Microbrewery expansion in the last decade sample countries by continent.
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.
- craft beer
- sour beer
- new adjuncts
- bottle fermentation
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 . 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 , 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  and chemical residue studies  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 . 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 , while in the Netherlands the craft revolution rouse during the year 1981 , in Australia, craft brewing started late 1984 . 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 . 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.
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 .
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 . Percentage of craft beer producers (2013–2017) can be seen in Figure 1.
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 . A significant growth in the number of breweries, the variety of styles and the total volume of production had been observed in previous years .
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 . 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 , 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 .
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).
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].
According to Kleban and Nickerson , small scale beers have different considerations:
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 . 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 .
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 .
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 . 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 CO2 pressure. However, the most interesting application is in the production of sour beers because of the natural biological acidification during wort fermentation . 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  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 . The sensory effect of this acidity is described as a citric acidity without dairy hints because of the low production of acetoin and diacetyl ; 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 . Also it is possible the use of this yeast sequentially or in mixed cultures with S. cerevisiae  or S. pombe . 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 . 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 . The release of polysaccharides is also improved by the fermentation with T. delbrueckii affecting mouthfeel and structure .
Hanseniaspora vineae is an apiculate yeast able to produce fresh and complex fermentation, increasing fruity aroma and producing full bodied structure . 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 . It is especially noticeable the production of 2-phenylethyl acetate by H. vineae , 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 . 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 . 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. . In fact, beers are quite similar in most respects but small differences in their composition can greatly affect both appearance and flavor .
We are going to examine each one of the raw materials separately.
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 .
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 . The variety of barely and the malting process influences the type and quality of beer . 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.
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 . 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 . Outside Europe, millet, rice, maize and tuber plants have been, and are still, commonly used.
Bogdan and Kordialik-Bogacka  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  and its associated cost.
Craft brewing is increasing the use of adjuncts  because they lead to create a unique beer flavor/aroma . Figure 3 shows the influence of different concentrations of roasted malt addition on sensory properties of beer.
Appropriately chosen adjuncts can contribute to light or dark colors, improved colloidal or foam stability and prolongation beer shelf-life . 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 . It contributes not only to bitter flavor but also with the particular character of the selected hop variety .
This is mainly due to its particular chemical composition in: the hops resins, the hop oil and hop polyphenols .
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  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 .
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  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 . 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 .
From a nutritional point of view , 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 . 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. , 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 . 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 .
5.4.3 Gluten free
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 , 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. .
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  and GF beer production. Mayer et al.  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 . 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 .
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 . 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 .
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 . Even when some temperature increasing is produced that can be quantified in 2–3°C/100 MPa in HHP  by compression adiabatic heat and until 100°C but just for 0.2 s in UHPH because of intense shear forces and impact . 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 . 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 (
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 . 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.