approximately 55–60°C appears to liberate bound ß-amylase and LD. The results in terms of DP enzyme release, thermostability, and activity were examined to understand the relative contributions of the three key DP enzymes to starch hydrolysis during different mashing conditions. Interestingly, we observed that both ß-amylase and LD retained significant levels of activity (approximately 40% total activity), even after mashing for 60 min at 65°C. These observations are of critical importance to brewers in meeting beer quality specifications when they manipulate mash temperatures to cope with variations in malt quality, developing new products, or producing beers requiring different wort qualities for production. The implications from these results of the choice of small-scale mash protocol for malt quality evaluation, the targeting of DP enzyme alleles for barley malt quality improvement, and the selection of malt for brewing are discussed.
fan levels (left) and wort gravity (right) (mean ± standard deviation) of the different samples (c: congress mash, f: final 65 °c mash, P: pregelatinization and e: addition of exogenous enzymes).
Wort was prepared according to the Congress mash protocol with the addition of 40% unmalted barley, tritordeum, or quinoa. Mashes with quinoa filtered significantly slower than mashes with barley. In contrast, tritordeum filtered similarly as barley, even though tritordeum does not possess a husk. The lack of husk may have contributed to a higher extract yield of tritordeum compared to barley. The final 65 °C mash protocol resulted in shorter saccharification times, but slower wort filtration compared to the Congress mash protocol. When unmalted adjuncts were pregelatinized by heating in water for 20 min at 95 °C, the filtration following the Congress mash protocol was slower and the filtration following the final 65 °C mash protocol was faster than the same mashes prepared without pregelatinization. Pregelatinization also inactivated the endogenous enzymes in the (pseudo)cereals used. This was especially noticeable for quinoa, resulting in wort with markedly lower glucose concentrations, most likely due to the inactivation of endogenous amyloglucosidases. Wort filtration improved for both mashing protocols when an exogenous enzyme mix (Brewers Compass®) was added to each of the three different (pseudo)cereals. Furthermore, addition of the enzyme mix increased the extract yield of the final 65 °C mashes and the FAN levels of the Congress mashes. These findings confirmed the benefit of using the Brewers Compass® enzyme mix during mashing processes with high percentages of (up to 40%) unmalted (pseudo)cereals.
Summary of key malt quality parameters. a. malt protein, key starch and cell wall degrading enzymes, B. DP and mash dependant malt quality parameters.
correlation matrix (linear regression) of malt parameters potentially linking lautering and wort/beer filtration efficiency (six rgt Planet samples were excluded, and one Scope sample was excluded as shown and described for figure S1).
Summary of step-wise multiple linear regression analysis for Swift.
correlation matrix (linear regression) of malt parameters potentially linked to fermentability (aal) and DP.
A largely defined series of hydrolytic enzymes active during malting and/or mashing, substantially determine the quality, profitability, and efficiency of the brewing process. These enzymes potentially hydrolyze starch, proteins and cell wall non-starch polysaccharides including β-glucan and arabinoxylan. Commercial malts (94) were assayed for the DP enzymes (limit dextrinase, beta/α-amylase), and NSP hydrolyzing enzymes (β-glucanase, xylanase, arabinofuranosidase, β-glucosidase). The levels of enzyme activity were related to conventional measures of malt quality such as extract, fermentability, protein, KI, DP, friability, wort viscosity, FAN, and β-glucan. These parameters were interrelated with less conventional measures of malt quality including coarse extract and fermentability (modified infusion mash 65 °C), lautering efficiency, the Small-scale Wort ‘I’ Filtration Test (SWIFT), and viscosity. Substantial variation was observed between the malt samples for all enzymes assayed. Australian barley, whether malted in Australia (n = 61) or China (n = 24), was observed to be of comparable quality. A limited set of Canadian barley samples (n = 9) were malted in China and produced malts with somewhat higher levels of extract, AAL, and some enzymes. Remarkably, the level of limit dextrinase was observed to be almost double that from previous investigations. Greater levels of steep water aeration were proposed to explain this dramatic increase. The interrelationships between the enzyme activities and malt quality identified, enable potential selection of novel malt quality parameters that are more predictive of a malt’s brewing performance (efficiency and quality) than current measures to provide a malt quality assessment system based on ‘functional’ malt quality.
Fermentations monitored.
Statistical evaluation of the curve fit of the Australian lager fermentation.
p-values resulting from F-tests of all seven fer- mentation types. The higher parameterised model incurs a significant reduction in error when p < 0.05. Furthermore, the highest e.
Understanding yeast dynamics during fermentation is important for quality control, whether monitoring fermentation consistency or identifying aberrant events, such as premature yeast flocculation (PYF). Previous models of fermentation dynamics tend to be parameter rich and require large time series, which are rare in industry. This research investigates five simpler models to 1) describe fermentation dynamics, 2) refine quality control sampling regimes to improve model fit, and 3) identify PYF fermentations. The ability of these models to describe yeast dynamics was evaluated using model fitting with time series data and Akaike Information Criterion (AIC) model selection. Data simulated from large time series was used with this model fitting approach to improve sampling schedules without increasing sampling effort. Lastly, PYF was identified in fermentations of fungal-contaminated malt using linear discriminant analysis (LDA). For large data sets, a four-parameter extension of the normal curve performed best while smaller data sets were better described by the 2-parameter gamma model. Moving sampling effort nearer the population peak improved model fits. Lastly, all models detected PYF, however the two-parameter gamma model provided a simple metric for distinguishing PYF. This research provides guidelines on appropriate model use, improving sampling regimes, and identifying PYF.
Change in headspace pressure (PSI) during growth of Lactobacillus brevis BSO 464 in pressurized gassed beer versus sterile beer at A, 22°C and B, 30°C. A 4°C bottle of beer was either inoculated with L. brevis BSO 464 and recapped or not inoculated and recapped, and shifted to either 22 or 30°C. The resultant change in dCO 2 (vol/vol) levels at both temperatures directly follows the pattern of headspace pressure cycling; therefore, this axis is not shown. Data shown are from two experiments at each temperature done with the same batch of commercial lager beer; an inoculated beer and a control sterile beer were run concurrently in each (the curves represent the average of the duplicate data).
Schematic of differences in RAST metabolic subcategories for the nine genome-sequenced isolates under study. In general, individual isolates differ most notably in the categories of amino acid and carbohydrate metabolism. When comparing isolates that were capable of growth in gassed beer to those that were statically able to survive in gassed beer, the next tier of most notable differences included the categories of stress responses, fatty acid metabolism, and nucleotide processing. dCO 2 -tolerant (those that can remain static or grow in pressurized gassed beer) and nontolerant organisms differed most notably in the categories of cell wall and capsule, membrane transport, and dormancy.  
Lactic acid bacteria (LAB) are frequently found as beer-spoilage organisms (BSOs). Correctly identifying a LAB as a BSO is problematic, given that there are few known genetic markers that distinguish beerspoiling from non-beer-spoiling LAB. Currently, genes purported to participate in hop-tolerance mechanisms are heavily relied upon to indicate LAB isolates with the potential to spoil beer, even though these genes do not consistently correlate with beer-spoilage. Though the presence of hops certainly is a significant physiological stress for bacteria in beer, we demonstrate here that the presence of CO2 dissolved in beer is a strong selective pressure for true LAB beer-spoilage ability (i.e., the ability to grow in and spoil a finished and packaged beer). We screened 20 LAB for their capability to survive and grow in gassed beer at 22 and at 30°C, and discuss the results in relation to ethanol and hop tolerance. Functional gene comparisons of nine dissolved CO2-tolerant and nontolerant genomesequenced isolates reveal potential metabolic pathways of interest for further study, specifically those that deal with cell dormancy and stress responses. These results further our understanding of LAB BSOs and have implications for how best to analyze these bacteria in laboratory settings and to test for these bacteria in the brewery.
To convert ferulic acid into 4-vinylguaiacol (4-VG), Saccharomyces cerevisiae must have intact PAD1 and FDC1 genes. British-type top-fermenting yeast strains have nonsense mutations in both of these genes; whereas, bottom-fermenting yeast strains have a nonsense mutation in their S. cerevisiae-type FDC1, and have lost their S. eubayanus-type FDC1 and PAD1 genes. Here, top-fermenting yeast transformants in which wild-type PAD1 and FDC1 derived from the laboratory yeast S. cerevisiae S288C were inserted in the genome, exhibited ferulic acid decarboxylation activity. Similarly, bottom-fermenting yeast transformants expressing wild-type S. cerevisiae-type FDC1 or S. eubayanus-type FDC1 also exhibited ferulic acid decarboxylation activity. Thus, the lack of ferulic acid decarboxylation activity in bottom-fermenting yeast is due to mutation of the S. cerevisiae-type FDC1 gene, coupled with absence of the S. eubayanus-type FDC1 gene.
A pyrolysis-gas chromatography method was developed for the determination of residual polyvinylpyrrolidone (PVP) in beers that had been treated with cross-linked PVP for the removal of chill haze. The method is more specific and much simpler to use than are existing methods, which are mostly based on the formation of complexes between PVP and certain phenolic dyes. The range of application of the method was 1-10 ppm in beer. The method involved a 10-fold sample preconcentration by precipitation with tannic acid, the pyrolytic decomposition of PVP, and the detection of the vinylpyrrolidone generated using a nitrogen detector. A quartz sample holder was used to obtain a linear calibration curve from 1 to 10 ppm PVP in beer. Several commercial beers were analyzed, and no soluble PVP was detected in any of them.
Top-cited authors
Paul Schwarz
  • North Dakota State University
Karl J. Siebert
  • Cornell University
David EVAN Evans
  • University of Tasmania
Katherine A Smart
Charles Bamforth
  • University of California, Davis