1.Is the world milling industry
growing?
The capacity of
the milling industry is slowly growing. This growths appears to be mostly due
to the growth of the world population. Only in a few regions, particularly in
Asia, the consumption of wheat flour is also growing. In contrast, the number
of mills is decreasing due to mergers and increasing capacities of new mills.
2.
Does the particle size of the flour influence the effect of the enzymes?
The finer the
particle size, the larger is the area that can be attacked by the enzymes.
Moreover, the constituents of the flour hydrate faster, and this makes them
more readily accessible to the enzymes, because a fine particle size is often
accompanied by greater damage to the starch (although this is not necessarily
the case). The damaged starch grains already swell in the dough and are thus
available to the amylases. Intact starch grains are not.
3.
Which particle size is better -90 or 150 microns?
That depends on
the properties you want the flour to have. Smaller particles usually mean more
damage to the starch if the small size was achieved with ordinary cylinder
mills. This results in greater water absorption and better breakdown by enzymes
and yeast, but also reduced stability of the dough. In coarser flours there is
not only less damage to the starch; the larger particles also swell more
slowly, with the result that the doughs stiffen subsequently and thus become
more stable. Coarser flours also cause less dust and have better flow
properties.
4.
How does the milling yield (extraction rate) affect protein and ash? Is there
some correlation between the protein and ash content of flour?
Endosperm
protein and the mineral content decrease from the outside of the kernel to the
centre. At higher extraction rates, the amount of the aleuron and outer
endosperm layers is larger than in flour from low extraction rates. This means
that ash and protein increase with the extraction rate. They are both
correlated to a certain extent.
5.
Why should the germ be removed from the kernel before milling? Why is there a
difference in shelf-life between white flour and whole meal flour?
The germ
contains about 10% lipids, mostly unsaturated. The milling process would
destroy the structure in which the lipids are bound, exposing them to
atmospheric oxygen. Rapid oxidation (both enzymatic and non-enzymatic) and thus
rancidity would occur. Whole meal flour containing the wheat germ is therefore
less stable than white flour.
6.
Why does flour from the wheat of a new crop/harvest display different
attributes from those of flour from wheat that has been stored for several
months?
Maturation of
flour is a natural process caused mainly by exposure to atmospheric oxygen. In almost
all cases freshly milled flour has a much poorer performance than flour stored
for 2 weeks.
7. Is there any way of adding chemicals at
the tempering stage, i.e. some water-soluble type, to achieve a whitening
effect?
There have been
partially successful attempts to improve the removal of the bran by adding
enzymes to the soaking water, which would result in a brighter colour of the
flour. The author is not aware of any trials with oxidizing substances such as
chlorine, benzoyl peroxide or hydrogen peroxide. The use of oxidizing agents
might have some effect on the colour, but access to the carotenoids of the
intact kernel is probably limited, so the approach would not be very effective.
8.
Why does the volume yield fall as the degree of extraction increases, although
the protein content rises with higher extraction?
The proteins of
cereal are unequally distributed over the layers of the grain. The water
insoluble protein fractions glutenin and gliadin that are important for baking
are mainly in the endosperm, whereas the aleuron layer, although rich in
protein, contains mainly water-soluble proteins that do not improve the baking
properties.
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