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Submitted to: CRC Press
Publication Type: Book / Chapter Publication Acceptance Date: 1/15/2011 Publication Date: 7/25/2011 Citation: Liu, K. 2011. Grain structure and composition, Ch.4, in "Distillers Grains: Production, Properties, and Utilization", Liu, K.S., and Rosentrater, K.A. Eds., pp 45-71, CRC Press, Baca Raton, FL Interpretive Summary: Cereals grains are the fruits of cultivated grasses. As members of the monocot family of Gramineae, cereal crops are mostly grown in the temperate and tropical regions of the world, and provide more food energy worldwide than any other type of crop. They are therefore staple crops. The principal cereal crops are corn (also known as maize), rice, wheat, barley, oats, rye, sorghum, triticale, and millets. In recent years, there emerges a new opportunity for production growth of cereals. As a feedstock for renewable fuel, millions of tons of grains are now converted to fuel ethanol, with distillers dried grains with solubles (DDGS) (which contain non-fermented residues) as the main co-product. Regardless whatever end uses for cereal grains, as food, feed, fuel ethanol or others, a knowledge of the structure and composition of cereal grains is necessary not only for understanding and optimizing plant growth and seed development to achieve the highest level of grain production, but also for developing improved methods of storage and handling for maximum preservation of grain quality, and methods of suitable processing for most efficient end utilization. Chapter 4 is aimed at providing general information about structure and composition of cereal grains as well as the unique features of each cereal grain. These pieces of information are important for understanding the principles for bio-ethanol production from grains. It is also important for maximizing efficiency of ethanol production and improving quality of the DDGS co-product. This chapter is an integral part of the book, Distillers Grains: Production, Properties and Utilization, (2011, by CRC Press, Baca Raton, FL), which brings together cutting edge information on many aspects of DDGS. More information can be found at the publisher’s website: http://www.crcpress.com/product/isbn/9781439817254 Technical Abstract: Chapter 4 covers general information about structure and composition of cereal grains as well as the unique features of each cereal grain. Cereal grains are the fruits of cultivated grasses and members of Gramineae family. The fruit of a cereal is botanically known as caryopsis, featured by fusion of fruit wall and seed coat. A cereal grain generally consists of embryo, endosperm, and tissues surrounding the embryo and endosperm. Some species also have hulls. Each of these structural parts also consists of different structural tissues and has different chemical composition. However, these structural parts are adapted differently among cereal species and there are wide variations in size and shape. In term of composition, cereal grains are characterized by a small amount of water, abundant starch, sufficient protein and fiber, and relatively lower amount of lipids. Minerals and vitamins are also present. However, there is considerable variation among species and among varieties within a species. During dry grind processing of grains into fuel ethanol, only starch is hydrolyzed to sugars which are fermented into ethanol and carbon dioxide. All other chemical components remained relatively unchanged chemically and end up in a co-product known as distillers dried grain with solubles (DDGS). Therefore, differences in grain species and feedstock composition will have impact on not only the yield and production efficiency of ethanol but also the composition and nutritional values of DDGS. |
