Maize

Ellen Messer. Cambridge World History of Food. Editor: Kenneth F Kiple & Kriemhild Conee Ornelas. Volume 1. Cambridge, United Kingdom: Cambridge University Press, 2000.

Maize (Zea mays L.), a member of the grass family Poaceae (synonym Gramineae), is the most important human dietary cereal grain in Latin America and Africa and the second most abundant cultivated cereal worldwide. Originating in varying altitudes and climates in the Americas, where it still exhibits its greatest diversity of types, maize was introduced across temperate Europe and in Asia and Africa during the sixteenth and seventeenth centuries.

It became a staple food of Central Europe, a cheap means of provisioning the African-American slave trade by the end of the eighteenth century, and the usual ration of workers in British mines in Africa by the end of the nineteenth century. In the twentieth century, major increases in maize production, attributed to developments in maize breeding, associated water management, fertilizer response, pest control, and ever-expanding nutritional and industrial uses, have contributed to its advance as an intercrop (and sometimes as a staple) in parts of Asia and to the doubling and tripling of maize harvests throughout North America and Europe. High-yield varieties and government agricultural support and marketing programs, as well as maize's biological advantages of high energy yields, high extraction rate, and greater adaptability relative to wheat or rice, have all led to maize displacing sorghum and other grains over much of Africa.

On all continents, maize has been fitted into a wide variety of environments and culinary preparations; even more significant, however, it has become a component of mixed maize-livestock economies and diets. Of the three major cereal grains (wheat, rice, and maize), maize is the only one not grown primarily for direct human consumption. Approximately one-fifth of all maize grown worldwide is eaten directly by people; two-thirds is eaten by their animals; and approximately one-tenth is used as a raw material in manufactured goods, including many non-food products.

Maize Literature


Principal sources for understanding the diverse maize cultures and agricultures are P. Weatherwax's (1954) Indian Corn in Old America, an account of sixteenth-century maize-based agriculture and household arts; S. Johannessen and C. A. Hastorf's (1994) Corn and Culture, essays that capture New World archaeological and ethnographic perspectives; and H. A. Wallace and E. N. Bressman's (1923) Corn and Corn Growing, and Wallace and W. L. Brown's (1956) Corn and Its Early Fathers, both of which chronicle the early history of maize breeding and agribusiness in the United States.The diffusion of maize in the Old World has been traced in J. Finan's (1950) summary of discussions of maize in fifteenth- and sixteenth-century herbals, in M. Bonafous's (1836) Natural Agricultural and Economic History of Maize, in A. de Candolle's (1884) Origin of Cultivated Plants, and in D. Roe's (1973) A Plague of Corn: The Social History of Pellagra. B. Fussell's (1992) The Story of Corn applies the art of storytelling to maize culinary history, with special emphasis on the New World. Quincentenary writings, celebrating America's first cuisines and the cultural and nutritional influence of maize, as well as that of other New World indigenous crops, include works by W. C. Galinat (1992), S. Coe (1994), and J. Long (1996).

More recent regional, cultural, agricultural, and economic perspectives highlight the plight of Mexico's peasant farmers under conditions of technological and economic change (Hewitt de Alcantara 1976, 1992; Montanez and Warman 1985; Austin and Esteva 1987; Barkin, Batt, and DeWalt 1990), the displacement of other crops by maize in Africa (Miracle 1966), and the significance of maize in African "green revolutions" (Eicher 1995; Smale 1995). The Corn Economy of Indonesia (Timmer 1987) and C. Dowswell, R. L. Paliwal, and R. P. Cantrell's (1996) Maize in the Third World explore maize's growing dietary and economic significance in developing countries.The latter includes detailed country studies of Ghana, Zimbabwe,Thailand, China, Guatemala, and Brazil.

Global developments in maize breeding, agronomy, and extension are chronicled in the publications of Mexico's International Center for the Improvement of Maize and Wheat (CIMMYT), especially in World Maize Facts and Trends(CIMMYT 1981, 1984, 1987, 1990, 1992, 1994), and in research reports and proceedings of regional workshops. Maize genetics is summarized by David B.Walden (1978), G. F. Sprague and J.W. Dudley (1988), and the National Corn Growers Association (1992). Molecular biologists who use maize as a model system share techniques in the Maize Genetics Cooperation Newsletter and The Maize Handbook (Freeling and Walbot 1993). One explanation for the extensive geographic and cultural range of maize lies in its unusually active "promoter," or "jumping," genes and extremely large chromosomes, which have made it a model plant for the study of genetics—the Drosophila of the plant world.

Geographic Range


Maize is grown from 50 degrees north latitude in Canada and Russia to almost 50 degrees south latitude in South America, at altitudes from below sea level in the Caspian plain to above 12,000 feet in the Peruvian Andes, in rainfall regions with less than 10 inches in Russia to more than 400 inches on Colombia's Pacific coast, and in growing seasons ranging from 3 to 13 months (FAO 1953). Early-maturing, cold-tolerant varieties allow maize to penetrate the higher latitudes of Europe and China, and aluminum-tolerant varieties increase production in the Brazilian savanna. In the tropics and subtropics of Latin America and Asia, maize is double- or triple-cropped, sometimes planted in rotation or "relay-cropped" with wheat, rice, and occasionally, soybeans, whereas in temperate regions it is monocropped, or multi-cropped with legumes, cucurbits, and roots or tubers. In North America, it is planted in rotation with soybeans.

Yields average 2.5 tons per hectare in developing countries, where maize is more often a component of less input-intensive multicrop systems, and 6.2 tons per hectare in industrialized countries, where maize tends to be input-intensive and single-cropped. The U.S. Midwest, which produced more than half of the total world supply of maize in the early 1950s, continued to dominate production in the early 1990s, with 210.7 million tons, followed by China (97.2 million tons), and then Brazil (25.2 million tons), Mexico (14.6 million tons), France (12.2 million tons), India (9.2 million tons), and the countries of the former Soviet Union (9.0 million tons). Developing countries overall account for 64 percent of maize area and 43 percent of world harvests (FAO 1993). The United States, China, France, Argentina, Hungary, and Thailand together account for 95 percent of the world maize trade, which fluctuates between 60 and 70 million tons, most of which goes into animal feed.

Cultural Range


Maize serves predominantly as direct human food in its traditional heartlands of Mexico, Central America, the Caribbean, and the South American Andes, as well as in southern and eastern Africa, where the crop has replaced sorghum, millet, and sometimes roots and tuber crops in the twentieth century. The highest annual per capita intakes (close to 100 kilograms per capita per year) are reported for Mexico, Guatemala, and Honduras, where the staple food is tortillas, and for Kenya, Malawi, Zambia, and Zimbabwe, where the staple is a porridge. Maize is also an essential regional and seasonal staple in Indonesia and parts of China.

However, maize is considerably more significant in the human food chain when it first feeds livestock animals that, in turn, convert the grain into meat and dairy products. In the United States, 150 million tons of maize were harvested for feed in 1991; in Germany, three-fourths of the maize crop went for silage. In some developing countries, such as Pakistan, India, and Egypt, the value of maize fodder for bovines may surpass that of the grain for humans and other animals. In Mexico, the "Green Revolution" Puebla Project developed improved, tall (versus short, stiff-strawed) varieties in response to demands for fodder as well as grain.

Since World War II, processing for specialized food and nonfood uses has elevated and diversified maize's economic and nutritional significance. In the United States, for example, maize-based starch and sweeteners account for 20 million tons (15 million tons go to beverages alone), cereal products claim 3 million tons, and distilled products 0.3 million tons. Maize-based ethanol, used as a fuel extender, requires 10 million tons; and plastics and other industrial products also employ maize. The geographic and cultural ranges of maize are tributes to its high mutation rate, genetic diversity and adaptability, and continuing cultural selection for desirable characteristics.

Biology and Biodiversity


More than 300 races of maize, consisting of hundreds of lineages and thousands of cultivars, have been described. But the precise ancestry of maize remains a mystery, and geographical origins and distributions are controversial.

Biological Evolution


Teosinte (Zea spp.), a weedy grass that grows in Mexico and Guatemala, and Tripsacum, a more distantly related rhizomatous perennial, are maize's closest wild relatives. All three species differ from other grasses in that they bear separate male and female flowers on the same plant. Key morphological traits distinguishing maize from its wild relatives are its many-rowed ear compared to a single-rowed spike, a rigid rather than easily shattered rachis, a pair of kernels in each cupule compared to a single grain per cupule, and an unprotected or naked grain compared to seed enclosed in a hard fruitcase. Unlike the inflorescence structures of other grasses, maize produces a multirowed ear with hundreds of kernels attached to a cob that is enclosed by husks, which makes it amenable for easy harvest, drying, and storage.

Based on interpretations of evidence from cytology, anatomy, morphology, systematics, classical and molecular genetics, experimental breeding, and archaeology, there are three recognized theories about the origins of maize: (1) the ancestor of maize is annual teosinte (Vavilov 1931; Beadle 1939; Iltis 1983; Kato 1984); (2) maize evolved from an as yet undiscovered wild maize or other ancestor (Mangelsdorf 1974); and (3) maize derived from hybridization between teosinte and another wild grass (Harsh-berger 1896; Eubanks 1995). Although the most popular theory holds that teosinte is the progenitor, present evidence does not clearly resolve its genetic role. Firmer evidence supports the idea that introgression of teosinte germ plasm contributed to the rapid evolution of diverse maize land races in prehistory (Well-hausen et al. 1952). Teosintes-which include two annual subspecies from Mexico (Z. mays ssp. mexicana and ssp. parviglumis), two annual species from Guatemala (Z. huehuetenangensis and Z. luxurians), and two perennial species from Mexico (Z. perennis and Z. diploperennis)—have the same base chromosome number (n = 10) as maize and can hybridize naturally with it. Like maize, teosintes bear their male flowers in tassels at the summit of their main stems and their female flowers laterally in leaf axils. Although the ears of teosinte and maize are dramatically different, teosinte in architecture closely mimics maize before flowering, and—so far—no one has demonstrated effectively how the female spike might have been transformed into the complex structure of a maize ear.

Tripsacum spp. have a base chromosome number of n = 18 and ploidy levels ranging from 2n = 36 to 2n = 108. Tripsacum is distinctive from maize and teosinte because it bears male and female flowers on the same spike, with the staminate (male) flowers directly above the pistillate (female) flowers. This primitive trait is seen in some of the earliest prehistoric maize (on Zapotec urns from the Valley of Oaxaca, Mexico, c. A.D. 500-900, which depict maize with staminate tips) and also in some South American races. Tripsacum plants also frequently bear pairs of kernels in a single cupule, another maize trait. The ears of F1 Tripsacum-teosinte hybrids have pairs of exposed kernels in fused cupules and resemble the oldest archaeological maize remains from Tehuacan, Mexico (Eubanks 1995). Although the theory that domesticated maize arose from hybridization between an unknown wild maize and Tripsacum is no longer accepted, and crosses between Tripsacum and maize or annual teosinte are almost always sterile, crosses between Tripsacum and perennial teosinte have been shown to produce fully fertile hybrid plants (Eubanks 1995), andTripsacum has potential as a source of beneficial traits for maize improvement.

Molecular evidence for maize evolution includes analyses of isozymes and DNA of nuclear and cytoplasmic genes. Results indicate that isozyme analysis cannot fully characterize genetic variation in Zea, and application of this technique to understanding evolutionary history is limited. In addition, certain maize teosintes (Z. m. parviglumis andZ. m. mexicana), thought to be ancestral to maize, may actually post-date its origin. In sum, the origins of maize remain obscure.

Geographic Origin and Distribution


Most scientists concur that maize appeared 7,000 to 10,000 years ago in Mesoamerica, but controversy surrounds whether maize was domesticated one or more times and in one or more locations. Based on racial diversity and the presence of teosinte in Mexico but not Peru, N. I. Vavilov (1931) considered Mexico to be the primary center of origin. The earliest accepted archaeological evidence comes from cave deposits in Tehuacan, Puebla, in central Mexico. The cobs found there ranged from 19 to 25 millimeters (mm) long and had four to eight rows of kernels surrounded by very long glumes. The remarkably well-preserved specimens provide a complete evolutionary sequence of maize dating from at least as far back as 3600 B.C. up to A.D. 1500. Over this time, tiny eight-rowed ears were transformed into early cultivated maize and then into early tripsacoid maize, ultimately changing into the Nal Tel-Chapalote complex, late tripsacoid, and slender popcorn of later phases (Mangelsdorf 1974). An explosive period of variation, brought about by the hybridization of maize with teosinte, began around 1500 B.C. (Wilkes 1989).

From Mexico, maize is thought to have moved south and north, reaching Peru around 3000 B.C. and North America sometime later. However, pollen identified as maize was present with phytoliths in preceramic contexts in deposits dated to 4900 B.C. in Panama and in sediments dated to 4000 B.C. in Amazonian Ecuador. Although the identification of maize pollen and phytoliths (as opposed to those of a wild relative) remains uncertain, some investigators (Bonavia and Grobman 1989) have argued that such evidence, combined with maize germ plasm data, indicates the existence of a second center of domestication in the Central Andean region of South America, which generated its own distinct racial complexes of the plant between 6000 and 4000 B.C. Fully developed maize appeared later in the lowlands (Sanoja 1989).

Maize arrived in North America indisputably later. Flint varieties adapted to the shorter nights and frost-free growing seasons of the upper Midwest evolved only around A.D. 1100, although maize had been introduced at least 500 years earlier. Ridged fields later allowed cultivators to expand the growing season by raising soil and air temperatures and controlling moisture. In the Eastern Woodlands, 12-row (from A.D. 200 to 600) and 8-row (from around 800) varieties supplemented the existing starchy-seed food complexes (Gallagher 1989; Watson 1989).

Germ Plasm and Genetic Diversity


Gene banks have collected and now maintain 90 to 95 percent of all known genetic diversity of maize. The largest collections are held by the Vavilov Institute (Russia) and the Maize Research Institute (Yugoslavia), which contain mostly Russian and European accessions. The genetically most diverse New World collections are maintained at the National Seed Storage Laboratory in the United States, CIMMYT and the Instituto Nacional de Investigaciones Forestales y Agropecuarios (INIFAP—the National Institute of Forestry and Agricultural Research) in Mexico, the National Agricultural University in Peru, the National Agricultural Research Institute in Colombia, the Brazilian Corporation of Agricultural Research (EMBRAPA), the Instituto de Nutricion y Tecnologia de los Alimentos (INTA—the Institute of Nutrition and Food Technology) at the University of Chile, Santiago, and the National Agricultural Research Institute (INIA) in Chile. International maize breeding programs operate at CIMMYT and at the International Institute for Tropical Agriculture (IITA), which interface with national maize breeding programs in developing countries (Dowswell, Paliwal, and Cantrell 1996).

The germ plasm collections begun by the Rockefeller Foundation and the Mexican Ministry of Agriculture in 1943 (which classified maize according to productiveness, disease resistance, and other agronomic characteristics) have since been supplemented by the collections of international agricultural research centers that treat additional genetic, cytological, and botanical characteristics (Wellhausen et al. 1952; Mangelsdorf 1974). All contribute information for the contemporary and future classification and breeding of maize.

Maize Classifications


Maize plants range from 2 to 20 feet in height, with 8 to 48 leaves, 1 to 15 stalks from a single seed, and ears that range from thumb-sized (popcorn) to 2 feet in length. The different varieties have different geographical, climatic, and pest tolerances. The mature kernel consists of the pericarp (thin shell), endo-sperm (storage organ), and embryo or germ, which contains most of the fat, vitamins, and minerals and varies in chemical composition, shape, and color.

The principal maize classifications are based on grain starch and appearance—these characteristics influence suitability for end uses. In "flints," the starch is hard. In "dents," the kernel is softer, with a larger proportion of floury endosperm and hard starch confined to the side of the kernel. "Floury" varieties have soft and mealy starch;"pop" corns are very hard. "Sweet" corns have more sugar, and "waxy" maizes contain starch composed entirely of amylopectin, without the 22 percent amylose characteristic of dents.

Dents account for 95 percent of all maize.The kernels acquire the characteristic "dent" when the grain is dried and the soft, starchy amylose of the core and the cap contract. Most dent maize is yellow and is fed to livestock; white dents are preferred for human food in Mexico, Central America, the Caribbean, and southern Africa. Flint maize, with its hard outer layer of starch, makes a very good-quality maize meal when dry-milled. It stores more durably than other types because it absorbs less moisture and is more resistant to fungi and insects. Flints germinate better in colder, wetter soils, mature earlier, and tend to perform well at higher latitudes. Popcorns are extremely hard flint varieties; when heated, the water in the starch steam-pressures the endosperm to explode, and the small kernels swell and burst.

Sweet corns are varieties bred especially for consumption in an immature state.A number of varieties of sweet corn, exhibiting simple mutations, were developed as garden vegetables in the United States beginning around 1800. Sweet varieties known as sara chulpi were known much earlier in the Andes, where they were usually parched before eating. Floury maizes are grown in the Andean highlands of South America, where they have been selected for beer making and special food preparations (kancha), and in the U.S. Southwest, where they are preferred for their soft starch, which grinds easily. Waxy varieties are grown for particular dishes in parts of Asia and for use in industrial starches in the United States.

In addition, maize grains are classified by color, which comes mostly from the endosperm but is also influenced by pigments in the outer aleurone cell layer and pericarp. Throughout most of the world, white maize is preferred for human consumption and yellow for animal feed, although Central and Mediterranean Europeans eat yellow maize and indigenous Americans carefully select blue (purple, black), red, and speckled varieties for special regional culinary or ritual uses. Color is probably the most important classification criterion among New World indigenous cultivators, who use color terms to code information on the ecological tolerances, textures, and cooking characteristics of local varieties.

Breeding


The early indigenous cultivators of maize created "one of the most heterogeneous cultivated plants in existence" (Weatherwax 1954: 182). They selected and saved seed based on ear form, row number, and arrangement; kernel size, form, color, taste, texture, and processing characteristics; and plant-growth characteristics such as size, earliness, yield, disease resistance, and drought tolerance. Traditional farmers planted multiple varieties as a hedge against stressors, and Native American populations have continued this practice in the United States (Ford 1994) and Latin America (Brush, Bellon, and Schmidt 1988; Bellon 1991). However, only a small fraction of the biodiversity of traditional maize was transported to North America, to Europe, from Europe to Asia and Africa, and back to North America.

During all but the last hundred years, maize breeding involved open-pollinated varieties—varieties bred true from parent to offspring—so that farmers could select, save, and plant seed of desirable maize types. Hybrid maize, by contrast, involves crossing two inbred varieties to produce an offspring that demonstrates "hybrid vigor," or heterosis (with yields higher than either parent). But the seed from the hybrid plant will not breed true. Instead, new generations of hybrid seed must be produced in each succeeding generation through controlled crosses of the inbred lines. Consequently, save for producing their own crosses, farmers must purchase seed each cultivation season, which has given rise to a large hybrid seed industry, particularly in developed countries.

Hybrid maize had its beginnings in the United States in 1856 with the development by an Illinois farmer of Reid Yellow Dent, a mixture of Southern Dent and Northern Flint types that proved to be high-yielding and resistant to disease.There followed a series of scientific studies demonstrating that increased yields (hybrid vigor) resulted from the crossing of two inbred varieties. W. J. Beal, an agro-botanist at Michigan State University, in 1877 made the first controlled crosses of maize that demonstrated increased yields. Botanist George Shull, of Cold Spring Harbor, New York, developed the technique of inbreeding. He showed that although self-pollinated plants weakened generation after generation, single crosses of inbred lines demonstrated heterosis, or hybrid vigor. Edward East, working at the Connecticut Agricultural Experimental Station during the same period, developed single-cross inbred hybrids with 25 to 30 percent higher yields than the best open-pollinated varieties. A student of East's, D. F. Jones, working with Paul Mangelsdorf, in 1918 developed double-cross hybrids, which used two single-cross hybrids rather than inbred lines as parents and overcame the poor seed-yields and weakness of inbred lines so that hybrid seeds became economically feasible.

By the late 1920s, private seed companies were forming to sell high-yield hybrid lines. Henry A. Wallace, later secretary of agriculture under U.S. president Franklin Roosevelt, established Pioneer Hi-Bred for the production and sale of hybrid seed in 1926, in what he hoped would herald a new era of productivity and private enterprise for American agriculture. From the 1930s through the 1950s, commercial hybrids helped U.S. maize yields to increase, on average, 2.7 percent per year. By the mid-1940s, hybrids covered almost all of the U.S. "Corn Belt," and advances were under way in hybrid seeds that were adapted to European, Latin American, and African growing conditions. Another quantum leap in yields was achieved after World War II through chemical and management techniques. New double- and triple-cross hybrids responsive to applications of nitrogen fertilizers substantially raised yields in the 1960s, and again in the 1970s, with the release of a new generation of fertilizer-responsive single-cross hybrids that were planted in denser stands and protected by increased quantities of pesticides. In the 1980s, however, concerns about cost reduction, improved input efficiency, and natural resource (including biodiversity) conservation supplanted the earlier emphasis on simply increasing yields, with the result that yields remained flat.

Breeders also have been concerned with diversifying the parent stock of inbred hybrids, which are formed by the repeated self-pollination of individual plants and which, over generations, become genetically uniform and different from other lines. To prevent self-pollination when two inbred lines are crossed to produce a hybrid, the tassels are removed from the male parent. Discovery of lines with cytoplasmic male sterility allowed this labor-intensive step to be eliminated, but although it was desirable for the seed industry, the uniform germ plasm carrying this trait (Texas [T] male-sterile cytoplasm) proved very susceptible to Southern Corn Leaf Blight. Indeed, in 1970, virtually all of the U.S. hybrid maize crop incorporated the male sterility factor, and 15 to 20 percent of the entire crop was lost. Researchers and the seed industry responded by returning to the more laborious method of detasseling by hand until new male-sterile varieties could be developed (National Research Council 1972).

Since the 1940s, international agricultural "campaigns against hunger" have been transferring maize-breeding technologies (especially those involving hybrid seed) to developing countries. Henry Wallace, mentioned previously, spearheaded the Rockefeller Foundation's agricultural research programs in Mexico and India, both of which emphasized hybrid maize. Nevertheless, in Mexico the maize agricultural sector remains mostly small-scale, semisubsistent, and traditional, and in much of Latin America, the public seed sector has been unreliable in generating and supplying improved seeds for small farmers working diverse environments; probably no more than 20 percent of Mexico's, 30 percent of Central America's, and 15 percent of Colombia's maize production has resulted from modern improved varieties (Jaffe and Rojas 1994). The Puebla Project of Mexico, which aimed to double the maize yields of small farmers by providing improved seeds, chemical packages, and a guaranteed market and credit, had only spotty participation as maize farming competed unsuccessfully with nonfarming occupations.

Agricultural research programs in British colonial Africa in the 1930s also emphasized the development of hybrid maize seed, an emphasis that was revived in Kenya, Zimbabwe, and Malawi in the 1960s and became very important in the 1980s (Eicher 1995). Zimbabwe released its first hybrid in 1949, and Kenya did the same with domestically produced hybrids in 1964. An advanced agricultural infrastructure in these countries has meant that the rate of adoption of hybrids is extremely high, and in Zimbabwe, the yields achieved by some commercial farmers approach those seen in Europe and the United States. In Ghana, the Global 2000 agricultural project, supported by the Sasakawa Africa Association, has sought to demonstrate that high yields are attainable if farmers can be assured quality seeds, affordable fertilizers, and market access. The success of hybrids in these contexts depends on timely and affordable delivery of seed and other inputs, particularly fertilizers. Tanzania, from the late 1970s through the 1980s, provided a case study of deteriorating maize production associated with erratic seed supply, elimination of fertilizer subsidies, inadequate market transportation, and insufficient improvement of open-pollinated varieties (Friis-Hansen 1994).

Under optimal conditions, hybrids yield 15 to 20 percent more than the improved open-pollinated varieties, and breeders find it easier to introduce particular traits—such as resistance to a specific disease—into inbred hybrid lines. The uniform size and maturation rate of hybrids are advantages for farmers who wish to harvest and process a standard crop as a single unit. From a commercial standpoint, hybrids also carry built-in protection against multiplication because the originator controls the parent lines, and the progeny cannot reproduce the parental type.

Conditions are rarely optimal, however, and a corresponding disadvantage is that the yields of hybrid seeds are unpredictable where soil fertility, moisture, and crop pests are less controlled. Although the introduction of disease-resistant traits may be easier with hybrids, the very uniformity of the inbred parent lines poses the risk of large-scale vulnerability, as illustrated by the case of the Southern Corn Leaf Blight. Rapid response by plant breeders and seed companies to contain the damage is less likely in countries without well-organized research and seed industries. Farmers in such countries may also face shortages of high-quality seed or other inputs, which potentially reduces the yield advantage of hybrid seed. Indeed, in years when cash is short, farmers may be unable to afford the purchase of seed or other inputs, even when available, and in any event, they lack control over the price and quality of these items—all of which means a reduction in farmer self-reliance. Analysts of public and private agricultural research systems further argue that the elevated investment in hybrids reduces the funds available for improving open-pollinated varieties and that some of the yield advantage of hybrids may result from greater research attention rather than from any intrinsic superiority.

Agricultural Research in Developing Countries


In 1943, the Rockefeller Foundation, under the leadership of Norman Borlaug, launched the first of its "campaigns against hunger" in Mexico, with the aim of using U.S. agricultural technology to feed growing populations in this and other developing countries. In 1948, the campaign was extended to Colombia, and in 1954 the Central American Maize Program was established for five countries. In 1957, the program added a maize improvement scheme for India, which became the Inter-Asian Corn Program in 1967. The Ford and Rockefeller Foundations together established the International Center for the Improvement of Maize and Wheat in Mexico in 1963, the International Center for Tropical Agriculture in Colombia in 1967, and the International Institute for Tropical Agriculture in Nigeria in 1967. These centers, with their maize improvement programs, became part of the International Agricultural Research Center Network of the Consultative Group on International Agricultural Research, which was established with coordination among the World Bank, and the Food and Agriculture Organization of the United Nations (FAO) in 1971. The International Plant Genetic Research Institute, also a part of this system, collects and preserves maize germ plasm.

Additional international maize research efforts have included the U.S. Department of Agriculture (USDA)-Kenyan Kitale maize program instituted during the 1960s; the French Institute for Tropical Agricultural Research, which works with scientists in former French colonies in Africa and the Caribbean region; and the Maize Research Institute of Yugoslavia. The Inter-American Institute of Agricultural Sciences (Costa Rica), Centro de Agricultura Tropical para Investigacíon y Enseñanzas (Costa Rica), Safgrad (Sahelian countries of Africa), Saccar (southern Africa), Prociandino (Andes region), and Consasur (Southern Cone, South America) are all examples of regional institutions for maize improvement (Dowswell et al. 1996).

Cultural History


Middle and South America


In the United States, which is its largest producer, maize is business, but for indigenous Americans maize more often has been considered a divine gift, "Our Mother" (Ford 1994), "Our Blood" (Sandstrom 1991), and what human beings are made of (Asturias 1993). Archaeological evidence and ethnohistorical accounts indicate that ancient American civilizations developed intensive land- and water-management techniques to increase production of maize and thereby provision large populations of craftspeople and administrators in urban centers. Ethnohistory and ethnography depict the maize plant in indigenous thought to be analogous to a "human being," and lexica maintain distinctive vocabularies for the whole plant, the grain, foods prepared from the grain, and the plant's parts and life stages (seedling, leafing, flowering, green ears, ripe ears), which are likened to those of a human. Indigenous terms and usage symbolically identify the maize plant and field (both glossed in the Spanish milpa) with well-being and livelihood. In addition, the four principal maize kernel colors constitute the foundation of a four-cornered, four-sided cosmology, coded by color.

An inventive indigenous technique for maize preparation was "nixtamalization" (alkali processing). Soaking the grain with crushed limestone, wood ash, or seashells helped loosen the outer hull, which could then be removed by washing. This made the kernel easier to grind and to form into a nutritious food end product, such as the tortilla in Mexico and Central America or the distinctive blue piki bread of the U.S. Southwest. In South America, maize was also consumed as whole-grain mote.

Tortillas, eaten along with beans and squash seeds (the "triumvirate" of a Mesoamerican meal), constitute a nutritious and balanced diet. In Mexico and Central America, dough is alternatively wrapped in maize sheaths or banana leaves. These steamed maize-dough tamales sometimes include fillings of green herbs, chilli sauce, meat, beans, or sugar. Additional regional preparations include gruels (atoles,) prepared by steeping maize in water and then sieving the liquid (a similar dish in East Africa is called uji); ceremonial beverages made from various maize doughs (pozole, which can also refer to a corn stew with whole grains, or chocolate atole); and special seasonal and festival foods prepared from immature maize (including spicy-sweet atole and tamales). Green corn—a luxury food for those dependent on maize as a staple grain (because each ear consumed in the immature stage limits the mature harvest)—can be either roasted or boiled in its husk.

Andean populations also made maize beers (chicha) of varying potency, which involved soaking and sprouting the grain, then leavening it by chewing or salivation (Acosta 1954). Brewed maize comprised a key lubricant of Incan social life (Hastorf and Johannessen 1993). Unfortunately, by the early period of Spanish occupation, indigenous leaders were reported to be having difficulty controlling intoxication, a problem heightened when chicha was spiked with cheap grain alcohol—a Spanish introduction.

Other special indigenous preparations included green corn kernels boiled with green lima beans, a dish introduced to the English on the East Coast of North America. The Hopi of the North American Southwest prepared piki, or "paper-bread," from a fine cornmeal batter spread on a stone slab lubricated with seed oil (from squash, sunflower, or watermelon seeds). They colored their cornbread a deep blue (or other colors) by adding extra alkalies and other pigments.

All parts of the maize plant were used by indigenous peoples. Tender inner husks, young ears, and flowers were boiled as vegetables, and fresh silks were mixed into tortilla dough.The Navajo prepared a soup and ceremonial breads from maize pollen; sugary juices were sucked out of the pith and stems; and even the bluish-black smut, Ustilago maydis, was prepared as a "mushroom" delicacy. Maize ear-sheaths wrapped tamales, purple sheaths colored their contents, and husks served as wrappers for tobacco. Maize vegetation was put into the food chain, first as green manure and, after Spanish livestock introductions, as animal fodder. The dried chaff of the plant was shredded for bedding material, braided into cord and basketry, and used to make dolls and other toys. Corn silks were boiled into a tea to relieve urinary problems, and the cobs served as stoppers for jugs, or as fuel. The stalks provided both a quick-burning fuel and construction material for shelters and fences. These uses continued during the Spaniards' occupation, which added poultry and ruminants as intermediary consumers of maize in the food chain and animal manure as an element in the nitrogen cycle. Indigenous peoples generally ate maize on a daily basis, reserving wheat for festival occasions, whereas those of Spanish descent raised and consumed wheat as their daily bread.

North America


In contrast to the Spaniards, English settlers in North America adopted maize as the crop most suited to survival in their New World environment and learned from their indigenous neighbors how to plant, cultivate, prepare, and store it. Although seventeenth-century Europeans reviled maize as a food fit only for desperate humans or swine (Gerard 1597; Brandes 1992), in North America the first colonials and later immigrants elevated the crop to the status of a staple food. For all Americans, it became a divine gift, a plentiful base for "typical" national and regional dishes, and a crop for great ritual elaboration, annual festivals, husking bees, shows, and later even a "Corn Palace" built of multicolored cobs (in Mitchell, North Dakota). In the process, maize became "corn," originally the generic term for "grain," shortened from the English "Indian corn," a term that distinguished colonial exported maize (also called "Virginia wheat") from European wheat and other grains.

Corn nourished the U.S. livestock industry, the slave economy, and westward expansion. It served as the foundation of the typical U.S. diet—high in meat and dairy products, which are converted corn—and, indeed, of the U.S. agricultural economy. North American populations of European and African ancestry historically turned maize into breads, grits, and gruels. They ate corn in the forms of mush; "spoon bread" (a mush with eggs, butter, and milk); simple breads called "hoecakes" (or "pone"); whole grains in "hominy"; and mixed with beans in "succotash." Coarsely ground "grits" were boiled or larded into "crackling bread," "scrapple," "fritters," and "hush puppies," or were sweetened with molasses and cooked with eggs and milk into "Indian pudding." Culinary elaborations of green corn, for which special varieties of sweet corn were bred, ranged from simple roasted (which caramelizes the sugar) or boiled "corn on the cob" with butter, to chowders and custards. Scottish and Irish immigrants fermented and distilled corn mash into corn whiskey ("white lightning" or "moonshine") or aged and mellowed it into bourbon, a distinctively smooth American liquor named for Bourbon, Kentucky, its place of origin.

Nineteenth-century food industries added corn syrup, oil, and starch to the processed repertoire, and then corn "flakes," the first of a series of breakfast cereals that promoters hoped would improve the healthfulness of the American diet. Popcorn, a simple indigenous food, by the mid-nineteenth century was popped in either a fatted frying pan or a wire gauze basket, and by the end of the century in a steam-driven machine, which added molasses to make Cracker Jacks, a popular new American snack first marketed at the 1893 Columbian Exposition in Chicago. By the late twentieth century, popcorn had become a gourmet food, produced from proprietary hybrid varieties, such as Orville Redenbacher's Gourmet Popping Corn, which boasted lighter, fluffier kernels and fewer "dud" grains and could be popped in a microwave (Fussell 1992). Twentieth-century snack foods also included corn "chips" (tortillas fried in oil). Moreover, North Americans consume large quantities of corn products as food additives and ingredients, such as corn starch, high-fructose syrup, and corn oil, as well as in animal products.

Europe


Maize, introduced by Christopher Columbus into Spain from the Caribbean in 1492-3, was first mentioned as a cultivated species in Seville in 1500, around which time it spread to the rest of the Iberian peninsula. It was called milho("millet" or "grain") by Portuguese traders, who carried it to Africa and Asia (the name survives in South African "mealies,"or cornmeal).

Spreading across Europe, maize acquired a series of binomial labels, each roughly translated as "foreign grain": In Lorraine and in the Vosges, maize was "Roman corn"; in Tuscany, "Sicilian corn"; in Sicily, "Indian corn"; in the Pyrenees, "Spanish corn"; in Provence,"Barbary corn" or "Guinea corn"; in Turkey, "Egyptian corn"; in Egypt, "Syrian dourra" (i.e., sorghum); in England, "Turkish wheat" or "Indian corn"; and in Germany, "Welsch corn" or "Bactrian typha." The French blé de Turquie ("Turkish wheat") and a reference to a golden-and-white seed of unknown species introduced by Crusaders from Anatolia (in what turned out to be a forged Crusader document) encouraged the error that maize came from western Asia, not the Americas (Bonafous 1836). De Candolle (1884) carefully documented the sources of the misconstruction and also dismissed Asian or African origins of maize on the basis of its absence from other historical texts. But inexplicably, sixteenth-and seventeenth-century herbalists appear to describe and illustrate two distinct types of maize, one "definitely" from tropical America, the other of unknown origin (Finan 1950).

English sources, especially J. Gerard's influential Herball (1597: Chapter 14), assessed "Turkie corne" to be unnourishing, difficult to digest, and "a more convenient food for swine than for man." Such disparagement notwithstanding, climate and low-labor requirements for its cultivation favored maize's dispersal. By the end of the sixteenth century, it had spread from southern Spain to the rest of the Iberian peninsula, to German and English gardens, and throughout Italy, where, by the seventeenth century, it constituted a principal element of the Tuscan diet. In both northwestern Iberia and northern Italy, climate favored maize over other cereals and gave rise to cuisines based on maize breads (broa and borona) and polenta. By the eighteenth century, maize had spread across the Pyrenees and into eastern France, where it became a principal peasant food and animal fodder.

A century earlier, maize had penetrated the Balkan Slavonia and Danube regions, and Serbs were reported to be producing cucurutz (maize) as a field crop at a time when other grains were scarce. By the mid-eighteenth century, it was a staple of the Hapsburg Empire, especially in Hungary. By the end of the eighteenth century, fields of maize were reported on the route between Istanbul and Nice, and it had likely been an earlier garden and hill crop in Bulgaria. Maize appears to have entered Romania in the beginning of the seventeenth century, where it became established as a field crop by midcentury. T. Stoianovich (1966) traces the complex of Greek-Turkish and Romanian-Transylvanian names for maize across the region and shows how the crop was incorporated into spring planting and autumn harvest rites of local peoples. In these regions, maize, which was more highly productive, replaced millet and, especially in Romania, has been credited with furthering a demographic and agricultural-socioeconomic transition. In the nineteenth century, Hungary was a major producer, along with Romania; by the mid-1920s, the latter country was the second largest exporter of maize (after Argentina) and remained a major producer and exporter through 1939. Romania maintained its own research institute and developed its own hybrids (Ecaterina 1995).

In contrast to the potato—the other major crop from the New World—maize appears to have been introduced across Europe with little resistance or coercion. In Spain, Italy, and southern France, its high seed-to-harvest ratio, relatively low labor requirements, high disease resistance, and adaptability allowed the plant to proceed from botanical exotic to kitchen-garden vegetable to field crop, all within a hundred years (Langer 1975). Throughout Europe, maize was prepared as a gruel or porridge because its flour lacked the gluten to make good leavened bread, although it was sometimes mixed into wheat flour as an extender. Although the custom of alkali processing, or that of consuming maize with legumes, had not accompanied the plant from the New World to the Old, maize provided a healthy addition to the diet so long as consumers were able to eat it with other foods. In the best of circumstances, it became a tasty culinary staple. In the worst, undercooked moldy maize became the food of deprivation, the food of last resort for the poor, as in Spain, where for this reason, maize is despised to this day (Brandes 1992).

Curiously, maize was never accepted in the British realm, where it continued to be "an acquired taste," a sometime famine or ration food, or a grain to feed livestock. During the great Irish famine of 1845, the British government imported maize for food relief—to keep down the prices of other foods and provide emergency rations for the poor. Maize boasted the advantages of being cheap and having no established private "free trade" with which government imports might interfere. Unfortunately, Ireland lacked the milling capacity to dry, cool, sack, and grind it, and in 1846 a scarcity of mills led to the distribution of the whole grain, which was described as irritating rather than nourishing for "half-starving people" (Woodham-Smith 1962). Maize shortly thereafter began to play an important role in British famine relief and as ordinary rations for workers in Africa.

Africa


Portuguese traders carried maize to eastern Africa in the sixteenth century, and Arab traders circulated it around the Mediterranean and North Africa. During the seventeenth century, maize traveled from the West Indies to the Gold Coast, where, by the eighteenth century, it was used as a cheap food for provisioning slaves held in barracoons or on shipboard during the Middle Passage. By the end of the eighteenth century, maize was reported in the interior of Africa (the Lake Chad region of Nigeria), where it appears to have replaced traditional food plants in the western and central regions, especially the Congo, Benin, and western Nigeria, although cassava—because it was less vulnerable to drought and locusts—later replaced maize in the southern parts of Congo (Miracle 1966) and Tanzania (Fleuret and Fleuret 1980).

By the end of the nineteenth century, maize had become established as a major African crop. People accustomed to eating it as the regular fare in mines or work camps, or as emergency rations, now demanded it when conditions returned to normal or when they returned home. Consumption also increased following famine years because people were able to sow earlier-maturing varieties, and even where sorghum remained the principal staple, maize became a significant seasonal food that was consumed at the end of the "hungry season" before other cereals ripened.The British also promoted African maize as a cash crop for their home starch industry.

Today in Africa, ecology, government agricultural and marketing policies, and the cost of maize relative to other staple or nonstaple crops are the factors influencing the proportion of maize in household production and consumption (Anthony 1988). Major shifts toward maize diets occurred in the latter part of the twentieth century, when improved varieties and extension programs, as well as higher standards of living, meant that people could enjoy a more refined staple food—with less fiber—without feeling hungry. Researchers in postcolonial times have developed hybrids adapted to African conditions, but these have met with mixed reactions. In Zimbabwe, where small farmers are well organized and can demand seed and access to markets, most of them plant improved hybrids (Bratton 1986; Eicher 1995). By contrast, in Zambia, smallholders continue to grow traditional varieties for a number of reasons, including the high cost of hybrid seed, shortages of seed and input supplies, inadequate storage facilities, and a culinary preference for varieties that are flintier. The latter are preferred because they have a higher extraction rate when mortar-pounded (superior "mortar yield"), they produce superior porridge, and they are more resistant to weevils. However, even where introduction of improved disease-resistant varieties has been successful, as in northern Nigeria, the gains will be sustainable only if soils do not degrade, the price of fertilizer remains affordable, markets are accessible, and research and extension services can keep ahead of coevolving pests (Smith et al. 1994).

African cuisines favor white maize, which is prepared as a paste or mush and usually eaten as warm chunks dipped in stews or sauces of meat, fish, insects, or vegetables. In eastern and southern Africa, maize is first pounded or ground before being boiled into a thick porridge. But in western Africa, kenkey is prepared from kernels that are first soaked and dehulled before being ground, fermented, and heated. Ogi is a paste prepared by soaking the kernels, followed by light pounding to remove the pericarp and a second soaking to produce a bit of fermentation. The bran is strained away, and the resulting mass cooked into a paste, mixed with the dough of other starchy staples, and baked into an unleavened bread or cooked in oil. Maize gruels can be soured or sweetened, fermented into a light or a full beer, or distilled. The kernels are also boiled and eaten whole, sometimes with beans, or beaten into a consistency like that of boiled rice. Alternatively, the grains can be parched before boiling, or cooked until they burst. Immature ears are boiled or roasted, and the juice from immature kernels flavored, cooked, and allowed to jell.

Asia


Portuguese introductions of maize to Asia likely occurred in the early 1500s, after which the grain was carried along the western coast of India and into northwestern Pakistan along the Silk Route. By the mid-1500s, maize had reached Honan and Southeast Asia, and by the mid-1600s it was established in Indonesia, the Philippines, and Thailand. In southern and southwestern China during the 1700s, raising maize permitted farming to expand into higher elevations that were unsuitable for rice cultivation, and along with white and sweet potatoes, the new crop contributed to population growth and a consequent growing misery (Anderson 1988). From there, maize spread to northern China, Korea, and Japan.

In the 1990s, maize was a staple food in selected regions of China, India, Indonesia, and the Philippines. Among grains in China, it ranked third in importance (after rice and wheat, but before sorghum, which it has replaced in warmer, wetter areas and in drier areas when new hybrids became available). Maize is consumed as steamed or baked cakes, as mush, in noodles mixed with other grains, and as cracked grain mixed with rice. It is the principal grain in the lower mountains of western and southern China and in much of the central North, and it increasingly serves as a food for the poor. Immature maize is eaten as a vegetable, and baby corn is an important specialty appreciated for its crunchy texture.

In Indonesia, maize is the staple food of some 18 million people (Timmer 1987). Farmers have responded favorably to new technologies and government incentives, such as quick-yielding varieties, subsidized fertilizers, and mechanical tilling and shelling devices. They demand improved seed and subsidized chemicals and carefully match seed varieties to local seasonal conditions in environments that (in places) allow for triple cropping (rice-maize-maize, rice-maize-soy, or rice-maize-cassava sequences). In the 1980s, breeders reportedly could not keep up with the demand for improved white varieties, which cover 35 percent of the area sown in maize and are preferred for human consumption. Humans still consume 75 percent of Indonesia's maize directly, and it is particularly important as a staple in the preharvest "hungry season" before the main rice harvest. Rice remains the preferred staple; the proportion of maize in the diet fluctuates relative to the price of maize versus rice and consumer income.

Summary of Culinary History


Kernels of the earliest forms of maize were probably parched on hot stones or in hot ash or sand. Small hard seeds, in which starch was tightly packed, also lent themselves to popping. Both Mexican and Peruvian indigenous populations grew selected popcorn varieties, which, among the Aztecs, were burst like flowers or hailstones for their water god. Parched maize, sometimes mixed with other seeds, was ground into pinole, a favorite lightweight ration for travelers that could be eaten dry or hydrated with water.

Maize grains more commonly were wet-ground—boiled and then ground with a stone quern or pounded with wooden implements (the North American indigenous procedure outside of the Southwest). After soaking the kernels in alkaline and washing to remove the hulls, native peoples either consumed the grains whole (as hominy) or wet-ground them into a dough used to form tortillas (flat cakes), arepas (thick cakes), or tamales (leaf-wrapped dough with a filling). The arduous process of grinding, which could require up to half of a woman's workday, was later taken over by water- or engine-powered mills; the time-consuming process of shaping tortillas by hand was facilitated by wooden or metal tortilla "presses"; and very recently, the entire process of tortilla manufacture has been mechanized. In 1995, the people of Mexico consumed 10 million tons of tortillas, each ton using 10,000 liters of water to soak and wash the kernels, water that, when dumped, created rivers of calcium hydroxide. An interdisciplinary team has formed a 1995 "Tortilla Project" to create a water-sparing, energy-efficient machine that will turn out a superior nutritional product with no pollutants.

Dry-grinding, characteristic of nonindigenous processing, produces whole maize "meal," "grits," or "flour," which can be "decorticated" (bran removed) or "degerminated" (most bran and germ removed), a separation process also called "bolting," to produce a more refined flour and an end product that stores longer. Hominy is the endosperm product left over after the pericarp is removed and the germ loosened; "pearl" or "polished" hominy has the aleurone layer removed as well. Although separating the bran and germ decreases the vitamin and mineral value, it makes the oil and residual "germ cake," pericarp, and hulls more easily available for livestock feed.

Simple, boiled maize-meal porridges, which combine whole or degermed meal with water, are the most common forms of maize dishes. In the United States, it is cornmeal mush; in Italy, polenta; in Romania, mamaliga; and in Africa,nshima, ugali, or foo foo. In Italy, polenta often includes grated cheese and extra fat, and in Yugoslavia, the corn mush contains eggs and dairy products. Maize meal, when mixed with water or milk, can be shaped into simple unleavened flat breads or cakes and baked over an open fire, or in an oven.These were called hoecakes in the early United States.

In Asia, maize is "riced"; the cracked kernels are boiled and consumed like the preferred staple of the region. Indeed, improved maize varieties must meet the processing criteria of cracking and cooking to resemble rice. Maize starch, especially in central Java, is processed into flour for porridge, noodles, and snack food. Green maize is also consumed.

Industrial Processing


Industrial processing utilizes either wet or dry milling. Wet milling steeps kernels in water, separates germ from kernel, and then separates germ into oil and meal portions. Each 100 kilograms (kg) of maize yields 2 to 3 kg of oil. Corn oil is popular for its ability to withstand heat, its high level of polyunsaturates, and its flavorlessness. The meal portions of the kernel become starch, gluten, and bran.

The dried starch portion is used in the food, textile, and paper industries. Starch, processed into glucose syrup or powder and high-fructose or dextrose products, sweetens three-fourths of the processed foods in the United States, especially confections and baked goods. In 1991, high-fructose corn syrup, manufactured by an enzyme-isomerization process that was first introduced in the 1960s, accounted for more than half of the U.S. (nondiet) sweetener market (National Corn Growers Association 1992).

Dry milling processes about 2 percent of the U.S. maize crop into animal feeds, beers, breakfast cereals, and other food and industrial products. In a tempering/degerming process the majority of the pericarp and germ are removed, and the remaining bulk of the endosperm is dried and flaked into products such as breakfast cereal.Whole (white) grains are ground into hominy grits and meal. These products, because they still contain the oily germ, have superior flavor but shorter shelf life. Industrialized alkali processing produces a dough that is turned into tortillas, chips, and other "Mexican" snacks.

Special maize varieties are also being bred for "designer" industrial starches. One, high in amylose starch, is used to create edible wrappers for pharmaceuticals, feeds, and foods. Another "super slurper" absorbs up to 2,000 times its weight in moisture and is employed in disposable diapers and bedpads. Still another is being developed into less-polluting road "salt," and other corn starches are being tailored into biodegradable plastic bags, cups, and plates. All told, industrial maize preparations place thousands of different maize-derived items on modern supermarket shelves, including flours and meals for breads and puddings, starch as a thickener, maize ("Karo") syrups or honeys as sweeteners, high-fructose and dextrose syrups as sweetening ingredients in beverages and baked goods, and processed cereals as breakfast or snack foods. Maize-based cooking oils, chips, beers, and whiskeys complete the spectrum. In fact, almost all processed foods (because they contain additives of starch or fat) contain some maize, as do almost all animal products, which are converted maize (Fussell 1992).

Animal Feed Products


Maize is the preferred feedgrain for animals because it is so rich in fat and calories; its high-starch/low-fiber content helps poultry, swine, cattle, and dairy animals convert its dry matter more efficiently than with other grains; it is also lower in cost. Feeds are formulated from whole, cracked, or steam-flaked grains and optimally supplemented with amino acids, vitamins, and minerals to meet the special nutritional requirements of particular domesticated animals. In industrial processing, by-products remaining after the oil and starch have been extracted—maize gluten, bran, germ meal, and condensed fermented steepwater (from soaking the grain), which is a medium for single-cell protein—also go into animal feed.

Silage uses the entire maize plant—which is cut, chopped, and allowed to ferment—to nourish dairy and beef cattle and, increasingly, swine. In developing countries, fresh or dried vegetation and substandard grains are household commodities used to produce animal products.When the entire maize plant (and, in traditional fields, its associated weeds) serves as a feedstuff, it surpasses all other plants in average yield and digestible nutrients per hectare (Dowswell et al. 1996).

Nutrition


Maize provides 70 percent or more of food energy calories in parts of Mexico, Central America, Africa, and Romania. In these regions, adult workers consume some 400 grams of maize daily, a diet marginally sufficient in calories, protein, vitamins, and minerals, depending on how the maize is processed and the supplementary foods with which it is combined. Maize is a better source of energy than other cereal grains because of its higher fat content. Ground maize meal has 3,578 calories per kg, mostly carbohydrate, with about 4.5 percent "good" fat (fat-rich varieties are double this figure), and is high in essential linoleic and oleic fatty acids. It contains about 10 percent protein, roughly half of which is zein that is low in the amino acids lysine and tryptophan. The protein quality is enhanced in traditional Latin American maize diets by alkali processing and consumption with legumes that are high in lysine. Potatoes, if eaten in sufficient quantity, also yield a considerable amount of lysine and consequently often complement maize in highland South America and parts of Europe. Of course, incorporating animal proteins improves the nutritional quality of any diet with grain or tubers as the staple.

Maize is also naturally low in calcium and niacin, but calcium, niacin, and tryptophan content are all enhanced by traditional alkali processing (in which the kernels are cooked and soaked in a calcium hydroxide—lime or ash—solution), which adds calcium and increases the available tryptophan and niacin in the kernels or dough. White maize, usually the favored type for human food, is also low in vitamin A, although this nutrient is higher in properly stored yellow maize. Moreover, in its traditional heart-land, maize is combined with chilli peppers, other vegetables, and various kinds of tomatoes and spices, all of which enhance the amount of vitamin A delivered to the consumer, along with other vitamins and minerals. In Africa and Asia, additional vitamins and minerals are added to maize diets when wild or cultivated greens, other vegetables, peanuts, and small bits of animal protein are combined in a sauce. Potash, burned from salt grasses, also enhances the otherwise poor mineral content of the diet (FAO 1953).

Diseases Associated with Maize


Pellagra and protein-deficiency disease (kwashiorkor) are historically associated with maize diets. In addition, as recently as the 1950s, rickets, scurvy, and signs of vitamin A deficiency have all been reported among populations consuming maize diets in Central Europe and eastern and southern Africa. Such deficiency diseases disappear with dietary diversification, expansion of food markets, and technological efforts to improve the micronutrient quality of maize diets.

Pellagra


Pellagra, now understood to be a disease caused in large part by niacin deficiency, was first observed in eighteenth-century Europe among the very poor of Spain, then Italy, France, Romania, Austria, southern Russia, the Ottoman Empire, and outside of Europe in Egypt, South Africa, and the southern United States. It was associated with extreme poverty and usually seen among land-poor peasants, whose diet centered much too heavily on maize. The main symptoms were described as the "three Ds" (diarrhea, dermatitis, and dementia), and four stages were recognized, from malaise, to digestive and skin disorders, to neurological and mental symptoms, and finally, wasting, dementia, and death (Roe 1973).

Although maize was adopted as a garden crop and within 100 years after its appearance was a field crop over much of the European continent, the disease manifested itself only when economic conditions had deteriorated to the point that pellagra victims ("pella-grins") could afford to eat only poorly cooked, often rotten maize. In Spain, this occurred in the 1730s; up to 20 percent of the population may still have been afflicted in the early twentieth century. In Italy, peasants also may have been suffering from the "red disease" as early as the 1730s. Despite efforts to protect the purity of the maize supply and improve diets through public granaries, bakeries, and soup kitchens, the disease persisted until the 1930s, when changes in diet were brought about by improved standards of living and the demise of the tenant-farmer system. In France, where maize had been sown since the sixteenth century and in some areas had expanded into a field crop by the late seventeenth, maize was not widely grown as a staple until the late eighteenth and early nineteenth centuries, when it became the main crop of the southern and eastern regions of the country and was accompanied by pellagra among destitute peasants. The physician Theophile Roussel recommended that the disease be prevented by changing the diet and agriculture so that there was less emphasis on maize.The government responded with legislation encouraging alternative crop and livestock production along with consumption of wheat, and by the early twentieth century, pellagra had largely been eliminated.

In the late nineteenth century, pellagra was reported by a British physician, Fleming Sandwith, in Egypt and South Africa. The disease was also present in the southern United States, although it did not reach epidemic proportions until the first decade of the twentieth century. In epidemiological studies begun in 1914, Joseph Goldberger, a physician working for the Public Health Service, determined that the disease was not contagious but was dietary. Furthermore, it was associated not so much with the consumption of maize as with the economic inability to obtain and consume other protective foods along with maize. For prevention and cure, Goldberger prescribed milk, lean meat, powdered yeast, and egg yolks. At the household level, he recommended more diversified farming, including milk cows and more and better gardens.

Goldberger traced the correlation between epidemic pellagra and economic downturns and demonstrated how underlying socioeconomic conditions restricted diets and caused dietary deficiencies among tenant farmers, who ordinarily ate mostly maize and maize products. The number of cases declined in the worst depression years (1932-4) because, when there was no market for cotton, farmers produced diversified food crops and garden vegetables for home consumption. Goldberger also demonstrated that pellagra mimicked "blacktongue" in dogs and used them as experimental animals to find what foods might prevent pellagra. He conceptualized the "pellagra-preventive" factor to be a water-soluble vitamin but could not identify it (Terris 1964). It was not until 1937 that C. A. Elvehjem and his colleagues demonstrated that nicotinic acid cured blacktongue in dogs, a finding carried over to demonstrate that nicotinic acid prevented pellagra in humans. Lest the public confuse nicotinic acid with nicotine, the Food and Drug Administration adopted the name "niacin" for their vitamin fortification program (Roe 1973: 127), which was designed to eliminate nutrition-deficiency diseases, and in southern states tended to include cornmeal and grits as well as wheat flours. Diversification and improvement of diet associated with World War II production, employment, and high-quality food rations mostly spelled an end to pellagra in the United States.

Since the 1940s, maize diets and pellagra have also been associated with imbalanced protein intake and selected amino acid deficiency. G.A. Goldsmith (1958) demonstrated that dietary tryptophan converts to nicotinic acid in humans at a ratio of 1:45, and anthropologists working with nutritional chemists were able to demonstrate that alkali processing of maize in traditional indigenous diets made more niacin and tryptophan available (Katz, Hediger, and Valleroy 1974). Traditional processing and food combinations also make more isoleucine available relative to leucine, and it has been suggested that excess leucine is another antinutritional factor in maize. Although pellagra has been eliminated in industrialized countries, it remains a plague among poor, maize-eating agriculturalists in southern Africa, where it was reported throughout the 1960s in South Africa, Lesotho, and Tanzania, and in Egypt and India among people who lack access to wheat.

Protein Deficiency


Another nutritional deficiency disease historically associated with diets high in maize is kwashiorkor, conventionally classified as a protein-deficiency disease and associated especially with weanlings and hungry-season diets in Africa (Williams 1933, 1935). Since the 1960s, international maize-breeding programs have sought to overcome lysine deficiency directly, thus giving maize a much better-quality protein. Maize breeders at Purdue University in Indiana, who were screening maize for amino acid contents, isolated the mutant "Opaque-2" gene and developed a variety that had the same protein content as conventional maizes but more lysine and tryptophan.

Although this variety possessed a more favorable amino acid profile, its yields were lower, its ears smaller, its chalky kernels dried more slowly, and it carried unfavorable color (yellow), texture, and taste characteristics. Its softer, more nutritious, and moister starch was more easily attacked by insects and fungi, and its adhesive properties did not make a good tortilla. Mexican researchers at CIMMYT in the 1970s and 1980s eliminated these deficiencies and in the mid-1980s introduced Quality Protein Maize (QPM) with favorable consumer characteristics. The remaining step was to interbreed this superior type with locally adapted varieties. But by the 1980s, nutritionists were questioning the importance of protein or selective amino-acid deficiencies as high-priority problems and focusing instead on improving access to calories. QPM became a technological solution for a nutritional deficiency no longer of interest, and CIMMYT was forced to end its QPM program in 1991. However, national programs in South Africa, Ghana, Brazil, and China are using QPM to develop maize-based weaning foods and healthier snacks, as well as a superior animal feed (Ad Hoc Panel 1988).

Additional Strategies for Nutritional Improvement


Strategies for improving maize diets focus on new varieties with higher protein quality and essential vita-min contents, better storage, wiser milling and processing, fortification, and dietary diversification. Conventional breeding and genetic engineering have enhanced essential amino acid profiles, especially lysine and methionine contents, although end products so far are principally superior feeds for poultry and pigs. Maize transformation by means of electroporation and regeneration of protoplasts was achieved in 1988, and subsequently by Agrobacterium (Rhodes et al. 1988). The first commercial varieties, with added traits of herbicide resistance and superior protein quality, were released in 1996. To improve protein content, maize meals are also fortified with soybean protein meal or dried food yeast (Tortula utilis). Nutritional enhancement through breeding or blending are alternatives to diversifying human (or animal) diets with legumes or animal foods.

Improperly stored maize, with moisture contents above 15 percent, also favor the growth of fungi, the most dangerous being Aspergillus flavus, which produces aflatoxin, a mycotoxin that causes illness in humans and animals. Efforts are being taken to eliminate such storage risks and losses.

Future Prospects


Maize has been expanding in geographical and cultural scope to the point where the world now harvests more than 500 million tons on all continents, and the crop is being increasingly directed into a number of nonfood uses, especially in industrialized countries. The supply of maize should continue to increase in response to a growing demand for animal products (which rely on maize feed), for food ingredients industrially processed from maize (such as good-quality cooking oil), and for convenience foods and snack foods (Brenner 1991). The biological characteristics of maize that have always favored its expansion support the accuracy of such a prediction: Its adaptability, high yields, high extraction rate, and high energy value deliver higher caloric yields per unit area than wheat or rice, and its high starch and low fiber content give the highest conversion of dry matter to animal product.Technology, especially biotechnology, will influence overall yields as well as nutritive value and processing characteristics. Genetic engineering has already allowed seed companies to market higher protein-quality maize designed to meet the specific nutritional needs of poultry and livestock. Other varieties have been designed to tolerate certain chemicals and permit higher maize yields in reduced-pest environments. The introduction of a male sterility trait, developed by Plant Genetic Systems (Belgium) in collaboration with University of California researchers, is expected to reduce the costs of manual or mechanical detasseling, estimated to be $150 to $200 million annually in the United States and $40 million in Europe (Bijman 1994).

Yet, the favorable agricultural, nutritional, and economic history of maize notwithstanding, the grain presents problems. As we have seen, maize diets have been associated with poverty and illness, especially the niacin-deficiency scourge, pellagra, and childhood (weanling) malnutrition. Moreover, the highly productive inbred hybrids, such as those that contain the trait for cytoplasmic male sterility, have created new genetic and production vulnerabilities (National Research Council 1972). Hybrid seeds also may increase the economic vulnerability of small-scale semisubsistence farmers who cannot afford to take advantage of new agricultural technologies and, consequently, find themselves further disadvantaged in national and international markets. Finally, and paradoxically, maize (like the potato) has been associated with increasing hunger and suffering in Africa (Cohen and Atieno Odhiambo 1989) and Latin America (Asturias 1993).