2009_Book_FoodChemistry

708 15 Cereals and Cereal Products
step, while the wheat germ is removed only on
sifters. The hull and a substantian part of the aleurone
layer is removed in the form of bran.
A portion (ca. 5–8%) of the starch granules is
mechanically damaged during milling. The extent
depends both on the type and intensity of milling
and on the hardness of the kernel. The harder the
structure of the kernel, the greater the damage.
Since the rate of water absorption during dough
making and the enzymatic degradation of starch
increase with increasing damage, they are important
for the baking process and desirable to a limited
extent. To measure starch damage, the amylose
extractable with a sodium sulfate solution is
determined. Alternatively, the amount of starch
degradable without gelatinization, e. g., at 30 ◦ C
by a- and/or β-amylase is determined. The starch
damage expected during the milling process can
also be estimated by determining the hardness of
the kernel, e. g., by NIR reflectance spectrophotometry
(cf. Table 15.34).
In addition, quality depends on whether the
milled flour comes from the inner or outer parts
of the endosperm. Therefore, milled flour is
controlled in the plant for its baking properties
and blended or mixed to yield a commercial
product based on present market standards (see
also below). The characteristics of a few milling
products and their applications are listed in
Table 15.35.
The chemical composition of the flour depends
on the milling extraction rate, e. g., flour weight
obtained from 100 parts by weight of grain.
Examples are given in Table 15.36. Increasing
the rate of flour extraction decreases the pro-
15.3.1.3 Milling Products
A miller distinguishes the end-products of
milling on the basis of particle size or diameter,
e. g., >500 µm for grist; 200–500 µm for
semolina from durum or farina from bread
wheats; 120–200 µm for “dunst”; and 14–120 µm
for flour. The larger flour particles can be felt
between the fingers (graspable flour), as opposed
to smooth or polished flours in which the average
particle size is 40–50 µm.
Differently milled flours vary considerably in
baking quality. Flours obtained also differ greatly
from cultivar to cultivar. This is especially
the case with wheat cultivars (cf. 15.4.1.1).
Fig. 15.23. Content of B vitamins and minerals in flour
as affected by milling extraction rate (according to
Lebensmittellexikon, 1979). —– rye, - - - wheat
a Calculated as percent of the total content present in
grain.
Table 15.35. Wheat and rye milling products
All purpose flour
Special flour
Compounded
(ready to use) flour
Groats (grist)
Whole grain
groats
Commercially available (retail market) flour for household preparations of baked products.
It is used for special baked products, e. g., strong gluten wheat flour for toast bread, wheat
flour with weak gluten for baked goods of loose tender or crispy structure as pastry etc.
Special flour that contains other ingredients such as milk or egg powder, sugar etc.,
required by formulation of a selected baked product.
Coarsely ground dehulled cereal (devoid of germ and seed hull).
Ground from whole kernel (including germ).