Final Exam, Fall
1. Summarize the different
branches of science that have relevance to dry milling of wheat.
Wheat grains have to go through a number of milling
processes so as to augment product quality and integrity. Dry milling in simple
definition refers to the separation of the structural parts of the grain as efficiently
as possible so as to realize the desired quality products. Wheat grains initially
have to pass through a rigorous meticulous cleaning process which can be up to
six steps of cleaning to get rid of all the unwanted impurities emanating from
the farmers field such ash debris, sticks and metal objects prior to milling.
The process of cleaning wheat is a continuous process throughout the milling of
the wheat, this is evidenced by the magnetic separators that are mainly used to
pick up all possible available metal objects.
The vibrating or rotating drum separators remove things
like woods, wheat straw. Aspirators then take advantage of the air power to
remove the dust form and other lighter impurities. Usage gravity (de-stoner)
comes in handy to remove stones that could be the same weight as the wheat
kernels. The grain then passes through a disc separation machine which mainly
analyses precisely the kernel size and deliberately rejects all anomalies in terms
kernels with irregular size and shape. The intense scourer action then removes
the outer husk of the kernel and the dirt in the kernel crease as this is
thought to be the breading point of unwanted microorganism. The entoleter will
then use the centrifugal force to break apart the faulty kernels or insect eggs
of which aspiration will then reject them from the milling flow. Recent advance
mills can actually utilize electronic color separators that makes the cleaning
process to be easy.
After cleaning the wheat grains the wheat will be ready for the milling
process but however a tempering process is needed prior to the grain being milled.
Tempering is a process of adding water into the wheat grain of which water enters
mostly through the wheat germ. Tempering is done so to toughen the bran skin to
hold water rather than creating bran powder which can lead to dark high mineral
flours. It is carried out to ensure the separation of the dark colored bran
from the light-colored endosperm which leads to a desirably good quality flour
to meet consumer needs. to ensure the
desired moisture content of finished products and to aim for consistency. Soaking
can be done for 6-24hrs depending on the wheat moisture level and also it
should be noted that temper water can be treated with either chlorine or ozone
to maintain sanitation throughout the tempering process.
After tempering the wheat grain is ready for milling. There are about 5
roller meals in a typical milling system. The main of the process of milling is
to successfully get as possible of the pure endosperm from the bran and the
germ. This process needs a lot of efficiency because it is standard milling practice
that the bran and the germ should not make its way into the flour as this leads
to undesirable flour quality. The broken wheat grains coming from the corrugated
fine rolls is sent back to the top and then allowed to drop through sifters to
reduce the presence of bran from the wheat granular particles. The sifting
process is a screening process that separates the large from the top while the
smaller particles sift to the bottom.