Beer may be defined as a cereal wine: an alcohol-fermented (and sometimes concomitantly lactic-acidfermented) beverage, produced from one or more malted cereals, such as barley, wheat, rye, oats, corn, or rice, or from mixtures of these and unmalted cereals. In the following, the product is called "beer" if barley is at least one of the main constituents of the malt; otherwise, it is called "wheat beer," "rye beer," "oat beer," etc., as appropriate.
The Basic Beer-Production Process
To ferment the starch inside the grains of the cereals, it is malted (softened by soaking in water and allowed to germinate) and mashed with warm water; this allows the diastases of the grains, which are activated by the malting and mashing processes, to break the starches into shorter carbohydrates, upon which yeasts can act. After separation, a clarified liquid, known as wort, is produced, which is then boiled with hops; this adds a note of bitterness to the beer's flavor while killing microorganisms. After chilling, yeast is added (either naturally from the environment or as an intentional addition), and fermentation takes place. After clarifying and storage, the beer is ready for consumption.
Classification of Beers
Beers can be categorized according to the type of cereal used, but it is more common to use the type of fermentation for this purpose: spontaneous fermentation, top fermentation, or bottom fermentation.
Spontaneous fermentation. Spontaneously fermented beers are produced without the active addition of any microorganisms to the wort. The microorganisms come from the surrounding air and the equipment used in the brewing process and are a mixture of yeast species and lactic-acid bacteria, a mixture that produces alcohols and lactic and other organic acids, and gives the product a sour taste. Examples are the Russian beverage kvass, which is typically made of rye, and Belgian Lambic beer and the old Berliner Weisse, which are both produced partly from wheat. All beers made before the introduction and knowledge of pure yeast cultures were in a sense made via spontaneous fermentation. However, most such beers (as well as wines) were made inside containers that were repeatedly used for this purpose. Such containers rapidly become infected with spores that continue to maintain the original species of yeasthat is, the ones that produced fermentation in the first place. The use of the same vessel and associated equipment from one batch to the next causes the cereal grains employed to continue to be cross-infected between brewings. Recent scientific studies indicate that these spores remain alive for decades, or even longer. Moreover, many beer-making traditions include the step of adding fruit, such as raisins, to the mixture; this practice assures that the yeasts that naturally reside on the surface of the fruit will become a significant part of the microorganisms that infect the mixture.
These types of beer are technically aleshat is, they are all top-fermented.
Top fermentation: ales. Top-fermented beers, ales, are fermented at a rather high temperature, about 642°F (182°C), letting the yeast float on the surface of the wort.
Typical ales are British and Irish pale ales, bitters, stouts, and porters; Belgian ales, such as Trappist and abbey beers; and western German ales, such as Alt Bier and Kölsch. The Bavarian wheat beersi>Weissbier (Weizenbier)re also top-fermented and are produced in different varieties: pale and dark, with and without yeasts remaining, and as bock and Doppelbock. Some of the British and Belgian ales can be very strong, up to about 127 percent alcohol by volume, while common ales have a concentration of 3.5.0 percent alcohol by volume. Ales were predominant before the great expansion in popularity of bottom-fermented beers, the lagers, in the nineteenth century.
It should be noted that the term "ale" has also been used to signify unhopped beer, as contrasted with hopped beer (Cantrell, p. 619).
Bottom fermentation: lagers. Bottom-fermented beers, lagers, originated in Bavaria, where a cold-adapted yeast strain had been developed over a period of many years in the cold caves used for fermentation and storage. A temperature of about 459°F (75°C) is typical for bottom fermentation. The cold fermentation and the location of the yeast cells at the bottom of the container yield better storage capabilities and a cleaner, more purely malty taste in lagers, in comparison with ales, which are usually more fruity and bloomy in flavor. The name "lager" implies it is stored in cold conditions. Lagers are the dominating beers of the world today: pilsner; Bavarian; Vienna; Münchener, pale and dark; Dortmunder; bock; and Doppelbock beers. The difference between them depends principally on the brewing liquid, the type of hops, and the type of malt used. Bock and Doppelbock beers have a higher alcoholic content, 6.0.0 percent by volume and 6.0.0 percent by volume, respectively, in comparison with the other lagers, 3.8.0 percent by volume. Bocks and Doppelbocks are spring beers; their high levels of alcohol were originally produced to compensate for Lenten fasting.
Barley. Barley is a grass of the genus Hordeum and of the family Gramineae; it is one of the most important cereals of the world, after wheat, maize (corn), and rice. Barley is mainly used for livestock feed and for beer malting. The world production for 1999 was 130 million tons, with the greatest producers being Germany (13.3 million tons) and Canada (13.2 million tons) (FAO, Production Yearbook, 1999). Barley is produced all over the world up to 70°N latitude; it prefers reliable rainfall, a long growing season, and deep rich soils, but it can stand much more difficult conditions. It is not as cold-resistant as wheat, and in some regions it is sown in the autumn (Kendall, pp. 10911).
For malt production, the two-rowed form of barley is often preferred over the six-rowed, although both give excellent malts. The advantages of barley for malting are principally the following:
- The husk gives each individual grain of barley microbiological protection during malting, thereby helping to prevent the growth of mold.
- The husk provides a useful filter during traditional wort separation. The filtered material, spent grains (trub), is composed of husks, proteins, a little starch, and minerals. The trub is used for animal food (Narziss, 1995, p. 176).
- The gelatinization temperature of malt starch is lower than the inactivation temperature for -amylase, which is one of the main enzymes breaking down the starch into shorter carbohydrates. (Gelatinization accelerates the transformation to sugars and makes it more thoroughgoing.) (MacLeod, pp. 501)
For more detailed reviews see Hough, Briggs, and Stevens (1971) and Adamic (1977).
Water. The different composition of natural brewing water, or production water, from Pilsen, the Czech Republic; Burton upon Trent, England; Munich; Dortmund, Germany; and Vienna characterizes five types of different beers. Pilsen water has low concentrations of ions and is suitable for highly hopped lager beers with pale malt. Burton upon Trent water has high concentrations of calcium, bicarbonate, and particularly sulfate, and this combination has been shown to be perfect for highly hopped ales with dark malt. The waters from Munich, Dortmund, and Vienna have rather high concentrations of alkaline ions, and Dortmund water in particular has rather high concentrations of calcium and sulfate. Vienna water is more highly mineralized than Munich water, with a rather low sulfate but a higher bicarbonate concentration. The waters from Munich and Vienna give a lager that is not heavily hopped and is used with both light and dark malts. The Dortmunder lager is more highly hopped and has a slightly higher alcohol content and a pale malt.
Brewing water must be of potable-water quality. The ion composition and pH can be adjusted by ion exchanges, for example. The pH before wort boiling should be 5.4, so as to obtain a pH after boiling of 5.2 (Moll, pp. 13839). The different ions of the brewing water have profound effects on the malting and brewing processes, the fermentation, the flavor, and, as a result, the type and quality of the beer. The previously mentioned famous beers are distinguished by the effects of geological conditions of their wells on the brewing water. The important cations are calcium, magnesium, sodium, potassium, iron, manganese, and trace metals. The anions are carbonate, sulfate, chloride, nitrate and nitrite, phosphate, silicate, and fluoride. Their concentrations in the brewing water should comply with those found in water suitable for drinking (for standards, see Moll, pp. 13435).
Some of the many effects of the ions are pH adjustments made by calcium, magnesium, carbonates, and sulfate from the brewing water and phosphate and organic acids from the malting. If calcium chloride is added, insoluble calcium carbonate, phosphate, and free hydrogen ions will form, which will decrease the pH. In contrast, pH can be increased when the brew is boiled, forming carbon dioxide from carbonate and hydrogen carbonate, which binds hydrogen ions. Many of the different anions such as carbonates, phosphates, and all the organic acids in the brew have buffering capacities (they minimize changes in the pH).
Besides these pH effects, many of the cations, including trace metals, work as coenzymes for many different enzyme systems. For example, magnesium is a cofactor in the metabolic enzymes necessary to produce alcohol and protect yeast cells by preventing increases in cell membrane permeability elicited by ethanol and temperature-induced stress. Other critical trace element cofactors are cobalt and chromium, which enhance the kinetics of alcohol fermentation.
Calcium, along with phosphates, provides thermal protection for mash enzymes and is the principal factor for pH adjustments during wort boiling. It also tends to inhibit color formation during the boil, and facilitates protein coagulation, oxalate sedimentation, yeast flocculation, and beer clarification. Magnesium works similarly to calcium and causes harsh bitterness (Fix, p. 5). Sodium, together with chloride, causes a salty taste in higher concentrations ( 400 mg/l), but in lower concentrations it can be used to increase the "mouthfullness." Sodium is also very important for sodium/potassium transport across cell membranes. The amount of potassium should not be excessive as it inhibits many enzymes in the wort preparation. Iron should be avoided as it inhibits the malting, gives color to the wort, decreases the "mouthfullness," and causes a bitter taste. Iron is essential for the oxidative processes of the yeasts, especially terminal oxidation. Manganese works as a coenzyme in many enzyme systems and stimulates cell division and protein generation.
Sulfate, with calcium and magnesium, decreases the pH and stimulates the carboxyl and amino peptidases. The sulfate concentration in the brewing water determines the concentration of sulfate in the final beer (malt and hops also contribute to the amount of sulfate) but does not increase the amount of sulfur dioxide. Sulfate also increases the flower flavor of hops and gives beer a dry, bitter taste. Chloride stimulates -amylases and gives a soft and full beer taste as calcium chloride. Often, the chloride/sulfate concentration ratio is used to describe the ratio of body and fullness in relation to dryness.
Nitrates and nitrites are the last stage in the oxidation of organic material and give beer a bad taste. Nitrites are toxic for the yeast cells. Phosphate ions in the brewing water are not acceptable because they indicate organic contamination. Silicates of calcium and magnesium have negative effects on the proteins and cause protein-unstable beers. Fluorides have no negative effects on the fermentation but cause the beer to become a little darker and have a broader taste (Narziss, 1992, pp. 172). For more details about the effects of the ions in brewing water, see Narziss, 1992; MacLeod; and Moll.
Hops. The cultivated hop plant, Humulus lupulus, with its relatives H. japonicus and H. yunnanensis, belongs, along with species of the genus Cannabis (e.g., C. sativa, hemp), to the family Cannabinaceae. Together with the nettle family, Urticaceae, they form the order Urticales. Hops are dioecious (i.e., there are individual male and female plants) and perennial and are indigenous throughout much of the Northern Hemisphere between 35° and 70° N, though mostly cultivated today between 43° and 54° N, and 37° and 43° S. The most important regions for hop cultivation are in South Africa, Australia, Argentina, the United States, Germany, the Czech Republic, and England, having an amount of daylight during the growing season of 15:278:42 hours, a mean temperature of about 506°F (109°C), and average rainfall of between 2.5 and 22.4 inches during the period of April to September in the Northern Hemisphere and October to March in the Southern Hemisphere (Barth, Klinke, and Schmidt, p. 49). The world production in 1999 was about 98,000 tons, with Germany contributing about 28,000 tons, the United States about 29,000 tons, and China about 15,000 tons (FAO, Production Yearbook, 1999). Many different varieties of hops with different contents of humulone (an antibiotic) and hop oils have been developed, particularly in Germany, England, and the Czech Republic. (For more details about the varieties, the history, and the trade, see Barth, Klinke, and Schmidt, pp. 183.)
Both pollinated and unpollinated cones (strobili) from the female plants are used, with the unpollinated ones used in Germany thought by some to yield a better taste than the seed (MacLeod, p. 80). Inside the infolded bases of the bracteoles (the small leaves from which the flowers grow) and on the seed are the resin-producing lupulin glands, which contain the essential compounds for use in beer: the resins humulone (the -acids) and lupulone (the -acids), and the aromatic hop oils. The -acids yield, after boiling and isomerization, iso-α-acids, which contribute bitterness to the beer, and hop oils, which contribute to the aroma. In addition, hops also benefit beer by improving clarity and foam stability, and, most important, flavor stability because of bacteriostatic activity of the iso-α-acids (flavonoids) (Grant, pp. 15767). Hops are the major preservative of beer.
Other herbs and spices. Down through history many types of herbs and spices have been added to beer (von Hofsten, pp. 20821; Rätsch, pp. 280), and many of them have been considered to be remedies. Besides hops, sweet gale (Myrica gale) and marsh tea (Ledum palustre), two of the constituents of the old European mixture of beer additives, grut, are believed to have been in widespread use. Placotomus mentions in his book from 1543 the use of more than twenty plants as additives for beer (von Hofsten, p. 212).
Since 1516, when the Reinheitgebot (Purity Law) was approved in Bavaria, the use of additives other than hops in beer has been prohibited there; this inhibited the use of new herbs and spices, and new combinations of old ones, in beer in Bavaria. However, in Belgium and its surrounding areas, and in Great Britain, other types of beers using wheat and herbs and spices were developed. Many of the recipes are secret, but we know of the use of coriander leaves and seeds, cardamom, camomile, clover, grains of paradise (the seeds of the West African plant Aframomum melegueta), cinnamon, plums, peaches, cherries, coffee, chilies, and chocolate ( Jackson, 1998, pp. 167).
Yeast. The living microorganism producing beer from wort by anaerobic degradation of sugars to alcohol is a yeast species, Saccaromyces cerevisiae, which is also used for baking and wine fermentation. The species has at least a thousand different strains (Barnett, Payne, and Yarrow, pp. 59597). Two of them are S. cerevisiae cerevisiae used for top-fermentation of ales and S. cerevisiae uvarum (carlsbergensis) used for bottom-fermentation of lagers. They differ from each other by the temperature used: as noted above, 642°F (182°C) for the ales and about 459°F (75°C) for the lagers. Further, S. c. uvarum (carlsbergensis) has the ability to ferment the disaccharide melibiose, which S. c. cerevisiae is unable to do, due to lack of the enzyme melibiase ( -galacoidase) (Russel, pp. 16970). Different breweries have developed their own strains or mixtures of strains of yeast to maintain the distinctive qualities of their beers. Important requirements for a good brewing yeast are flocculating power (i.e., the capability of forming loose, fluffy clumps), ability to ferment maltotriose (a complex sugar found in the wort), head-forming potential, fermentation efficacy, interaction with isohumulones (forms of the antibiotic -acids produced by hops), response to fining (clarifying and purifying), and propensity for producing important individual flavor components (MacLeod, p. 84). In the San Francisco beer Anchor Steam, lager yeast is used for fermentation at a high ale-fermentation temperature, which gives a very interesting beer with the roundness and cleanness of a lager and the fruitiness and some of the complexity of an ale.
Outline of Modern Brewing Procedures
Detailed descriptions of this highly technological and scientifically based process can be found in de Clerck (1957958); MacLeod (1977); Hardwick (Handbook of Brewing,
An outline of the different procedures is given by Hardwick ("An Overview of Beer Making," 1995, p. 88).
Malting. The process of malting grain starts with steeping it in water. After several hours, the embryo begins to take up water and to grow. To produce energy, the growth hormone giberellinic acid is formed and transported to the aleurone cells around the starch-rich endosperm to start the formation of hydrolytic enzymes such as -amylase, endo-β-glucanase, and peptidase. The cell walls of the endosperm contain -linked glucan and pentosan, which are degraded by the endo-β-glucanase and pentosanases. The net action is to solubilize and break down the cell walls and the small starch granules in the endosperm. The peptidases break down the peptides into amino acids, which are essential for yeast nutrition; the large polypeptides, which have not been used by the yeast cells during fermentation, are important for foam stability in the final beer, but in conjunction with polyphenols have the potential to form undesirable haze in the beer.
When the malting is completed, the malt has to be kiln-dried to stop the enzymatic activities and to reduce the water content so as to allow storage of the finished malt. The kilning is divided into two steps: the drying, at temperatures up to 176°F (80°C), giving a moisture content of 4 percent; and the curing process, at higher temperatures, yielding flavor components through the Maillard reaction. This reaction browns the malt, producing amino acidarbonyl compounds, which undergo further transformations to yield the colored, aromatic compounds known as melanoidins. The higher the temperature, the darker the malt will be and the more the enzymes will be inhibited (Kendall, pp. 11718; Fix, pp. 415). These compounds contribute both to dark color and to different varieties of burnt-sugar or caramel taste. The malt type and the mixture of malts forms the body or the "mouthfullness" of the beer and produces the basis of classification into pale, medium, and dark beers. If the malt is kilned over an open fire, it will acquire a definite smoky taste like the Bavarian Rauchbier, "smoke beer." The feeling of "mouthfullness" can be decreased by splitting the residual sugar of the beer, the -glucans, dextrins, by exogenous enzymes during the malting process. The resulting carbohydrates will finally be fermented by the yeast. The process is used to produce diet, lite, light, and dry beers.
Mashing. The type of brewing liquid used for beer production plays a very great role. However, with modern technology, any type of liquid with the optimal concentrations of the different ions can be created from any water. Calcium ions contribute to a more acid mash by precipitating as calcium phosphate and thus setting hydrogen ions free from phosphate ions. The pH obtained in this way, 5.4, is favorable for the activities of amylases. Bicarbonate ions act in the opposite way and give a more alkaline mash, which is unfavorable, and thus they should typically be removed. Calcium sulfate is often added to the mash to decrease the pH and to give bitterness to ale. Nitrates and iron ions have deleterious effects on yeasts. For detailed discussions on brewing liquids and salts, see Moll (pp. 13356).
Germany complies with the Reinheitsgebot, the Purity Law, which, except for Weissbier, permits only barley malt, hops, and water for beer brewing. In most other countries, however, adjuncts up to 50 percent by volume are added to the mash to decrease the cost and to balance the taste of the beer. The adjuncts can be sugar solutions, other malts, or other unmalted cereals, such as rice, maize, wheat, or barley (though both rice and maize must be precooked before their incorporation into the mash, as their starches have high gelatinization points) (Stewart, pp. 12132).
The mashing can be performed by either infusion or decoction. Infusion mashing is performed in a single vessel at a uniform temperature of about 150°F (65°C), and after the mashing, filtration is performed in the same vessel. The decoction system starts with a low temperature, which is then raised by the removal, boiling, and return of a part of the mash. The whole mash finally is transferred to a separate vessel, the lauter tun, for filtration. In Britain, the infusion is used with well-modified and coarsely ground malt, whereas in continental Europe the larger decoction method is used with a finer grind and less well-modified malt. Decoction mashing is a more versatile procedure for different malts and also has the advantage of low temperature, which helps to maintain the stability of such heat-labile enzymes as proteinases, -glucanases, and -amylase (MacLeod, pp. 593; Narziss, 1999; Rehberger and Luther, pp. 24722).
The objective of the mashing is to produce fermentable sugars from the degradation of solubilized starch, amylose, and amylopectin. The sugars obtained are glucose, maltose, maltotriose, maltotetraose, and higher dextrins to a total of about 70 to 75 percent, with the higher values coming from decoction malting. Unfermentable dextrins persist to the finished beer and are an important part of the mouth-filling experience of the beer. Proteins, peptides, and amino acids, as well as vitamins, inorganic ions, fatty acids, organic acids, tannins, and lipids, are extracted during the mashing and all are important for yeast fermentation.
The amount of malt used is directly proportional to the alcoholic concentration of the finished beer. About one-fourth to one-third of the weight of the malt is metabolized to alcohol.
Wort boiling. The filtered sweet wort from the mashing is transferred to the wort vessel for boiling, which inactivates the enzymes, sterilizes the wort, lowers the pH via precipitation of calcium phosphate and removal of carbon dioxide from bicarbonate, concentrates the wort, denatures and precipitates proteins, dissolves any additional sugars used, isomerizes hop -acids, and removes unwanted flavor components. A long boiling process increases the shelf life of beer. Elimination of high-molecular-weight material (i.e., flocculation of the proteins) is increased by stirring and adding carrageen, a colloid typically extracted from the red alga Chondrus crispus. It has also been shown that the malty full-bodied flavor of beer declines and sharper notes are enhanced with rising temperature of heat treatment. The color of the wort is also increased with higher temperatures, aeration, and higher contents of soluble nitrogen. The process is the same as the one that occurs during kilning, the Maillard reaction (MacLeod, pp. 731).
During the wort boiling, hops, whole or powdered, are added to give their characteristic bitterness and aroma to the beer and, because of their antimicrobial action, to increase its shelf life. Principally, there are two types of acids contributed by the hops: -acids such as humulone, cohumulone, and adhumulone; and -acids such as lupulone, colupulone, and adlupulone. The bitter taste of fresh hops derives almost entirely from the -acids, but they have only limited solubility in the wort. However, during the boiling, the -acids are transformed into soluble, bitter iso-α-acids, which contribute to the hoppy bitterness of the beer. There are at least six cis-and transiso-α-acids and their overall level in beer is about 0.0002 to 0.0005 oz/gal (Neve, pp. 338). The -acids are largely unchanged during boiling.
The aroma of the hops comes from a very complex mixture of compounds and most of the volatile hop oils are lost in boiling, but a late addition of aroma hops increases the flavor. A discussion and list of the hop compounds in beer is found in Hardwick ("The Properties of Beer," pp. 57377).
Fermentation. The principal pathway for carbohydrate metabolism is the Embdeneyerhofarnas pathway, which is the anaerobic metabolism of glucose to pyruvates and alcohol by the yeast cells:
1 mole of glucose gives 2 moles of pyruvates, which will give 2 moles of alcohol and 2 moles of carbon dioxide (CO2).
A more comprehensive equation that describes a brewery fermentation is given by Bamforth (p. 143):
Maltose (100 g) + amino acid (0.5 g) yeast (5 g) + ethanol (48.8 g) + CO2 (46.6 g) + energy (50 kcal)
Glucose and fructose are the first carbohydrates to be absorbed by the yeast cells from the wort. For the uptake of maltose, the principal sugar of the wort, maltose permease must be synthesized, and before maltotriose can be used, the maltose of the wort has to be almost completely depleted. The formation of maltose permease is the time-limiting effect on the speed of fermentation of the wort. This enzyme is also inhibited by glucose, thus yielding a longer lag period in glucose-supplemented wort (MacLeod, pp. 8103).
Amino acids can be divided into four groups according to their uptake into the yeast cells: A, B, C, and D in that sequence for both S. c. cervisiae and S. c. carlsbergensis. The A and C amino acids appear to compete with the same permease. Proline, which is the only member of the D group, disappears very slowly, implying that a substantial amount of this amino acid will remain in the final beer: about 0.003 to 0.004 oz/gal.
Unwanted products from the fermentation process, which are closely related to amino-acid metabolism, are certain higher alcohols: 3-methylbutanol, fusel alcohol, and vicinal diketones (diacetyl). Presence of diacetyl seems to depend on a deficiency of the amino acid valine. A deficiency of methionine or an excess of threonine gives unacceptable levels of hydrogen sulfide (MacLeod, p. 91). Consequently, careful control of the amino-acid composition of the wort is essential. Esters (e.g., ethyl acetate) are also important as taste-and aroma-producing compounds. Their formation is favored by high-gravidity brewing followed by dilution, ample supplies of assimilable nitrogen, and relatively high concentrations of alcohol (MacLeod, pp. 8103). For further discussion on fermentation, see Munroe (1995, pp. 32353).
The wort is rather rich in B vitamins, but this content, particularly the content of thiamine, is decreased during fermentation by the yeasts (Hardwick, pp. 57677).
Aging and finishing. Newly fermented beer, often referred to as green beer, has to mature in flavor through storage at low temperatures and should be removed from the yeast. It may also require being clarified, stabilized, carbonated, blended, or standardized. The processes involved include filtrations, CO2 additions, pasteurization, and additions of tannic acid and proteolytic enzymes for clarification of the product. For a more detailed discussion, see Munroe (pp. 35579). Storage of green beer together with its yeast cells decreases the amount of diacetyl and 2,3entanedione, which have a buttery taste that is undesirable in lighter beers. Sulfur-containing compounds, such as hydrogen sulfide, sulfur dioxide, and dimethyl sulfide, may also show up in the beer, producing unattractive flavors and aromas.
During storage, a secondary fermentation can be performed to accelerate aging and the maturation of taste. A secondary fermentation can also be performed in the bottle, as is done in many Belgian ales and Trappist beers, for example. Another method used is to add up to about 20 percent of highly fermenting primary beer (high-kräusen) to the green beer in storage. Also during storage, aroma hops may be added to increase the aroma of the beer, and iso-α-acids from hops can be added to help control bitterness in the beer.
Modern industrial processes of aging and finishing beer, with ultrafiltrations, pasteurization, and total separation of yeast cells, give the modern-style clear, "dead" beer, which has a long shelf life. This contrasts with "real" beer or ale, which retains living yeast cells and thus exhibits richer taste and aroma, but has a shorter shelf life and often greater variation in taste and aroma. Most lagers do not contain yeast cells, but many bottom-fermented beers such as Weissbier mit Hefe (literally, "wheat beer with yeast"), Belgian beers, and British ales and stouts do. A comprehensive summary of the chemical constituents and the physical properties of beer can be found in Hardwick, "The Properties of Beer" (pp. 55185).
Beer aging and oxidation. Beer is a fresh food product, which undergoes chemical changes during storage. Some of these are expressed as sensory changes shown in the schematic graph given by Bamforth (p. 68). The progression of these changes has been described by Dalgliesch (1977, cited in Fix):
Stage A is the period of stable, "brewery-fresh" flavor.
Stage B is a transition period in which a multitude of new flavor sensations can be detected.
Stage C products exhibit the classic flavor tones of beer staling.
Stage D, not included in Dalgliesch, "is the development of 'kaleidoscopic flavors,'" as exemplified in Rodenbach's Grand Cru and in Trappist beers, "recalling the subtlety and complexity of great wines" (Fix, pp. 12728).
Most of these changes are due to a range of oxidative reactions in the beer. Hence, it is extremely important for the quality and shelf life of beer that the beer be oxygen-free. The alcohols in beer can be oxidized to aldehydes and acids, and the iso-α-acids can also be oxidized, with the formation of free fatty acids. All these compounds have prominent effects on aroma and taste. Free fatty acids can also form esters with the alcohols and the unsaturated fatty acids as well as the melanoidins produced via browning of the malt can undergo auto-oxidation. The fatty acids will give fatty and soapy flavor notes. Melanoidins may oxidize alcohols to aldehydes or acids. However, melanoidins can also be reduced by the oxidation of iso-α-acids and work as antioxidants, thereby protecting the beer from oxidation, as is the case in dark beer. The same effects are seen from malt-and hop-based phenols. Together with fatty acids, they interact in a complex electron exchange system.
The different kinds of phenols, from cathecin to polyphenols (also called tannins and flavonoids), which originate from the malt, the hops, and also from the fermentation process itself play a large role in these chemical reactions. They can act as useful antioxidants in the beer and add to the sensory impression of freshness. However, if they themselves become oxidized, they contribute astringency and harshness. Another very important result of the chemical reactions is the reduction of unsaturated fatty acids. This inhibits the development of long-chained unsaturated aldehydes, such as trans-2-nonenal, which is a prominent factor for the development of staling and cardboard and/or papery notes. Because of these reactions, highly hopped beer is less prone to develop the staling effect (Fix, pp. 12739).
Beer and Social Use
Throughout history, beer-drinking peoples have considered beer an essential part of both their food supply and their enjoyment of life. Bread and beerood and beverageere two parts of nutrition united via having almost the same process of fabrication. In earlier times, beer was thought of as liquid bread. As a beverage, it was also preferred over water, partly because water was often contaminated by bacteria, whereas beer became almost sterilized through the boiling of the wort and the antiseptic qualities of hops.
Beer and other alcoholic beverages have played a very important religious and social role: maintaining ties within groups and between people and their deities. It is not surprising that man has considered intoxicated humans to be in close contact with the deities and acquiring spiritual and supernatural forces from them. In Old Norse mythology, mead (an alcoholic beverage fermented from honey) gave humans immortality, wisdom, and poetic abilities. Mead and beer were considered to contain the spirit of the gods, and hence people ingested the gods by drinking the beverages in the same way as Christians drink the blood and eat the flesh of Christ at communion, in the form of bread and wine (Thunaeus, vol. 1, pp. 174; Wiegelmann, pp. 53337).
At the ceremonial feasts of the Nordic people in the tenth century, the beer and food were first blessed and then highly ornamented horns of beer went to everybody to make toasts to the gods: to Odin for victory and power for the king, and then to Njord and Frej for a good harvest and peace. Then they drank minne, memory, for their ancestors and relatives. The ceremony formed and strengthened bonds both between the gods and men, and among men (Thunaeus, vol. 1, pp. 174; Wiegelmann, pp. 53337). In medieval times and persisting until the nineteenth century, important ceremonies such as baptisms, weddings, funerals, and harvest celebrations had öl, beer, in their names; there were, for instance, dopöl, the celebration of baptism, and gravöl, the funeral feast. For the various celebrations, a strong beer was produced. On other days, a much weaker beer was consumed, which was sometimes even mixed with milk. People showed their hospitality by having a tankard with beer standing on the table, and everyone was welcome to take a sip.
These examples from the Nordic countries exemplify the general pattern of mankind using alcoholic beverages as ceremonial links to the gods and a method of creating and increasing social contacts among people. Many of these ceremonies and social implications of drinking together are still active today.
Mixtures of Beer and Other Beverages
In Berliner Weisse, juices of red raspberry, green sweet woodruff, or, more recently, pineapple may be added. To Belgian Lambic, different fruits can be added to the second fermentation to create, for example, Kriek (using cherries) and Framboise (using raspberries) ( Jackson, 1991, pp. 9500).
The English shandy (beer mixed with lemonade or ginger beer) and the German Radler and Alsterwasser (beer mixed with a clear soft drink, typically lemon or lemonime soda) are quite popular today. Shandy has a tradition that dates back to the tenth century (Zotter, pp. 22223). Alsterwasser has also become popular with cola and tequila (Pini, pp. 88 and 788). Radler was earlier a common mixture for children and young people in Germany. In southern Sweden, the mixture of beer (svagdricka) and milk called drickablandning (mixture of drinks) was very popular until about the middle of the twentieth century.
Food and Beer
Beer is used as an ingredient in food preparation in soups and stews, for marination of meat, as a liquid for boiling, and in sauces. Many German examples are given by Lohberg (pp. 26931). Traditional soups with beer in northern Europe are Biersuppe, lebröd, and supa, which are boiled mixtures of beer and meal and/or milk and egg, with ginger, cinnamon, and fruits. Carbonade, beef stewed in beer, is a favorite dish in northern France, Belgium, and the Netherlands.
The specific types of beer used traditionally in an area almost always fit very well with traditional local food. The most popular type of beer in the world today, pilsner or light lager, which is served cold and has low levels of bitterness and maltiness, is a good partner with almost any kind of food, which may well be an important reason for its popularity.
Other types of beers, which have a more complex taste, should be paired with different foods using some care, as the combination should not overpower the individual flavors of either the beer or the food, but enhance the positive features of both. A nice introduction with illustrative food and beer combinations has been presented by Jackson (1998). In general, beer can be paired with different kinds of food as well as wine can be, and sometimes better.
Drinking vessels and beer containers. In Latin America, the Incas and the Mayas developed very elaborate containers both for the production of chica and for storage and ritual drinking. The malting and fermentation took place in hollow tree trunks that were often decorated and covered with carpets or palm leaves. The bottles were ceramic stirrup vessels with a long neck, sometimes two joined into one, with a round bellow that could be formed as a human head. Ordinary ceramic cups were also used. The ceramics were painted with many different scenes, often with a strong erotic touch. Bottles filled with chicha were buried with the dead (Rätsch, p. 103).
The serving of beer in Mesopotamia and in ancient Egypt was from ceramic containers, both large ones from which people drank with straws (primarily to penetrate the top-fermenting yeast and floating husks) and smaller ones like our cups. For ceremonial drinking, elaborate bull's horns were used in northern Europe. After the ceramic period and persisting into the twentieth century, the wooden barrel and the wooden tankard were the principal storage and drinking containers. In Scandinavia, it was common to have elaborate drinking bowls, often in the form of a goose, for ceremonial feasts, and during the sixteenth century, the upper class used ornamental wooden drinking vessels (Hirsjärvi, pp. 578; Cleve, pp. 152; Gjærder). Drinking vessels were also later made of lead, tin, copper, silver, stoneware, ivory, china, or glass. Tankards usually had the same general design whether or not they were lidded. Lids were usually metallic, and the rest of the tankard was made of glass, ceramic, or wood. There were very elaborate, expensive tankards and also simple and practical ones ( Jung; Lohberg).
Although its history is very long, perhaps as long as the history of beer itself, before the nineteenth century the beer glass was seen only among the upper classes. It was the technique of glass pressing in great industrial scale in the nineteenth century that made the glass available to everyone. The design of the beer glass has developed in some distinctive ways, with special sizes and shapes for specific types of beers and special glasses displaying the names and logos of the brewers for almost every brand of beer (Lohberg; Jackson, 1998). Jackson includes color images of both the glass and the bottle for each type of beer presented in the book.
The original wooden barrel was generally replaced in the twentieth century by the steel barrel. At the end of the nineteenth century, glass bottles were introduced, and beginning in 1935, they were joined by metallic containerseer cans.
Serving temperature. There is a correct serving temperature for every beer. The richer the flavor and aroma of a beer is, the higher its serving temperature should be. A very low temperature is suitable if taste is secondary. The only beers that are appropriate to serve cold, about 39°F (4°C), are light, pale lagers. More tasty lagers should be served between 43 and 50°F (6 and 10°C), and ales between 54 and 64°F (12 and 18°C). Jackson (1998) is a good source for recommendations of serving temperatures for specific beers.
Beer and Traditional Medicine
Hans Zotter's book (pp. 22223) contains medical recommendations and rules from Ibn Butlan from the tenth century. It illustrates how beer was looked upon medically in the old tradition of Hippocratic medicine, a tradition that prevailed until about the seventeenth century. Its view was that
Beer is "hot and humid"; or "cold and humid."
The best beer is sharp and spicy.
Beer drinking relieves the sharpness of heat and drunkenness.
It dilates the vessels and creates discomfort.
In contrast, the mixture of beer and lemon juice or citric acid helps.
Beer drinking creates "malicious body fluids," which are good for people with hot "complection" and for young people, especially during hot weather and in hot countries.
In 1614, the philosopher and alchemist Paracelsus wrote: "Cerevisia malorum divina medicina" (Beer is a divine medicine against harms) (Rätsch, pp. 124). Beer was also used as a carrier or solvent for many different folk remedies (Rätsch, pp. 280). The use of herbs and spices, such as hops and sweet gale, in beer may well have its origin in folk medicine.
Interestingly, beer is still prescribed today in the United Kingdom as a medication for the elderly.
See also Alcohol; Fermentation; Fermented Beverages Other than Wine or Beer; Wine.
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Sven-Olle R. Olsson