Biomedical Engineering Reference
In-Depth Information
Chapter 2
Chemistry of Cereal Grains
Peter Koehler and Herbert Wieser
2.1
Introductory Remarks
Cereals are the most important staple foods for mankind worldwide and represent
the main constituent of animal feed. Most recently, cereals have been additionally
used for energy production, for example by fermentation yielding biogas or bioetha-
nol. The major cereals are wheat, corn, rice, barley, sorghum, millet, oats, and rye.
They are grown on nearly 60% of the cultivated land in the world. Wheat, corn, and
rice take up the greatest part of the land cultivated by cereals and produce the largest
quantities of cereal grains (Table
2.1
) [
1
]. Botanically, cereals are grasses and belong
to the monocot family
Poaceae
. Wheat, rye, and barley are closely related as mem-
bers of the subfamily
Pooideae
and the tribus
Triticeae
. Oats are a distant relative of
the
Triticeae
within the subfamily
Pooideae
, whereas rice, corn, sorghum, and mil-
let show separate evolutionary lines. Cultivated wheat comprises five species: the
hexaploid common (bread) wheat and spelt wheat (genome AABBDD), the tetra-
ploid durum wheat and emmer (AABB), and the diploid einkorn (AA). Triticale is
a man-made hybrid of durum wheat and rye (AABBRR). Within each cereal species
numerous varieties exist produced by breeding in order to optimize agronomical,
technological, and nutritional properties.
The farming of all cereals is, in principle, similar. They are annual plants and
consequently, one planting yields one harvest. The demands on climate, however,
are different. “Warm-season” cereals (corn, rice, sorghum, millet) are grown in
tropical lowlands throughout the year and in temperate climates during the frost-
free season. Rice is mainly grown in flooded fields, and sorghum and millet are
adapted to arid conditions. “Cool-season” cereals (wheat, rye, barley, and oats)
grow best in a moderate climate. Wheat, rye, and barley can be differentiated into
