The document discusses the milling process of corn. It begins with an overview of corn composition and uses. It then describes the two main milling processes - dry milling and wet milling. Dry milling produces less refined starches for foods and animal feed. Wet milling is more complex but extracts the highest value from corn through separation of the germ, fiber, gluten, and starch. The key steps of each process and uses of byproducts like corn oil, gluten meal, and steep liquor are outlined.

1. Milling of Corn

2. Corn (Maize) is one of the most
versatile emerging crops having
wider adaptability under varied agro-
climatic conditions. Globally, maize is
known as the queen of cereals
because it has the highest genetic
yield potential among the cereals.

3. As a cereal, maize is used as ingredient in
food preparation; it is feed for poultry and
livestock; it is feedstock for biofuel
(ethanol); it is used as raw material in
distilleries; and for starch production
because of its high starch content.
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4. STRUCTURE AND COMPOSITION
C o m p o n e n t s o f Yellow Dent Corn
Starch 61.0 %
Corn Oil 3.8 %
Protein 8.0 %
Fiber 11.2 %
Moisture 16.0 %
The mature corn is composed of four major parts:
Endosperm 82%
Germ 12%
Pericarp 5%
Tip cap 1%

6. Corn Properties
Approximately 20% of the Annual Corn Harvest is used to
produce products such as Sweeteners, Starches, Oils, Ethanol
and Animal Feeds.
The remainder quantity is fed to Livestock, Poultry & Fish.
Corn’s components are Starch (72%), Corn Oil (4.3 %), Protein
(9.5%) and Fiber (9.5%).
Approximately 16% of the Corn-Kernel’s weight is moisture.

7. Corn
Starch Corn Oil Protein Fiber
Moisture

8. Why Need of Corn
A high potential business
Contributes in food security
Contains a lot of nutrients i.e.
Folate, fiber etc
Daily life contains maize directly
or indirectly i.e. a huge proportion
maize is used in feeding livestock
A list of by products are produced

9. Types of Corn
Corn, Zea Mays, is grown in most countries throughout the world
and it require Warmer-Climate.
Following are different kinds of corn,
1) DENT CORN
2) FLINT CORN
3) WAXY CORN
4) SWEET CORN
5) POP CORN
6) INDIAN CORN
7) FLOUR CORN

10. Dent Corn
It contains both hard and soft starch and become indented
at maturity, a major crop used to make food, animal feed,
and industrial products and starch production

11. Flint Corn
It has hard, horny, rounded, or short and flat kernels with the
Soft and starchy endosperm. It is similar to Dent and is used
for the Same Purposes. Most of it is grown in South America.

12. Waxy Corn
WAXY corn is a corn variety with grains that have a waxy
appearance when cut, and that contains only branched-chain
starch. It is grown to make special starches for thickening foods.

13. Sweet Corn
It is grown in many horticultural varieties, and is considered specific
mutation of dent corn, it contain high sugar level at Milk-Stage
when suitable for Table use.

14. Indian Corn
This corn has white, red, purple, brown, or multi-colored kernels. It
was the original corn grown by the Indians. And it is known by the
scientific name Zea Mays.

15. Pop Corn
It has small ears and rounded kernels which on
exposure to dry heat, are popped or everted by the
expulsion of the contained moisture, and form a white
starchy mass many times the size of the original kernel.

16. Flour Corn
It is composed almost entirely of soft starch.
The USA grows small amounts of blue flour corn to make tortillas,
chips, and baked goods.

17. Milling of Corn
The basis of the maize milling process is the separation of the
maize kernel into its different parts.
Starch has been produced from corn for many years by two
general procedures, namely
1. Dry milling
2. Wetmilling
Both dry and wet milling procedures accomplish separation of
the germ from which corn oil is obtained and removal of the hull
which constitutes the majority of the high fiber portion.

18. Dry Milling
Dry milling
starches.
refining processes provide less highly refined
dry-milled products find use in many applications, such as in
cereals, snack foods, pancake mixes, cookies, biscuits and in the
brewing industry.
It is a major object of this invention to provide a process for
producing high purity starch from corn which eliminates the long
steeping times normally required for wet milling production of
starch.

19. The corn dry milling process is a less versatile, less capital
intensive process that focuses
primarily on the production of grain ethanol.
The products of a traditional dry grind ethanol facility are fuel
mainly ethanol and Dried
Grains (DDG), a lowvalue animal feed product.
Distillers

20. CORN DRY MILLING
Dry milling process consists of the following steps:
Cleaning
Conditioning
Degerming
Drying
Cooling
Grading
Grinding

21. Cleaning
When corn is received at the mill, it is cleaned by both dry
and wet process. Cleaning steps are sieving, separating
particles by shape and density and removing ferromagnetic
metals by permanent magnets.
Conditioning
The cleaned corn is conditioned, which basically means that
water is added and the moisture allowed to equilibrate
within the kernels.
A moisture content of 21% is considered optimal.

22. Degermination
The purpose of degerming is to remove hull, tip cap and
germ and leave the endosprum into large grits.
Drying
The degermer product are to be dried to 15-18% moisture
content for proper grinding and sifting. Drying is performed
by conventional rotary steam tube dryers.
Cooling
Counter-flow or cross flow rotary cooler can be used for
cooling the dried products.

23. Grading
Recovery of various primary products is the next step. The
through-stock is sifted or classified by particle size and enters
into a conventional long reduction system having the function
of removing bran and germ while releasing a maximum
amount of clean large grits.
Milling
The milling operation consists of the steps of
grinding, sifting, classifying, purifying, aspirating and in some
case, final drying.
The normal flow is through break rolls and then to sifters. The
break rolls are followed by reduction roll which grind the
endosperm to the desired particle size.

24. Wet-Milling Process……
This process is expensive as compare to Dry-
Milling, and it requires more time, space, energy
and waste treatment.
It is designed to extract highest use and value of
product low water consumption.
The Corn-Wet Milling process is the industry
standard, implemented in more than 170 plants
around the world.

25. Principle
The corn is steeped in an aqueous solution of Sulphur-Dioxide
at a temperature of about 120° F or higher for extended periods of
anywhere from 24 to 60 hours.
The steep water is collected and concentrated for the recovery
therefrom of soluble components.
Softened corn is subjected to a series of grinding and separating
operations to separate the corn kernel components, namely the
Germ
Hull
Endosperm

26. Principle……
The mixture contain starch granules imbedded
in a Proteinaceous matrix (gluten).
For highly refined starch, additional separating
procedures are necessary to separate the starch
from Protein (Gluten).
The remaining components then screened to
remove fibre.
In Centrifugation the mixture is separated to
lighter Gluten and Heavier Starch.

27. Steps……
Following are the steps
1) CLEANING
2) STEEPING & SO2 ADDITION
3) GERM SEPARATION
4) FINE GRINDING & SCREENING
5) FIBRE DRYING

28. Steps……
6) GLUTEN DRYING
7) STARCH REFINING
8) STARCH DRYING
9) MODIFICATION

29. Cleaning……
The Dent-Corn is supplied in bulk.
First, we clean the shelled corn to ensure
that they are free from dust and foreign
bodies.
The cleaning is normally done twice
before wet processing.

30. Steeping……
The corn is soaked in Hot-Water, called
Steep-Water, at 50˚C for between 20
and 30 hours, during which time it
doubles in size.
The steeping is carried out in a
continuous counter-current process.
The moisture level is increased from
15% to 45%.

31. SO2……
Sulphur dioxide is added to the water to
prevent excessive bacterial growth like
bacteria, moulds, fungi and yeast.
It enhance the growth of favorable micro-
organism like Lacto-Bacillus.

32. Water Evaporation……
The mixture is condensed on a multistage condenser
and water is evaporated.
Most organic acids which are formed during
fermentation are also volatile and evaporated.

33. Wet-Milling Process……
The Steep-Water is not wasted. We concentrate
it in an evaporator to capture nutrients, which
are used for animal feed and fermentation.

34. Germ Separation……
The kernels are broken-up to loos the
hull and break the bonds between
germ and endosperm.
Water is added to assist the wet
milling.
Corn germ contain 85% of corn oil.
Germs then dried to 4% moisture level
and oil can be extracted from germs.
Recovery Cyclone

35. Milling……

36. Fine Grinding……
The remaining slurry is then subjected to fine
grinding.
This process release Starch and Gluten from
fibre.
The slurry flows over fixed concave screens
which catch the fibre.
But allow the starch and gluten to pass through.

37. Corn Fibre……
The collected fibre is dried for use in animal
feed.
Corn-Fibre

38. Starch-Gluten Separation……
The starch-gluten suspension passes
through a centrifuge where the gluten,
which is less dense than starch, is easily
spun out.
Gluten is then dried to 10% moisture and
after hammering and processing it is sold
as 60% Protein.

39. Starch Refining……
The purified starch milk is discharged to a peeler
centrifuge for dewatering.
The starch, which still has a small percentage of
protein remaining, is washed to remove the last
traces of protein and leave a 99.5% pure starch.
Starch is among the purest of all agricultural
products and purity makes it competitive.

40. Drying……
Starch is subjected to Flash Dryer and moisture level is
reduced up to 12-13%.
Before delivery the starch is screened on a fine sieve for
impurities.

41. Modification……
The starch can either be dried and sold as corn
starch, or it can be modified to turn into other
products, such as corn sweeteners, corn syrups,
dextrose and fructose.
Many techniques are applies for modification for
example
1. ph
2. Temperature
3. Additives addition

42. Germ
Steeping
Receipt
Fiber
Storage
Cleaning
Steeped
corn
Steeped water
Hydro cyclones
Degermination
Slurry
Fiber,
starch,
gluten
Animal Feed
Evaporation Corn steep liquor Corn Gluten Meal
Oil Extraction
Residues
Impact Mill
Starches &
Gluten
Centrifugation
Gluten Starch
Ethanol
Production

43. By Product Processing

44. The major products to be produced in
the plant are:
1. Maize/ Corn Starch Sorbitol & Dextrose
2. Corn Flakes
3. Dextrose Powder
4. Maize Processing (Glucose, Sorbitol and
Oil)

45. 5. Edible Corn Oil
6. Liquid Glucose From Maize
7. Corn Oil (Maize Oil)
8. Maize Processing Unit (Starch, Glucose,
Gluten, Germ, Fiber, Steep Water)
9. Sorbitol
10. Wet Milling

46. Corn steep liquor
The water drawn off the steeping process, known as
light steep water
Almost 6 percent of the original dry weight of the grain
35 to 40 percent is protein
Steep water is sent to an evaporator where
it is concentrated to 30 to 55 percent solid
Residues of fiber milling are added in it
Steep liquor is blended with fiber and corn gluten
feed is prepared
It can be sold wet or dried to extend shelf life

47. Corn Gluten Meal
The extracted gluten is a protein-rich
It is dried and sold for animal feed as gluten meal
Contains about 60 % protein in it
Used in poultry feed

48. Applications in Industry

49. Applications……
Being a pure renewable natural polymer, starch
has a multitude of applications.
Starch finds uses in fast food, sweets, sausages,
tablets, and paper industry.
Maize starch forms viscous, relatively short and
opaque paste which stiffen the gel.

50. Applications……
In 2004 more than fifty percent of starch was
converted to High Fructose Syrups (HFS).
In textile industry, starch is used in sizing to
strengthen fabric after it is bleached, dyed or
printed.
Now some By-Products of Maize-Processing are
given below

51. Steep Liquor……
Corn Steep Liquor also known as
condensed fermented corn.
It is a high protein ingredient.
It may be sold as 23% protein and
50% dry substance for cattle
feeds.
. Also it is a large source of biogas,
which is being used as fuel for
driers.

52. MAIZE GLUTEN……
Maize Gluten contains high protein
content and it is used as cattle and
poultry feeds.
Corn Gluten Meal is the dried
gluten from
concentration.
the gluten
A typical yield per ton corn is 50 kg
corn gluten meal with 60% protein.

53. MAIZE HUSK……
It contains starch, protein and fat
as minor components and mainly
consumed as cattle feed.

54. Starch Sweeteners……
Starch based sweeteners are other
class of products manufactured in
starch industries.
These are useful products.
Malto Dextrin: In syrup and powder
form used in food, baby food and
medical preparations as a non-sweet,
nutritive agent.

55. Liquid Glucose: Widely used in
the confectionary bakery, jam,
canning and leather industries.
Liquid Dextrose: In
fermentation industries for the
manufacture
monohydrates,
Sorbitol syrups.
of dextrose
fructose and

56. Applications……
High Maltose Syrup:
As a malt replacement in brewing industry, in
confectionary for Candy making.

57. Applications……
Liquid Sorbitol:
It is hydrogenated dextrose
syrup not having any reducing sugars
widely used by tooth paste,
pharmaceuticals, cosmetics and
tobacco industries.