Grain: Morphology of Internal Structure

Abstract

Understanding grain structure is an essential foundation to understanding the processing of cereal grains through wet or dry milling. A first step in domestication of a cereal grain species (e.g., wheat) is the genetic mutation that produces a nonbrittle rachis. The rice grain has a tightly attached hull (palea and lemma), so initial dehulling is required; the wheat grain is ‘naked,’ that is, the hull is loose and easily detaches from the grain. Removal of the rice bran results in white polished grain; in wheat, bran removal followed by particle size reduction results in white flour. The distribution of starch, protein, and oil in the maize grain enables fractionation of these components by wet milling.