Sorghum: A Novel and Healthy Food

Sorghum (Sorghum bicolor (L.) Moench) ranks the fifth most important cereal crop in the world in terms of total production and constitutes a major source of proteins, calories, and min- erals for millions of people (Figure 1). Total world annual sorghum production is about 60 million tons from cultivated area of 46 million hectares. The most important producers of sorghum are the United States, Sudan, Nigeria, Mexico, India, China, Burkina Faso, Brazil, Australia, and Argentina (Figure 2). More than 35% of sorghum is grown directly for human consumption. The rest is used primarily for animal feed, alcohol production, and industrial products. With increasing world population and decreasing water supplies, sorghum represents an important crop for future human use. While sorghum is a vital food crop for millions of people in parts of Africa and Asia, it is an underutilized resource in most developed countries, with sorghum being primarily used as animal feed. The use of sorghum not only provides farmers with a market for their products but also saves money, which would otherwise be required to import cereals, which can be very costly. The demand for gluten-free foods for people with celiac disease and other intolerances to wheat is growing particularly in the developed countries. The develop- ment of white, tan plant, the so-called food-grade sorghum lines (Figure 3), has enabled white, bland-tasting flour to be produced from sorghum grain. This flour is useful in food products because it does not impart unusual colors or strong flavors and it may be desired over maize flour for these reasons. The most common foods prepared with sorghum are tortillas; thin porridge, for example, 'bouillie'; stiff porridge, for exam- ple, to^ ; couscous; injera; nasha and kisra; traditional beers, for example, dolo, tchapallo, pito, and burukutu; ogi; and baked products, for example, cakes, cookies, muffins, bread, and pizza. The purpose of this article is to summarize the charac- teristics of sorghum as a plant species and as human food and to discuss the relevance of experimental results obtained with food-grade sorghum cultivars grown in field trials in San Bar- tolomeo in Galdo, southern Italy, since 2006. These results demonstrate that sorghum cultivars grow well in Mediterra- nean environment and that it is possible to obtain white flour for the production of gluten-free cookies of high quality and palatability as food suitable for both celiac patients and healthy population. These studies also provided evidence that DNA sequences encoding toxic proteins for celiac patients are absent in the sorghum genome as also shown by biochemical and immunochemical analyses. Botanical Nomenclature Sorghum is a plant belonging to the tribe Andropogoneae and the family Poaceae. Linnaeus described three species of cultivated sorghum in 1753: Holcus sorghum, Holcus saccaratus, and Holcus tricolor. Later, Moench distinguished the genus Sorghum from the genus Holcus, and Person suggested the name Sorghum vulgare for Holcus sorghum (L.). In 1961, Clayton proposed the name Sorghum bicolor (L.) Moench as the correct name for cultivated sorghum and this is currently the accepted nomenclature. Like most angiosperm (flowering plant) line- ages, sorghum is thought to be rv200 Ma old. Sorghum, maize, rice, and wheat diverged from a common ancestor only 50-70 Ma. Sorghum is a C4 crop particularly adapted to drought- prone areas: hot, semiarid tropical environments with 400-600 mm rainfall - areas that are too dry for other cereals (except for the millets). Sorghum is also found in temperate regions and at altitudes of up to 2300 m in the tropics. It is well suited to heavy soils commonly found in the tropics, where tolerance to water logging is often required. The main races of cultivated sorghum are bicolor, vulgare, caudatum, kafir, guinea, and durra. Common names of sor- ghum vary from continent to country levels. Sorghum is a vigorous grass that varies between 0 and 6 m in height. It has deep and spreading roots with a solid stem. Sorghum leaves are long (0.3-1.4 m) and wide (1-13 cm), with flat or wavy margins. The flower is a panicle, usually erect, but sometimes recurved to form a goose neck. The sor- ghum kernel is a naked caryopsis and consists of three main anatomical parts - seed coat (testa or pericarp), endosperm (storage tissue), and germ (embryo), which generally account for 6%, 84%, and 10% of the seed mass, respectively (Figure 4). Sorghum is the only cereal grain known to have starch in the mesocarp layer of the pericarp. The endosperm, which is composed of an aleurone layer and peripheral, corneous, and floury areas, is the main storage tissue. The grain or caryopsis is usually partially covered by glumes. Glumes are the maternal plant tissues in the panicle that holds the developing caryopses after pollination. The caryopsis is round and bluntly pointed, from 4 to 8 mm in diameter, and varying in size, shape, and color with variety. Caryopsis color is an important trait that affects grain quality in sorghum. In some sorghum genotypes, the testa is highly pigmented. The presence of pigment and the color are genetic characters controlled by the R and Y genes. The thickness of the testa layer is not uniform and is governed by the Z gene. In some genotypes, there is a partial testa, while in others, it is not apparent or is absent. Sorghum does not develop significant levels of aflatoxins and fumonisins in the field prior to harvest.