2009_Book_FoodChemistry

15.1 Foreword 671
America. Cereals designated as millet have had
a role from antiquity in subtropical and tropical
regions of Asia and Africa. True millet from the
subfamilies Eragrostoideae and Panicoideae, to
which many regionally important cultivars belong
(for instance, Eragrostis tef, Eleusine coracan,
Echinochloa frumentacea, Pennisetum glaucum,
Setaria italica), is distinguished from sorghum
(Sorghum bicolor), which belongs to the subfamily
Andropogonoideae and is cultivated worldwide.
Rye (Secale cereale) and oats (Avena sativa) are
so-called secondary culture plants. Initially hardy
and unwanted escorts of cultivated plants, they
prospered and established themselves in northern
regions with unfavorable climates. Their high tolerance
for unfavorable climates surpassed that of
both wheat and barley. Rye and oats have been
cultivated for millenia.
Breeders have for many years attempted to combine
the baking quality of wheat with the hardiness
of rye. Triticale, the man-made hybrid of
wheat and rye, does not yet fulfill this aim, hence
its economic significance is low.
15.1.3 Production
Cereals are of great importance as raw materials
for production of food and feed. Accordingly,
they are grown on close to 60% of cultivated
land in the world. Wheat production takes up
the greatest part of land cultivated with cereals
(Table 15.1) and wheat is produced in the largest
Table 15.1. Land cultivated with a cereal crop as %
of the world total area under cereal cultivation (1979:
7.6 ×10 8 ha)
Cereal 1966 1976 1984 1988 1990 1996
Wheat 30.6 31.5 34.5 31.2 32.7 32.4
Rice 18.8 19.2 21.9 20.9 20.6 21.2
Corn 15.5 15.9 19.3 18.2 18.3 19.7
Millet 15.4 a 15.6 a 12.3 a 5.7 5.3 5.1
Sorghum 6.6 6.3 6.6
Barley 12.2 11.9 11.7 10.8 10.1 9.4
Oats 4.5 3.8 3.8 3.2 3.1 2.4
Rye 2.4 2.1 2.6 2.3 2.3 1.6
a Sum of millet and sorghum.
quantity (Table 15.2). Wheat surplus producers
are the USA, Canada, Argentina, Australia, and
France. In the Federal Republic of Germany
(FRG), winter wheat (92%) and spring wheat
(8%) are both cultivated. The rise of cereal production
in the world is shown in Table 15.3. The
yields per hectare vary greatly from one country
to another (Table 15.4). Due to an intensive
effort in breeding and crop production programs,
the yields per hectare in the FRG are very high
and are surpassed by only a few countries, e. g.,
Holland. The FRG utilized 25.7 × 10 6 tons of
cereals in 1976/77, of which 38% was bread
and 62% feed cereals.
15.1.4 Anatomy – Chemical Composition,
aReview
Cereals, in contrast to forage grasses, form a relatively
large fruit, termed a caryopsis, in which
the fruit shell is strongly bound to the seed shell.
The kernel size, which is expressed as grams
per 1000 kernels (Table 15.5), is not only dependent
on the kind of cereal but on the cultivar and
crop production techniques, hence it varies
widely.
In oats, barley, and rice the front and back husks
are fused together with the fruit. In contrast,
threshing separates wheat and rye kernels from
the husks as bare seed.
The major constituents of seven kinds of cereal
are fairly uniform (Table 15.6). Noteworthy variations
are the higher lipid content in oats and
a lower fiber content in millet and rice. The available
carbohydrates consist mainly of starch. Oats
are especially rich in nonstarch polysaccharides
(cf. 15.2.4.2). These cereals also differ in their vitamin
B content (Table 15.6).
Fruit and seed coats enclose the nutrient tissue
(endosperm) and germ in the kernel (Fig. 15.2).
Botanically the endosperm consists of the starchy
endosperm (70–80% of the kernel; Table 15.7)
and the aleurone layer, which, with exception of
barley, is a single cell layer.
The aleurone layer is rich in protein and also
contains fat, enzymes and vitamins (Table 15.8
and 15.9). The proteins, of which half are watersoluble,
appear as granules in the aleurone cells.
They have no influence on the baking properties