|Juliano, Bienvenido - PHILIPPINE RICE RES. INST|
Submitted to: Rice Chemistry and Technology
Publication Type: Book / Chapter
Publication Acceptance Date: July 12, 2003
Publication Date: August 20, 2004
Citation: Champagne, E.T., Wood, D.F., Juliano, B.O., Bechtel, D.B. 2004. The Rice Grain and its Gross Composition. In: Rice Chemistry and Technology. Third Edition, Chapter 4. American Association of Cereal Chemists Press. Minneapolis, MN. p77-107. Interpretive Summary: This review updates the 1985 American Association of Cereal Chemists (AACC) publication on Rice Structure and Composition in the book Rice Chemistry and Technology and covers the general structure of mature paddy rice (the grain and hull). Obtaining a good understanding of rice structure and composition is central to developing alternative processing technologies and end-products. The review is beneficial to food scientists where the grain is to be used for consumption as well as to engineers who will develop new non-food products from the rice hull.
Technical Abstract: Rice (oryza sativa L.) is harvested as paddy rice, or spikelets. Each spikelet consists of a caryopsis, the brown rice grain, and the surrounding hull. The hull consists of a palea and lemma which are subtended by two the upper and lower glumes and the supporting rachilla. The lemma and palea consist of silica-containing outer epidermis, highly lignified sclerenchyma, spongy parenchyma and an inner epidermis. The caryopsis consists of a seed and a tightly adherent pericarp. The pericarp is comprised of a thin cuticle covering the epidermis; several layers of partly crushed, "spongy" parenchyma; cross and tube cells. The seed includes the testa, nucellus. embryo and endosperm. The testa and nucellus consist of a single crushed layer of cells, the testa and nucellar cuticles and the remains of the nucellar cells. The embryo consists of the scutellum embryonic axis and various sheathing structures containing storage proteins, lipids and meristematic tissues. The aleurone layer is tightly bound to the starchy endosperm and contains storage proteins with globoid inclusions. The starchy endosperm contains parenchyma cells filled with compound starch granules and protein bodies.