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Cereals are the most important crops in the world and are destined to become both human food and animal feed. Cereals, which belong to the grass family (Gramineae), produce dry, one‐seeded fruits. These fruits are, botanically speaking, caryopses, but they are commonly referred as “grains” or “kernels.” The cereal grains such as wheat, rice, maize, barley, oats, rye, sorghum and millet provide 50% of the food energy and 50% of the protein consumed on earth. Wheat, rice and corn constitute around 75% of world’s grain production (Ramaswamy and Riahi 2003). In this chapter, wheat is used as reference to explain the structure of cereal grain. Its kernels contain three main parts: embryo, endosperm and their covering layers. The last are, in milling, often separated as the bran fraction (Figure 1.1A). If all the parts of the kernel are retained in processing, one can speak of whole grain. If either the bran or germ is separated from the kernel during milling, then it is a “refined grain.”

Figure 1.1 A: General structure of a cereal grain); B: Epifluorescence micrograph of parts of rye grain. The sections were stained with Acid Fuchsin and Calcofluor: protein appears red, cell walls rich in β‐glucan appear light blue and lignified cell walls of the pericarp appear yellowish‐orange. Structure of cereal foods

(Source: Hemery et al. 2007).