Note: Descriptions are shown in the official language in which they were submitted.
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BACKGNOUND OF r~lE INVENTION
This invention relates to the processing of grains and, more
particularly, to an improved process especially useful fo~ milling grain
sorghum.
Grain sorghums offer a tremendous potential as a world food
supply. Sorghums grow over a wide range of climatic conditions. Tlley provide
a higher yield per acre than smaller cereal grains, comparable to or greater
than corn. Additionally, grain sorghums have a higher protein content than
corn, although less than that of hard winter wheat. However, in spite of the
foregoing advantages, grain sorghums are not used widely for human
consumption in the United States and other highly developed countries. This is
due to the ~act that flour milled by conventional processes from grain
sorghums has a bitter taste from the tannic acid content of the grain. ~lso,
the color of the conventionally processed flour makes it undesirable for baked
goods. Additionally, it has been found that if a conventional roller mill is used
in processing grain sorghums, the flour has a gritty aftertaste .
It would be desirable to provide a method for processing grain
sorghums that overcomes those disadvantages because flour made from grain
sorghums has the potential for being a superior food product. Such flour is a
low gluten flour, desirable for making soft baked goods. When grain sorghum
flour is blended with wheat flour, the mi2cture has baking qualities equivalent
to soft wheat flour but at a savings in cost on the order of 10%. By controllingthe ratio of sorghum flour to wheat flour, the quality of the mixture can be
maintained constant, even though the quality of the individual flour may vary
as a result of changing climatic conditions. Additionally, flour produced from
grain sorghum is bland and accepts flavors very well, thereby reducing the
amount of flavoring and sweeteners required by many recipes. Still further,
grit by-products from the processing of grain sorghums can be utilized to
replace corn grit in extruded food products at savings in the order of lû%. Thisgrit in large particles can also be substituted for rice with a higher nutritional
value at less than half the cost and can be precooked and reshaped to be
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equivalent to instant rice products. The grit products
tend to hold up better than similarly prepared rice, and
can be prepared in the same manner as regular rice.
Th~ls, with a proper processing method, grain
sorghums have the potential of providing an economical
food product which additionally gives the capability to
develop new products and flavors.
SUMMARY OF THE INVENTION
In accordance with an aspect of the invention
there is provided a method of processing grain comprising
the steps of: mixing water with the grain to form a
slurry; pumping the slurry successively through a
plurality of pump stages to separate the husks from the
kernels of the grain without cracking a substantial
percentage of the kernels; removing excess water from the
grain slurry to leave moist kernels and moist husks;
surface drying the moist kernels and moist husks to leave
a surface dried mixture of husks and kernels; and
aspirating the surface dried mixture to remove the husks
from the kernels.
In accordance with the principles of this
invention, an improved method for the processing oE grain
includes the steps of mixing cleaned grain kernels with
water to form a thick slurry, pumping the slurry through a
plurality of stages of pumps equipped with throttle valves
to remove the husks from the kernels, centrifuging the
slurry to remove excess water, surface drying and
aspirating to separate the husks from the kernels. Grains
other than sorghums-can then be milled. However, in the
case of sorghums, the additional steps of separating the
germ and oil from the endosperm is necessary and preferably
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a hammer mill is used to form the flour. A centrifugal
impact cracker is preferred for performing the separation
step.
~ESCRIPTION OF THE DRAWINGS
The foregoing will be more readily apparent upon
reading the following description in conjunction with the
drawings in which:
FIG. 1 is a flow diagram illustrating steps in
accordance with the principles of this invention for.
removing the husks from the grain sorghum kernels;
FIG. 2 is a flow diagram showing the steps in the
processing of grain sorghum after the husks have been
removed in accordance with the steps of FIG. l;
FIG. 3 is a flow diagram showing steps in
producing corn meal to form masa if corn rather than grain
sorghum is processed in accordance with the flow diagram
of FIG. l; and
FIG. 4 is a flow diagram showing steps involved
in producing wheat flour if wheat is processed in
accordance with the flow diagram of FIG. 1.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, shown therein is a flow diagram of an
ilnproved method for removing and separating grain husks from kernels. This
method is especially useful in the processing of grain sol'ghums and in
particular for the processing of milo. The method is initiated by removing the
grain from storage, step 10, and then cleaning the grain at step 12. This step of
cleaning is to remove dirt, trash, cracked or small seed and other grains which
- may be utilized as feed, 1~}. A conventional cleaner may be utilized such as
that used for cleaning seed. The cleaned grain is then put in intermediate
storage, 16, until further processing is to take place.
When it is desired to continue processing the grain, it is sent to a
tank for mi~ing, at step 18, with water, 20, to form a very heavy slurry.
During the mixing process, the water level in the mix tank is preferably
maintained so that there is approximately two pounds of water for every one
pound of grain. It has been found that this heavy slurry gives improved results,but the ratio of water to grain is not critical.
The slurry is then sent through a plurality of pumping stages, 22,
each consecutive pair of which is separated by a pressure reducing valve, 24.
Improved results are achieved by using an open bowl turbine pump with the
impellers raised to make the pump inefficient and to pass the grain as a whole
kernel without cracking the grain. In some instances, it is necessary to remove
some of the material, of which the pump impellers are constructed, from the
pump impellers to provide the necessary clearance. It has been found that as
many as 60 or more pump stages may be utilized to give the desired result,
which is a removel of the husk from the kernel~ The purpose of each of the
valves, 24, is to act as a pressure reducing valve and to retard flow of
material. The output of each pump stage is suitably at a pressure of
approximately 20 psi and that the pump input is suitable at a pressure in the
range of 2 to 3 psi. It is possible to work at higher pressures but the lo~ver
pressure provides a lower power consumption and hence a lower cost. The
valve, 24, is a pinch valve in which air pressure against a deformable tube
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within a casting is utilized to reduce tlle pressure but the deformable tube does
not nllow any clogging to take place. Ill~!stratively, the transit time through
the pump stages is in the order of eighteen minutes.
After the slurry has passed through the pumps, it is sent through
a centrifuge, 26, which removes excess water, 28. The slurry is then surface
dried, 30, illustsatively by means of a fluidized bed dryer which only removes
the surface moisture, 32. In effect, the surface drying only dries the husk and
the surface of the kernel while much of the internal moisture of the kernel
remains. As part of the dryer there is provided an aspirator hood which
aspirates, 3~, the surface dried mixture of husk and kernel to remove the dried
and lighter husk, 36. The step of surface drying, 30, is relatively short and
provides many advantages. Primarily, the cost of drying is significantly
reduced, a relatively low temperature of approximately 150F being used. It
has also been found that if the kernels of the grain sorghum are moist, the
succeeding process steps are much more effective. A moisture content of
approximately 22% at the output of the fluidized bed dryer is suitable. It is
only necessary that the husk be sufficiently dry to be removed by the
aspirator. While the surface moisture is removed, much of the internal
moisture remains.
Ref erring now to FlG . 2 depicted therein is a flow diagram
showing the processing of dehusked grain sorghum kernèls, picking up at point
A denoted by reference numeral 38, ~rom FI(3. 1. The dehusked kernels can be,
but are not necessarily, sent through a No. 10 mesh vibrating screen stage, 40.
The pieces which do not pass through the screen, but rather remain on the
screen, are sent to a centrifugal impact eracker 42~ The cracker is suitably a
centrifugal fan which has flat blades extending radially outward from a central
rotating shaft and a conical member at its input side to direct the incoming
kernels toward the outer hal~ of the blades. The impact of the blades hitting
flat against the kernels causes the kernels to be broken into smaller pieces.
The presence of internal moisture contributes to better separation of the germ
and oil from the endosperm. These pieces are sent to an aspirator stage, 44,
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which separates the very fine and dust-like particles from the heavier and
larger broken pieces. These dust-like particles are then sent to a final sifter,the output of which is grain sorghum flour, 48, suitable for human
consumption. The larger pieces which pass through the aspirator stage 44, are
then sent to a No. 7 mesh vibrator screen stage, 50. The unbroken pieces
which do not fall through the screen, 50, are normally grains other than
sorghum, and are utilized as animal feed, 52. The smaller pieces which fall
through the No. 10 mesh vibrating screen, 40, and the No. 7 mesh vibrating
screen, 50,-are sent through a sizing screen stage, 54, which includes Nos. 10,
14, 24 and 35 sizing screens and a pan for collecting the fines.
In sizing screen stage 54, the pieces of kernel are separated into
four sized groups. The pieces of a size larger than No. 10 mesh go to gravity
separator stage, 56. The pieces in size between No. 10 and No. 14 mesh go to
gravity separator stage, 58. The pieces in size between No. 14 and No. 24 mesh
lS go to gravity separator stage, 60. The pieces between No. 24 Rnd No. 35 mesh
go to gravity separator stage 62. The pieces that are smaller than No. 35 mesh
are collected in a pan and are fines that can go directly to the sifter. The first
three gravity separator stages separate their respective particles into heavy,
Ihedium and light weights. The last gravity separator stage, 62, separates its
pnrticles into heavy and light weight.
The lighter mass particles have been found to contain the germ
and oil of the kernels and may be used as a feed by-product or the germ and oil
may be extracted at stage, 64. The medium density particles usually comprise
some germ or oil attached to an endosperm particle, and are returned to the
cracker, 42. The heavy endosperm particles are sent to a hammer mill stage,
66.
When processing grain sorghums, it has been folmd that a more
suitable product may be obtained through the use of a hammer mill or honey
comb mill rather than a conventional roller mill since a higher moisture
content can be tolerated. If a grain sorghum is processed in a roller mill, it
has been found that the flour produced thereby has a gritty aftertaste, whereas
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the flour produced by the use of other mills, such as a hammer mill has no such
bad aftertaste. It is believed that the presence of moisture during milling
contributed to the reduction in the gritty aftertaste.
The output o the hammer mill stage, 66, is sent to an aspirator
stage, 68. The fine dust-like particles pickup up by the aspirator are sent
through sifter 46 where they are turned into flour 48 suitable for human
consumption. The heavy grit particles not pickup by the aspirator stage, 68,
- can be either returned to the hammer mill, if only flour is desired as indicated
by the dash line 71, or sent to a sizing screen stage 70, from which they may bemarketed, 72, as a by-product suitable, for example, for making extruded food
products.
The method disclosed with reference to FIG. 1 may also be
applied to dehusking corn and wheat. It has been found that utilizing the
method disclosed with reference to FIG. 1, approximately a 10% savings in
capital equipment cost and a 20% savings in operating cost may be achieved
due to the fact that a continuous process is utilized rather than a conventionalbatch process for dehusking corn and wheat.
If it is desired to manufacture masa, a corn maan product, the
method disclosed in FIG. 3 for using the dehusked corn which is present at
point ~ in FIG. 1, may be ~Itilized. In this method, the dehusl<ed corn is cooked,
74, utilizing steam, 76. The cooking lasts about 18 minutes, depending on the
required glutenization. The cooked corn is then sent through a wet grind
stage, 78~ and then air column dried, 80, to form the masa, 82. This is a
significant improvement over present methods which include adding lime and
boiling to glutenize the starches, and steeping at 150~- for 9 to 18 hours to
remove the husk. It is important to note that the quality of corn required for
making masa using the process of the present invention is much lower than
that required in conventional processes, since kernels with stress fractures canbe used.
If it is desired to process wheat which has been dehusked using
the method disclosed in FIG. 1, as shown in FIG. 4 the dehusked wheat at point
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A is sent to a mill, 84, which provides wheat flour, 86, at its output.
Conventional sifting and purifying steps, not shown, can be incorporated.
Accordingly, there has been described an improved method for
processing grain sorghums, which method may also be utilized for dehusl~ing
corn and wheat with a substantial savings in both capital equipment costs and
operating expenses. When grain sorghums are processed9 according to the
disclosed method, the resulting product is substantially less expensive than a
corresponding wheat product. A low gluten flour is produced which is
especially good for baking soft goods, this flour being bland and accepting
flavoring and sweeteners very well. By-products include animal feed having a
value which will be nearly equal to the cost of the grain being processed. A
grit suitable for use as a rice substitute, but which is more nutritional and less
than one-halE the cost of commercially available rice products can be
obtained. The grit can also be utilized to manufacture extruded food products.
It is thus apparent that the improved method according to this invention is a
substantial improvement over prior art methods and provides a new use for a
widely available and highly advantageous grain.
What is claimed is:
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