The document summarizes the key steps in wheat milling: storage and blending of wheat, cleaning, conditioning by adjusting moisture levels, milling through processes like breaking, sieving, grading, purification, sizing, and reduction using roller mills. The objective is to separate the bran and germ from the endosperm to produce flour while minimizing contamination. Conditioning prepares the wheat for grinding by making the bran elastic and endosperm soft. Milling gradually separates the parts using rollers and sieves to produce flour and byproducts like bran and germ.

1. WHEAT MILLING

2. Wheat
Processing/Milling
 Storage
 Blending
 Cleaning
 Conditioning
 Milling

3. Storage
o It is important to preserve the quality and economic value of wheat
as it moves from the field into storage at the processing mill.
o If not properly stored, insects, moisture damage, or other
conditions may cause losses.
o Moisture and temperature are two main factors that influence
the development of grain molds and insects in stored wheat
o Wheat should be carefully dried to a moisture below 12.5%, a
level regarded as safe for storage.

4. Blending
o Usually a mill is designed for milling wheat of a certain class and physical
characteristics.
o However, a mill designed for one class of wheat (e.g., hard or soft) does
not ensure uniformity of end-product quality.
o Wheat arriving at the mill usually varies in quality and requires blending to
deliver a "wheat mix" of uniform qualities
o Wheat blending is the initial step in providing bakers with uniform flour.
o Accordingly, mills prepare "wheat mixes" of certain protein levels or other
quality characteristics.
o There are different methods of blending. Some millers blend wheat directly
in storage bins, others during grinding.

5. Cleaning
o Intensive cleaning of the wheat before milling ensures that bacteria, mold,
undesired seeds, infested kernels, shrunken and broken kernels, and other
foreign materials do not contaminate the mill products or damage the
equipment.
o Aspirator: The aspirator sucks up foreign matter which is lighter than the
wheat and removes it.
o Disc separator : it moves the wheat over a series of disks with
indentations that collect objects the size of a grain of wheat.
o Scourer : Scrape off dirt and hair by vigorous rubbing action of beaters
and polish the outer surface
o Magnetic separator : With the help of magnets it removes small pieces of
metals.
o Washer stoner : High speed rotors spin the wheat in the water bath.
excess water is thrown out by centrifugal force. stones drop to the bottom
and are removed. Lighter material float off leaving only the clean wheat

6. Conditioning
o Increasing the MC From 12.55 to 16-20 %
o Conditioning, a process that adjusts the moisture level of wheat
before milling, achieves a mellow endosperm and tough bran.
o Bran that absorbs proper amounts of moisture becomes elastic
and will not splinter during grinding to contaminate the flour
with fine particles.
o Mellow endosperm breaks off the bran during grinding, and
less power is required to reduce large pure particles to flour.

7. Cont…
o Another objective of wheat conditioning is to equalize the hardness of
the different kernels in the wheat mix before processing.
o Different methods could be used to condition the wheat before milling.
 Heating wheat in water/ Hot conditioning (Difficult to control the
moisture) Warm conditioning involves soaking the wheat in
water at a temperature (46°C) for 60-90 minutes and letting it
rest for one day
 Cold Conditioning (The soaking time ranges from 12 to 16 hours
until grains are permeated with moisture.)
 Application of live steam of H2O
 Intensive mixing of wheat and water
 The current method most frequently used is termed
“TEMPERING.”
 In tempering, a calculated amount of water is added to the
wheat, which is then intensively mixed in a continuous mixer
in order to maximize a uniform dispersion of the water on all
wheat kernels.

8. Milling
o Wheat flour milling is a process that consists of controlled
breaking, reduction, and separation.
o The objective during milling is to separate the branny cover and
germ of the wheat kernel from the endosperm.
o Breaking : Rollers crush the seeds into smaller fractions
o Wet milling - It is a maceration process in which complete
dissociation of the endosperm cell contents with the release of the
starch granules from the protein network. it is done by steeping
wheat for 10 days.
o Dry milling - It is a fractionating process in this endosperm merely
fragmented into cells. it is done by soaking wheat in water for 8-12
hrs.

9. Cont..
o The flour-milling process consists of numerous stages and
sub-processes:
 Breaking
 Sieving
 Grading/Re-dusting
 Purification
 Sizing
 Reduction
o Materials at different stages of the milling process differ in
quality or in the ratio of bran to endosperm and particle size.

10. Breaking
o The initial grinding stages in the milling process are named “breaks”
o Breaking of the wheat kernel is affected by corrugated cast steel rolls that gradually
separate the endosperm, bran, and germ.
o The breaks are used in the grinding steps of the milling process to separate the bran,
germ, and endosperm from each other.
Stage 1: The grist is passed through a series of fluted 'break' rolls rotating at different
speeds, they do not crush the wheat but split it open, separating the white endosperm
Stage 2: The fragments of wheat grain are separated by a complex arrangement
of sieves. stages 1 and 2 are repeated until the flour, bran and wheat germ are
completely separated.
o White endosperm particles or chunks of endosperm are channeled to a series of
smooth 'REDUCTION' ROLLS for final milling into white flour.
'REDUCTION' ROLLS
Reduction of particle size of semolina into fine flour by passing it through a pair
of smooth rolls.

11. The rolls are paired & rotate inward against each
other, moving at different speeds Just one pass
through the corrugated "first break" rolls begins the
separation of bran, endosperm and germ
In a typical mill, there may be up to 4 break rolls
and 12 reduction rolls, leading to 16 flour streams, a
bran stream, a germ stream and a bran/flour/germ
wheat feed stream
Milling of Kernel (Breaking in operation)

12. Sieving
o Particles of the grounded material are separated
according to size.
o Available in two, four, six, and eight sections.
o The sieves in a sifter section are divided into groups.
o At the top of the section, there are usually coarser sieves
separating the larger material that flows out of the sifter
through a side channel.
o 6 different sizes of particles may come from a single
sifter, including some flour with each sifting. Larger
particles are shaken off from the top, or "scalped,"
leaving the finer flour to sift to the bottom.

13. o Graders are sifter sections used to handle mainly materials
directed from the breaks.
o A blend of medium-sized and fine sizing's as well as middling's
is directed to the graders.
o Materials from primary breaks are directed to the first grader.
o Materials from secondary breaks (e.g., the third or fourth) are
directed to second or third graders.
o The main objective of the grader is to remove the remaining
flour from the middling's and to separate the granular
material to narrow particle size ranges for better efficiency
in the purifiers.
Grading

14. Purification
o Coarse endosperm chunks (SEMOLINA) and finer endosperm particles
(MIDDLINGS) are separated in the purifier and sent to the reduction
rolls.
o Purifier's main purpose is to separate particles into fractions of
pure endosperm and achieved by using sieves and air currents.
o Any remaining fine bran particles may be removed by the purifier using
a combination or sieves and air currents.
o Purifiers classify the material into several fractions according to size,
shape, and specific gravity.
o Endosperm particles, free from bran and germ are guided to smooth
rolls, where they are ground into flour.
o Particles to which bran and outer layers of kernel are still attached are
delivered to different pairs of rolls ("sizings") for careful reduction and
separation of the bran.

15. Sizing
o The material at each of the sizing stages is a mixture of
particles close in size range, some pure endosperm, and others
still with attached bran.
o The objective of the sizing stages is to reduce the particle
size and during reduction, to separate the still attached
bran from the endosperm.
o Material from the sizing stages can be diverted to purifiers, for
final reduction, or to flour as a final product.

16. Reduction
o Coarse and fine pure endosperm particles from breaks,
purifiers, sizings, and reductions in the mill are reduced to flour
on smooth rolls.
o The number of reduction stages depends on the flour yield
required.

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