Charles W. Bamforth

The Microbiology of Malting and Brewing

SUMMARY Brewing beer involves microbial activity at every stage, from raw material production and malting to stability in the package. Most of these activities are desirable, as beer is the result of a traditional food fermentation, but others represent threats to the quality of the final product and must be controlled actively through careful management, the daily task of maltsters and brewers globally. This review collates current knowledge relevant to the biology of brewing yeast, fermentation management, and the microbial ecology of beer and brewing.

Brewhouse-Resident Microbiota Are Responsible for Multi-Stage Fermentation of American Coolship Ale

American coolship ale (ACA) is a type of spontaneously fermented beer that employs production methods similar to traditional Belgian lambic. In spite of its growing popularity in the American craft-brewing sector, the fermentation microbiology of ACA has not been previously described, and thus the interface between production methodology and microbial community structure is unexplored. Using terminal restriction fragment length polymorphism (TRFLP), barcoded amplicon sequencing (BAS), quantitative PCR (qPCR) and culture-dependent analysis, ACA fermentations were shown to follow a consistent fermentation progression, initially dominated by Enterobacteriaceae and a range of oxidative yeasts in the first month, then ceding to Saccharomyces spp. and Lactobacillales for the following year. After one year of fermentation, Brettanomyces bruxellensis was the dominant yeast population (occasionally accompanied by minor populations of Candida spp., Pichia spp., and other yeasts) and Lactobacillales remained dominant, though various aerobic bacteria became more prevalent. This work demonstrates that ACA exhibits a conserved core microbial succession in absence of inoculation, supporting the role of a resident brewhouse microbiota. These findings establish this core microbial profile of spontaneous beer fermentations as a target for production control points and quality standards for these beers.

Nutritional aspects of beer—a review

Much has been written about the favourable impact on the body of moderate consumption of red wine. Critical assessment of the literature, however, indicates that beer appears to be just as beneficial in countering diseases such as coronary heart disease. Additionally beer can make a substantial contribution to the diet in respect of certain B vitamins, minerals, antioxidants and perhaps fiber.

Brewing and brewing research: past, present and future

Whilst remaining largely traditional in approach, malting and brewing have become highly efficient processes through a substantial understanding of their underpinning science. Technological change in the industry is driven by four criteria: cost reduction, quality enhancement, maintenance of safety and wholesomeness and opportunity for enhanced sales. Whilst there are some opportunities for cost reductions by savings on raw materials, the major cost components in brewing involve production and packaging. Hence the focus is on energy reduction, maximising vessel utilisation and use of automated control strategies. There is scope in the future for production of beer by novel approaches, involving downstream establishment of quality parameters, though this is likely to be resisted. Quality of beer embraces both package and product. The shift towards enhanced use of non-returnable green or clear glass has focused attention on eliminating undesirable lightstruck characters from the product as well as the use of oxygen-scavenging crown corks to minimise the development of stale characters due to carbonyl-containing substances. There is an increased understanding of how to control the various species that primarily determine the flavour of fresh beer, including sulphur-containing substances, esters, higher alcohols, vicinal diketones and the bitter resin and oil fractions from hops. The achievement of stable foam on beer is dependent on the presence of foam-stabilising components, principally amphipathic polypeptides, but is determined by the physical behaviour of bubbles, notably the phenomenon of disproportionation. Malt and beer are at risk over a range of safety issues, but all can be avoided through attention to raw material selection and processing conditions. Moderate consumption of beer is now considered to be potentially beneficial. © 2000 Society of Chemical Industry

Release of β-Glucan from Cell Walls of Starchy Endosperm of Barley

ABSTRACT β-Glucan can be solubilized from barley by warm water, with increasing solubilization as the temperature is increased. Substantially less glucan is extracted if the barley is dehusked using sulfuric acid, particularly if the dehusked barley is denatured. This indicates that enzymes capable of solubilizing glucan are present in barley. Various purified enzymes promote the solubilization of glucan from denatured and dehusked barley. Apart from endo-β-(1→3)(1→4)-glucanase, these enzymes include endo-xylanases, arabinofuranosidase, xyloacetylesterase, and feruloyl esterase. Ferulic acid and, probably, acetyl groups are esterlinked to arabinoxylan, not β-glucan, in the cell walls of barley starchy endosperm, so the ability of the esterases, xylanases, and arabinofuranosidase to solubilize glucan indicates the pentosan component of the cell wall can restrict the extraction of glucan.

Silicon in beer and brewing

BACKGROUND It has been claimed that beer is one of the richest sources of silicon in the diet; however, little is known of the relationship between silicon content and beer style and the manner in which beer is produced. The purpose of this study was to measure silicon in a diversity of beers and ascertain the grist selection and brewing factors that impact the level of silicon obtained in beer. RESULTS Commercial beers ranged from 6.4 to 56.5 mg L(-1) in silicon. Products derived from a grist of barley tended to contain more silicon than did those from a wheat-based grist, likely because of the high levels of silica in the retained husk layer of barley. Hops contain substantially more silicon than does grain, but quantitatively hops make a much smaller contribution than malt to the production of beer and therefore relatively less silicon in beer derives from them. During brewing the vast majority of the silicon remains with the spent grains; however, aggressive treatment during wort production in the brewhouse leads to increased extraction of silicon into wort and much of this survives into beer. CONCLUSION It is confirmed that beer is a very rich source of silicon.

Beer foam: achieving a suitable head

The brand image of a beer is inexorably linked to the quality of the foam on that beer after dispense as a quality indicator that can be easily applied by all consumers. This is not surprising due to the visual appeal of the foam, its subtle role as a conduit for beer aromas and its contribution to the beer mouth feel. Similarly it is noted that consumers from different nations, regions or even genders have different preferences for the foam on their beer. This is divided by visual cues that include the foam stability, cling, strength, creaming, bubble size and whiteness. Thus Bamforth’s (1999) erstwhile boss who said “that generations of biochemists have done less for beer foam than the widget” is alienating a substantial portion of potential consumers from their beer brands because such foam does not meet their expectations. Foam quality is not just about “quick” fixes such as the inclusion of widgets, ever greater levels of tetra hop or gas composition but attention to the beer making process from grass to glass (malting variety breeding to dispense). Brewers do have solid options in manipulating the quality and quantity of malt foam positive proteins and selection of hop acids, the interaction of which provides the basis for foam stability and quality. Brewers also have a range of palliative options such as additives, gas composition, widgets and methods for dispense that can be used if suitable to the style of beer being produced. The main game is to use these options to optimise the foam quality of their brands and to consistently meet the expectations of the consumers that the brewer is targeting.

Barley Contains Two Cationic Acetylxylan Esterases and One Anionic Feruloyl Esterase

ABSTRACT Various carbohydrate-active esterases are detected in extracts of malted barley when analyzed by polyacrylamide gel electophoresis. The slowest migrating and most heat-resistant of these are relatively cationic acetylxylan esterases. Two such activities, one with a high affinity for esterase substrates including acetylated xylan, and one with a low affinity, are indicated. These enzymes did not hydrolyze methyl ferulate. A relatively heat-labile anionic feruloyl esterase has also been purified. It has some, albeit low, ability to act on acetylated xylan. The feruloyl esterase effects extensive release of ferulate from endosperm cell walls isolated from barley, whereas the acetylxylan esterases are only capable of very limited release of acetate.

A two-substrate kinetic study of peroxidase cationic isoenzymes in barley malt

Abstract Ten active cationic peroxidase isoenzymes were identified by polyacrylamide gel electrophoresis of extracts from malt of Triumph barley. These were partially separated on CM-Sepharose CL-6B and their properties examined. The five active peaks had different pH optima for the oxidation of 2,2′-azinobis(3-ethylbenzthiazoline 6-sulphonate) (ABTS), ranging from pH 3.25 to 3.73, and different inactivation rates at 55°, two being significantly more stable than the rest. A two-substrate kinetic study revealed a parallel pattern of double reciprocal plots for some of the active peaks, a converging pattern for others and a range of true K m values for the isoenzyme peaks varying from 76 to 710, μM for hydrogen peroxide and 2–310, μM for ABTS. The significance of the observations is discussed in relation to the known activity of peroxidase during brewery mashing.

Esterases in barley and malt

ABSTRACT Several esterases from barley and malt have been separated on polyacrylamide gels. The slowest moving bands appear to represent a single enzyme displaying a spread of migration owing to differences in surface charge. During malting, this enzyme, which is located in the starchy endosperm, shifts to a more migratory form. Two other main esterase groups are identified through gel electrophoresis, notably a highly anionic, highly labile enzyme, MW 62,000, located in the aleurone. The slowest and fastest moving bands have been partially purified using salt fractionation and ion-exchange chromatography. The former, MW 47,000, has strong capability for hydrolyzing acetylxylan and it is speculated that its role in the starchy endosperm is as part of the enzyme system that hydrolyzes the cell walls.