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International Journal of Wine Business Research

ISSN : 1751-1062

Article publication date: 3 November 2021

Issue publication date: 5 May 2022

In recent years, the craft beer (CB) industry has gained impetus and has experienced significant growth in scientific publications. This study aims to present a systematic review of the literature on CB in areas related to economic and business sciences.

Design/methodology/approach

Based on the data from Scopus, Web of Science and a set of articles not indexed to these databases until June 2021, a total of 132 articles were included for analysis, using bibliometric and content analysis techniques.

The study allowed us to identify that CB has four main clusters/themes of research, namely, CB industry and market, marketing and branding, consumer behavior and sustainability. Detailed information on the clusters is provided. In addition, the results showed that publications addressing CB have grown significantly from 2015 onwards and are dispersed across many journals, with none assuming a clear leadership. Quantitative approaches account for more than half of publications.

Research limitations/implications

This study is a useful guide for academics intending to develop studies with CB. It provides a framework to structure future research by identifying existing literature clusters and proposes several research propositions.

Practical implications

The findings from this study are useful for CB companies to get an overview of the main issues affecting the CB industry and market to be able to adapt their strategies and stay aligned with market tendencies in the four main clusters identified.

Originality/value

This is the first systematic review of CB. Therefore, it provides a significant contribution to frame and strengthening the literature on CB and serves as a reference for future research. Based on the content analysis and cluster identification, the findings portray the status of current research. Accordingly, a set of research opportunities are offered.

• Consumer behaviour
• Globalization
• Systematic literature review
• Conceptual/theoretical

Acknowledgements

The authors thank NECE-UBI, Research Centre for Business Sciences, Research Centre funded by FCT – Fundação para a Ciência e a Tecnologia, IP, under the project UIDB/04630/2020.

Nave, E. , Duarte, P. , Rodrigues, R.G. , Paço, A. , Alves, H. and Oliveira, T. (2022), "Craft beer – a systematic literature review and research agenda", International Journal of Wine Business Research , Vol. 34 No. 2, pp. 278-307. https://doi.org/10.1108/IJWBR-05-2021-0029

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Home > Books > New Advances on Fermentation Processes

Craft Beers: Current Situation and Future Trends

Submitted: 13 February 2019 Reviewed: 02 October 2019 Published: 27 November 2019

DOI: 10.5772/intechopen.90006

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New Advances on Fermentation Processes

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During the twentieth century, the consolidation of large multi-national beer companies and the homogenization of the specified beer types have led to a considerable growth in the beer industry. However, the growing demand by consumers of a single and distinctive product, with a higher quality and better sensory complexity, is allowing for a new resurgence of craft beer segment in recent years. This chapter reviews some different alternatives of innovation in the craft brewing process: from the bottle fermented beers with non-Saccharomyces yeast species, to the use of special malts or specific adjuncts, hop varieties, water quality, etc. All of them open a lot of new possibilities to modulate flavor and other sensory properties of beer, reaching also new consumers looking for a specific story in one of the oldest fermented beverages.

• non-Saccharomyces
• new adjuncts
• bottle fermentation

Author Information

María jesús callejo *.

• Universidad Politécnica de Madrid, Spain

Wendu Tesfaye

María carmen gonzález, antonio morata.

*Address all correspondence to: [email protected]

1. Introduction

Beer brewing is an established ancient art in different civilization and cultures, but there is no a precise and unanimous agreement on the origin of beer. Recent evidences predominantly based on the archeological and historical evidences explain the origin of brewing across time and space [ 1 ]. The timespan for its existence differs over a wide range of geography, from as far back as “The Neolithic Revolution” to the early horizon in South America. It commenced in the agricultural or “Neolithic” revolution period as early as 9000 BC with the advent of the Sumerians in the lowlands of the Mesopotamian alluvial plane [ 2 ,  3 ]. Evidence of rice-based fermented beverage has been found in between 7000 and 5000 BC in China [ 4 , 5 , 6 , 7 ] and ancient Mesopotamia back to about 6000 BC [ 8 , 9 , 10 ]. Similarly, in Northern Africa highlighting Egypt at about 3500 BC [ 11 ], in Europe around 3000 BC [ 12 , 13 ] and in South America 900-200 BC [ 14 , 15 , 16 ], locally fermented alcoholic beverages have been produced. Recent starch [ 17 ] and chemical residue studies [ 18 ] extend this period as far as 11,000 BC. In broader terms, all these fermented beverages may be considered as a craft beer based on the production scale.

2. Craft beer: as a movement from bottom to top fermentation. The reemergence of craft brewing

Different cultures and different civilization historically produced a number of fermented beverages/beer with different raw materials, which allowed them to have different attributes and different names. Beer is a relatively simple fermented product, mainly water in its composition, which makes easily produced locally; however, for a long time the difficulty to move long distances permits to flourish craft brewers everywhere in the world [ 19 ]. However, at present, it is not an impediment due to technological advances and transportation progress.

The craft beer movement or revolution began in the USA after the 13 years of national prohibition of alcohol or “the noble experiment” 1919–1933. In 1965, Fritz Maytag, the man of the craft beer renaissance, bought the Anchor Steam Beer Company of San Francisco with a capacity of 50,000 barrels and developed it as a craft brewery outlet [ 20 , 21 ]. Regarding the USA, this was the milestone to the expanding innovation and an increasing trend in terms of production and sales of beers with differentiated quality.

Even though this movement marked a shift in several countries recently, to mention some, in 1988 the earliest brewpub lay foundation in Italy [ 22 ], while in the Netherlands the craft revolution rouse during the year 1981 [ 23 ], in Australia, craft brewing started late 1984 [ 24 ]. At the same time, it is very difficult to put a time limit for the beginning of craft beer production in some European countries like the UK, Belgium and Germany where these countries were either with a long tradition in “special beers” or the historical existence of small and local producers back to the 1970s [ 25 , 26 ].

3. Craft beer: statistical viewpoint

One of the indicators for the expansion of craft beer renaissance in different countries is the statistical approach. However, there is no common shared definition of craft beer but different associations and entities of different countries remark based on the size of the firm, production volume raw materials used to produce such drink, degree of independence and way to brew [ 27 ]. Even though there is data scarcity on the numbers of microbreweries of different countries, in Table 1 , those microbreweries actually existing in different countries of the five continents are represented, where beer production is traditional or its consumption is highly relevant at present. The statistical data reflected in this chapter encompasses all beer producers recognized as craft brewery, artisanal brewery, microbrewery, independent brewery, specialty brewery, Brewpub, local brewery, Regional brewery and Contract brewing company in accordance with the regulation rules of different countries without establishing any distinctions among them.

Microbrewery expansion in the last decade sample countries by continent.

[ 24 , 26 ].

Even though Mergers and acquisitions seem to reduce the number of major brewing firms, the total production in volume is not affected. This tendency provides an opportunity to the merged breweries to take advantage over the microbreweries in terms of economical scale and increased market share. Despite the macrobrewers dominance, worldwide craft beer numbers are increasing at a rapid rate [ 28 ].

4. New tendencies: is the glass half-full or half-empty for brewers?

The last two decades brewing landscape continues to rise in number of micro and craft breweries almost everywhere in the world. As it is shown below ( Table 1 ), in the last decade, from 2008 to 2017, the number of craft breweries significantly increased globally. In fact it passed from 671 to 2378 in the UK (traditionally beer-producing and beer-drinking country), and from 1321 to 6266 in the USA, an increase of 354 and 474% respectively, within the same period (not traditional beer producer country). This increase in number of craft breweries and production volume run up to an increase in compound annual growth rate (CAGR) within the sector. Craft brewing continues to take market share away from the largest brewing companies. According to Brewers Association report (the U.S. beer sales volume growth 2017, National beer sales and production statistical data), the overall U.S. beer volume sales were down 1% in 2017, whereas craft brewer sales continued to grow at a rate of 5% by volume, reaching 12.7% of the U.S. beer market by volume. Craft production grew the most for microbreweries. Retail dollar sales of craft increased 8%, up to $26.0 billion, and now account for more than 23% of the $111.4 billion U.S. beer market [ 27 ]. Percentage of craft beer producers (2013–2017) can be seen in Figure 1 .

Percentage of craft beer producers (2013–2017).

There are various factors, which favored this increase in overall craft beer consumption. These factors include per capita income growth, the availability of alternatives toward the production of successful and high levels of quality beers, increased health concerns, and the emergence of new government regulations that affects directly the sustainability issue and consistency and innovation among many others.

5. Craft and special beers: classification

A single beer style, lager beer, has long been the main dominant beer in the world market. However, a worldwide change in trend for the last decade has been registered due to the growing interest in craft and specialized beer [ 34 ]. A significant growth in the number of breweries, the variety of styles and the total volume of production had been observed in previous years [ 35 ].

But the reasons for the growth are multiple: first, increase in the demand for high more flavorful and stronger beers [ 34 , 36 ]. This is particularly important in the case of American consumers, often not satisfied with the dominant in the market American pale lagers. An increase in flavors (malted barley, chestnut, honey flavored) and a more readily quality perceived are the main factors to choose craft beer instead of commercial beer between habitual beer drinkers [ 37 ]. Second, exclusivity and “unique drinking experiences” are also highly rated by craft beer consumers [ 34 , 38 ]. Finally, even though traditional brands of beer are closely linked to very specific places [ 39 ], craft beer is part of a broader neolocalism movement in which people are demanding goods and services that have a connection with the local community [ 36 ].

Taking into account that all beer types evolve from the combination and relationships among ingredients, processing, packaging, marketing and culture, it is therefore necessary to establish some criteria to establish differences between special and craft beers.

This section analyzes the main criteria for classifying beers as special or craft beers ( Figure 2 ).

Main criteria to classify craft and special beers.

The first element taken into account is the production output of beer per year ( criterion 1 ). Craft beer are characterized by small production output and their “small,” “independent,” and “traditional” character. These characteristics are compatible with others which have been traditionally used to classify beer styles and now they are assuming new importance and making possible to enrich traditional beer brewing: we refer to type of fermentation and yeast strain selection ( criterion 2 ). Here, we will look at non- Saccharomyces brewing yeasts which require special attention [ 40 , 41 ]. While malted barley remains the main source of sugars for fermentation in the production of beer, the ingredients can be changed based on the region and preference of the consumer. Innovative ingredients in wort production can be used as a valuable source of variation in craft beer production ( criterion 3 ) The two last criteria are relatively recent and novel and are related with the development of special beers in the perspective on health and nutrition ( criterion 4 ) and with the use of emerging technologies in brewing ( criterion 5 ).

5.1 Production output of beer per year (scope of craft beer)

The annual beer production allows distinguishing between larger breweries mass-producing beer (annual production capacity of up to 6 million barrels) and craft beers or “small” scale breweries (less than 6 million barrels; where 1 BBL = 339 12 oz bottles of beer or 235 half-liter bottles of beer) [ 26 , 42 ].

Minimum production quantity: Nanobreweries .

The place of sale of beer: production is sold outside (Microbreweries) or on the same floor of production ( Brewpub ).

Brewing companies that outsource their production to other already established breweries ( Contract Brewing Company ).

Over 50% or more of their volume production focuses on all-malt beers and/or their malt flagship ( Regional Craft Brewery ).

The American craft brewing industry assumes that in addition to low volume production, further requirements are expected by the craft beers [ 36 ]. They are independent in that and not more than 25% of the business is owned by another member of the alcohol industry who is not a craft brewer. Traditional ingredients (water, malt, hops, yeast) must also be used in the brewing process although innovation in terms of reinterpreting historic beer styles or developing new styles is a hallmark of the industry.

5.2 Selection of the yeast strain and type of fermentation

The main brewing classification criterion particularly relies on the selection of the yeast strain and type of fermentation [ 35 , 41 ]. Two types of brewing yeast were originally classified based on their flocculation behavior during fermentation.

Beers are classified into two large groups according to the yeast strain and type of fermentation: Ale beers and Lager beers. Ale yeasts or top-fermenting yeasts , which are Saccharomyces cerevisiae strains, rise up to the surface of the vessel with the escaping carbon dioxide gas bubbles and become entangled in the fermentation head, facilitating their collection by skimming.

Ale yeast fermentation temperature ranges between 15 and 20°C. Lager yeast or bottom-fermenting yeast does not rise and becomes entrapped in the foam but settles out at the end of the fermentation. Lager worts often ferment at lower temperatures (8–14°C) than ale yeasts and are therefore much slower.

Ale beers represent only a small percentage of the total beer consumption. They are very common in Britain, Germany, Canada’s eastern provinces, the United States and, last but not least, Belgium. Until the sixteenth century, ale was the main type of beer in Europe [ 43 ].

Standard/ordinary bitter (Britain), English pale ale (Britain), Mild (Britain), Brown Porter (Britain), Robust Porter (Britain), Dry stout (Ireland), Sweet stout (Britain), Kölsch (Germany, Cologne), Lambic (Belgium), Rauchbier (Germany) and Weizen/Weissbier (Germany) are some examples of ale beer types.

Lager beer is the dominant style in almost all countries and represents more than 90% of the beer produced worldwide [ 43 ].

Some principal Lager beer types are: German Pilsner (Pils) (Germany), Bohemian Pilsener (Czech Republic), Classic American Pilsner (United States), Vienna Lager (Austria), Oktoberfest/Märzen (Germany), Dark American Lager (United States), Munich Dunkel (Germany), Schwarzbier (Black Beer) (Germany), Maibock/Helles Bock (Germany), Traditional Bock (Germany), Doppelbock (Germany), Eisbock (Germany).

In all beers cited, the flavor-active compounds such as acids, alcohols, aldehydes, ketones and esters are produced by yeast during fermentation. Although there are many strains of brewing yeast ( Saccharomyces cerevisiae ) for beer production, the choice of suitable yeasts to produce desirable tastes and flavors in beer is very important and significant.

5.2.1 Use of non- Saccharomyces

Several non- Saccharomyces yeasts can be used successfully in the making of craft beers with interesting possibilities. Yeasts such as Lachancea thermotolerans , Torulaspora delbrueckii , Hanseniaspora vineae and Schizosaccharomyces pombe can help to modulate acidity, aroma, mouthfeel or even color [ 41 , 44 ]. As the final alcoholic degree in beers is lower than in wines, and normally ranging between 4 and 8% vol, the use of medium fermentative power non- Saccharomyces species is possible because most of these yeasts are able to ferment reaching this ethanol level.

Lachancea thermotolerans is trending yeast in fermented beverages because of its ability to ferment until 4–9% vol producing high amounts of lactic acid from sugars. Therefore, it can be used to decrease pH of beverages [ 45 , 46 , 47 ]. Moreover, interesting effects in beer aroma can be reached by the production of fruity esters [ 48 ]. The use of L. thermotolerans has been also described in beer technology [ 49 , 50 ]. In the brewing of craft beers, L. thermotolerans can be used not only in the primary fermentation of the wort but also during the second fermentation in bottle to produce the suitable foam and CO 2 pressure. However, the most interesting application is in the production of sour beers because of the natural biological acidification during wort fermentation [ 46 ]. Moreover, even when the early use of L. thermotolerans has been proposed in winemaking in which the use of suitable species of these yeasts can produce pH reductions of 0.5 pH units [ 47 ] and the use in beer technology is even more effective due to the lower buffer effect in beer compared with wine. In our lab, we reached pH reductions of 1 pH unit [ 51 ]. The sensory effect of this acidity is described as a citric acidity without dairy hints because of the low production of acetoin and diacetyl [ 47 ]; moreover, the volatile acidity produced by L. thermotolerans is very low compared to volatile acidity produced by selected S. cerevisiae .

Torulaspora delbrueckii is another versatile yeast suitable for beer production. It has a medium fermentative power and improves the formation of fruity esters in addition to a low production of volatile acidity. These characteristics make it a good yeast for the initial fermentation of the must and the subsequent in bottle [ 50 ]. Also it is possible the use of this yeast sequentially or in mixed cultures with S. cerevisiae [ 52 ] or S. pombe [ 53 ]. It has been described as yeast able to decrease volatile acidity during fermentation. The ability to ferment sugars easily reaching 7–9% vol makes it interesting also for secondary bottle fermentation [ 52 ]. The production of 2-phenylethyl acetate, a floral ester with positive floral aroma, is increased during fermentation with T. delbrueckii ; moreover, high amounts of 3-ethoxy propanol are formed by this species [ 52 ]. The release of polysaccharides is also improved by the fermentation with T. delbrueckii affecting mouthfeel and structure [ 54 ].

Hanseniaspora vineae is an apiculate yeast able to produce fresh and complex fermentation, increasing fruity aroma and producing full bodied structure [ 55 ]. It is possible to find strains with fermentative power close to 9% vol, which facilitate its use not only for primary fermentation but also for bottle fermentation. Moreover, it is a persistent yeast that can be found until the end of the alcoholic fermentation in wines and therefore also in beers because of the lower alcoholic degree. During the fermentation with H. vineae , an increase in the concentration of acetyl esters, benzenoids, and sesquiterpenes [ 56 , 57 ], and a decrease in the contents of alcohols and acids occurs. Intense either β-glucosidase or β-xylosidase activities has been described in some strains of H. vineae increasing the levels of hotrienol and 2,6-dimethyl-3,7-octadien-2,6-diol during fermentation [ 58 ]. It is especially noticeable the production of 2-phenylethyl acetate by H. vineae [ 55 ], compared with other Hanseniaspora / Kloeckera species.

Schizosaccharomyces pombe is a fission yeast able to produce maloalcoholic fermentation, and some strains can reach 13–15% vol of ethanol during fermentation [ 59 , 60 ]. The peculiar metabolism of S. pombe produces an intense degradation of malic acid together with a significant release of pyruvate in the fermentative media [ 60 ]. S. pombe is especially resistant to some common preservatives such as sulfur dioxide, actidione, benzoic acid, and dimethyl dicarbonate [ 59 , 61 ]. The main drawback of this yeast is the high production of volatile acidity. Concerning its structure this species has a peculiar and dense 2-layer cell wall. The autolysis produces the release of high amount of polysaccharides during maturation improving the mouth feel of beers [ 62 ]. This property can be especially interesting to produce full-bodied and soft bottle-aged beers. Moreover, we have observed intense bottle fermentation with good foam properties. The aromatic profile in beers is fruity and fresh when this is yeast is used specially in bottle fermentation.

5.3 Innovative ingredients

Raw material in wort production and parameters in production lead to produce an unlimited number of beer types. It might be argued that beer is a horizontally differentiated product . [ 35 ]. In fact, beers are quite similar in most respects but small differences in their composition can greatly affect both appearance and flavor [ 63 ].

We are going to examine each one of the raw materials separately.

5.3.1 Water

Water is quantitatively the main ingredient of beers; it forms more than 90% and often even more than 94% of the final product. The chemical composition of water has a determinant effect on beer properties and contributes significantly to the final beer flavor. The balance of minerals in brewing water will affect the flavor character and flavor perception of malt, hops, and by-products of fermentation. It may also influence the performance of yeast, which in turn influences the flavor, aroma, and mouthfeel of beer.

Chemical composition of water of the localities where famous beer styles were originated are very different in approximate ionic concentrations (in ppm). The chemical composition of water of Pilzen, Munich, Dortmund or Vienna is typical between Lager examples. Burton-on-Trent, Dublin or Edinburgh are typical between ale examples.

Malted barley is the main source for fermentable sugars used by yeasts in the traditional brewing of beers [ 64 ].

Depending on the conditions (time and temperature), pale or amber-colored or even dark malts are obtained; the color being due to caramelization of sugars and to Maillard-type reactions [ 65 ]. The variety of barely and the malting process influences the type and quality of beer [ 66 ]. To elaborate craft beer, the right malt is a key factor because craft beers include high proportion of adjuncts and enzymatic activity of malt has to ensure adequate hydrolysis of all the starch present in the wort.

5.3.3 Adjuncts

Malted barley is the main source for fermentable sugars used by yeasts in the traditional brewing, Other grains, malted or not, have been included to provide fermentable carbohydrates to the wort in addition to those from malt [ 63 ]. In former times, most cereals were used for malting, emmer, oats, spelt wheat, bread wheat were widely used and, in Estonia, rye was used up until the nineteenth century [ 67 ]. Outside Europe, millet, rice, maize and tuber plants have been, and are still, commonly used.

Bogdan and Kordialik-Bogacka [ 64 ] estimate that 85–90% of beer worldwide is now produced with adjuncts. Traditionally they had been used because they lead to reduce the cost of raw materials. When adjuncts are selected as unmalted grains, they present the added advantage of improved sustainability, by reducing reliance on the malting process [ 68 ] and its associated cost.

Craft brewing is increasing the use of adjuncts [ 68 ] because they lead to create a unique beer flavor/aroma [ 69 ]. Figure 3 shows the influence of different concentrations of roasted malt addition on sensory properties of beer.

Effect of roasted barley addition on beer sensory properties.

Appropriately chosen adjuncts can contribute to light or dark colors, improved colloidal or foam stability and prolongation beer shelf-life [ 64 ]. The flavor profile can also be changed by altering the sugar and amino acid spectra in wort.

Hops ( Humulus lupulus L.) are almost exclusively consumed by the brewing industry. Although hops are only a minority ingredient, they have significant impact on the sensory properties of beer [ 65 ]. It contributes not only to bitter flavor but also with the particular character of the selected hop variety [ 66 ].

This is mainly due to its particular chemical composition in: the hops resins, the hop oil and hop polyphenols [ 70 ].

In the closing years of the twentieth century, the hop became an icon of the “craft beer revolution” that swept across the United States. The “hopped up” vats created more flavorful and aromatic beers, making them more akin to European specialty varieties than anything seen in United States markets since before prohibition. The hops also became an effective marketing tool [ 39 ] from a nutritional and health point of view. It had recently come to light the effect antiviral and anti-HIV of xanthohumol, a phenylated flavonoid isolated from hops [ 66 ].

5.4 Perspective on health and nutrition

This section also includes a part on special or craft beers, which meet the new consumer requirements related with health and nutrition. In this context, it should include categories such as [ 66 ] light or low-calorie beers, low alcohol or non-alcohol beers, gluten free beers and functional beers.

5.4.1 Light beers

Light beer is a relatively new product on the market. Light beers contain at least one-third less calories than conventional beers [ 71 ]. However, these products are not widely accepted in Europe compared to North America and Australasia because of their lack of fullness in the taste and low bitterness compared with conventional beer. Enhanced hop character and addition of a low level of priming syrup have been proposed to the production of a low-calorie beer with a well-balanced and full beer flavor [ 38 ].

From a nutritional point of view [ 71 ], light beer contains less carbohydrate than regular beer, low alcohol beer or non-alcoholic beer. Surprisingly, light beer presents more calorie supply than such beers. This may be explained considering that light beer has a significant amount of alcohol (3%) providing a high calorie value.

5.4.2 Low alcohol beers

Low-alcohol beer is a beer with very low- or no-alcohol content. The alcohol by volume (ABV) limits depends on laws in different countries. In recent years, there has been an increased market share for low alcohol beers . This is mainly due to health and safety reasons and increasingly strict social regulations [ 72 ]. The alcohol-free beers also claim beneficial effects of healthy beer components with a simultaneous effect of the lower energy intake and complete absence of negative impacts of alcohol consumption.

According to Blanco et al. [ 73 ], the dealcoholization processes that are commonly used to reduce the alcohol content in beer have negative consequences to beer flavor. Several processes (physical and biological) have been developed for the production of low-alcohol or alcohol-free beer [ 74 ]. The physical processes include thermal and membrane processes such as thin-layer evaporation; falling film vacuum evaporation; continuous vacuum rectification; reverse osmosis; and dialysis. The biological processes include cold contact process (CCP); arrested fermentation; and use of special yeasts ( S. ludwigii ).

Overall, the taste defects in alcohol-free beer are mainly attributed to loss of aromatic esters, insufficient aldehydes, reduction or loss of different alcohols, and an indeterminate change in any of its compounds during the dealcoholization process or as a consequence of incomplete fermentation [ 73 ].

5.4.3 Gluten free

The market segment for gluten free (GF) products continues to grow rapidly and gluten free beers are a niche market with increasing demand [ 75 , 76 ].

Beer is considered unsuitable for people suffering from gluten intolerance, but with some modification and removal of proteins which occur during traditional beer processing. The majority of the precipitated protein remains in the spent grain after the lautering process and only a small proportion of gluten passes from malt to sweet wort. A study conducted by [ 77 ], in twenty-eight commercial beers, found that 10 of the tested beers contained less than 20 ppm gluten.

There are different alternatives for the reduction of gluten levels below the legislative gluten-free threshold (≤20 ppm) (EC No. 41/2009, 2009), on a daily basis, including precipitation and enzymatic hydrolysis. Deglutinization treatments by enzymatic process were proposed by Fanari et al. [ 78 ].

Furthermore, gluten free beers can be produced using gluten free cereals and pseudocereals . Currently only sorghum, rice, maize, millet, and buckwheat appear to be successful GF beer ingredients, while others have only shown adjunct possibilities. Among cereals, Teff is gaining a lot of popularity in GF beer production. Teff grain nutrients are promising and it is also an excellent GF alternative for people with celiac disease and other gluten allergy. Though the α- and β-amylase activities of teff malt are lower than that of barley, it has sufficient level of enzyme activities to be used as a raw material for malting [ 79 ] and GF beer production. Mayer et al. [ 80 ] has also prepared a GF beer from all-rice malt with sufficient endogenous enzyme activity for degradation of the rice components.

A third approach is the production of yeast fermented beverages based on fermentable sugars/syrups [ 75 ]. The search for new gluten-free brewing materials is still in its infancy and researchers in this field of study are continuously researching on the malting, mashing, fermentation conditions [ 78 ].

5.4.4 Functional beer

There is also scope for positioning low-calorie beers as a source of good carbohydrates, such as the soluble fiber and prebiotics derived from the β-linked glucans and arabinoxylans in the cereal walls [ 81 ]. Because these carbohydrates are neither metabolized by the brewing yeast nor they do not contribute toward calorie count but exert health benefits. Prebiotics are dominantly oligosaccharides that are nondigestible to human being but selectively stimulate growth and activity of beneficial bacteria (probiotics) in the human gastrointestinal tract.

Further, β-glucans could enhance stress tolerance of intestinal lactobacilli, which may have a positive impact on survival of probiotics. Nonetheless, high molecular weight b-linked glucan materials may have a negative impact on filtration efficiency and optimization of a filtration process will be required.

Probiotics are not limited to bacteria, and there is a well-known probiotic yeast strain of S. cerevisiae var. boulardii . A novel unfiltered and unpasteurized probiotic beer could be produced by fermenting wort with a probiotic strain of S. cerevisiae . A new category of functional beer could be the specialty beer of the future, given the rising consumer recognition and acceptance of probiotics [ 38 ].

5.5 Use of new technologies

Emerging technologies as high hydrostatic pressure (HHP) and ultra-high pressure homogenization (UHPH) open new possibilities in beer production. Both technologies are considered as cold techniques allowing the control of microorganisms in beverages [ 82 ]. Even when some temperature increasing is produced that can be quantified in 2–3°C/100 MPa in HHP [ 83 ] by compression adiabatic heat and until 100°C but just for 0.2 s in UHPH because of intense shear forces and impact [ 84 ]. The use of HHP is able to eliminate yeasts at pressures of 400 MPa-10 min but Gram-positive bacteria needs 600 MPa-10 min and spores remain unaffected even with these pressures [ 85 ]. Also it has the drawback of being a discontinuous technology. UHPH is now currently highly developed being a fast technology with a good industrial scale-up with equipment that are working at a flow of 10,000 l/h ( https://www.ypsicon.com/ ). Moreover, UHPH is a continuous technology and able to produce sterilization due to the extreme impacts and shear forces produced when the fluid pumped at 300 MPa cross the depressurization valve [ 84 ]. In beer production theoretically is possible to pump the beer at 300 MPa and release the pressure until 4 bar, later is possible to make a sterile iso-barometric bottling. The intense de-polymerization produced by UHPH can also disaggregate colloidal particles improving the beer structure and stability. Potentially it is possible to produce the mechanically lysis of the yeasts formed during fermentation increasing the amount of small size polysaccharides.

Other interesting technology that can be quite useful in beer production and sterilization is pulsed light (PL). This technology produces high energy light during a very short time (few μs) with a strong capacity to inactivate microorganisms and spores allowing sterilization [ 85 ]. The light is applied by flash lamps with a range spectra of 160–2600 nm with an intensity 105 folds the sunlight intensity at the seaside level. Power peak can reach 35 MW. PL technology is also a cold technology being a gentle process with sensory quality of beverages. This technique can be applied continuously during beer processing previously to packaging. It is also possible to use this technology to sterilize bottles or packages.

The use of these new technologies opens new possibilities in the processing and preservation of beer. UHPH and PL can be applied in a continuous way being efficient and easily implemented at industrial scale. Both sterilization technologies have a gentle repercussion in sensory quality of beverages.

6. Future trends

The development of new craft and special beers will be focused in the improvement on sensory properties and differentiation. Moreover, health care connotations are essential and should be supported by traditional processes but improved with both new biotechnologies and emerging processes.

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More than just a beer—the potential applications of by-products from beer manufacturing in polymer technology

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• Volume 5 , pages 765–783, ( 2022 )

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Beer is the most popular alcoholic beverage in the world, and its popularity is continuously growing. Currently, global beer production is estimated at around 2 billion hectoliters. Nevertheless, the increasing production capacity implicates the rising issue of generated by-products—brewers’ spent grain, spent hops, spent yeast, and wastewater. They are generated in massive amounts, so having in mind the current pro-ecological trends, it is crucial to look for their utilization methods. Among the possibilities, particular attention should be drawn to polymer technology. This sector can efficiently use different lignocellulosic materials, which could be applied as fillers for polymer composites or sources of particular chemical compounds. Moreover, due to their chemical composition, brewing industry by-products may be used as functional fillers and additives. They could be introduced to enhance the materials’ resistance to oxidation, microbes, or fungi. These issues should be considered especially important in the case of biodegradable polymers, whose popularity is growing over the last years. This paper summarizes the literature reports related to the composition and potential applications of the brewing industry by-products in polymer technology. Moreover, potential directions of research based on the possibilities offered by the brewing industry by-products are presented.

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1 Introduction

As a process aimed at beer production, brewing is known for thousands of years [ 1 ]. Depending on the times and mainly the development of humanity and science, the specifics of this process were changing [ 2 ]. Figure  1 presents the current general scheme of beer production. Generally, the brewing process consists of the following stages, starting from the malt: crushing of malt, mashing, lautering, filtration, boiling, and fermentation. At first, malt is crushed to break apart the kernel and facilitate the extraction of sugars during mashing [ 3 ].

The general scheme of beer production with an indication of generated by-products

Then, crushed malt is mixed with hot water in a mash tun creating the cereal mash. Naturally occurring enzymes present in the malt convert the starch extracted from the malt into simpler fermentable and non-fermentable sugars in the saccharification process [ 4 ]. To enhance the yield of mashing, in the end, the mas is often heated up to 76–78 °C, which is called mashout, and sprinkled with additional water during sparging [ 5 ]. Such processes are implemented to reduce mash viscosity, free up more starch, and extract additional sugars [ 6 ]. As a result, a sugar-rich liquid called wort is obtained after separation from the solid residue of mashing called the brewers’ spent grain (BSG) [ 7 ].

The wort is moved to the kettle, where it is boiled with hops (and sometimes other ingredients). The boiling process aims to terminate the enzymatic processes, precipitate proteins, concentrate and sterilize the wort, as well as extract compounds from hops to beer and isomerize hop resins to add bitterness to beer [ 8 ]. Moreover, boiling may induce caramelization and Maillard reactions in wort [ 9 ]. In the end, the hopped wort is cooled down and separated from the trub, which includes the hop residues and colloidal proteins coagulated during boiling [ 10 ].

Cooled and hopped wort is transferred to the fermentation tanks and pitched with yeast, converting the fermentable sugars into alcohol and carbon dioxide. Moreover, depending on the type of yeast, different reactions occur, which account for the beer’s final taste and aroma profile [ 11 ]. After complete fermentation, the beer is separated from the surplus yeast, called spent yeast, conditioned in the additional tank, and packed into bottles, casks, or cans [ 12 ].

2 Beer production statistics

Beer is the most popular alcoholic beverage globally and the third most popular beverage after water and tea [ 13 ]. The global beer production size is relatively stable in the last decade and accounts for 1.91–1.97 billion hectoliters [ 13 ]. The leading producer is China, whose production in 2019 equaled 376.5 million hectoliters and accounted for ~ 20% of global production [ 14 ]. The Americas occupy the following positions—the United States, Brazil, and Mexico with 210.3, 144.8, and 124.2 million hectoliters, respectively [ 15 ]. Considering Europe, the size of production exceeds 420 million hectoliters annually [ 16 ]. The share of particular continents in the global beer production is presented in Fig.  2 . The biggest producer is Germany, the country with great brewing traditions. In 2019, Germans produced 91.6 million hectoliters of beer, mostly pilsener and wheat beer [ 17 ]. In Europe, Germany is followed by Poland and the UK, whose production is around 40 million hectoliters [ 18 ]. It is also essential to mention Russia as a critical producer with 77.4 million hectoliters produced in 2019 [ 19 ]. Russia is one of the few countries where beer is not the most popular alcoholic beverage, with a higher vodka share [ 20 ]. Presented data indicate that global beer production is distributed across all the regions of the world. Therefore, research activities related to the manufacturing, consumption, and health aspects and the utilization of by-products of beer production are essential because these aspects may affect an enormous number of people worldwide.

The share of particular continents in the global beer production

3 Beer production by-products

Conventionally, beer is produced from barley and, to a noticeably lesser extent, from wheat [ 21 ]. Such a production model is commonly applied in Europe. Moreover, in Germany, such issues are regulated by Germany’s Beer Purity Law, originating from the medieval Bayreisches Reinheitsgebot [ 22 ]. Nevertheless, in different regions of the world, other starch sources are also applied, such as maize in America [ 23 ], rice in Asia [ 24 ], or sorghum in Africa [ 25 ]. Considering hops and yeast, their use is associated with the desired beer style. The market offers an enormous range of hops and yeast varieties [ 26 , 27 ].

According to the brewing scheme presented in Fig.  1 , the main by-products of beer manufacturing are the brewers’ spent grain, trub removed after wort boiling, and spent yeast. The generation of brewing by-products is very similar globally, with possible differences in their composition, depending on the location. These materials are currently often unutilized and present hardly any market value. Generally, considering the current pro-environmental trends in scientific and industrial activities partially stimulated by the changing law regulations established worldwide, waste and by-products management are essential [ 28 ]. Except for the environmental motivations, the application of such materials in various production processes can generate added value for the resulting products (enhanced performance or new properties) or reduce their manufacturing costs [ 29 ].

One of the industry branches where by-products from beer manufacturing could be potentially applied in polymer technology. This sector of the industry is enormously dependent on petroleum price and availability [ 30 ]. It is commonly known that its resources are constantly shrinking, and it is essential to seek new raw materials, which could substitute petroleum, beneficially from renewable resources [ 31 ]. In the following sections, the literature reports on the applications of brewing by-products in polymer technology would be discussed.

3.1 Brewers’ spent grain

3.1.1 overview.

The main and the most abundant by-product generated by the brewing industry is brewers’ spent grain. It is generated in high amounts and accounts for over 85% of beer manufacturing by-products [ 32 ]. During the mashing process, around 69% of the initial malt mass is extracted and converted to sugars soluble in wort [ 33 ]. Considering that production of the one hectoliter of beer uses 20 kg of malt, around 6.2 kg of dry BSG is generated. Such values are typical for the most popular beer style worldwide—light lager [ 34 ]. Other beer styles, especially those characterized by higher original gravity, require higher malt loadings, even up to 45 kg for strong stouts or porters [ 35 ]. Keeping in mind the size of the global beer production, almost 12 million tonnes of brewers’ spent grain is generated worldwide. The biggest producer, China, accounts for over 2.3 million tonnes, followed by the USA with 1.3 million tonnes, while European production generates around 2.6 million tonnes of BSG [ 34 ].

3.1.2 Composition

One of the main drawbacks of BSG as a potential raw material for other processes is its high moisture content, exceeding 75% [ 36 ]. Together with the presence of polysaccharides, this factor makes the BSG a perishable material. Drying of brewers’ spent grain, which could be easily performed using conventional dryers, might noticeably enhance its attractiveness for other industry branches, including polymer technology [ 37 ]. Moreover, BSG is characterized by the relatively low activation energy values during drying, comparable to other food industry by-products such as carrots, beans, or general vegetable waste [ 38 ]. The drying of BSG requires less energy than, e.g., olive processing by-products, probably due to their high lipid content [ 38 ].

The brewers’ spent grain can be characterized by a similar composition to various lignocellulose materials except for the high moisture content. As presented in Table  1 , the total content of carbohydrates in BSG is around 50%, which is noticeably lower compared to other lignocellulose waste materials, e.g., barley straw (56%) [ 39 ], rye, or oat straw (66–68%) [ 40 ], sunflower or cotton stalks (72–73%) [ 40 ]. Such a phenomenon is attributed to the partial reduction of carbohydrate content during mashing when starch is removed [ 41 ].

Moreover, brewers’ spent grain contains from 10 to even 28% of lignin, depending on the reports [ 48 ] and a significant amount of proteins, which is attributed to their high content in barley grain [ 52 ]. The detailed composition of proteins in BSG may differ depending on the determination method, source of by-product, and applied malts, mostly crop species [ 33 ]. According to Robertson et al. [ 53 ], the glutamine is the primary amino acid of BSG (around 19–20% of total proteins), followed by a proline (~ 9%), asparagine, and leucine (both ~ 8%), arginine, phenylalanine, and valine (~ 7%). On the other hand, Waters et al. [ 54 ] reported that histidine is present in the highest amount exceeding 26% of total proteins, followed by glutamine (~ 16%), lysine (~ 14%), and leucine (~ 6%), while the content of other amino acids does not exceed 5%. Nevertheless, irrespectively of the detailed composition of amino acids, BSG should be considered as protein-rich material.

Brewers’ spent grain often contains noticeable amounts of phenolics, which may provide additional value for various applications due to their antioxidant and antimicrobial properties [ 55 ]. The main phenolic components of BSG are hydroxycinnamic acids (HCAs) and hydroxybenzoic acids (HBAs), particularly ferulic, p -coumaric, sinapic, syringic, and caffeic acids [ 56 , 57 , 58 ]. The first two compounds are present in the highest amounts, but the literature reports indicate that their contents depend strongly on the type of malts used for brewing [ 59 ]. McCarthy et al. [ 59 ] showed that the roasting of pale barley malt reduced the total HCAs content in BSG by 57%. Also, Moreira et al. [ 60 ] pointed to the reduction in total phenolic content due to increasing malt kilning temperature. For chocolate and black malts, kilned at temperatures exceeding 220 °C, the content of ferulic and p -coumaric acids was reduced by over 50%. The effect was significantly smaller for melanoidin and carared malts, which were subjected to a temperature in the range of 120–160 °C.

Generally, the structures of the major phenolic acids present in brewers’ spent grain are presented in Fig.  3 . Their detailed composition in particular BSG samples and other by-products, may noticeably differ depending on the method of their extraction, selection of solvents, and method of the quantitative analysis [ 35 ]. Nevertheless, despite the differences in reported contents of HCAs and other phenolics, they significantly enhance the antioxidant activity of BSG compared to other lignocellulose materials.

The structures of the major phenolics of BSG: a ferulic, b p -coumaric, c sinapic, and d caffeic acid

These compounds mentioned above present in BSG are considered strong antioxidants and may enhance the stability of polymeric materials [ 61 , 62 , 63 ]. Considering the antioxidant activity of BSG, it may contain noticeable amounts of melanoidins, mainly when it originated from the production of darker beers. Melanoidins are generated during Maillard reactions occurring between carbonyl groups of reducing sugars and amino groups of amino acids present in proteins [ 64 ]. As a result, the complex mixture of higher molecular weight oligomeric and polymeric compounds is obtained [ 65 ]. They are responsible for the browning reactions of various food products after applying temperature, e.g., during baking, frying, or cooking [ 66 ].

Moreover, the brewers’ spent grain contains multiple micro- and macroelements, mostly silicon, phosphorous, calcium, and magnesium [ 32 ]. Combining their content with the presence of vitamins, primarily B3, B4, and B5, the BSG is often investigated in food additives [ 48 , 67 ].

3.1.3 Current applications and potential in polymer technology

Animal feed.

Nowadays, the main application of brewers’ spent grain is low-value animal feed with relatively low market value. It is often sold to farmers, mainly in a wet state [ 68 ]. It is associated with the composition of this by-product, particularly protein content [ 45 ]. As a result, Belibasakis and Tsirgogianni [ 69 ] and Sawadogo et al. [ 70 ] reported the enhanced milk production for cows fed with BSG. Also, other works reported the beneficial impact on animal nutrition, including fish, pigs, and chickens [ 71 , 72 , 73 ]. In the case of lack of potential recipients of BSG for animal feed, this by-product may be deposited in the fields, where in moderate amounts, it can act as natural fertilizer [ 55 ].

Considering the nutrition, brewers’ spent grain was also investigated as a human food ingredient. Because of its composition and origin, it was introduced into bakery products as a flour substitute [ 74 ]. Ground BSG is characterized by a darker color than the lightest types of flour, so it could not be applied in white bread [ 75 ]. Nevertheless, BSG showed a very beneficial impact on the bread protein content due to its composition, increasing it by ~ 50%, when only 10% of traditional flour was replaced [ 76 ]. Combining the protein content with the lack of starch (which is removed during mashing—see Fig.  1 ), the caloric density of bread containing 10% of BSG may be even 7% lower compared to the conventional bread [ 77 ]. Except for the bakery products, brewers’ spent grain can be incorporated into other high-fiber foods [ 78 , 79 , 80 , 81 ]. In general, the food-sector applications of brewers’ spent grain were comprehensively discussed in the excellent review works of McCarthy et al. [ 82 ], Lynch et al. [ 48 ], and lately Rachwał et al. [ 83 ].

Energy production

Like other types of waste biomass, BSG was also investigated in energy production, which may be implemented within the brewery, leading to reduced production costs [ 84 ]. It can be directly combusted. However, it may cause problems related to the high nitrogen content and resulting generation of nitrogen oxides [ 85 ]. Such an effect can be reduced by the application of pyrolysis [ 86 ]. Another possibility is converting BSG into charcoal bricks, which increases its calorific value from ~ 20 to 27 MJ/kg [ 87 , 88 ]. Multiple works also reported microbial fermentation of brewers’ spent grain into bioethanol [ 89 , 90 , 91 ] or biogas [ 92 , 93 , 94 , 95 ], which can be applied as biofuels.

Fermentation

Considering fermentation, BSG was investigated as a growth medium [ 96 ], e.g., substitute of sucrose or glucose in the lactic fermentation [ 97 , 98 , 99 ], medium for pullulan production [ 100 ], and introduced into manufacturing of xylitol [ 101 , 102 , 103 ] or citric acid [ 104 ]. The application of wastes and residues for fermentation is a very common and often investigated approach [ 105 ].

Among the mentioned fermentation products, lactic acid is an exciting compound for polymer technology. It is commonly applied in poly(lactic acid) manufacturing—one of the most popular biodegradable, thermoplastic polyesters [ 106 ]. Over the last years, it attracted much attention due to the application in 3D printing [ 107 ]. Moreover, due to the current law regulations, its popularity in manufacturing packaging materials is increasing, often combined with other, less expensive materials like thermoplastic starch [ 108 ].

Except for lactic acid, other BSG fermentation products, which could be applied in polymer technology are citric acid [ 109 ] and propionic acid [ 110 ]. The first one can be applied as a co-monomer in manufacturing of polyesters [ 111 , 112 , 113 , 114 ] or as a crosslinking agent [ 115 , 116 ]. Propionic acid is a substrate in the production of polymers based on cellulose derivatives, such as cellulose propionate [ 117 ]. Their popularity is growing over the last years due to the current pro-environmental trends related to bio-based polymer materials and their potential novel applications, e.g., in 3D printing [ 118 , 119 , 120 ].

Figure  4 summarizes the potential applications of BSG fermentation products in polymer technology. Nevertheless, to the best of our knowledge, no works deal with the application of BSG fermentation products in polymer technology. More details related to the recent developments in the biotechnological valorization of these by-products were presented recently in the comprehensive review work by Puligundla and Mok [ 121 ].

Potential applications of BSG fermentation products in polymer technology

Extraction of celluloses and lignin

Except for the microbial conversion, various compounds present in BSG, which may find application in polymer technology, can be extracted using different techniques [ 122 , 123 , 124 ]. Among the most noticeable components of BSG in terms of polymer technology are celluloses and lignin [ 125 ]. They could be applied as fillers for composites and intermediates in manufacturing other raw materials used in polymer technology.

Mishra et al. [ 126 ] presented the multi-stage process of BSG conversion into cellulose nano-fibers consisting of alkali treatments and bleaching. They isolated nanosized fibers with an average diameter of 4.6 nm, shown by atomic force microscopy. Similar fibers are often investigated as fillers for polymer nanocomposites [ 127 , 128 , 129 ]. The efficient isolation of fibers and removal of other components of BSG was confirmed by thermogravimetric analysis (lack of decomposition step attributed to the presence of lignin) and X-ray diffractometry (gradual increase in crystallinity index). Similar observations were made by dos Santos et al. [ 130 ].

Mussatto et al. [ 131 ] investigated the recovery of lignin from BSG. The by-product was subjected to the soda pulping process, comprehensively described in other work [ 132 ]. The resulting black liquor was treated with sulfuric acid, which enabled the separation of lignin by precipitation. Except for the lignin, the investigated process enabled the removal of ferulic, p -coumaric, p -hydroxybenzoic, vanillic, and syringic acids from black liquor. Such an effect points to the presence of these compounds in obtained lignin, which could be applied, e.g., as a filler for wood-polymer composites.

Quite interesting is also the extraction of arabinoxylans from brewers’ spent grain. They are hemicelluloses found in plants' primary and secondary cell walls, which consist of copolymers of arabinose and xylose [ 133 ]. They play a structural role in plants, and interestingly the significant amounts of phenolic acids are bound to them, so they show noticeable antioxidant activity [ 134 ]. Arabinoxylans and their esters are applied in polymer technology to develop biodegradable and even edible films [ 135 , 136 ], which could be efficiently applied in food packaging applications [ 137 , 138 , 139 ]. They could be enzymatically extracted from BSG in a multi-step procedure [ 140 , 141 , 142 ]. The extraction efficiency can be significantly enhanced by the proper particle size distribution of BSG adjusted by milling and sieving, as proven by Reis et al. [ 143 ]. Moreirinha et al. [ 144 ] used the brewers’ spent grain arabinoxylans to prepare composite films with a different share of nanocellulose. Moreover, selected composite films were modified with ferulic acid or feruloylated arabinoxylo-oligosaccharides obtained from BSG. All prepared films were characterized by the onset of thermal decomposition exceeding typical sterilization or autoclaving temperatures ~ 150 °C. They were characterized by satisfactory mechanical performance, with Young’s modulus in the range of 4.3–7.5 GPa (the highest for composite containing 50% of nanocellulose) and tensile strength of 71–110 MPa (the highest for 75% nanocellulose loading). Modifications of films unfavorably affected the mechanical performance but increased the antioxidant activity determined by DPPH assay from the initial 2% to 64–90%. Also, a noticeable reduction in bacterial ( Staphylococcus aureus ) and fungal ( Candida albicans ) growth is beneficial for the potential applications in food packaging.

Extraction of phenolics

Except for cellulose, hemicellulose, or lignin, also other compounds can be extracted and isolated from brewers’ spent grain. Very auspicious are the phenolics mentioned above, primarily hydroxycinnamic acids, showing antioxidant properties. The BSG should be considered an inexpensive source of these compounds, which could be efficiently applied not only in the food or cosmetic industry [ 145 , 146 , 147 ] but also as potential antioxidants for polymer materials [ 148 , 149 , 150 ]. Phenolics can be recovered from brewers’ spent grain by different variants of extraction, e.g., solid–liquid type or assisted by supercritical fluids, microwaves or ultrasounds, and enzymatic or alkaline reactions [ 151 , 152 , 153 ]. As mentioned above, the yield of their recovery strongly depends on the extraction method and its parameters, e.g., selected solvents [ 154 ]. Similar phenomena were reported for other by-products, e.g., from the coffee industry, also characterized by high phenolics content [ 155 , 156 , 157 ]. The recent advances in the extraction of bioactive compounds, including phenolics, from brewers’ spent grain, were comprehensively summarized in the excellent work of Bonifácio-Lopes et al. [ 158 ]. Nevertheless, to the best of our knowledge, there are no literature works reporting the application of BSG-originated phenolics in polymer materials.

Liquefaction

Considering other, more direct uses of brewers’ spent grain in polymer technology, in our previous work [ 159 ], we used the brewers’ spent grain as a biomass feedstock for crude glycerol-based microwave liquefaction aimed at manufacturing biopolyols for polyurethanes. The general scheme of the process is presented in Fig.  5 . The spectroscopic investigation of obtained polyols revealed that biomass was partially decomposed during the process and reacted with solvent particles. Nevertheless, the efficiency of the process was relatively low, and the hydroxyl values were in the range of 900–1050 mg KOH/g. Such values are very high and could be suitable only for manufacturing very crosslinked and stiff materials. Further studies should include the application of catalysts and optimization of process conditions to enhance its efficiency.

The general scheme of microwave-assisted liquefaction of BSG resulting in biopolyol for polyurethanes [ 159 ]

Filler for polymer composites

On the other hand, the relatively high fiber content in brewers’ spent grain makes it attractive for the preparation of wood-polymer composites, possibly applied in various branches of industry [ 160 ]. Other fillers, either conventionally applied wood flour or waste-based, are characterized by a relatively similar composition [ 161 , 162 ]. Moreover, the presence of proteins, which may act as plasticizers, may facilitate the melt processing of composites [ 163 ].

Revert et al. [ 164 ] introduced the BSG as a filler into the polypropylene matrix. Nevertheless, due to the polarity differences between filler and matrix, the interfacial interactions were fragile, and the significant deterioration of mechanical performance was noted. The only positive effect of the BSG incorporation was the shift of the oxidation onset temperature attributed to the presence of phenolics showing antioxidant activity. The addition of 10–40 wt% of by-product shifted the oxidation onset by 10–23 °C.

Barbu et al. [ 165 ] introduced BSG into particleboards as a partial replacement of wood, which is a common trend in the case of wood-polymer composites [ 166 , 167 , 168 ]. The appearance of BSG without additional treatment (presented in Fig.  6 ) is quite similar to the wood chips, so this by-product can be easily applied as substitute for conventional raw materials. Particleboards bonded with polymeric 4,4′-methylene diphenyl isocyanate, urea–formaldehyde, or melamine urea–formaldehyde resin. Nevertheless, according to the presented results, to maintain the satisfactory level of the mechanical properties, the content of BSG should be kept at low levels (up to 10%). The structural differences associated with the reduction in particle–particle bonding between wood particles were noted at higher loadings due to the high consumption of glue by BSG. Authors suggested that at higher contents, brewers’ spent grain should be combined with innovative glues, based on casein or tannins, which could improve the particle–particle bonding. Similar conclusions about the potential, beneficial share of BSG in wood-based particleboards were provided by Klimek et al. [ 169 ], who also suggested the 10% substitution of wood with BSG.

The appearance of BSG without additional treatment

A very interesting application of BSG in polymer technology was also presented by Ferreira et al. [ 170 ], who used it to prepare disposable trays for food packaging. They were obtained by compression molding of BSG with potato starch applied as a continuous phase. The process was aided with the addition of glycerol, water, and in some cases gelatin, chitosan, or glyoxal applied as crosslinkers. After compression, trays were covered with beeswax. Obtained materials were characterized by significantly higher flexural strength and modulus than commercial trays from expanded polystyrene. Independently of the BSG content (from 20 to 80% in the whole tray), trays showed strength in the range of 1.51–2.62 MPa, compared to the 0.64 MPa for commercial material. Also, the modulus was noticeably higher (1.1–2.0 MPa) compared to polystyrene trays (0.28 MPa). Nevertheless, due to their composition and hydrophilic character of applied raw materials, trays showed significantly higher water absorption than polystyrene, which resulted in a significant 80–90% decrease in mechanical parameters. Such an effect was attributed to the plasticizing effect of water. The application of crosslinkers or beeswax slightly reduced the water absorption. However, deterioration was still noted after immersion, and polystyrene trays showed noticeably superior properties. Nevertheless, presented results indicate that such a solution is quite promising, especially for applications that do not require exceptional resistance to water.

Generally, multiple works dealing with the application of brewers’ spent grain in the polymer sector, especially these dealing with its use as a filler for composites or substitute of wood in particleboards, indicate the necessity for modifying this by-product [ 171 , 172 ]. Modifications should be aimed at enhancing the interfacial interactions with polymer matrices by the change of their hydrophilic character. Such an effect could be achieved by thermo-mechanical treatment resulting in non-enzymatic browning in the caramelization process and mostly Maillard reactions, as presented in our previous works [ 34 , 173 ]. It is also essential that melanoidins show noticeable antioxidant activity, which can be very beneficial for the oxidative stability of polymer composites [ 174 ].

In previous works, we reported the application of thermo-mechanically modified BSG as a potential filler for wood-polymer composites [ 175 , 176 ].

In the case of poly(ε-caprolactone) composites, their mechanical performance was noticeably affected by the parameters of thermo-mechanical treatment of BSG [ 175 ]. The increase of modification temperature noticeably affected the interface surface area, resulting in an even 30% increase in composites’ toughness. Dynamic mechanical analysis indicated over 30% drop in the adhesion factor and increased the constrained chain volume exceeding 27%. Such an effect points to the significant enhancement of the interfacial interactions.

On the other hand, modified BSG could be effectively applied to substitute traditional wood flour in polyethylene-based composites [ 176 ]. Nevertheless, due to the differences in the chemical composition between fillers (presence of proteins, lipids, and melanoidins in BSG, lower content of holocellulose compared to wood flour), the composites’ performance was differing. The introduction of BSG resulted in significantly higher values of melt flow index. When wood flour was completely substituted, it increased from 3.23 to 10.56 g/10 min, which was attributed to the drop in viscosity from 1.02 to 0.30 Pa s. A similar effect was noted in our other work [ 163 ]. The density and porosity of materials were slightly reduced with the increasing share of BSG due to the presence of proteins, which may enable better encapsulation of filler particles with polymer macromolecules. However, it also caused changes in the composites’ mechanical performance. Tensile strength and modulus were reduced by ~ 27% and ~ 42%, respectively, but the elongation at break was doubled. Concluding, modified brewers’ spent grain could be introduced as partial replacement of conventional wood flour to engineer materials with desired properties.

Other, less popular methods of BSG utilization include the manufacturing of adsorbents [ 177 , 178 , 179 ], paper [ 47 , 180 ], bricks [ 87 ], or activated carbon [ 181 ]. Brewers’ spent grain-based adsorbents, and activated carbons were found efficient in the removal of dyes [ 182 , 183 , 184 , 185 ], volatile organic compounds from the gas phase [ 186 ], but mostly metal ions from aqueous media [ 187 , 188 , 189 , 190 , 191 ].

3.2 Trub, spent hops

3.2.1 overview.

Trub is generated during filtration of wort before the fermentation. After cooling down, the wort is separated from the trub, accounting for around 0.2–0.4% of the wort volume [ 28 ]. The precipitate contains coagulates of high molecular weight proteins [ 192 ]. They are generated during the heat-induced denaturation of proteins. Except for coagulates, the residual hops may be present in trub, because according to the literature data, around 85% of the initial hops mass introduced into wort is removed as a by-product [ 77 ]. After extracting the compounds that create the flavor, aroma, and bitterness of the final beer, the solid residues of hops are discarded. However, their content in trub depends on the applied technology of beer hopping [ 193 ]. Therefore, the composition of this by-product may be very diverse, depending on the share of coagulates and spent hops.

3.2.2 Composition

Separately, trub contains mostly significant amounts of proteins, even up to 70% of dry matter [ 83 ]. Considering spent hops, the proteins account for around 22–23% of dry matter, with a similar share of fiber [ 194 ]. According to Mathias et al. [ 42 ], around 20% of the residual reducing sugars may also be present in trub. Both trub and spent hops contain relatively low amounts of ash, ~ 2%, and ~ 6%, respectively. Interestingly, this by-product may contain noticeable amounts of essential oils and phenolics due to the hop presence. Such an effect is attributed to the low solubility of various compounds in the wort, e.g., in the case of lupulones [ 195 ]. On the other hand, phenolics such as hydroxycinnamic acids, gallic acid, catechins, anthocyanidines, and others, are precipitated with proteins and removed as a part of hot trub [ 196 ]. The essential oils contain noticeable amounts of terpenes [ 67 ]. Moreover, myrcene, alpha-humulene, or beta-ceryophyllene are present. They account for ~ 47% of the essential oil [ 197 ]. The structures of main components of essential oils are presented in Fig.  7 .

The main components of spent hops essential oil: a myrcene, b α-humulene, c β-caryophyllene, and d 2-undecanone [ 197 ]

3.2.3 Current applications and potential in polymer technology

Contrary to the brewers’ spent grain, the trub and spent hops are significantly less frequently used in animal feeding, despite the beneficial composition, relatively high fiber content, and mostly the presence of proteins. Such an effect is attributed to the presence of hops, particularly bitterness [ 198 ]. Another issue is the low energy value of spent hops, which is around 50% lower than spent grains, despite the relatively high fiber content [ 77 ]. On the other hand, some research works investigated the combination of spent hops with other brewery by-products, which resulted in acceptable feed, e.g., for pigs [ 199 ]. According to the works of Huszcza et al. [ 200 , 201 ], the bitter acids originated from spent hops can be removed or degraded by yeast or fungi. More recent works dealing with the trub and spent hops investigated the reduction of bitterness by the multi-step extraction of bitter compounds [ 202 ]. During extraction, most carbohydrates were removed together with tannins and phenolics, which are often bound to the carbohydrates. As a result, the share of proteins and fat was increased from the initial 26.5% and 5.2% to 70.3% and 9.9%, respectively. Due to the significant drop of phenolics content (from ~ 350 to ~ 125 mg gallic acid equivalents/100 g), the antioxidant activity was also noticeably reduced. Nevertheless, changes resulting from the extraction allowed the use of modified trub in food applications.

Considering the most popular uses of biomass and brewery by-products, except for the animal feed, trub and spent hops may be applied as a soil conditioner and fertilizer, which is associated with their high nitrogen content [ 42 , 203 ].

As mentioned above, the trub and spent hops contain noticeable amounts of essential oils and phenolics. These compounds can be effectively extracted from this by-product and potentially applied in polymer technology. Bedini et al. [ 197 ] reported that the terpenes present in spent hops could be applied as the repellents against the insects, e.g., Rhyzopertha dominica or Sitophilus granarius . Spent hops essential oils were 2–5 times more effective against R. dominica than Laurus nobilis oils [ 204 ] and showed similar repellency against S. granaries as Hyptis suaveolens oils [ 205 ]. Bartmańska et al. [ 206 ] also showed antifungal activity of spent hops extracts against Botrytis cinerea , Fusarium oxysporum , Fusarium culmorum , and Fusarium semitectum . Therefore, the application of spent hops or only their essential oils in manufacturing the packaging materials seems reasonable. The extraction and isolation of essential oils from spent hops can be performed by hydrolysis, steam distillation, but also using supercritical CO 2 or eutectic solvents [ 207 , 208 , 209 , 210 ].

Moreover, this by-product can be applied in fermentation processes as a supplement for microbes due to the high nitrogen content [ 83 ] and the presence of lipids and zinc [ 211 ].

3.3 Spent yeast

3.3.1 overview.

During the initial stage of fermentation, the intensive proliferation of yeast is occurring, so after fermentation and maturation, the surplus of yeast is present and should be removed from beer [ 212 ]. Partially, they are recovered by natural sedimentation, but for higher efficiency, additional filtration or centrifugation may be applied [ 213 ]. The actual amount of this by-product depends on the type of yeast used for fermentation, but it can account even for 15% of total by-products generated during beer production [ 214 ]. Around 0.3 kg of spent yeast is generated per hectoliter of beer. Depending on the properties of yeast, in particular their flocculation, this by-product is characterized by the high moisture content in the range of 75–90%. Therefore, portion of beer is removed along with yeast, which may generate the 1.5–3.0% loss of beer [ 28 ].

3.4 Composition

Considering the composition, spent yeast contains a noticeable amount of carbohydrates and proteins. Among the first group, the most abundant are non-cellulose compounds (25–35%), mainly β-glucans, mannoproteins, and glycogen, followed by cellulose (17–25%) [ 215 ]. Proteins may account for more than 50% of the spent yeast dry mass [ 195 , 216 ]. Jacob et al. [ 217 ] reported even value of 74.3 wt%. Therefore, the spent yeast is characterized by the lowest carbon:nitrogen ratio among the brewing by-products, around 5 [ 42 ]. Literature works report different amino acid compositions of spent yeast. According to Vieira et al. [ 218 ], the most common amino acids in spent yeast are alanine (even over 9%), arginine, aspartic acid, and cysteine. At the same time, Jaeger et al. [ 219 ] indicated that glutamic acid is the most abundant one (~ 15%), followed by histidine, alanine, arginine, and aspartic acid. Such an effect may be associated with the differences between particular Saccharomyces cerevisae strains applied worldwide [ 220 ].

Brewery spent yeast are also a great source of micro- and macroelements, as well as vitamins. Nevertheless, the mineral composition of yeast can differ depending on the length of fermentation and fermentation cycles [ 67 ]. Among the most abundant minerals are sodium, potassium, and magnesium, but noticeable amounts of phosphorous may be present, which could be associated with yeast nutrients in breweries [ 195 ]. Considering the vitamins, the B type is the most popular, especially niacin, thiamin, pantothenate, and riboflavin [ 218 ].

3.4.1 Current applications and potential in polymer technology

Due to the high content of proteins, vitamins, and minerals, the spent yeast is mostly applied as an additive in animal feeding [ 221 ]. It has been repeatedly proven that such application of this by-product shows very positive effects on the animals’ health. It may result in increased milk production, improved microflora, and enhanced resistance to various microorganisms [ 222 , 223 , 224 ]. Except for the animal feed, spent yeast was also investigated in human consumption. However, they show great potential due to the high contents of nucleic acids (6–15%), in particular ribonucleic acid, their use in an unmodified state is somewhat limited [ 216 ]. The ribonucleic acid is metabolized to the uric acid in the human body, which can cause gout [ 225 ]. Generally, the spent yeast application in animal and human nutrition was comprehensively discussed in dedicated review works [ 219 , 226 , 227 , 228 , 229 ].

Another broadly investigated application of spent yeast is cultivating microorganisms and other biotechnological processes [ 230 , 231 ]. Due to the beneficial composition of brewery spent yeast, various microorganisms cultivated on this by-product may grow noticeably faster than other yeast types, as reported by Ferreira et al. [ 232 ]. As a result, the spent yeast may be applied as a very efficient source of multiple enzymes, including proteinases [ 233 ], proteases [ 234 , 235 ], or pectinases [ 236 , 237 ]. Moreover, brewery spent yeast can be applied as nutrients during ethanol or lactic acid fermentation [ 238 , 239 ]. Pietrzak and Kawa-Rygielska [ 240 ] showed that the 5% addition of brewery spent yeast might increase the rate of sugar consumption and ethanol production resulting in even 11% enhancement of ethanol yield. Such an effect was ascribed to the high nitrogen content of the medium.

Other, less popular uses of spent yeast from beer production include methane production or application as biosorbent. Considering the energy production, spent yeast can be considered an excellent substrate for co-digestion purposes with other materials, including swine manure [ 241 ], spent grains [ 242 ], or crude glycerol [ 243 ].

Considering the polymer technology point of view, the brewery spent yeast show hardly any applications. The most promising and the closest to polymer technology is their use in fermentation processes generating lactic or succinic acid. The use of lactic acid in polymer technology was described in Sect. 3.1.3 . The succinic acid can be applied in the manufacturing of polyesters or alkyd resins [ 244 , 245 ].

Rakin et al. [ 246 ] reported that the application of spent yeast might increase the rate and yield of lactic acid fermentation due to the presence of amino acids, vitamins, and minerals. Similar observations were made by Champagne et al. [ 247 ]. According to Radosavljević et al. [ 248 ], the brewery spent yeast, combined even with other brewery by-products, can act as a low-cost fermentation medium for manufacturing of lactic acid.

Considering succinic acid production, the substitution of conventional yeast extracts with hydrolysate of spent brewery yeast as a nitrogen source was successfully achieved by Jiang et al. [ 249 ] and Chen et al. [ 250 ].

Nevertheless, to the best of our knowledge, there are no literature reports directly connecting the brewery spent yeast with the polymer technology.

4 Conclusions, future trends, and developments

The presented review summarized the literature works associated with the by-products of beer production. Their generation during brewing was discussed, and the beer market size, which affects the amount of by-products. Reported data about the composition of brewers’ spent grain, trub, spent hops, and spent yeast indicate that the application in polymer technology should be considered an auspicious method of their utilization, viable from the ecological and economic point of view. Moreover, their chemical composition, particularly the presence of compounds showing antimicrobial, antifungal and antioxidant activity, puts the brewing by-products as potential active fillers providing additional properties to polymer materials and promising intermediates in manufacturing various raw materials for polymer technology.

In order to take full advantage of the brewing by-products potential in polymer technology, future works should focus on the following issues:

Partial substitution of conventional lignocellulosic fillers in wood-polymer composites with brewers’ spent grain, which could enhance the resistance to thermooxidation.

Investigations related to the mechanisms of the enhancement of thermooxidative stability of various polymer materials by antioxidants present in brewing by-products.

The applications of brewing by-products in packaging materials or even edible films for food protection.

Liquefaction of brewing by-products resulting in raw materials for manufacturing of polyurethanes or polyester resins.

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This work was supported by the National Science Centre (NCN, Poland) in the frame of SONATINA 2 project 2018/28/C/ST8/00187–Structure and properties of lignocellulosic fillers modified in situ during reactive extrusion.

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Hejna, A. More than just a beer—the potential applications of by-products from beer manufacturing in polymer technology. emergent mater. 5 , 765–783 (2022). https://doi.org/10.1007/s42247-021-00304-4

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Brewing and Craft Beer

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Beer is a beverage with more than eight thousand years of history, and the process of brewing has not changed so much over the centuries. However, important technical advances have allowed us to produce beer in a more sophisticated and efficient way. The proliferation of specialty hop varieties has been behind the popularity of craft beers seen in the last few years around the world. Craft brewers interpret historic beer with unique styles. Craft beers are undergoing an unprecedented period of growth, and more than 150 beer styles are currently recognized.

This Special Issue, “Brewing and Craft Beer”, is aimed at giving the floor to the craft brewers who wish to share their findings, as well as to academic and industrial researchers. Coverage includes a selection of original research and current review articles related to the whole process, from cereal to beer, with particular emphasis on:

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A Hands‐On Guide to Brewing and Analyzing Beer in the Laboratory

Florian a. thesseling.

1 Laboratory of Systems Biology, VIB Center for Microbiology, Leuven Belgium

2 Laboratory for Genetics and Genomics, Center of Microbial and Plant Genetics (CMPG), Department M2S, KU Leuven, Heverlee Belgium

Peter W. Bircham

Stijn mertens, karin voordeckers, kevin j. verstrepen.

Beer would not exist without microbes. During fermentation, yeast cells convert cereal‐derived sugars into ethanol and CO 2 . Yeast also produces a wide array of aroma compounds that influence beer taste and aroma. The complex interaction between all these aroma compounds results in each beer having its own distinctive palette. This article contains all protocols needed to brew beer in a standard lab environment and focuses on the use of yeast in beer brewing. More specifically, it provides protocols for yeast propagation, brewing calculations and, of course, beer brewing. At the end, we have also included protocols for analyses that can be performed on the resulting brew, with a focus on yeast‐derived aroma compounds. © 2019 The Authors.

INTRODUCTION

Beer brewing is intrinsically a biotechnological process: the conversion of raw materials into beer relies on many different enzymatic reactions and microbial activity. Beer is traditionally made from four key ingredients: malted cereals (barley or other), water, hops, and yeast. Each of these ingredients contributes to the final taste and aroma of beer.

Beer production starts with the malting of barley (or other cereals, such as wheat, sorghum, rye, or oats). The main goal of malting is to activate enzymes within the grain. These enzymes will hydrolyze starch and other compounds within the kernels during mashing (Goldammer, 2008 ; Kunze, 2004 ). During malting, barely kernels are soaked in water and periodically aerated, the so‐called steeping and germination phase. During germination, three important groups of enzymes are activated: (i) amylases, (ii) proteases/peptidases, and (iii) beta‐glucanases. Each of these enzymes have an important function during the malting and downstream brewing process: (i) amylases convert starch, present in the barley kernels, into fermentable sugars; (ii) proteases and peptidases break down proteins and release free amino nitrogen (FAN), while (iii) beta‐glucanases degrade the endosperm cell wall, allowing other enzymes access to the endosperm. Next, in the drying and kilning phase, kernels are dried and heated. This stops germination, arrests enzymatic activity within the kernels, reduces spoilage risks, and determines the impact of malt on the final aroma and color of the beer.

The actual brewing process consists of five steps. The main goal is to convert insoluble malt or grain material into a soluble and fermentable extract.

Milling of malted grains (i) and mashing (ii)

In this step, milled grains are mixed with warm water. This mash is kept at specific temperatures and pH to ensure proper enzymatic conversion of starch and proteins. Traditionally, a starting temperature of 45°C is used. At this temperature, proteases are activated and degrade proteins to short peptides and amino acids, that will form the major nitrogen source for yeast during fermentation. The mash is then heated to 62°C‐64°C, at which starch will gelatinize and become accessible to amylases. Beta‐amylases will cleave off maltose from starch molecules. The mash is then heated to 72°C for 15‐25 min, allowing further breakdown of long chain polysaccharides by alpha‐amylases. Finally, the temperature of the mash is raised to 78°C, stopping nearly all enzymatic activity.

Modern, highly modified malts allow mashing in directly at temperatures >60°C since the protein breakdown has already been completed by the maltster.

Filtering/lautering (iii)

During this step, the insoluble fraction (spent grains) is separated from the soluble extract. The remaining extract (wort) is transferred to the boiling vessel.

Boiling (iv)

During boiling, hops and other spices are added. These contribute to bitterness and aroma of the final beer. More specifically, hops contain alpha acids and during boiling, these acids will isomerize into iso‐alpha acids, the major bittering substances in beer.

Bitter hops contain high concentrations of alpha acids (6%‐16%) and are often added at the beginning of the boil. Aroma hops have a high hop oil content (>1%), which contains 200‐250 different compounds that contribute to the characteristic aroma of hops (e.g., myrcene, linalool, and nonenal) (Kunze, 2004 ). Aroma hops are typically only added towards the end of the boil, or in the dry‐hopping of green beer to reduce the stripping of aroma‐active compounds.

Other major effects of wort boiling include protein denaturation and aggregation, concentration of the wort, stripping of off‐flavors such as dimethyl sulfide (DMS), and sanitization of the wort. The boiled wort is then transferred to a whirlpool to remove the aggregated protein and insoluble hop components (hot trub). Finally, the wort is cooled, aerated, and transferred into the fermentor, where yeast is added.

Fermentation (v)

During fermentation, yeast converts fermentable sugars into CO 2 and ethanol. At the same time, hundreds of secondary metabolites that influence the aroma and taste of beer are produced. Variation in these metabolites across different yeast strains is what allows yeast to so uniquely influence beer flavor. Examples of typical yeast‐derived beer flavors are the esters isoamylacetate (banana aroma), ethyl acetate (solvent‐like aroma), and ethyl hexanoate (pineapple aroma). For reviews on the different aroma's produced by yeast, and the biochemical pathways involved, see for example (Dzialo, Park, Steensels, Lievens, & Verstrepen, 2017 ; Pires, Teixeira, Branyik, & Vicente, 2014 )

Primary fermentation is typically completed within 10 days, and the end‐product of this fermentation is called green beer. Afterwards, most of the yeast is removed, and the green beer is transferred to a maturation tank and stored at low temperatures (−1°C to 5°C), for several days (ale beers) or up to a couple of weeks (lager beers). During this maturation, the remaining yeast are still metabolically active and can produce additional CO 2 and ethanol as well as reduce off‐flavors such as diacetyl (buttery, rancid aroma).

Many breweries have their own proprietary yeasts for their specific beers. Two main types of yeast are used in brewing: Saccharomyces cerevisiae is a top‐fermenting yeast used to make ales while Saccharomyces pastorianus is a bottom‐fermenting yeast used in lager brewing. The latter is actually a hybrid yeast and combines phenotypes of both its parental species: the high fermentation capacity of S. cerevisiae and the cold tolerance of S. eubayanus (Libkind et al., 2011 ).

Although most breweries use pure yeast cultures for fermentation, spontaneous or mixed fermentation is still used for some specialty beers. These kinds of fermentations usually involve a mix of different yeast species (and bacteria as well) that appear sequentially over time, giving the beer an added complexity. For example, Brettanomyces yeast species are commonly present during the later stages of Belgian lambic beer fermentation (Bokulich, Bamforth, & Mills, 2012 ; Steensels et al., 2015 ). Commonly referred to as Brett by brewers, these yeasts can metabolize longer chain carbohydrates and produce a number of distinctive compounds that provide the characteristic Brett aromas (barnyard, spicy, smoky, metallic etc.).

Since yeast is the driving force behind making beer, this protocol will focus on the yeast side of beer brewing. More specifically, this article describes the different steps in producing your own beer, starting from some basic brewing calculations to yeast propagation and chemical analysis of the end product. We deliberately only included one beer recipe, so you can experiment with how different yeast strains can influence beer aroma. Since the brewing world is full of its own jargon, we have included a glossary of brewing terminology and abbreviations (Table ​ (Table1). 1 ). The methods provided in this protocol are designed to have a minimal equipment requirement and is similar to a small‐scale home brewing approach. Far more advanced brewing setups are available but are often costly and vary greatly in the specifics of usage and are, thus, beyond the scope of this protocol unit. Each of the brewing‐specific materials can be purchased from various suppliers, we have listed some of them in Table ​ Table2 2 .

Glossary of Brewing Terms

Suppliers for Brewing Equipment

Please note that it is beyond the scope of this article to give you a detailed overview of all different beer brewing methods and recipes available. For this, we refer readers to, for example Goldammer, 2008 ; Snyder, 1997 , and to the Internet Resources listed at the end of the article.

Basic Protocol 1. PREPARING 20 L OF 12°P WORT STARTING FROM WHOLE GRAINS

Wort production can be broken down into three essential steps − mashing, lautering, and boiling. Making a wort recipe from scratch allows complete control of this process. This can be important if the experiments in question require specific modifications to wort composition. Here we provide a basic wort recipe starting from whole grains that can easily be scaled or modified as needed.

The recipe is for a generic ale beer with 25 international bittering units (IBU) (see also Support Protocol 1 ). It is not designed to mimic a specific beer style but rather produce a lightly hopped wort that can be used as a growth medium for fermentation assays. Individual styles are beyond the scope of this method but there are many resources and software available for developing recipes within individual beer style guidelines, see Internet Resources.

This protocol uses a single temperature infusion mash—a compromise between the different thermal optima of malt enzymes and overall efficiency. For yeast propagation and simple fermentation tests, wort prepared according to Alternate Protocol 1 can also be used.

• 70% (v/v) ethanol
• Pale ale malt
• Bittering hops (such as magnum hops 15% alpha acids)
• 200 ppm zinc stock solution (see recipe)
• Roller mill for grinding malt (optional if buying pre‐ground malts)
• 30‐L stainless steel electric kettle with stainless steel tap for use as mash tun
• Thermometer
• Brewers paddle or large spoon to stir the mash
• 30‐L stainless steel pot with tap and false bottom for use as a lauter tun
• 500‐ml beaker
• 30‐L stainless steel electric kettle with stainless steel tap for use as boil kettle
• Cooling coil with hose tap attachments
• Sterile 20‐L canister
• Four sterile 5‐L canisters
• Additional reagents and equipment for performing an iodine start test (see Support Protocol 4 )

Prepare equipment

Do not use ethanol with additives such as methyl ethyl ketone (MEK), since this is not suitable for human consumption.

See Support Protocol 2 for grain bill calculation.

Properly ground malt should have particles small enough to facilitate efficient hydration. It should also still include unshredded husks to create a stable grain bed during the lautering and prevent a stuck mash (see also Troubleshooting).

See Support Protocol 3 for the calculation of strike water temperature.

• 4 Gently stir in the grist (ground malt produced in step) ensuring that any clumps of malt are broken up.

The mash temperature can be between 63°C and 72°C. Lower temperatures will result in a highly fermentable wort, whereas higher temperatures will increase the amount of non‐fermentable sugars in the wort and can increase mouthfeel and apparent sweetness in the final beer.

See Support Protocol 4 for the iodine starch test.

During this step, residual amylases will be deactivated. The wort's viscosity is also decreased at higher temperatures, which helps in the subsequent lautering. Make sure not to heat above 80°C as this would release undigested starch to the wort.

Make sure to elevate the lauter tun, so that its contents can drain back into the cleaned electric kettle.

• 9 While the mash is settling, heat up 16 L of water in the cleaned mash tun to 78°C for use in the sparge.

The first runnings will be cloudy and full of particulate matter.

• 11 Repeat this process until the wort begins to run clear.

Start draining with a low flow rate, which can be increased as a stable grain bed settles on the false bottom of the mash tun (see also Troubleshooting). A low flow rate is needed to avoid collapse or creation of channels through the grain bed.

• 13 As the mash drains, additional sparge water can be gently added on top of the mash and continually collected as the mash drains into the boil kettle. As the lautering progresses keep track of the wort gravity (see Basic Protocol 2 or Alternate Protocol 2 ).

Note that this percentage can be adapted to match the evaporation rate of your brewing setup in the subsequent boiling step.

• 15 Turn on the kettle heating and bring the wort to a boil.

See Support Protocol 1 for calculating how much hops need to be added to reach a specific IBU.

• 17 Boil for 60 min.
• 18 Attach the sanitized cooling coil to a cold water outlet and place the coil into the brew kettle. Turn on the water and allow to run until the wort has cooled below 25°C.
• 19 Remove the cooling coil and transfer the cooled wort into a 20‐L canister and store overnight at 4°C.
• 20 Decant the wort, leaving as much of the trub behind as possible.

Ideally, the final volume should be 20 L but this will depend on the efficiency of the mashing and lautering procedures, which can be influenced by a number of factors (see Troubleshooting).

If needed, wort can be sterilized by autoclaving for 10 min at 105°C.

• 23 Optional : Centrifuge for 5 min at 1,500‐3,000 × g , 4°C, completely separate any remaining trub.
• 24 Collect the clarified wort in sterile 5 L canisters.

For long‐term storage, the wort can be kept at −20°C (>6 months).

Support Protocol 1. PREDICTING BITTERNESS

Bitterness of beer is measured in international bittering units (IBU), which represent the amount of iso‐alpha acids per liter (quantified as mg/L or ppm). Importantly, the IBU value of a beer may not match its perceived bitterness. The bitterness of a beer can be affected by, among others, the alcohol level, residual sugars or the use of roasted malts.

Estimation of the expected bitterness of a beer can be calculated using the following formula:

This is provided by the hop producer. Alpha acid% greatly depends on hop variety, harvest year, and hop storage conditions.

The hop utilization rate represents the percentage of hop alpha acids that are first solubilized in wort and later isomerized into iso‐alpha acids. This isomerization reaction requires heat and is dependent on the time of hop addition to the boil and the gravity of the wort. In Table ​ Table3, 3 , utilization% is provided for a range of boiling times and wort gravities (Mosher & Finkel, 1993 ).

Utilization%, Adjusted From Mosher & Finkel ( 1993 )

• V = volume of cooled wort (L)

Support Protocol 2. DETERMINING THE GRAIN BILL TO ACHIEVE A TARGET EXTRACT AND WORT VOLUME

The grain bill is the amount of malt needed to produce a wort of desired final gravity (FG) and volume. It can be estimated using the following formula

• V [L] = the desired volume of cooled wort at 20°C

Conversion of °P to SG and density at 20°C

• °P [% w/w] = the desired wort gravity expressed in degrees Plato

The brewhouse yield displays the relation between the mass of the malt used and the mass of the dissolved extract obtained in the wort (Kunze, 2004 ). It is unique to each brewing setup and recipe and has to be determined empirically. However, a 60% brewhouse yield can be used as a reasonable estimate to calculate the first brew. For more details on brewhouse yield estimation, see Kunze ( 2004 ).

For example, for 20 L of a 12°P wort with a brew house yield of 60%, we need the following amount of malt:

g r a i n b i l l k g = 4.2 k g .

Support Protocol 3. CALCULATE REQUIRED STRIKE WATER TEMPERATURE

The required temperature of the strike water can be determined according to (Holle & Klimovitz, 2003 ):

• GW [kg] = the weight of the added malt/grain
• WW [kg] = the weight of the added strike water
• TM [°C] = wanted final temperature of the mash
• TG [°C] = the temperature of the added malt/grain

Support Protocol 4. IODINE TEST FOR SACCHARIFICATION OF MASH

During mashing, complex carbohydrates need to be hydrolyzed into sugars that can be consumed by yeast, such as glucose, maltose, and maltotriose. This protocol describes how to check if the starch has been sufficiently hydrolyzed.

• Mash solution (see Basic Protocol 1 )
• Lugol's iodine solution (see recipe)
• White porcelain bowl

Avoid any grain particles as these can lead to a false‐positive reaction.

Yellow‐amber red colors indicate complete conversion of starch (Fig. ​ (Fig.1C). 1 C). Blue/black indicates incomplete conversion of starch (Fig. ​ (Fig.1A‐B) 1 A‐B) and the mash should be given an additional 15 min to complete.

Iodine starch test. ( A ) Positive starch result, sample from the beginning of a mash. ( B ) Partial starch conversion mid‐mash. ( C ) Negative starch result, complete starch conversion from the end of a mash.

Alternate Protocol 1. DRIED MALT EXTRACTRECIPE OF 12°P WORT (1 L)

This recipe is ideal for yeast propagation and simple tests (e.g., characterization of the basic fermentation properties of different yeasts). Dried malt extract (DME) wort offers a very reproducible recipe that can be easily prepared without the specialized equipment required for an all grain‐derived wort (see Basic Protocol 1 ). DME, or spray malt, is available in a range of colors and comes in hopped and unhopped varieties. Here we use light unhopped DME, but the recipe can be readily adapted using other DME variants. This recipe can also be used as a concentrated stock if lower gravity wort is required (e.g., for yeast propagation).

• Light unhopped dry malt extract [DME: color: 8 European Brewery Convention (EBC)]
• Deionied water
• Zinc chloride solution at 200 ppm (see recipe)
• 5‐L bottle
• Sterile 500‐ml buckets/bottles to centrifuge wort
• Density meter (e.g., Anton Paar DMA 35)

During autoclaving, proteins precipitate and the wort needs to be clarified afterwards. Because of this, twice the volume is prepared to ensure there is sufficient clarified wort harvested in the end.

Do not autoclave at 121°C as this temperature facilitates maillard reactions between carbohydrates and amino‐compounds.

This will assist protein precipitation and improve the clarity of the final wort.

• 4 Gently decant the wort into sterile 500‐ml centrifuge buckets, leaving as much of the trub behind as possible.
• 5 Centrifuge for 5 min at 1,500‐3,000 × g , 4°C. Collect 1 L of the clarified wort.
• 6 Measure gravity of the wort with the density meter and dilute to 12°P using sterile water if required (see Basic Protocol 2 or Alternate Protocol 2 ).

Zinc is required as a co‐factor for a number of enzymes, such as alcohol dehydrogenase (Kunze, 2004 ), and is commonly added as supplement to wort.

Basic Protocol 2. EXTRACT MEASUREMENT OF WORT USING A HYDROMETER

For brew house calculations, brewers mostly rely on measurements of the wort's or beer's density. Traditionally, wort density is measured using a hydrometer. A hydrometer is a floating body with a thicker bulb for a base, sometimes containing a thermometer, and a thinner upper stem holding a mass percentage (°P) or specific gravity (SG) scale, or both. The value can be determined as the point to which the stem sinks into the fluid. A hydrometer will sink deeper into a sample with lower density and vice versa.

The extract measured before fermentation is called original extract (OE) if measured in °P, or original gravity (OG) if measured as SG. Extract values measured after the fermentation is finished are called residual extract (RE) or FG, respectively.

Here, we give a protocol to determine wort extract using a hydrometer.

• Wort sample (see Basic Protocol or Alternate Protocol 1 )
• 250‐ml glass bottle with screwcap
• Cooling bath at 20°C
• 200‐ml glass cylinder

Close the bottle to avoid evaporation during the cooling process.

Avoid foam on top of the wort sample.

Make sure no gas bubbles adhere to the hydrometer.

Hydrometers for brewing are often calibrated to be read at the highest point of the meniscus which forms around the stem, whereas hydrometers for laboratory use are calibrated to be read at the lowest point of the meniscus. Please check the user manual.

Alternate Protocol 2. EXTRACT MEASUREMENT OF WORT USING AN OSCILLATING U‐TUBE DENSITY METER

A faster and easier way of measuring the wort's extract is using a density meter. The working principle of a density meter is based on an oscillating U‐tube made of glass. The U‐tube gets excited to vibrate at its characteristic frequency. Depending on the density of the tested sample this characteristic frequency changes, which allows calculation of the actual density (DMA 35 Portable Density Meter, Instruction Manual, Anton Paar GmbH, Austria, 2009). This calculation is automatically done by density meter devices for beverage use (e.g., Anton Paar DMA 35).

• Wort sample (see Basic Protocol 1 or Alternate Protocol 1 )
• Warm tap water (40°C)
• Demineralized water
• 100‐ml glass bottle with screwcap
• Plastic syringes

Close the bottle to avoid evaporation.

• 2 Rinse the density meter's U‐tube with your sample before you take the actual measurement. To this end, aspire the liquid into the U‐tube using the built‐in sample tube and pump lever or inject the sample with a plastic syringe. Then dispose of the liquid by depressing the pump lever.
• 3 Take the actual sample in the same way as for the rinsing step; the device will automatically show the density value or any other derived value by choice (e.g., °P or SG).
• 4 Take additional two readings to ensure consistency.
• 5 Rinse the U‐tube with warm tap water followed by a final rinse with demineralized water.

Basic Protocol 3. YEAST PROPAGATION FROM CRYO CULTURES, AGAR PLATES, OR SLANTS

Because of the tremendous effect of yeast‐produced aroma compounds on the quality and character of the final beer, selecting an appropriate yeast is an important and crucial step during brewing. Nowadays, different brewing yeasts are commercially available. These yeast strains are most often supplied as liquid yeast slurries or as active dried yeast powder. For use of these yeast starter cultures, we refer to the manufacturers protocol. Another option is to start from a yeast strain that is stored at −80°C (see Support Protocol 5 ). The protocol below describes how to propagate yeast from such a cryo culture to sufficient cell densities to pitch it into 20 L of a 12°P wort. Using the protocol below, a cell density of ∼2 × 10 8 cells per ml with a viability >95% can usually be obtained. Please check Critical Parameters and Troubleshooting if the cell counts are much lower than expected.

• Yeast strain of choice, as cryo culture or streaked on an agar plate or agar slant
• YPD (2% glucose) agar plate
• Liquid wort (see Alternate Protocol 1 ) or YP maltose (see recipe)
• Sterile wooden sticks (toothpicks work fine) or inoculation loop
• Sterile test tubes
• Shaking incubator
• Test tube rotator
• Sterile Erlenmeyer flasks

This step can be skipped if starting from agar plate or slant.

For lager yeasts, incubate at 20°C rather than 30°C.

Make sure to not thaw and refreeze the cryo culture, since this will significantly reduce cell viability.

Avoid starting with a single colony as this will increase the risk of selecting a colony that may have acquired a deleterious mutation.

Use either wort or YP maltose as starter medium.

If starting from a commercially available yeast strain, check instructions of yeast supplier for exact temperatures to grow your yeast at.

Starter wort gravity is advised to be between 7 and 10°P when brewing a beer with an OE of 10 to 14°P.

Note that using medium containing only glucose as the carbon source is not recommended as the yeast will need time to adapt metabolism to utilize the maltose in wort. The pH of the starter wort should be around 5.

Support Protocol 5. STORING ANY YEAST STRAIN AT −80°C BY MAKING A GLYCEROL STOCK

For the long‐term storage of any yeast strain we recommend glycerol cryo stocks stored at −80°C.

• Dried yeast
• YPD (2% glucose) agar plates
• YPD (2% glucose) liquid medium
• 50% glycerol (sterile)
• Inoculation loop/sterile wooden sticks
• 2‐ml Cryo‐vials (Corning, REF 430659)
• −80°C freezer

When starting from (commercially available) liquid cultures or dried yeast

• 1 Rehydrate dried yeast following the manufacturers protocol.
• 2 Dilute liquid (rehydrated) yeast culture to ∼2‐3 × 10 3 cells/ml (see Basic Protocol 4 ).

For commercially available strains, check the manufacturers protocol for recommended incubation temperatures.

When yeast strains are already streaked on agar plates

• 5 Submerge the inoculation loop/wooden stick in 5 ml YPD liquid medium in test tube and gently shake yeast cells free.
• 7 Transfer 500 µl of the overnight culture into a cryo‐vial.
• 8 Mix gently with the same amount of 50% glycerol (final glycerol concentration 25%).
• 9 Freeze to −80°C until further use.

Basic Protocol 4. ASSESSING YEAST CELL NUMBER AND VIABILITY

Prior to pitching the starter culture, most brewers check cell count and cell viability. One of the most widely used methods in the brewing industry requires a microscope, hemacytometer, and staining with methylene blue or methylene violet (Smart, Chambers, Lambert, Jenkins, & Smart, 1999 ). All yeast cells take up the dye, but only viable cells can reduce it to a colorless product.

This protocol describes how to determine the total number of cells in a liquid culture, as well as the number of viable cells, using a methylene violet staining protocol. Cell counts and viability measurements can also be automated, for example by using a TC20 Automated Cell Counter (Bio‐Rad).

• Deionized water
• Yeast sample
• 0.9% (w/v) NaCl solution or PBS
• 0.1 M glycine buffer, pH 10.6 (adjusted with NaOH)
• Methylene violet solution (0.1% w/v), filter sterilized
• Hemacytometer (Neubauer‐improved type) with cover slips or, alternatively, Kova Glasstic slides (e.g., from FisherScientific)
• Lint‐free paper tissues (e.g., Kimwipes)
• Brightfield microscope (total magnification of 400×)

Prepare the cell count

This step is not required when using Kova Glasstic slides.

Try to have around 100 cells or less per microscope field. Usually a 1:100 or a 1:1000 dilution of your original culture works well. Dilute your samples in 0.9% (w/v) NaCl solution or PBS.

If yeast cells are flocculent, make your dilution using EDTA (50 mM, pH 7.0). This will break up the clumps and will allow you to count the individual cells.

• 3 Mix the sample well by pipetting up and down several times.
• 4 Dilute methylene violet stock solution 1/10 using 0.1 M glycine buffer at pH 10.6.
• 5 Add 1 ml of a methylene violet solution to 1 ml of (diluted) yeast culture.
• 6 Mix the sample well by pipetting up and down several times.

Count the yeast cells

The sample will almost immediately be pulled under the coverslip by capillary action.

When using Kova Glasstic slides, simply pipette 6.6 µl (the maximum volume of each chamber) of the well‐mixed sample onto the slides.

• 8 Place the hemacytometer on the microscopy stage.
• 9 Locate yeast cells and focus the microscope.

If yeast cells are evenly distributed over sample, you can count within the five numbered squares (see Fig. ​ Fig.2 2 ).

A hemacytometer is used to count the number of cells in a suspension. It basically comprises a chamber, created by a grid of perpendicular lines that are carved into glass (upper panel). The area bound by each line, as well as the volume of each chamber that is created in this way, is known. By counting cells in a specific area of the grid (e.g.,, in the five indicated areas in lower panel), it is possible to calculate the original overall cell concentration in the suspension that was pipetted in the chamber.

Be consistent when counting and make sure to establish a counting protocol (e.g., always count cells on upper and right edge, and never on lower and left edge of the squares).

For the Kova Glasstic slides: Count 10 of the small grids.

Dead cells stain violet, viable (or at least metabolically active) cells do not have a color. In general, pale violet cells and budding yeast cells are considered as viable cells.

• 12 Determine fraction of viable cells.

This equation is for a Neubauer‐improved type of hemacytometer.

This calculation assumes you only counted 5 of the in total 25 squares of the counting chamber. Each counted square holds the precise volume of 4 nl. If you counted 5 squares, you have the cell count for a total volume of 20 nl. To determine cell count in 1 ml, multiply by 50,000 (5 × 10 4 ). Please note that volume of counting chamber is given for a Neubauer‐improved hemocytometer. If you are using a different type, please check the manufacturer's instructions on how to determine total cell count. For example, for the Kova Glasstic slides, the volume of each small grid is 0.011 µl; so, if you counted 10 small grids, you have determined the total number of cells in 0.11 µl.

When calculating the dilution factor, take into account that the addition of methylene blue also dilutes your cells twofold.

Basic Protocol 5. BATCH FERMENTATION AND BOTTLING OF BEER (12 L)

This protocol describes how to perform batch fermentations and how to bottle the resulting beer.

• Wort (see Basic Protocol 1 )
• Propagated yeast with sufficiently high cell number (see Basic Protocol 3 )
• Priming sugar (Sigma)
• Sterile 15‐L bottle
• Air pump with 0.2 µm filter attached and sterile tubing (e.g., Eheim 400 air pump)
• Balance (min. 0.1 g resolution)
• Sanitized automatic siphon with bottle filling attachment/bottling wand
• Sanitized/aseptic beer bottles (330 ml)
• Crown capper (with 26‐mm attachment)
• Sanitized crown caps 26 mm
• Incubator that can maintain 20°C

Fermentation of the wort

• 1 Transfer 12 L of 12°P wort into a 15‐L sterile bottle and bring to the desired fermentation temperature.
• 2 Count the yeast cell concentration in the starter culture (see Basic Protocol 4 ).

Alternatively, the starter culture can be centrifuged for 5 min at room temperature, to facilitate this step.

Maintain a sufficiently low flow rate to prevent excessive foaming of the wort.

For the given protocol, this sums up to 108 billion cells and 216 billion cells, respectively.

Avoid temperature shocking the yeast by keeping the starter culture in a range of ±2°C of the wort/fermentation temperature.

The exact fermentation temperature depends on your experimental setup.

Maturation of the beer

Degas samples before measuring gravity (see Support Protocols 6 ‐ 7 ).

Alternatively, fermentation progress can be tracked by monitoring weight loss, using a balance. This process will take around 6 days for an ale and 10 days for a lager.

The 16°C step during maturation of lager beer allows the yeast to reduce the off‐flavor diacetyl (buttery, rancid aroma) to acetoin and, subsequently, 2,3‐butanediol.

During the cold temperature step (also referred to as  “cold crash”) yeast cells, as well as cold trub, settle to the bottom of the fermentation vessel, allowing them to be easily separated from the finished beer.

Bottling the beer

The siphon should not be lowered completely to avoid disturbing the sediment layer at the bottom of the fermenter.

Avoid splashing or excessive air contact of the green beer during steps 10 and 11, as this will lead to oxidation of the final beer.

For a standard pale ale beer, a carbonation level of 0.5 g CO 2 /100 g beer is often suggested. For fermentation at 20°C, add 2.37 g of pure glucose per bottle of 330 ml.

See the Internet Resources to calculate the amount of sugar needed for other conditions.

• 13 Place a sanitized crown cap on each bottle and crown bottles following the manufacturer's instructions.
• 14 Allow secondary fermentation in the bottles to complete for 14 days at 20°C.

Basic Protocol 6. SMALL‐SCALE FERMENTATIONS AND SAMPLING

Here we describe a setup for small lab‐scale fermentations that can be useful when comparing a large number of yeast strains or brewing variables. Often it is useful to take samples throughout the fermentation process to measure metabolite production or track fermentation kinetics. Here we describe a setup where samples can be taken while avoiding contamination of the beer (see also Fig. ​ Fig.3). 3 ). Full‐scale industrial fermentations take place under very different physical conditions compared to lab‐scale fermentations. There is a number of ways to mimic the conditions of larger scale fermentations. One method is to simply use stirred fermentations. This protocol is described below.

Schematic of small‐scale fermentation setup in bottles. The 2‐µm filters allow gas escape as CO 2 is produced during fermentation. The septum allows for sampling without risk of contamination.

• Saline solution (0.9% w/v NaCl)
• Dual port GL45 screw caps (e.g., Duran, cat. no. 1129750)
• 12‐mm silicone septa (e.g., Duran, cat. no. 292460503)
• GL14 screw caps with aperture (e.g., Duran, cat. no. 292270508)
• Straight tubing connector for GL14 cap (Duran, cat. no. 292550603)
• Silicone tubing (5 mm internal, 8 mm external diameter)
• 25‐mm PTFE 0.2‐µm filters with female luer lock
• 4‐mm polypropylene hose barbs with male luer lock
• Rubber stopper with airlock
• 30‐mm magnetic stir bars
• Sterile cylinder (250 ml; to transfer wort to bottles)
• Sterile conical centrifugation tubes (50 ml)
• 250‐ml GL45 glass bottles for fermentations (GL45 thread)
• Magnetic stir plates (e.g., IKA RT 15)
• 70‐mm, 20‐G needles with luer adapter
• Syringes with luer adapter

Preparation of the fermentation vessels

• On one port, place a silicone septum and secure it with a GL14 screw cap with aperture.
• To the other port, attach a tubing connector and secure with a GL14 screw cap with aperture.
• Attach 50‐mm silicone tubing to the tubing connector and insert a hose barb into the free end.

If sampling is not required throughout the experiment, a simple rubber stopper with airlock can be used instead. In this case, the stopper and airlock should be sanitized with 70% ethanol prior to use.

• 2 Autoclave bottles with magnetic stir bar and caps for 20 min at 121°C.

This protocol can be scaled up to use glass bottles of any size. Do not use more than 80% of the total volume to avoid over foaming. In some cases, with yeast that ferment heavily or produce large krausen even smaller volumes should be used.

Inoculate the ferementations with yeast

• 4 Prepare a 50 ml yeast starter culture as described in Basic Protocol 3 (steps 1 to 5).
• 5 Transfer the yeast starter into a 50‐ml conical centrifuge tube.
• 6 Centrifuge for 3 min at 1,500‐3,000 × g , room temperature.
• 7 Discard the supernatant.
• 8 Resuspend the cell pellet in 5 ml saline solution and take a cell count (see Basic Protocol 4 ).

The exact pitch rate will depend on your experimental conditions. The given protocol will lead to total pitch rates of 1.35 billion cells for ale yeasts and 2.7 billion cells for lager yeasts.

• 10 Attach caps and place fermentation bottles on magnetic stir plates with stirring at 200 rpm in an incubator set to 20°C.

Monitor and sample the fermentations

The fermentation is complete when the mass of fermentation bottles stays constant.

Sanitize septa with 70% ethanol prior to sampling.

If monitoring fermentation progression by weight loss, be sure to take measurements before and after sampling.

Basic Protocol 7. SPECTROPHOTOMETRIC METHOD TO DETERMINE THE COLOR OF WORT AND BEER

In Europe, the color of a beer is specified in European Brewery Convention (EBC). EBC can be converted to standard reference method (SRM), which is used in the Americas.

EBC can be measured spectrophotometrically at 430 nm wavelength and is defined as:

• d = the dilution factor of the wort/beer sample
• A 430 nm = the measured absorbance at λ ex  = 430 nm.
• Wort (from Basic Protocol 1 ) or degassed beer (see Basic Protocols 5 and/or 6 )
• Membrane filter (0.45 µm)
• Syringe membrane filter
• Small plastic vessel to collect filtered samples
• 10‐mm cuvettes
• Spectrophotometer
• 1 Filter 5 ml of wort or degassed beer through a 0.45‐µm membrane filter (see Support Protocol 7 or 8).
• 2 Fill a 10‐mm cuvette with demineralized water, place it in the spectrophotometer, and capture a blank measurement at 430 nm.

Make sure the measured value is within the linear range of the spectrophotometer. In case the measured absorbance is too high, use a dilution of the sample.

• 4 Calculate the EBC value using Equation 6.

Basic Protocol 8. SPECTROPHOTOMETRIC MEASUREMENT OF BITTERNESS

The following protocol describes the procedure to determine the IBU of a sample spectrophotometrically.

• Degassed beer sample (see Basic Protocols 5 and/or 6 )
• 6 M hydrochloric acid
• Iso‐octane for UV spectroscopy (e.g., from Sigma‐Aldrich)
• 50‐ml Erlenmeyer flask with ground glass joint and glass stopper
• Orbital shaker
• UV spectrophotometer
• 1‐cm silica cuvettes
• 1 Transfer 10 ml of a degassed beer sample into a 50‐ml Erlenmeyer flask with ground glass joint. (see Support Protocols 6 ‐ 7 ).
• 2 Add 0.5 ml hydrochloric acid and 20 ml iso‐octane to this sample.
• 3 Close the flask with a glass stopper.

The shaking frequency and duration have to be optimized for the given equipment by repeated measurement of samples from the iso‐octane layer at an absorption wavelength of 275 nm of until no further increase can be detected.

• 5 Measure pure iso‐octane at 275 nm as a blank.
• 6 Measure the absorbance of the iso‐octane layer of each sample at 275 nm.

where A 275 nm = the absorbance of a sample at λ ex  = 275 nm.

Basic Protocol 9. APPARENT ATTENUATION OF A FERMENTATION

The degree of attenuation achieved at the end of a fermentation is an important characteristic of the yeast strain used. In contrast to the wort, which can be considered as a mixture of water and dissolved extract, the final beer also includes alcohol. Therefore, only the apparent attenuation can be determined based on density measurements.

The apparent degree of attenuation (ADA) can be determined as follows:

• ADA [%] = apparent degree of attenuation
• RE [°P] = residual extract
• OE [°P] = original extract

Basic Protocol 10. ESTIMATED ALCOHOL CONTENT OF A BEER

Based on the OG of the wort before fermentation and the FG after fermentation, the alcohol content of a beer can be predicted using:

• ABV [% (v/v)] = percentage alcohol by volume
• OG [SG] = original gravity
• FG [SG] = final gravity

For this calculation gravity values in °P have to be converted to SG using Table ​ Table4. 4 . Specialized equipment, such as an Anton Paar Alcolyzer, can be used to measure alcohol content of the final beer.

Basic Protocol 11. GC MEASUREMENT OF VOLATILE ESTERS

During fermentation, yeast produces hundreds of secondary metabolites that influence the aroma and taste of beer. Variation in these metabolites across different yeast strains is what allows yeast to so uniquely influence beer flavor. The protocol below describes how to detect several of the most important yeast‐produced flavor compounds, namely ester compounds.

• Internal standard (10× stock solution of 2‐heptanol = 129.8 ppm in EtOH)

External Standards for GC Measurements

• NaCl (e.g., from VWR or Sigma‐Aldrich)
• Degassed samples (see Support Protocols 6 ‐ 7 )
• GC vials (Headspace screw neck vials with precision thread, ND18; e.g., VWR International)
• Chemical hood
• Headspace autosampler (PAL system, CTC analytics)
• HS‐GC‐FID‐FPD system (e.g., from Shimadzu)
• Chromatography column (e.g., DB‐WAXETR column (length: 30 m, internal diameter: 0.25 mm, layer thickness: 0.5 mm) from Agilent Technologies)
• Analysis software (e.g., GC solutions software, Shimadzu)

Prepare this in volumetric 10‐ml flasks.

Make sure to properly close stock solutions to prevent evaporation.

Prepare this in a volumetric 10‐ml flask.

Dilutions used to generate standard curve are: 1:2; 1:3; 1:4; 1:8; 1:9; 1:27; 1:81; 1:162

Prepare each dilution in triplicate.

Adding NaCl increases the efficiency of extraction of less volatile compounds in the sample.

Make sure to immediately close and cool each vial to minimize evaporation of volatile compounds.

Dilute the internal standard in water.

The internal standard allows calculation of the actual concentrations of each compound after analysis.

Final concentration of the internal standard in each sample is 2.44 ppm.

For external standards, measure the triplicates of each dilution.

• Temperature split‐splitless injector: 250°C
• Temperature FID: 250°C
• Temperature injection needle: 105°C
• Flow rate carrier gas (N 2 ): 2.6 ml/min
• Sample heating: 70°C for 25 min

Temperature Profile Oven for GC Measurements

• 6 Use data acquisition software to acquire chromatograms and interpolate concentrations of esters in samples from standard curve.

Basic Protocol 12. SPECTROPHOTOMETRIC MEASUREMENT OF PHENOLIC OFF‐FLAVORS

During the mashing process, hydroxycinnamic acids such as ferulic acid are released into the wort by hydrolase activity. Decarboxylation of ferulic acid by yeast during fermentation leads to formation of 4‐vinyl guaiacol (4‐VG). 4‐VG has a very distinctive smoky, clove‐like aroma. In most beers, except for particular styles such as Belgian witbier and German hefeweizen, 4‐VG is considered a yeast‐derived off‐flavor; often also referred to as a phenolic off‐flavor (POF).

The protocol below tests the capacity of a yeast strain to convert ferulic acid to 4‐VG (Mertens et al., 2017 ). The method measures absorbance of ferulic acid before and after fermentation as a measure of ferulic acid consumption, inferring 4‐VG production.

Please note that this protocol only tests the capacity of a yeast strain to produce 4‐VG. Whether 4‐VG will actually be produced during fermentation or perceived in the final beer, depends on many additional factors.

• Yeast strain(s) of interest
• POF + control strain: e.g., SafAle WB‐06 (Fermentis)
• POF ‐ control strain: e.g., SafLager W34/70 (Fermentis)
• YPD (see recipe)
• Ferulic acid, 50 g/L (500×) stock concentration in 96% EtOH
• 96‐well plates (e.g., CellStar 96‐well plates, flat bottom)
• Aluminum seals for 96‐well plates (e.g., silverseal aluminum seals, Greiner BioOne)
• Incubator at 30°C
• Plateshaker (e.g., Heidolph Titramax 1000)
• Plate reader (e.g., Tecan Infinity Pro)

Test each strain of interest in biological and technical replicate.

Ferulic acid is added to YPD medium after autoclaving.

Include non‐inoculated wells as blanks.

• 2 Seal the plates with aluminum seal.
• 3 Incubate for 5 days on a shaking platform (900 rpm) in an incubator at 30°C.
• 4 Centrifuge the plates for 3 min at 1,500‐3,000 × g , room temperature.
• 5 Transfer 100 µl of the supernatant into a new 96‐well plate.

Strains are considered POF + if the measured amount of ferulic acid is below the 90% confidence interval of the blank.

Support Protocol 6. DEGASSING OF SAMPLES

Every sample taken during or after the fermentation process needs to be degassed prior further analysis due to the CO 2 produced during fermentation. This is to avoid false results due to gas bubbles adhering to measuring devices (e.g., hydrometer) or emerging during an actual measurement (e.g., density meter). For all protocols handling fermenting wort or beer, this degassing protocol should be followed.

• Sample to degass
• 0.5‐L Erlenmeyer flasks with stopper
• Plastic funnel
• Filter papers (e.g., MACHERY‐NAGEL MN 713 ¼)
• 1 Transfer 150‐200 ml of the sample into a 0.5‐L Erlenmeyer flask.

An overpressure might develop within the flask during this step. Release the pressure carefully by lifting the stopper from time to time.

• 3 Pour the sample through the funnel containing a filter paper. Discard the first 20 ml of flow through and collect the rest into the second Erlenmeyer flask.
• 4 Repeat steps 1 and 2 until the sample appears sufficiently degassed.

Support Protocol 7. DEGASSING OF SMALLER VOLUMES

This protocol can be used when smaller volumes (<5 ml) need to be degassed prior to analyses.

• 20‐ml plastic syringe (sterile)
• Stopper for plastic syringe
• 1 Aspirate ∼5 ml of your fermenting wort or beer using a (sterile) plastic syringe.
• 2 Close the syringe using a stopper
• 3 Pull the lever of the syringe to create an under pressure within the syringe and wait until no more CO 2 degasses from the liquid.
• 4 Release the CO 2 carefully from the syringe without losing any sample volume.
• 5 Repeat steps 1 to 4 until the sample appears sufficiently degassed.

REAGENTS AND SOLUTIONS

Lugol's iodine 1% (w/v).

• Weigh 0.1 g iodine (I 2 ) and 0.2 g potassium iodide (KI).
• Dissolve the solids in 30 ml dH 2 O.
• Store up to 1 year at room temperature
• Weigh 10 g yeast extract and 20 g bactopeptone into a 1‐L bottle
• Add 900 ml of dH 2 O
• Sterilize by autoclaving for 20 min at 121°C
• After autoclaving, add 100 ml of a 20% (w/v) maltose stock solution
• Store up to several weeks at room temperature
• Weigh 10 g yeast extract and 20 g bactopeptone in a 1‐L bottle
• Add 900 ml of dH 2 O
• After autoclaving, add 100 ml of a 20% (w/v) d ‐glucose stock solution

Zinc chloride solution

• Prepare a stock solution of zinc chloride at 200 ppm (417 mg/L ZnCl 2 ).
• Store up to several at room temperature

Background Information

Humans have been brewing beer and other fermented beverages in one way or another since prehistoric times (Barnett, 1998 , 2000 , 2003 ; Hornsey & Royal Society of Chemistry (Great Britain), 2003 ). Initially, the production of beer was a spontaneous, uncontrolled process that relied on microbes that were haphazardly present, for example on the raw materials or instruments used for brewing. Because of this spontaneous process, fermentation results often varied a lot, with big differences in flavor and aroma between different fermentation rounds. To create more consistency and predictability in the quality of the end product, early brewers started using a small fraction of a previously fermented batch to inoculate a new batch; effectively (but unknowingly) recycling the microbes from the previous fermentation round to the next. This practice is called backslopping and promoted adaptation of microbes to the fermentation environment, a process called domestication. This backslopping, and the concomitant domestication, ultimately resulted in the present‐day yeast strains that are used in current breweries (Fay et al., 2019 ; Gallone et al., 2018 ; Gallone et al., 2016 ; Goncalves et al., 2016 ; Hornsey & Royal Society of Chemistry (Great Britain), 2003 ; Liti et al., 2009 ). The process of backslopping is not used often anymore in modern‐day breweries. Instead, brewers preserve pure yeast strains as frozen stock and only recycle their yeast from one fermentation to another for a couple of batches before starting a new culture from their frozen stock.

It was not until 1680 that yeast was discovered by Antonie van Leeuwenhoek, and even later that Pasteur discovered that fermentation was carried out by yeast cells. Many scientific breakthroughs were made during brewing‐related research. For example, in 1883, Emil Christian Hansen, while working at the Carlsberg Laboratory in Copenhagen, developed a method that allowed the isolation of pure yeast cultures (Barnett & Lichtenthaler, 2001 ; Hornsey & Royal Society of Chemistry (Great Britain), 2003 ).

Recently, there is an increasing customer demand for product diversity, both in terms of flavor and alcohol content. Driven by this demand, brewers and researchers are currently investigating the potential of alternative yeast species (both Saccharomyces and non‐ Saccharomyces ) for creating beers with different, more complex flavor profiles as well as the production of flavorful low/no alcohol beers (Gibson et al., 2017 ; Steensels & Verstrepen, 2014 ).

Critical Parameters and Troubleshooting

Stuck mash during lautering.

A stuck mash is a common issue during lautering. Follow the tips below to avoid or solve the problem.

• Grind the malt in a way that the husks are still intact, and the starch body is broken up but not ground too finely. Avoid a high flour percentage.
• Allow the solid to settle down properly before starting the lautering process (∼20‐30 min).
• Do not lauter too fast. It helps to fully open the tap of the lauter tun two to three times in the beginning for a short time (∼2 s) to remove bigger particles from underneath the false bottom. Afterwards open the tap just far enough to get a constant flow of 0.5 L/min.
• If the flow rate starts to decrease, do not open the tap further to compensate. This will most likely just worsen the problem by contracting the filter bed. Instead, lower the flow rate and carefully cut the filter bed with a long knife in a rhombus like pattern. Don't cut all the way down to the false bottom.
• If everything fails and the mash is stuck: Close the tap completely, stir up the filter bed completely, and start all over again.

Yeast cell number is too low after propagation

A number of factors can be checked/adjusted to increase yeast cell number during propagation.

• Make sure to use “fresh” yeast as much as possible: Do not use agar plates or slants older than 4 weeks and re‐streak from a cryo stock.
• Always pick multiple colonies from an agar plate to avoid starting from cells that may have acquired deleterious mutations.
• Aerate larger volumes of propagation medium and stir or shake during incubation to keep the yeast in suspension.
• Some yeast strains grow slower than others. In this case extend the incubation time.
• Incubate each strain at its optimal temperature.

Low yield of brew

If the yield of the brew was low (less wort or less extract than expected) there a number of factors that can be adjusted to compensate for this.

• A finer malt grind can improve the yield. Beware that this can also lead to lautering problems (see above).
• Monitor the pH of your mash. Allow the mash to equilibrate and take the first measurement after 10 min. A typical mash pH should be between 5.2 and 5.5, but depends on the malt and water used. If necessary, adjust the pH by titrating with food grade hydrochloric/lactic acid or sodium hydroxide.
• Allow the trub to settle as much as possible before removing the wort from it.
• If there was more than the expected 20 L of wort then the boil may not have been strong enough. Adjust by boiling more vigorously, increasing the duration or by reducing the sparge water volume.
• Moderately modified malts may require multiple mash temperature steps for complete saccharification, using highly modified malts helps to avoid this.
• Last resort: Increase the amount of malt in the recipe to compensate the low efficiency.

Fermentation stops unexpectedly early

Typically, beer yeast strains reach an ADA of ∼80%, based on the sugar composition of the wort. Check the following points if the fermentation stops with an unexpectedly low ADA.

• Check if the yeast strain is able to ferment maltotriose. Strains unable to ferment this trisaccharide typically yield ADA around 60%.

Streaking a strain on YP maltotriose plates and checking for growth is a quick test to see if strains can use maltotriose.

• If propagating yeast from a cryo culture; make sure to aerate both the propagation medium and the wort before fermentation. Insufficient aeration limits cell membrane production can lead to unhealthy yeast.
• Increasing fermentation temperature towards the end of the fermentation by 2°C can support the yeast to completely finish fermentation.
• A lack of FAN can also lead to a stuck fermentation. Moderately modified malts may require a protease rest while mashing to release enough FAN to the wort.

Off‐flavors are present in final beer

See Table ​ Table7 7 .

Off‐Flavors

Understanding Results

Production of wort and fermentation with any beer yeast strain.

The basic protocols produce 20 L of a wort with 12°P. The wort can subsequently be used for two purposes as described here: (i) Batch fermentation of the wort using a single yeast strain with the aim to bottle beer for later use, or (ii) small‐scale fermentation experiments, which allow monitoring the fermentation characteristics of multiple yeast strains at a time. Using the calculations and techniques given in these protocols, up or downscaling of the process is possible. Please check the Critical Parameters and Troubleshooting section if unanticipated results occur.

Measurement of beer/fermentation characteristics

Basic Protocols 8 to 12 enable the reader to determine several standard characteristics of beer (color, bitterness, alcohol content, apparent attenuation, and volatile composition). All of these characteristics are influenced by multiple parameters of the brewing process, e.g., malt composition, fermentation temperature, hop variety, and yeast. Using controlled conditions, a standard wort, and consistent fermentation conditions, these measurements can be used to characterize a given yeast strain. These measurements can be further used, for example, to check if the resulting beer falls within specific style guidelines.

Table ​ Table8 8 lists values for typical color, bitterness, alcohol, and attenuation values for a few common beer styles, which can be used for comparison (Brücklmeier, 2018 ).

Values for Typical Color, Bitterness, ABV, and Attenuation Values for Some Common Beer Styles (Brücklmeier, 2018 )

GC‐based analysis

The proposed gas chromatography method explained in Basic Protocol 11 allows to determine concentrations of 17 different yeast related aroma active compounds. If the compounds are present in beer below the detection limit of the used setup, they are often represented as “not detected” (N.D.). Table ​ Table9 9 contains data of these aroma compounds for two “standard” types of beer, as well as the concentration ranges in beer reported for each of these compounds, found in literature (Chemists).

Expected Concentrations of Aroma Active Yeast Metabolites a

a In column two, the measured concentration ranges for 17 different yeast‐related aroma active compounds in beer are represented (according to Chemists). As an example, the obtained results of a standard, laboratory‐brewed American ale (OE = 13°P, fermented at 20°C with a commercial American ale yeast) and lager beer (OE = 12°P, fermented at 12°C with a standard lager yeast) are reported.

b Abbreviations: N.D., not detected.

Spectrophotometric measurement of phenolic off‐flavors

Basic Protocol 12 enables the reader to test whether a given yeast strain has the capability of transforming the malt derived compound ferulic acid to 4‐VG. In contrast to the protocols before, this experiment does not include the production of a wort but can be performed in standard YPD medium. Production of POF is undesirable for most beer yeast strains and beer styles, with a few exceptions. In some Belgian specialty beers POF is tolerated and for Wit as well as German Hefeweizen, it is even a characteristic of the style.

Time Considerations

An example brewing experiment, following the recipes and protocols given in this article, would look similar to the following:

• Streak yeast strain from stock (15 min of work, 2 days incubation).
• Prepare wort (1 day initial preparation, 30‐60 min clarification)
• Grow yeast strain to sufficiently high densities and pitch into wort: Pre‐growth (1 day) and propagation (1‐2 days)
• Fermentations: 6 days for ale beer, 10 days for lager beer.
• Maturation: 3 days for ale beer, 12 days for lager beer.
• Bottling: 30‐60 min
• Secondary fermentation in bottle: 14 days.
• Flavor analyses using GC protocol: 53 min/sample.

Acknowledgments

FAT is supported by the 3rd Hydrophobin Chair and ASBC Research Council Grant 2019. KV is supported by a FWO postdoctoral fellowship. Original research in the lab of KV is supported by KU Leuven Program Financing, European Research Council (ERC) Consolidator Grant CoG682009, VIB, European Molecular Biology Organization (EMBO) Young Investigator program, FWO, and VLAIO (Vlaams Agentschap Innoveren en Ondernemen).

Thesseling, F. A. , Bircham, P. W. , Mertens, S. , Voordeckers, K. , & Verstrepen, K. J. (2019). A hands‐on guide to brewing and analyzing beer in the laboratory . Current Protocols in Microbiology , 54 , e91. doi: 10.1002/cpmc.91 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]

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Internet Resources

Brew recipe developer software, free of charge.

BeerSmith, commercial Web site.

• http://brewrecipedeveloper.de/?setlang=en
• http://beersmith.com/
• Beersmith.com
• Brewersfriend.com
• Beerandbrewing.com
• Homebrewersassociation.org

Web sites with recipes for different beer types

This database gives an overview of the different aroma compounds in beer including their concentration range in beer.

• http://methods.asbcnet.org/Flavors_Database.aspx

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Beer Research Guide: Past Paper Topics

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Introduction

Students in past HST 417: History of Beer and Brewing classes have worked on a variety of topics. Some examples on this page are broad and in need of focus, but give you an idea of what has been researched and written about in the past.

• NOTE: these are topics, not thesis statements. 

Remember to be specific when choosing a topic and writing a thesis statement. Narrow to a place or time frame, compare companies or styles, and make sure there are primary sources to support your research. 

• If you are measuring success of a company, change in a demographic, or the impact of a law make sure you have measurements for evaluating. Success might mean more production or more awards won. Change in a demographic might mean fewer 20-25 year old consumers are drinking beer. The impact of Prohibition might have meant an increase in soda factories or closing of family businesses.  
• For example, if you are interested in beer advertising, considering narrowing it to changes in beer advertising in American print media in the 1980s. There is a section on this guide to get you started , are print primary sources in the Oregon Hops and Brewing Archives collections, and are digitized newspaper materials in the New York TimesMachine and advertisements in the Digital Public Library of America .

ADVERTISING AND MEDIA Impact of television advertising on midsize or small breweries. Government regulation of beer advertising. Alcohol advertising and adolescent drinking.  Music in beer commercials.  History of logos, branding, and trademarking of early beer brands. 

BIOGRAPHY Fred Eckhardt and his influence on homebrewing / craft beer in Oregon.  Joseph Owades and his influence on the creation of light beer.  History of the Anheuser-Busch family.  Carrie Nation and her work during Prohibition. 

BUSINESS History of X Brewing Company. History of consumer boycotts and labor disputes at the Coors Brewing Company.   

CHURCH Relationship of religion and beer.  Brewing and Catholic Saints.  Monastic influence on beer and brewing. Medieval guilds, economics, and the Catholic Church.  History of brewing and the Grimbergen Abbey.  Prohibition and anti-Catholic sentiment. 

CIDER History of Cider making in Oregon. Cider production in America (or England, or Europe).  Gender and cider production in Colonial Chesapeake.  History of orchard planting and management for cider apples. 

CULTURE Pub culture in England.  Saloons in American culture during the 19th and early 20th century. Intersection of beer and politics. Indigenous brewing in America (or Mexico).  Cultural and economic significance of Viking beer.  Comparison of Oktoberfest festivals in America and Germany.  Japanese drinking rituals.  Frontier alcohol culture: beer in Alaska-Yukon Territory mining towns. Baseball and beer.  Study of race or class in brewing industry.  Beer production and consumption in the COVID-19 era.

FOOD Beer in cooking.  Beer and food pairings. 

GENDER Women's role in the Temperance movements. Women in modern craft beer.  Women and beer production in ancient eras (e.g., Mesopotamia, Jaihu, China, Egypt).  Women, beer, and witches.  History of the Pink Boots Society Representation of women in beer advertising in the 1950s.  History of Japanese women and sake production. 

HEALTH Changes in perceived health benefits of fermented foods or drinks.   Hangover cures.  Preventative properties of hops compounds. 

HOMEBREWING Women and home brewing in Colonial America.   Home brewing in the middle ages in England. Historical brewing processes used in modern home brewing. 

HOPS Willamette Valley hop growing and the link to growth of craft beer in Oregon.  History of hop research in Corvallis, Oregon (OSU, USDA). Impact of the Cascade hop on the popularity of India Pale Ale. History of Chinese hop growers in the Pacific Northwest. Study of the demographics of hop pickers on the West Coast between 1860 and 1920. History of hop research in England.  Study of how monks used hops in beer. Pest management in hops / Insect ecology and hops. 

IMMIGRATION Impact of German and Austrian immigrants on Mexico’s brewing history.  German immigration and the impact on 19th century American beer styles.

INDUSTRY Impact of the Industrial Revolution on brewing in Chicago.  Workers and the industrialization of brewing in London. Impact of the three-tier system on microbreweries. 

OREGON Change in local media coverage of Oregon beer between the 1980s and the present. Impact of breweries on Bend’s local economy. History of brewing and saloons in Junction City. The Weinhard family and 19th century brewing in Oregon.  19th century German and Swiss immigrant brewers in Portland.  History of Great Western Malting Company. 

PLACE Study of craft brewing on the West Coast (looking at 2-4 companies or cities).  Beer and the revitalization of small towns in the Pacific Northwest.  Alaska Brewing Company, Yukon Brewing Company and craft beer in Alaska/Canada.  Beer in Asheville, North Carolina. Impact of brewing industry on regional identities in Bohemia and Germany. Beer-making in Scandinavia. 

PROHIBITION Adaptation of breweries in New York during Prohibition.  Impact of Prohibition on American beer consumption. Key people in the Woman’s Christian Temperance Union and/or Anti-Saloon League. Near beer and/or needle beer. Bootlegging during Prohibition. Prohibition and organized crime in Chicago Prohibition outside of the United States.

STYLE Chicha and maize beers in the South American Andes. Sake in Japan in the 20th century. History of Marzen beers. Development of the taxonomy of beer styles. India Pale Ale in Oregon (see also standard bitter IPA, aromatic IPA, Hazy IPA in New England). Czech brewing styles in America.  Porter and early industrial brewing in Britain. Gluten free beer in Africa.

SUSTAINABILITY Use of geothermal energy and other renewable resources in brewing. The influence and impact of sustainability practices at of Hopworks Urban Brewery.  Using waste water to brew beer. Sustainability efforts and marketing in the brewing industry.

TECHNOLOGY Evolution of equipment technologies for beer production History of carbonation in beer.  Evolution of the beer can. Impact of bottling technology on beer distribution.  Artificial refrigeration and American lager beer in the late 19th century.  Carlsberg Laboratory and its impact on scientific brewing.

WAR Growth in the Japanese brewing industry after WWII.  Canned beer and the Vietnam war. Beer in American soldier’s rations during WWII.  Brewing in Germany in World War I and World War II. The growth of Anheuser-Busch after WWII (1945-1980).

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Alcohol research and the alcoholic beverage industry: issues, concerns and conflicts of interest

Affiliation.

• 1 Department of Community Medicine and Health Care, University of Connecticut School of Medicine, Farmington, CT 06030-6325, USA. [email protected]
• PMID: 19133913
• DOI: 10.1111/j.1360-0443.2008.02433.x

Aims: Using terms of justification such as 'corporate social responsibility' and 'partnerships with the public health community', the alcoholic beverage industry (mainly large producers, trade associations and 'social aspects' organizations) funds a variety of scientific activities that involve or overlap with the work of independent scientists. The aim of this paper is to evaluate the ethical, professional and scientific challenges that have emerged from industry involvement in alcohol science.

Method: Source material came from an extensive review of organizational websites, newspaper articles, journal papers, letters to the editor, editorials, books, book chapters and unpublished documents.

Results: Industry involvement in alcohol science was identified in seven areas: (i) sponsorship of research funding organizations; (ii) direct financing of university-based scientists and centers; (iii) studies conducted through contract research organizations; (iv) research conducted by trade organizations and social aspects/public relations organizations; (v) efforts to influence public perceptions of research, research findings and alcohol policies; (vi) publication of scientific documents and support of scientific journals; and (vii) sponsorship of scientific conferences and presentations at conferences.

Conclusion: While industry involvement in research activities is increasing, it constitutes currently a rather small direct investment in scientific research, one that is unlikely to contribute to alcohol science, lead to scientific breakthroughs or reduce the burden of alcohol-related illness. At best, the scientific activities funded by the alcoholic beverage industry provide financial support and small consulting fees for basic and behavioral scientists engaged in alcohol research; at worst, the industry's scientific activities confuse public discussion of health issues and policy options, raise questions about the objectivity of industry-supported alcohol scientists and provide industry with a convenient way to demonstrate 'corporate responsibility' in its attempts to avoid taxation and regulation.

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