Chapter 2: Overview of Brewing Stephen R. Holle and Steve Presley Beer is a fermented beverage made from grain. While barley is by far the most common type, many grains are used for brewing, including wheat, rye, corn, rice, sorghum, millet, and other starchy seed-producing grasses. Because this main ingredient in beer is so widespread and affordable, beer, like bread, is found in nearly every culture in which farming is practiced. Fermentation is a natural process that mankind has used for millennia to produce many kinds of food, including sauerkraut, cheese, and even chocolate. Yeast is the fermentation microbe in beer that converts grain-derived sugar to alcohol. Innumerable yeast strains are Figure 2.1. Beer comes in all kinds of colors, flavors, and arofound across the globe, and over mas directly shaped by the ingredients and brewing methods time, brewers domesticated cer- used. (Š iStockphoto.com) tain strains that were best suited to make beer in their regions. Each region also developed its own brewing techniques, selected indigenous flavoring ingredients, and adapted to the unique local water supply. These endless combinations of grain, yeast, flavorings, water, and brewing techniques make beer not only one of the most ubiquitous beverages but also one of the most diverse in style (Fig. 2.1). The quality of water, malt, and hops can vary from year to year. Unlike wine drinkers, who often embrace the flavor variances from vintage to vintage, beer drinkers typically expect their brands to taste the same year in and year out. Therefore, the commercial brewer must not only develop a recipe but also have the skill to manage a complex process and produce a consistent product even though the inputs are constantly changing. This chapter leads readers through some common methods to brew beer. Not every brewing method is discussed, nor are readers expected to gain the knowledge of a professional brewer. Rather, the chapter exposes readers to the main processes of modern brewing so that they can understand and better identify why the beer in their glass tastes the way it does.
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In its basic form, modern brewing can be broken down into the following 10 steps. 1. Malting—preparing raw grain for brewing through controlled germination and drying 2. Mashing—converting starch to sugar to create a sugary liquid called sweet wort 3. Wort Separation—separating dissolved sugar from the residual grain 4. Boiling—stabilizing the wort with heat and extracting bitterness from the hops 5. Wort Clarification and Chilling—removing wort solids and cooling to fermentation temperature 6. Fermentation—yeast converting sugar to alcohol and carbon dioxide and creating flavor compounds 7. Conditioning—allowing time for beer flavors to mature 8. Filtration—removing suspended yeast and haze (optional process not used in all beers) 9. Packaging—filling containers (cans, bottles, kegs, or serving tanks) 10. Pasteurization—protecting beer from spoiling (optional process not used in all beers) A diagram and brief explanation of the brewing process is in Appendix A. The reader may find it helpful to refer to this diagram while reading the following narrative.
Malting For most fermented beverages, nature supplies the sugar that yeast converts to alcohol. Examples include grape juice for wine, apple juice for cider, and honey for mead. In contrast, the raw grains used in brewing store their sugar as unfermentable starch, so brewing requires an extra step to convert the grain starch to sugar. This conversion process starts with malting the grain, most commonly barley (Fig. 2.2). Figure 2.2. Barley, the main ingredient in making beer, grows in The conversion of starch to North America in the Midwest, western United States, and westsugar is a fundamental process ern Canada. Spring varieties are most common, which are harfor plants and animals. A seed vested each summer. (Courtesy S. Presley) stores energy in the form of stable complex carbohydrates until it is time to release that energy to the sprouting plant. When the seed is ready to sprout, naturally occurring enzymes in the kernel converts the starch to sugar. Humans also use enzymes in saliva in the mouth to begin starch conversion that is then completed by enzymes in the gut. This is why a starchy cracker may become sweet tasting when chewed. Malting is essentially controlled germination to produce enzymes that convert starch to sugar in the mash and soften the kernel for milling. A seed contains two primary parts, the embryo (or germ) that produces a new plant and the starchy endosperm that feeds the sprout until it is mature enough to feed
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Figure 2.3. Grain enters the steeping tank in the malt house and is mixed with water. Steeping wakes up the barley kernel and start its germination. (Courtesy Weyermann Specialty Malting Company)
itself through photosynthesis. To sprout in nature, the seed must have moisture, warmth, and oxygen. These conditions are the signals to germinate, which initiates enzyme production, followed by conversion of the starchy endosperm to sugar. The kernel also softens as the enzymes break down the structural gums and proteins that surround the starch. Likewise, malting begins by steeping grain in a tank of relatively warm water accompanied by aeration (Fig. 2.3). After about 2 days of steeping, the moist kernels are transferred to a chamber where they are allowed to germinate (Fig. 2.4). After the kernels have germinated for 3–5 days and a sufficient degree of softening (modification) has occurred, the malt is transferred to the kiln. Hot air forced through the grain bed slowly dries the malt until the moisture content is reduced to 5% or less. Drying arrests germination, removes cucumber and grassy flavors, further softens the kernel, and stabilizes the grain for storage. Unkilned malt tastes raw and vegetable-like. Heat drives off most of these unwanted flavors and develops additional pleasant ones in the same manner that roasting improves the taste of nuts and coffee beans. During kilning, the combination of protein and sugar in the malt with heat also produces a browning reaction that creates flavor and color compounds called melanoidins. Melanoidins are also present in other foods, such as caramel and bread crust. Varying the levels of moisture, heat, and time during kilning or roasting creates a wide range of malt flavors and colors. Just like coffee beans, the level of heat applied to the malt helps determine its color and the intensity of its flavor. Light kilning at 185°F (85°C) produces a pale-colored and neutral-tasting malt that is used for brewing pale-colored beers, such as American standard lagers. More intense kilning at 221°F (105°C) produces amber malts rich in caramel flavors and toasty aromas that are desirable for brewing brown ales and copper-colored Märzen lagers. Roasting at high temperatures for longer periods creates dark acrid malt with chocolate and coffee flavors that is used in black porters and stouts (Fig. 2.5).
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High levels of heat destroy (denature) malt enzymes, which renders dark malts that are useless in converting starch to sugar. Brewers use a darker malt to achieve color and flavor changes in their beer. When doing so, they must ensure that they use enough paler malt, with its enzymes still active, to convert the starches in the dark malt into sugars. The same condition exists when a brewer uses a portion of unmalted grain, such as rice or corn, which contains starch but no enzymes. Malting is a costly and timeconsuming process in comparison to the significantly less time needed for the preparation of the raw materials used in wine and cider production. Once malted, barley becomes an ingredient that is stable and capable of being stored without any deterioration in quality and usability for an extended period of time. This stability is one reason why beer Figure 2.4. Top, After steeping, the wet barley is transferred to is such a common and affordable germination beds where it begins grow. Bottom, Germinating drink. Beer does not have to be barley transforms itself from seeds to plants. During the transproduced immediately after harformation, or modification, the seed goes from hard and steely to vest before the fruit rots, as is soft and crumbly, making it easier to mill and brew at the brewery. (Courtesy Anheuser-Busch InBev) required with grapes and apples. Brewers not only can store malt to produce fresh beer year-round but they can also transport it inexpensively. For this reason, a brewer thousands of miles from Germany can still produce a fresh authentic German-style lager with malts and hops transported from Germany. Affordable access to quality ingredients helps put brewers on a relatively level playing field, where the brewer’s skill becomes a major factor in determining the quality of the beer.
Mashing The brewing process utilizes a series of cooking vessels and is done in the brewhouse; this is the “brewmaster’s kitchen”. Brewhouse vessels in a large brewery (Fig. 2.6), a craft brewery (Fig. 2.7), and a brewpub (Fig. 2.8) vary. The vessels in all three accomplish the same operations but in a different scale.
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Figure 2.5. Drum roaster discharging crystal malt. Some specialty grains are heated in large roasters, which helps develop characteristic colors and flavors. (Courtesy Great Western Malting Co.)
Figure 2.6. Brewhouse vessels in a large American lager brewery: mash tuns, lauter tun, brew kettles, and tanks. (Courtesy Anheuser-Busch InBev and S. Presley)
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Figure 2.7. Brewhouse vessels in a regional craft ale brewery: British-style mash tun with mash mixer inlet (Steele’s Masher), brew kettle, whirlpool tank, and hopback (hop jack). (Courtesy BridgePort Brewing Company)
Figure 2.8. Brewhouse vessels in a pub: small combination mash/lauter tun and combination brew kettle/whirlpool tank. (Courtesy Rock Bottom Brewery)
Mashing is the combining of brewing-quality hot water and crushed malt to activate dormant malt enzymes that convert starch to sugar. Before mashing begins, the malt is coarsely crushed in a mill to make the inner parts of the starchy endosperm accessible to malt enzymes and water (Fig. 2.9). Otherwise, much of the potential sugar would re-
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main in the spent grain as unconverted starch. However, care must be taken not to grind the malt too finely. If too much flour is created or the grain husks are finely shredded, the lautering process described later will be impeded. Finely shredded husk can also contribute to the leaching out of an increased amount of harshtasting phenols, which can have a direct impact on the resultant beer’s flavor and appearance. After milling, the malt and hot water are mixed in an insulated Figure 2.9. The brewing process begins with milling the grain mash tun. The mash, as this com- through the malt mill. This four-roll mill grinds 1 ton of malted grain per hour into an assortment of husk, grist, and flour. bined mixture is called, is held (Courtesy BridgePort Brewing Company) for 30–60 minutes, during which time the starch conversion to sugar occurs (Fig. 2.10). Mashing can be accomplished by holding the mash at one temperature, by heating the mash through a range of temperatures, or by removing a small portion of the mash to a separate cooker, boiling it, and returning it to the main mash to increase the overall mash temperature. The time needed to complete mashing and the choice of mashing technique is dependent on the malt quality, beer style, economics, brewing system, and brewer’s Figure 2.10. Freshly mashed grain rests in the mash tun for 2–8 preference. Mashing cycles can be hours until the sugary liquid, called sweet wort, is drawn off and anywhere from 2 to 8 hours long. the husk-laden spent grain is left behind. (Courtesy BridgePort Starch is a series of long Brewing Company) chains of individual sugar molecules. Enzymes in the malt called beta amylase and alpha amylase produce sugar by cleaving sugar molecules off these starch chains. Maltose consists of two sugar molecules and is the primary wort sugar. Single-molecule glucose is the second most numerous type of sugar in wort. Brewer’s yeast is generally capable of converting sugars up to three molecules in size (known as maltotriose) to alcohol. More-complex sugars of four or more molecules are called dextrins. Dextrins are unfermentable by brewer’s yeast and add body and sweetness to the beer. Enzyme starch-converting efficiency is time and temperature dependent. The length of time a mash is held at conversion temperature determines the amount of fermentable and nonfermentable sugars developed.
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Beta amylase is useful in cleaving small fermentable sugars from the end of starch chains, while alpha amylase cleaves unfermentable dextrins and some fermentable sugars from the starch units. Beta amylase works optimally between 140 and 150°F (60 and 65°C) and alpha amylase works optimally between 158 and 167°F (70 and 75°C). Consequently, long, low-temperature mashes (140°F/60°C) produce an abundance of maltose, which is highly fermentable, because of beta amylase. Worts of this type produce beers with elevated alcohol content, thinner body, and lower residual sweetness. Short, hot mashes limit beta- and alpha-enzyme activity and produce worts that lead to beers that are lower in alcohol content, full bodied, and sweet. The cool maritime climate in Great Britain is conducive to growing barley that is easily converted in the brewhouse. For this reason, English brewers developed a simple, single-temperature infusion mashing technique that occurs in a combination mashing/ lautering vessel. A single mash temperature of 150–153°F (65–67°C) is used because both beta and alpha amylase enzymes are active at this compromise temperature. Because of its simplicity and low equipment costs, brewpubs frequently use single-temperature infusion mashing. In earlier times, before maltsters could produce highly modified malt and soft, friable, low-protein kernels, more-intensive mashing techniques were developed to break down gums, proteins, and starches that the maltsters of the day could not. The undermodified malt was hard and contained few enzymes. Brewers discovered that boiling a portion of the malt would break down its starchy endosperm, making it more accessible to the action of the sugar-producing enzymes. The boiled mash, or decoction, is combined with the regular mash to raise its temperature to a point more conducive to the limited amount of enzymes present. Brewers using this method employ from one to three decoction mashes to achieve a rising series of mash temperature rests that are designed to be at the optimum points for enzyme activity. This multistage process is called decoction mashing. Decoction was most common in continental Europe in earlier times when lessmodified malt was produced. Even though improved barley varieties and malting techniques produce well-modified malts on the Continent today, decoction mashing is still widely used in Germany, where brewers continue to follow the timehonored tradition to produce beers that benefit from it. Because extended boiling of the mash creates dark, caramel-tasting melanoidins, many such brewers prefer decoction for malty, caramel-colored beers. However, debate now exists whether decoction mashing is really necessary to produce amber beers because of improved techniques Figure 2.11. The sweet mash is rinsed, or sparged, leaving spent that produce these same melagrain in the lauter tun and sweet wort in the brew kettle. (Cournoidins during malting. Because tesy Newlands Systems Inc.)