Barley (Encyclopedia of Food & Culture)
BARLEY. Barley is recognized as one of the very first crops to be domesticated for human consumption. It remains one of the major cereal crops grown in the world: barley is grown on every continent on which crops are grown. It is well adapted to diverse environmental conditions and thus it is produced across a broader geographic distribution than most other cereals. Relative to other cereal crops, barley ranks fourth in total grain production. The grain of barley enters the human food chain via distinctly different routes. First, barley is used as an animal feed and therefore makes an essential contribution to the human diet indirectly through meat production. Second, barley serves as a substrate for the production of alcoholic beverages, in particular beer. Third, a minor amount of barley is used to produce a diverse range of foodstuffs eaten by humans.
The Biology of the Barley Plant
The scientific name of barley is Hordeum vulgare L. Barley is a flowering plant belonging to the family Poaceae (the grasses). In addition to barley, the grass family includes the crops most important to human existence, including rice, wheat, and maize, and other species such as sorghum, oats, rye, millet, and sugarcane. In European contexts, barley grain is often referred to as "corn." The genus Hordeum includes approximately thirty species that are indigenous to at least four continents. Barley is the only domesticated species to have emerged from the genus Hordeum, in contrast to other crop genera such as Triticum (the wheats) and Phaseolus (the dry beans), which each contain several domesticated species. The other members of the genus Hordeum exist as wild plants.
Growth and development. The life cycle of the barley plant first begins with seed germination underground. The first visible sign of germination is root emergence, followed by the emergence of the cylindrically shaped coleoptile, which is the first structure to appear above ground. Interestingly, most above-ground tissues of the barley plant initially develop from the crown, a structure located below ground. The first leaf grows upward within the cylinder of the coleoptile, and emerges above the soil. This and other leaves do not expand along their entire length; rather the outer section (the blade) does so, while the base (the sheath) remains formed in a hollow cylinder. New leaves emerge in succession up through the sheaths of the older leaves.
The barley plant is not restricted to the development of one main stem, as observed in maize. Rather, like most other small-grain cereals such as wheat and rice, barley produces several additional secondary stems termed tillers that emerge up from the crown beginning a few weeks after the emergence of the main stem. The number of tillers produced varies depending upon the barley genotype and the environment. For instance, under highly fertile conditions, plants will produce more tillers than if nutrient starved.
Reproduction. Barley varieties are classified as spring or winter types, depending on whether they need a cold treatment, ranging from two to several weeks before making the transition to the reproductive phase of growth. When barley switches to its reproductive phase, the true stems of some of the tillers, called culms, elongate upward. The flowering structure, known variously as the spike, ear, or head, is borne upward, ultimately emerging from the "boot," which is the sheath of the uppermost leaf on the culm (the flag leaf). The height of a barley plant when the spike has emerged varies greatly, but averages approximately eighty centimeters. The spike consists of a large number of individual flowers called florets, which are present in individual spikelets that are attached to a central stemlike structure called the rachis. Spikelets are attached in groups of three on opposite sides of the rachis. The total number of spikelets on a spike varies, but averages approximately sixty. The awns are a notable feature of the spike. They are hairlike extensions that emerge upward from the lemma, one of two thin sheets of cells that surround the floret (the other is the palea). Awn length varies considerably among barley varieties.
Barley is also classified based upon the fertility of the florets on the spike. In six-rowed barleys, all of the florets are fertile, leading to six vertical rows of seeds on the spike. In contrast, in two-rowed types only the central floret of the three at each node is fertile, and thus just two rows of seeds develop on opposite sides of the rachis. The fertile florets consist of both male and female reproductive structures, and fertilization occurs as the spikes are emerging from the boot. Barley is thus predominantly self-pollinated. Between twenty-five and sixty seeds per spike are produced, and for spring barley the seed matures three to five months after planting.
Characteristics of the barley grain. Barley seeds are approximately eight millimeters in length and weigh approximately fifty milligrams when mature, though there is a considerable range in these values between varieties. In most cases, the harvested barley grain includes the seed, a small structure called the rachilla, and both the palea and lemma, all of which adhere firmly to the seed. Barley grain in which these structures remain attached is referred to as covered barley, with the palea and lemma, collectively termed the hull. However, barleys in which the palea and lemma do not adhere to the seed are also well known. These hulless barleys share harvesting features similar to wheat, because when harvested the seed is cleanly separated from all other components of the spike.
The barley seed consists of the embryo, a series of outer layers of cells called the pericarp, and the endosperm. The endosperm contains different nutrients that the embryo draws upon as it grows into a plant. The principal compound found in the endosperm is starch, which represents about two-thirds of the mass of the seed. This starch serves as an energy source for the seedling. Another significant carbohydrate, the -glucans, are components of the endosperm cell walls. The second largest component of the barley endosperm is protein. The amount of protein present is generally inversely proportional to the amount of starch. This protein provides a source of amino acids that can be used for protein synthesis by the seedling. The amount of protein present in a seed is positively correlated with the amount of nitrogen fertilizer applied when the parent plant is being grown. Additionally, the barley grain contains a large variety of other compounds present in minor amounts, including mineral nutrients and different organic compounds, including various vitamins.
The History of Barley Use
The progenitor of cultivated barley is Hordeum vulgare subspecies spontaneum, or wild barley. Wild barley is still
Along with wheat, barley was one of the first crops to be domesticated by humans and thus it played an important role in the emergence of agriculture in the Old World. There is rich evidence of barley in the archaeological record from numerous sites throughout the Near and Middle East, supporting the notion that it was a common and important crop in ancient times. It is likely that barley was already domesticated and being cultivated as early as ten thousand years ago, though wild barley was likely being harvested as a food long before this. Further, early written records from various cultures bear frequent mention of barley, as does the Bible, reinforcing the fact that barley was an important crop. Indeed, barley remained an important human food crop for many millennia, but it was gradually supplanted by wheat. The rapid spread of agriculture from the Near East into Europe and Asia led to the broad dissemination of barley and its cultivation. In more recent history, barley was brought to the New World as far back as the explorations of Columbus. Barley was introduced to the eastern United States early in the seventeenth century, and the west coast of the Americas in the eighteenth century.
Barley is grown on nearly sixty million hectares of land worldwide, resulting in the production of approximately 140 million metric tons of grain. The top ten barley producing countries include Russia, Germany, Canada, Ukraine, France, Australia, the United Kingdom, Turkey, United States, and Denmark. Barley producers select the appropriate varieties to be grown and crop management schemes to produce grain well suited to a particular end use. Specific producer considerations vary widely, but include the choice of variety to plant, the timing of planting and grain harvesting, and agricultural inputs such as fertilizers, herbicides, fungicides, and insecticides. In the Northern Hemisphere, in regions where winters are too severe to allow winter barleys to survive overwintering, spring barleys are planted, usually in April or May. In warmer regions where winter barleys can overwinter, planting is done in September or November.
Given that the producer obtains only a small profit margin for barley produced, additional agricultural inputs are minimized. For instance, nitrogen fertilization is managed to maximize yield without compromising end-use quality. Barley is also subject to damage by a range of diseases, including powdery mildew, stem and leaf rust, smuts, leaf blotches, viral diseases, and head blights. Thus these diseases are managed by a combination of strategies including the use of disease-resistant varieties, application of fungicides, tillage practices, timing of crop planting, and crop rotation.
When the barley crop is mature, harvesting is accomplished either by direct combining or by first swathing, which entails cutting the culms and allowing the grain to dry in the field, and then harvesting. Technology for harvesting ranges from a simple sickle in developing countries to sophisticated mechanical combines that cut the culms above the soil, move the harvested plants between rollers to dislodge seeds, and pass this over mesh screens, allowing the grain to fall into a collection bin and the chaff to blow back out to the ground. Once the grain is harvested, it may either be stored in bins on the farm, or delivered to a local grain elevator where it is purchased from the producer. The price paid for barley grain depends on its intended end use. After purchasing the grain, the elevator cleans, dries, and stores it, and ultimately resells the grain to the various businesses that use barley (feed, food, and malt industries).
Animal feed. The principal use of barley grain is as feed for poultry, swine, sheep, and cattle. Worldwide, 60 percent or more of the barley that is produced is used for animal feed. The particular barley varieties used as animal feed are sometimes specially developed "feed barleys" with attributes such as high protein that are geared specifically toward this end use. Sheep can be fed whole barley; however, before barley is fed to other animals it is ground using a hammer mill or rolling mill, or may be flaked with steam-heated rollers. Thus, the final feed product may be whole, ground, flaked, or pelleted barley. Since the phosphorus in barley is generally more readily absorbed by animals than it is from other feed grains, the use of barley as animal feed tends to result in less potential environmental phosphorus contamination from the animal waste runoff. While barley grain is the principal part of the plant used as animal feed, in some instances barley plants themselves may be used as a forage hay for animals.
Human consumption of barley. Less than one-half of the barley produced throughout the world is used for the preparation and production of products directly consumed by humans. Only a minor amount of barley is actually used in the production of foods for human consumption, though the range of uses for barley within this context are diverse. In some regions of the world, barley is grown for human consumption where other grains do not grow well. When consumed as grain, hulless barley is generally used because the absence of the hull makes the product more palatable and easier to process. Barley can be pearled, which removes the outer layers of the seed and the embryo, followed by processing to produce small rounded pieces of the endosperm. Covered barley can also be dehulled, milled, and polished to remove the bran layers, to produce a ricelike product. Pearled and polished barley are used in porridges and soups and as rice substitutes. Other food uses include barley flakes, flour for baking purposes (either alone or in mixtures with wheat flour) to produce breads and crackers, grits, breakfast cereals, pilaf, noodles, and baby foods. Lastly, some barley is used for the production of distilled spirits such as whiskey, vodka, and gin, and for making vinegar and malted beverages.
Beer: the main use of barley for human consumption. The truly unique feature of barley that sets it apart from other small-grain cereals such as wheat is that the vast majority of barley that humans consume is not in the form of solid food derivatives, but rather in the form of a single product, the alcoholic beverage beer. The production of beerlike alcoholic beverages dates back several thousand years, and beer may be the oldest fermented beverage consumed by humans. Many barley varieties are developed specifically to possess the chemical and biochemical properties desirable for this purpose; such barleys are called malting barleys. In contrast to feed barley, malting barley has a high starch content. Because of the greater value of the end product of malting barley compared to feed barley, malting barley brings the producer more money. However, barley must meet stringent specifications of the malting and brewing industries before it will be used for this purpose. Both two-rowed and sixrowed barley are used to make beer, with six-rowed types preferred in the United States and two-rowed varieties preferred elsewhere. Beer production is divided into two processes, barley malting and brewing, which are undertaken by independent industries.
The beer-making process. Beer production requires just four ingredients: barley, water, hops, and yeast. Barley provides sugars and amino acids for yeast growth, and the yeast converts the sugars to ethyl alcohol in a process called fermentation. Before barley is used to make beer, it is converted to "malt" to render it a better substrate for brewing. Malting is essentially a process of truncated seed germination. When grain enters a malt house, it is first steeped in water for two to three days. After steeping, the barley is transferred to germination beds for three to four days. Here the grain begins to produce enzymes capable of degrading the starch, protein, and the cell walls of the endosperm, and degradation of protein and cell walls proceeds. The barley grains are then subjected to heat that kills the growing seedling and dries the remnant grain, but leaves intact the components of the endosperm as well as the enzymes capable of degrading them. The product that emerges is malt. Major malt producing countries include the United States, Germany, and France, while major importers of malt include Japan, Germany, and Brazil.
Malt is used by breweries for beer production. The malt is first milled and mixed with water in a process called mashing. This mash is allowed to rest at temperatures that encourage degradation of starch from the endosperm into sugars, by the enzymes present in the malt. The mash is then transferred to a container with a sieve on the bottom, called a lauter tun. Here the liquid fraction of the mash, called wort, is separated from the residual solids by filtration. Traditionally, covered barley is used for beer production because the hulls of the barley malt settle in the lauter tun and participate in filtering out residual solids. The resultant wort contains the soluble components derived from the malt, such as sugars and amino acids liberated by enzyme action. Hop plant flowers (or a derivative of them) are added to the wort and boiled. The hop oils add certain bitter flavors to the beer and protect it from bacterial contamination. The wort is then cooled, transferred to a fermentation vessel, and inoculated with yeast. The yeast use the sugars and amino acids from the malt to grow, and as it grows the metabolism of the sugar maltose leads to the production of ethyl alcohol and carbon dioxide as by-products of the fermentation process. After fermentation, the yeast and other solids are allowed to settle out. This is followed by an aging period, carbonation, and final packaging to produce the finished beer. Thus, the role of barley grain in beer production is similar to its role in the barley life cycle: to provide nutrients for growth. However, in beer production the benefactor of the nutrients is the yeast and not the growing seedling.
Worldwide, well over one billion hectoliters of beer are produced annually, from approximately sixty million metric tons of barley. It takes approximately fifty grams of malt to produce a 375-milliliter bottle of beer, though this amount can be less depending on the type of beer and whether adjuncts (nonbarley sources of sugars, often rice or corn) are used. The largest beer producing countries include the United States, China, Germany, Brazil, Japan, the United Kingdom, and Mexico.
Traditions. The principal barley product consumed by humans, beer is produced and drunk in large quantities worldwide. Beer is probably recognized as the beverage most strongly associated with celebration, relaxation, and social interaction, and has become a ubiquitous component of recreational activities. Beer is commonly consumed in a diverse range of settings, including the home, restaurants, and bars, and for a broad range of occasions, particularly social gatherings. For instance, beer is a fixture at professional sporting events of all kinds held around the world. The increasing demand for beer is reflected in the rapid expansion in the number of micro-breweries, and in the growth in popularity of home brewing. Beer consumption continues to grow in popularity, with production doubling over the last thirty years to keep up with demand. In addition, barley plays a ceremonial role in some societies. For instance, in India barley is often used in marriage and other ceremonies.
See also:Beer; Cereal Grains and Pseudo-Cereals; Grain Reserves; Livestock Production; Maize; Rice; Wheat.
Bamforth, Charles. Beer: Tap into the Art and Science of Brewing. New York: Plenum Press, 1998.
Barley: Origin, Botany, Culture, Winter Hardiness, Genetics, Utilization, Pests. Agriculture Handbook No. 338. Washington, D.C.: U.S. Department of Agriculture, 1979.
Briggs, D. E. Barley. London: Chapman and Hall, 1978.
Cook, A. H., ed. Barley and Malt: Biology, Biochemistry, Technology. New York: Academic Press, 1962.
Davies. M. S., and Gordon C. Hillman. "Domestication of Cereals." In Grass Evolution and Domestication, edited by G. P. Chapman, 19924. Cambridge: Cambridge University Press, 1992.
Heiser, Charles B., Jr. Seed to Civilization. The Story of Food. Cambridge, Mass.: Harvard University Press, 1990.
Lewis, Michael J., and Tom W. Young. Brewing. London: Chapman and Hall, 1995.
Rasmussen, Donald C., ed. Barley. Madison, Wisc.: The American Society of Agronomy, 1985.
Renfrew, Jane M. Paleoethnobotany: The Prehistoric Food Plants of the Near East and Europe. London: Methuen, 1973. Good illustrations of barley seed morphology and additional useful information on archaeological record in Near East, though barley taxonomy is outdated.
Shewry, Peter R., ed. Barley: Genetics, Biochemistry, Molecular Biology, and Biotechnology. Wallingford, U.K.: CAB International, 1992.
U.S. Department of Agriculture (USDA) Foreign Agricultural Service Website. This website is a gateway to a wealth of information on global agriculture, including world production of crops including barley (see crop production tables at http://www.fas.usda.gov/wap/circular/2002/02-01/grains.pdf).
Zohary, Daniel. "The Origin and Early Spread of Agriculture in the Old World." In The Origin and Domestication of Cultivated Plants, edited by C. Barigozzi, pp. 30. Amsterdam: Elsevier, 1986.
Zohary, Daniel, and Maria Hopf. Domestication of Plants in the Old World: The Origin and Spread of Cultivated Plants in West Asia, Europe, and the Nile Valley. 2nd ed. Oxford, U.K.: Clarendon Press, 1993.
David F. Garvin Harsh Raman Kevin P. Smith