Food Chemistry

15.1 Foreword 673

Table 15.2.Continued

Country Millet Country Sorghum Country Cereals, grand total

India 10 , 100 Nigeria 9866 China 445 , 355
Nigeria 7705 India 7240 USA 346 , 562
Niger 3200 USA 7050 India 239 , 130
China 1821 Mexico 5487 Russian Fed. 76 , 866
Burkina Faso 1199 Sudan 5203 Indonesia 66 , 011
Mali 1060 China 2490 France 61 , 813
Sudan 792 Argentina 2328 Brazil 59 , 017
Uganda 687 Ethiopia 2313 Canada 50 , 895
Russian Fed. 600 Brazil 1556 Bangladesh 45 , 010
Chad 590 Burkina Faso 1554 Germany 43 , 475

∑(%)a 87 ∑(%)a 80

Vietnam 39 , 648

Turkey 34 , 598

Ukraine 33 , 698

Argentina 33 , 556

Thailand 33 , 146

Pakistan 32 , 839

Mexico 31 , 959

∑(%)a^75

Table 15.3.World production of cereals 1948–2006
(10^6 t)

Year Amount Year Amount

1948 683 1988 1742
1956 789 1989 1881
1964 1019 1990 1955
1968 1180 1996 2050
1976 1456 2004 2239
1984 1802 2006 2221

of wheat. Millers regard the aleurone layer as part
of the bran.
The starchy endosperm is the source of flour.
Its thin-walled cells are packed with starch
granules which lie imbedded in a matrix which
is largely protein. A portion of these proteins,
the gluten proteins, is responsible for the baking
properties of wheat. The concentrations of the
proteins and some other constituents (vitamins
and minerals) decrease from outer to inner cells
of the endosperm. The germ is separated from
the endosperm by the scutellum. The germ is
rich in enzymes and lipids (Table 15.8). Ta-
ble 15.9 shows that wheat milling, when starchy
endosperm cells are separated from germ and
bran, results in a substantial loss of B-vitamins
and minerals.

15.1.5 Special Role of Wheat–Gluten

Formation

After addition of water a viscoelastic cohesive

dough can be kneaded only from wheat flour.

The resulting gluten, which can be isolated as

a residue after washing out the dough with water,

removing starch and other ingredients, is respon-

sible for plasticity and dough stability.

Gluten consists of 90% protein (cf. 15.2.1.3),

8% lipids and 2% carbohydrates. The latter

are primarily the water-insoluble pentosans

(cf. 15.2.4.2.1), which are able to bind and hold

a significant amount of water, while the lipids

(cf. 15.2.5) form a lipoprotein complex with

certain gluten proteins. In addition, enzymes such

as proteinases and lipoxygenase are detectable in

freshly isolated gluten.

The gluten proteins, in association with lipids, are

responsible for the cohesive and viscoelastic flow

properties of dough. Such rheological properties

give the dough gas-holding capacity during leav-

ening and provide a porous, spongy product with

an elastic crumb after baking.

Rye and other cereals can not form gluten. The

baking quality of rye is due to pentosans and

to some proteins which swell after acidification

(cf. 15.4.2.2) and contribute to gas-holding prop-

erties.