Farina milling process

The process of milling wheat to produce a large proportion of coarse farina in which double tempered wheat is passed through a series of four identical sets of deeply and coarsely corrugated break rolls run sharp to sharp. The output of each roll is separated in size ranges. Substantially oversized particles from each break roll set are fed into the next break roll set in the series. Slightly oversized particles are fed through corrugated rolls to slightly reduce the size thereof, and to remove bran coat therefrom. Properly sized particles are air purified to remove bran particles and oversized bran particles are passed through additional breaking roll operations to further separate any endosperm particles therefrom.

BACKGROUND OF THE INVENTION 
The present invention relates to the milling of grain and more particularly 
to the production of farina. 
Farina, as defined by U.S. government standards, is the food prepared by 
grinding and bolting cleaned wheat, other than durum and red durum wheat, 
to such fineness that it passes through a No. 20 U.S. standard sieve but 
not more than 3 percent passes through a No. 100 U.S. standard sieve. 
Farina is normally produced as a co-product of flour milling. In the 
conventional flour mill, the wheat is passed through a series of breaking 
and reduction operations designed to rapidly reduce the endosperm portion 
of the wheat berry to flour. The breaking operations typically include up 
to five roller milling units and the output of each unit is classified by 
size. A certain amount of flour is produced at each break and that is 
separated from the larger particles by bolting. The largest particles are 
directed to the next break roll, while the intermediate size particles 
(which include those of farina size) are air purified to remove bran 
particles and are passed to reduction roller mill units to be ground into 
flour. In the conventional flour mill a considerable portion of the output 
of the breaking operations in fine farina, and the mill operators can 
elect to extract a portion of this farina for use as hot breakfast cereal 
rather than use it to produce flour. 
Most farina sold as hot breakfast cereal contains a high percentage of fine 
farina, i.e. particles which will pass through a No. 40 U.S. standard 
sieve. There is, however, a popular hot breakfast cereal product composed 
predominately of coarse farina particles of a size too large to pass 
through a No. 40 standard sieve. The conventional flour mill produces a 
very small amount of farina in the No. 20 to No. 40 standard sieve size. 
Therefore, in order to obtain a sufficient quantity of coarse farina to 
nationally market a popular breakfast cereal, it is necessary to purchase 
coarse farina from a large number of flour mills when and where it is 
available. Since flour mills differ in the way they grind, classify and 
purify their stock it is necessary to carefully blend the farina from 
various sources in order to provide a high quality and uniform product. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to provide a process for milling 
wheat which provides a high proportion of coarse farina. 
According to the present invention, the foregoing object is accomplished by 
providing a process of milling wheat comprising the steps of tempering the 
wheat, passing the tempered wheat through a series of deeply and coarsely 
corrugated break rolls to slowly reduce the particle size of the wheat, 
separating the particles exiting from the break rolls into a plurality of 
size ranges, passing the substantially oversized particles to the next 
break roll, passing slightly oversized endosperm particles between deeply 
corrugated sizing rolls to reduce their size slightly and remove bran coat 
therefrom, and air purifying all properly sized particles to remove bran.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings there are shown milling processes according to 
the present invention which comprises first and second tempering 
arrangements, a number of break roll sets, a number of sizing roll sets, a 
number of sifters, and a number of purifiers. The wheat utilized in 
connection with the processes of this invention are preferably of the hard 
spring or hard winter varieties, however, any hard wheat other than durum 
or red durum can be used. The wheat is processed to remove foreign matter 
and is scoured and air washed in accordance with standard procedures. The 
wheat is then given a first temper in which it is mixed with sufficient 
water to bring it from its natural moisture content of 11% to 13% to a 
moisture content of between about 13.5 and 16%. The moistened wheat is 
held in a tempering bin for from about 5 to 64 hours, and preferably from 
8 to 64 hours, to allow the moisture to penetrate and become evenly 
distributed in the endosperm. The wheat is then given a second temper in 
which the total water content is raised by about 0.5 to 4% to a total 
moisture content of 15 to 18%. The wheat is then held for 10 to 120 
minutes before milling to allow the moisture to be absorbed by the bran 
coat. The first temper is to condition the endosperm to reduce shattering 
of the endosperm and bran during milling. The second temper toughens the 
bran coat so that during milling it tends to be released from the 
endosperm in large pieces which are more readily separated from the 
endospem particles. 
Following the second tempering period, the wheat berries are fed between 
the first set of break rolls. It is a feature of this invention that the 
size of the wheat particles is gradually reduced by the use of a large 
number of break roll sets, each set to provide a limited reduction in the 
size of the larger particles produced by the preceding set. The surface of 
the break rolls are cut to provide tooth shaped corrugations which are 
coarse and deep and extend helically along the length of the rolls. In 
FIG. 1 there is shown a representative break roll set which comprises a 
roll 10 that is driven slowly and a roll 11 that is driven at a 
substantially faster speed. The rolls 10 and 11 are formed with teeth 12 
each of which have a generally radially oriented edge 14 and a generally 
tangentially oriented edge 15. On the roll 10, the teeth are oriented so 
that the edges 14 face away from the direction of rotation. The rolls are 
therefore arranged in the sharp to sharp tooth configuration wherein the 
wheat particles are held on one side by the edge 14 of a tooth on the slow 
roll 10 while the edge 14 of a tooth on the fast roll 11 moves against the 
other side of the particle tending to cut a large piece from the particle. 
Referring now to FIG. 2, there is shown a milling process in accordance 
with the present invention which comprises, in addition to the tempering 
arrangements, five pairs of break rolls, three pairs of sizing rolls, 
seven sifters and three purifiers. 
The first, second and third break roll sets have 10 corrugations per inch 
making the pitch of the teeth 2.54 millimeters. The depth of the teeth 
measured radially with respect to the roll is 0.48 millimeters or 480 
microns. It will be seen therefore that the first break rolls can be set 
so that the wheat berries fed into the rolls are cut into large pieces. 
The percentage of large particles produced by the first break roll can be 
controlled by adjusting the spacing between the two rolls. For example, 
using the break rolls described above, the percentage of the particles 
which will pass through a No. 20 U.S. standard sieve (particles less than 
840 microns) can be varied between 9.5% and 40%. In either instance the 
particles which pass through the No. 20 standard sieve are mostly in the 
coarse farina size range with only about 6% being sized to pass through a 
No. 40 U.S. standard sieve (420 microns) and about 3% being sized to pass 
through a No. 60 U.S. standard sieve (250 microns). The second break rolls 
are set closer together to further subdivide the large pieces generated by 
the first break, and the third breakrolls are set still closer together to 
further subdivide the largest particles produced by the second break. 
There is, of course, some disintegration of the endosperm particularly 
along the cleavage line, also the wheat particles tend to fracture upon 
the impact of the teeth. 
The fourth break rolls have the same tooth shape as that shown in FIG. 1, 
however, the size of the teeth is reduced to provide 16 teeth per inch of 
circumference, the pitch of the teeth being 1.58 millimeters and the depth 
of the teeth is 297 microns. The fifth break rolls also have the same 
tooth shape as that shown in FIG. 1 with 20 corrugations per inch to 
provide a tooth pitch of 1.27 millimeters and tooth depth of 240 microns. 
The wire bolting cloth used in the sifters and purifiers in each of the 
embodiments described herein is a commercial cloth which has larger 
openings for each mesh size than the U.S. standard. 
The wheat particles flowing from the 1st break roll set are fed into sifter 
#1 which has four screen sets for separating the particles into size 
ranges. Those particles over 1410 microns (which will not pass through the 
No. 16 commercial sieves of the first screen set) are fed to the 2nd break 
rolls. The particles which pass through the No. 16 sieves and are too 
large to pass through the No. 26 commercial sieves of the second screen 
set are directed to purifier #1. Particles in this size range are between 
787 and 1410 microns. The particles which pass through the No. 26 sieves 
but will not pass through the No. 30 commercial sieves of the third screen 
set have a size range of 787 to 682 microns and are fed into purifier #2. 
Purifier #3 receives the particles in the size range between 682 and 437 
microns which pass through the No. 30 sieves but are stopped by the No. 44 
commercial sieves of the fourth screen set. 
The sifters #2 and #3 each have four screen sets. The "overs" from the 
first screen set in each of the sifters are over 1410 microns and are fed 
to the next break rolls for further reduction in size. The "overs" of the 
second screen sets are fed to purifier #1, the "overs" of the third screen 
set are fed to purifier #2, and the "overs" of the fourth screen set are 
fed to purifier #3. The "overs" of the second and third screen sets sifter 
#3 range between 787 and 1410 microns and between 682 and 869 microns 
respectively. In sifter #3 the second screen "overs" are between 787 and 
1410 microns while the third screen "overs" are between 682 and 787 
microns. The fourth screen "overs" are between 437 and 682 microns for 
sifter #3. 
Sifters #4 and #5 have three screen sets each. In sifter #4, the first 
screen set is made up of No. 20 commercial sieves and the "overs" are 
directed to the fifth break roll. The second screen set is made up of No. 
28 commercial sieves with the "overs" directed to purifier #2. The third 
screen set is made up of No. 44 commercial sieves and the overs are 
directed to purifier #3. Sifter #5 is provided with a No. 22 commercial 
sieve first screen set, a No. 28 commercial sieve second screen set, and a 
No. 44 commercial sieve third screen set. The "overs" of the first screen 
set are large bran particles and are sent to a bran duster in which the 
bran is impacted and bolted to remove any flour which might be adhering 
thereto. The "overs" of the second screen set are shorts, that is, smaller 
bran particles and wheat germ particles. The shorts are passed through a 
shorts duster to remove adhering flour and are sold as feed. The dusted 
bran may be combined with the shorts as feed or sold separately. The 
"overs" of the third screen set are directed to purifier #3. 
Each of the purifiers have four screens positioned edge to edge and at a 
slight angle so that with vibration of the screens the particles move from 
screen to screen until they pass through one of the screens or move off 
the end of the last and lowest screen. The screens vary in mesh size, the 
smallest mesh screens being on the high end of the screen set and the 
largest mesh screen being on the low end of the set. The particles to be 
purified are deposited on the small mesh screen at the high end of the 
screen set and flow downhill across the larger mesh screens while an air 
current is directed upwardly through the screens to stratify the 
particles. The vertical air flow produces a lifting effect upon the 
particles, the intensity of which depends upon the size, shape and density 
of the individual particles. The bran particles generally have a large 
ratio of surface area to weight and tend to be lifted by the air to form a 
layer riding on top of the endosperm particles which normally have less 
surface area for a given weight. Small bran particles are carried off with 
the air stream. 
As the particles move across the screen set, progressively larger particles 
pass through the progressively coarser screens. Not all of the particles 
in the mass of the material treated at any one time pass through the first 
screen which will accept them. A significant portion of the particles 
become entrained with larger particles and pass through the screen with 
those particles. The particles flowing through the individual screens are 
directed (by gravity alone or by internal baffles) into one of a number of 
collecting hoppers. The upper stratified layer of bran particles moves off 
the tail end of the screen. 
The particles directed to purifier #1 from the sifters generally have a 
particle size range of 787 to 1410 microns, however, some particles will 
be included therewith which are more than 1410 microns in length but have 
a transverse dimension of less than that figure and have passed through 
the screens endwise. Purifier #1 has three collecting hoppers 20, 21, and 
22. The purified particles which are directed into the first hopper 20 are 
those which have a particle size of less than 840 microns and therefore 
have a general size range of between 787 and 840 microns. These particles 
are collected as coarse farina. The purified particles which are directed 
to the second hopper are generally those which are slightly oversized 
including sizes from 840 microns to the 1000 to 1200 micron range. These 
particles are directed to the second sizing rolls for size reduction. The 
particles directed to the third hopper are larger oversized particles 
ranging up to 1410 microns and include those elongated particles 
substantially oversized in one direction which passed through the sifter 
screens endwise. These particles are directed to the first sizing rolls 
for size reduction. 
The particles in the upper layer which move off the tail end of the 
purifier screening are predominately bran particles to which endosperm 
particles may be adhering. These "overs" are directed to the 4th break 
rolls for dislodging the endosperm particles from the bran fibers. 
The particles directed to purifier #2 from the sifters have a particle size 
range between 682 and 1050 microns. The purifier #2 has two collecting 
hoppers 24 and 25. The particles directed to the first hopper 24 range in 
size generally from 682 to about 840 microns and are collected as coarse 
farina. The particles directed to the hopper 25 are slightly oversized 
ranging from 840 to about 978 and are directed to the second sizing rolls 
for size reduction. Slightly oversized endosperm particles and stratified 
bran particles constitute the "overs" of the purifier and are directed to 
the first sizing rolls. The oversized particles are reduced in size by the 
sizing rolls. The bran particles flow through the sizing rolls and are 
directed to the fourth break roll from the first screen in sifter #6. 
The third purifier receives particles ranging in size from 437 to 716. The 
purified particles between 437 and about 546 flow into the hopper 26 and 
are collected as coarse farina. The particles generally between 546 and 
716 flow to the hopper 27 and are directed to the third sizing rolls to 
dislodge endosperm particles from bran particles so that the bran can be 
stratified and passed off the tail of the purifier screens. The larger 
particles and the stratified bran particles flowing off the end of the 
screen are directed to the second sizing rolls where the oversize 
endosperm particles are reduced in size. The bran particles are retained 
by the No. 30 screen in sifter #7 and are cycled through purifier #2 and 
the first rolls to the bran duster. 
The first sizing rolls receive particles generally between about 1000 and 
1410 microns from the purifier #1 and particles having a dimension larger 
than about 978 microns from the purifier #2. As previously stated those 
particles from purifier #1 are made up of slightly oversized endosperm 
particles, some elongated endosperm particles which are substantially 
oversized in one dimension, and coarse bran fibers attached to endosperm 
particles. The material received from purifier #2 is largely coarse bran 
fibers weighted down by endosperm particles attached thereto. 
The first sizing rolls are formed with deep tooth shaped corrugations, 
there being 20 corrugations to the inch. The rolls are driven at different 
speeds, the fast roll being driven at a rate of 1.5 times the rate of the 
slow roll. The tooth shaped corrugations of the two rolls are oriented so 
that the teeth are driven in a "sharp to sharp" configuration. The first 
sizing roll operates to slightly reduce the size of the oversized 
endosperm particles, to dislodge endosperm particles from bran fibers in 
order that the purifier may effect a separation of endosperm and bran 
particles. 
The particles issuing from the first sizing roll is directed into sifter #6 
which contains a set of No. 24 sieves, a set of No. 30 sieves and a set of 
No. 44 sieves. 
The "overs" on the No. 24 sieves are more than 869 microns and are largely 
large bran particles. These are directed to the 4th break rolls to 
dislodge any endosperm particles adhering thereto. The particles which 
pass through the No. 24 sieves but are stopped by the No. 30 sieves are 
large farina particles with some bran flakes. These particles are returned 
to the purifier #2 for repurification and separation. The particles which 
pass through the No. 30 sieves and are stopped by the No. 44 sieves are 
between 437 and 682 microns in size. These particles also are coarse 
farina together with some bran flakes and are directed to the purifier No. 
3 for purification. 
The 2nd sizing rolls receive slightly oversized endosperm particles, in the 
range of 840 to 1190 microns, from purifier #1 and slightly oversized 
endosperm particles in the range of 840 to 978 microns, from purifier #2. 
The output of the 2nd sizing rolls is directed to the sifter #7 which is 
provided with a set of No. 30 sieves and a set of No. 44 sieves. The 2nd 
sizing rolls performs the same general functions as the 1st sizing rolls. 
The 2nd sizing rolls have the same type of tooth configuration except they 
are formed with 24 corrugations per inch. The fast roll is driven at a 
speed of 1.5 times the speed of the slow roll and the teeth are oriented 
in a sharp to sharp configuration. The particles which are stopped by the 
No. 30 sieves of sifter #7 are directed to purifier #2. The particles 
which are stopped by the No. 44 sieves are directed to purifier #3. 
The third sizing rolls are formed with the same shape tooth as the other 
sizing and break rolls but the teeth are smaller, there being 28 
corrugations to the inch. The rolls are driven with a differential of 1.5 
to 1 and the teeth are oriented in the sharp to sharp configuration. The 
particles exiting from the 3rd sizing roll set are directed into sifter #8 
which has a single set of No. 44 sieves. The particles which do not pass 
through the sieves contain some endosperm particles and bran and are 
returned to purifier #3 for farina recovery, the bran being removed 
through purification. 
EXAMPLE #1 
As a specific example, hard winter wheat having a moisture content of 12.0% 
was mixed with sufficient water to bring the total water content to 14.3%. 
The wheat was stored in a tempering bin for 18 hours to allow the moisture 
to diffuse throughout the wheat berries. The wheat was then fed through a 
mixing conveyor where it was mixed with sufficient water to bring the 
total water content to 15.2%. The wheat was held for 20 minutes to allow 
this added water to soak into the bran coat of the wheat berries and then 
fed into the 1st break rolls of the system of FIG. 2 at a rate of 125 
bushels per hour. The spacing between the break rolls in each set was 
adjusted so that the break release, that is, the percentage of wheat 
particles issuing from the break rolls which will pass through a No. 20 
standard sieve, were as follows: 1st break -- 19.5%, 2nd break -- 24.5%, 
3rd break -- 38%, 4th break -- 68%, 5th break -- 64%. 
In this milling operation, 33.17% of the output consisted of coarse farina 
of which 6% was larger than 840 microns, 24.5% was between 595 and 840 
microns, 52.5% was between 420 and 595 microns, 14.5% was between 250 and 
420 microns, and 2.5% was smaller than 250 microns. In this example, the 
fine material which passed through the finest sieves of each of the 
sifters was passed through a series of reduction rolls and reduced to 
flour according to standard practice. Of the total output of the system, 
40.39% was flour, 6.98% was clear flour, and 19.46% was feed. 
Of the coarse farina produced, 19.71% was extracted at the purifier No. 1, 
29.16% was extracted at purifier No. 2, and 51.13% was extracted at 
purifier #3. Of the farina from purifier #1, 58% was over 840 microns, 
40.5% was between 595 and 840 microns, and 1.4% was between 420 and 595 
microns. The farina from purifier #3 consisted of 1.0% which was over 840 
microns, 19.0% which was between 595 and 840 microns, 67.5% which was 
between 420 and 595 microns, and 12.5% was between 250 and 420 microns. 
The size distribution of the particles being directed to purifier No. 2 
was not specifically measured during this trial, however, it can be stated 
with accuracy from experience and observation that substantially all of 
this material was between 420 and 840 microns with more material being 
above 595 microns than below that value. 
EXAMPLE #2 
In a second trial run with the similar wheat used in Example #1, the 
spacing of the 1st, 2nd and 3rd break rolls were changed so that the 
percentage of material exiting from the rolls which would pass through a 
No. 20 standard sieve was as follows: 1st break -- 34.5%, 2nd break -- 
44.5%, 3rd break -- 47.0%. In this run, the output of the milling 
operation consisted of 34.15% coarse farina, 32.96% flour, 7.29% clear 
flour, and 25% feed. The coarse farina consisted of 6% larger than 840 
microns, 29% between 595 and 840 microns, 50.5% between 420 and 595 
microns, and 1.5% smaller than 250 microns. The farina produced from 
purifier #1 consisted of 50.5% over 840 microns, 48% between 595 and 840 
microns, and 1.5% between 420 and 595 microns. The farina from Purifier #3 
consisted of 1% larger than 840 microns, 24% between 595 and 840 microns, 
66.5% between 420 and 595 microns, and 8.5% between 250 and 420 microns. 
The coarse farina was extracted as follows: 20.99% from Purifier #1, 
27.48% from Purifier #2, and 51.53% from Purifier #3. 
Referring now to FIG. 3, there is shown another embodiment of the present 
invention which includes in addition to the two tempering arrangements, 
six pairs of break rolls, two pairs of sizing rolls, eight sifters and 
four air purifiers. 
The first, second, third and fourth break rolls each have 10 corrugations 
per inch, the tooth shape and dimensions being identical to that of the 
FIG. 2 embodiment. The fifth break rolls have the same tooth shape as that 
shown in FIG. 1, however, the size of the teeth is reduced to provide 16 
teeth per inch of circumference. The sixth break rolls have the same shape 
teeth with 20 corrugations per inch of circumference. The particles 
flowing from each break roll set are directed to the corresponding sifter. 
Sifters #1, #2 and #3 each have four sets of screens, the four sets being 
made of No. 16, No. 20, No. 30 and No. 40 commercial sieves respectively. 
In each instance, the substantially oversized particles, that is, those 
which are above 1410 microns and therefore will not pass through the No. 
16 sieves, are directed to the next break roll set. The particles which 
cannot pass through the No. 20 sieves range in size from 1050 to 1410 
microns and are directed to the 1st sizing rolls for size reduction. The 
particles which are smaller than 1050 microns and larger than 682 microns 
are caught by the No. 30 sieve and are directed to air purifier #2. The 
particles which are smaller than 682 microns and larger than 471 microns 
are stopped by the No. 40 sieve and are directed to Purifier #3. These 
last two size ranges of particles are within the desired size range for 
coarse farina and are fed into the air purifiers to separate bran 
particles mixed therewith. 
Sifters #4, #5 and #6 each have three sets of screens. Sifter #4 has a 
first screen set made up of No. 20 sieves, a second set made up of No. 30 
sieves, and a third set made up of No. 40 sieves. The "overs" on the No. 
20 sieves are directed to the fifth break rolls. These are largely bran 
particles which may have endosperm particles adhering thereto. The "overs" 
on the No. 30 and the No. 40 sieves are respectively directed to purifier 
No. 2 and purifier No. 3 to remove bran particles from these coarse farina 
particles. Sifter #5 has a first screen set of No. 24 sieves, a second 
screen set of No. 30 sieves, and a third screen set of No. 40 sieves. The 
"overs" on the No. 24 sieves are directed to the 6th break rolls. The 
coarse farina sized overs on the No. 30 and No. 40 sieves are directed to 
purifiers #2 and #3 respectively for removal of bran particles. Sifter #6 
has a No. 20 sieve screen set, a No. 34 sieve screen set and a No. 60 
sieve screen set. The "overs" on the No. 20 sieve are bran particles and 
are directed to a bran duster for dislodging flour and other small 
endosperm particles adhering thereto. Both the "overs" and the "throughs" 
of the No. 60 sieve are combined with the "throughs" of sifters #1 to #5. 
These particles include flour and fine farina. The fine farina particles 
may be separated from the flour for use in hot cereals or they may be 
passed through a reduction system to reduce them to flour. 
Each of the purifiers have four or more screens positioned edge to edge and 
at a slight angle and are vibrated so that the particles move from screen 
to screen. The screens vary in mesh size, the smallest mesh screen being 
on the high end of the set and the largest mesh screen at the low end. The 
particles are deposited on the high end and move down hill across the 
screens as an air current is moved upwardly through the screens. 
The particles flowing to purifier #2 have passed through a No. 20 sieve 
having openings of 1050 microns and have been caught by a No. 30 sieve 
having opening of 682 microns. These particles therefore generally range 
between 682 and 1050 microns and include some elongated endosperm 
particles and bran fibers which exceed 1050 microns in length and some 
particles smaller than 682 microns which have become entrained with the 
larger particles. As the particles pass through the purifier, the lighter 
bran particles unencumbered by endosperm particles are stratified by the 
air current. Purifier #2 is provided with two collection hoppers 30 and 
31. The endosperm particles generally smaller than 840 microns are 
directed to the hopper 30 and are collected as coarse farina. The larger 
particles up to about 1410 microns are directed to Purifier #1. The 
"overs" of purifier #2, which include large particles and stratified bran, 
are directed to the fourth break rolls where large endosperm particles are 
reduced in size and where endosperm particles are dislodged from large 
bran particles. 
Purifier #1 is provided with two collection hoppers 32 and 33. The 
particles directed to Purifier #1 from Purifier #2 are generally up to 
about 1410 microns. Those particles which are below 840 microns are 
directed to hopper 32 and are collected as coarse farina. The largest 
particles are directed to the 4th break rolls. The particles which are 
generally between 840 and about 1000 microns are directed to hopper 33 and 
[are directed to hopper 33 and] are recycled to the input end of purifier 
#1 to separate out and remove loose bran and maintain efficiency by 
keeping sufficient material on the screens to keep the air velocity down 
to a value which will not carry away excessive quantities of fine 
endosperm particles. 
Purifier #3 receives the "overs" of the No. 40 screens of sifters 1 through 
5, 7 and 8 which are between 682 and 471 microns and may contain elongated 
particles having greater maximum dimensions and entrained smaller 
particles. The particles within the stated range and those smaller are 
directed to a hopper 35 and are collected as coarse farina. Larger 
particles (up to about 1410 microns) are redirected to purifier No. 2 for 
further bran separation and the largest particles are directed to the 
flour production system which contains further sifters for removing bran 
particles from the flour produced. 
The particles aspirated from Purifier #1 are fed into purifier #4 and may 
contain both bran and flour or fine farina particles. The flour and finest 
farina particles are collected in the hopper 37 and are directed to the 
flour production system. The medium range particles are collected in 
hopper 38 and are recycled to Purifier #2. The large and the stratified 
particles (the "overs") are directed to the flour production system. 
The first and second sizing rolls have 24 and 28 corrugations per inch 
respectively and are driven sharp to sharp with the fast roll being driven 
1.5 times the speed of the slow roll. 
The sifters #7 and #8 each have three sets of screens, the first set 
containing No. 20 sieve commercial screens, the second set containing No. 
30 sieve commercial screens, and the third set containing No. 40 
commercial screens. 
The first sizing roll receives the slightly oversized particles which 
cannot pass through the No. 20 commercial sieve screens in sifters #1, #2 
and #3. These particles are given a light grind by the first sizing rolls 
to slightly reduce their size. The particles exiting from the first sizing 
rolls and which are not yet small enough to readily pass through the No. 
20 sieves of sifter #7 are passed through the second sizing rolls. Any 
particles exiting from the second sizing rolls which will still not pass 
readily through a No. 20 commercial sieve are directed to the 4th break 
rolls. These particles are normally bran particles having endosperm 
particles adhering thereto. The particles which are "overs" of the No. 30 
screens of the sifters 7 and 8 are directed to purifier #2 and the "overs" 
of the No. 40 screens are directed to purifier #3. The particles passing 
through the No. 40 screens are collected as fine farina or reduced to 
flour. 
EXAMPLE #3 
Hard winter wheat having a moisture content of 12.6% was tempered for 18 
hours to bring its moisture content to 14.0%. It was then given a second 
temper for about 20 minutes to raise the total moisture content to 15.4% 
to toughen the bran coat. The tempered wheat was then fed into the 1st 
break rolls of the system of FIG. 3 at a rate of 110 bushels per hour. The 
spacing between the break rolls were adjusted so that the break release 
(the percentage of ground wheat particles which will pass through a No. 20 
U.S. standard screen were as follows: 1st break -- 10%, 2nd break -- 19%, 
3rd break -- 17.5%, 4th break -- 36.5%, 5th break -- 51%, 6th break -- 
61%. The fine particles generated during the milling were ground to flour 
according to standard procedures. 
The output of this milling operation consisted of 30.3% coarse farina, 
31.93% flour, 7.71% clear flour, and 29.33% feed. The course farina 
consisted of 3.0% larger than 840 microns (over a No. 20 standard sieve), 
48% between 595 and 840 microns (over a No. 30 standard sieve), 42.5% 
between 420 and 595 microns (over a No. 40 standard sieve), 4% between 250 
and 420 microns (over a No. 60 standard sieve) and 2.5% smaller than 250 
microns (through a No. 60 standard sieve). 
Of the coarse farina produced, 38.16% was extracted from purifier No. 1, 
35.99% was extracted from purifier No. 2, and 25.85 was extracted from 
purifier No. 3. Of the coarse extracted from purifier No. 1, 10% was 
greater than 840 microns, 66% was between 595 and 840 microns, 23% was 
between 420 and 595 Microns, and 0.5% was between 250 and 420 microns. The 
coarse extracted from purifier No. 2 consisted of 4% over 840 microns, 53% 
between 595 and 840 microns, 38.5% between 420 and 595 microns, and 3% 
between 250 and 420 microns. The coarse farina from purifier No. 3 
consisted of a trace larger than 840 microns, 24.5% between 595 and 840 
microns, 72% between 420 and 595 microns, and 4% between 250 and 420 
microns. 
EXAMPLE #4 
In another milling run hard winter wheat having a moisture content of 12.6% 
was given a long first temper to raise the moisture content to 13.8% and a 
short second temper to raise the moisture content to 15.4%. The wheat was 
then milled by the system disclosed in FIG. 3. The break rolls were 
adjusted to give the following break release values with respect to a No. 
20 standard sieve: 1st break -- 10%, 2nd break -- 19.5%, 3rd break -- 18%, 
4th break -- 34%, 5th break -- 49.5%, 6th break -- 61.0%. The output of 
the milling run was composed of 26.69% coarse farina, 31.49% flour, 6.94% 
clear flour, and 34.88% feed. The coarse farina included 1.5% over 840 
microns, 48% between 595 and 840 microns, 45% between 420 and 595 microns, 
4% between 250 and 420 microns, and 1.5% smaller than 250 microns. 
The percentage of the total coarse farina which was extracted from each of 
the purifiers was as follows: 19.01% from purifier #1; 50.65% from 
purifier #2; and 30.34% from purifier #3. The coarse farina extracted from 
purifier #1 was composed of 3% over 840 microns, 62% between 595 and 840 
microns, 32.5% between 420 and 595 microns, and 2% between 250 and 420 
microns. The farina particles from purifier #2 included 2.5% over 840 
microns, 60% between 595 and 840 microns, 31% between 420 and 595 microns, 
and 3.5% between 250 and 420 microns. The distribution of farina particles 
from purifier #3 consisted of 12.5% between 595 and 840 microns, 77.5% 
between 420 and 595 microns, and 10% between 250 and 420 microns. 
It will be seen from the foregoing that the present invention provides a 
process for milling wheat which provides a high proportion of coarse 
farina in the No. 20 to No. 40 U.S. standard sieve size.