This presentation is about wet milling procedure and by products produced after wet milling.

1. Wet Milling of Corn
Presented By: Faisal Aziz
Presented To : Dr. Haseeb

2. Definition
• Wet-milling is a process in which feed material is steeped in water,
with or without sulfur dioxide, to soften the seed kernel in order to
help separate the kernel's various components.

3. Corn
Starch Corn Oil Protein Fiber
Moisture

5. 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

6. Germ
Steeping
Receipt
FiberStorage
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

7. 1. Receipt, inspection and storage
 On the arrival of corn moisture is checked and should be below 15%
 After all formalities, vehicle is allowed to go on unloading area
 Corn is dumped on the dumping pit, from here bucket elevator are
used to transfer the grain storage facilities i.e. silos

8. 2. Cleaning
 Unwanted particles accounts a small portions but cleaning is necessary
prior to processing
 Mostly passed through screeners and scalpers to remove over sized
particles i.e. corn cobs, husk etc
 Destoner is also used which classify particles according to their size also
removes heavier objects
 For removing chaff and dust pressurized air may be used
 Beside all this process magnetic separation is also done

9. 3. Steeping
 The purpose of steeping is to soften the corn kernels for subsequent
processing
 The kernels are added to large tanks of water, held at 125˚F/ 52˚C
SO2 is added to optimize pH, for prevention of bacterial growth
 Soaking time is 28-48 hours, corn size becomes almost double in size
 Acidity helps in releasing of gluten and starch
 When one steeping is complete, tank is emptied
 Fresh corn is added again but fresh water is not added every time
 Water from steeping tank goes to small tanks, when fresh corn is added
then this water is added to the tank
Fresh water is added to those tanks which have steeped excessively

10. 3. Germ Separation
 Steeped corns are sent to degerminating mil, which tear the
kernels apart to free the germ and about half of the starch and
gluten
 The resultant slurry is pumped through hydro cyclones to
extract the germ from the mixture of fiber, starch, and gluten
 The corn germ, which contains about 85% of the corn’s oil, is
removed from the slurry and washed
It is then dried and sold for further processing to recover the oil

11. 4. Fiber Separation
The fiber, starch, and gluten slurry is pumped to an impact mill,
where further grinding completely frees the bran-rich fiber from
the starch and gluten
The fiber is then physically separated from the gluten and
starch using a series of fixed, concave screens. The collected
fiber is washed with water and screened again to remove any
additional starch and gluten
 The remaining starch and gluten mixture is known as mill
starch

12. 5. Starch Separation
 The mill starch is pumped to a centrifuge where the low-
density gluten is spun out of the mixture, leaving a starch-rich
stream ready for further processing
 The starch is washed 8 to 14 times in water, re-diluted, and
passed through hydro cyclones to completely remove any
remaining gluten
 The starch is over 99.5 percent pure at this point and can be
used to produce ethanol

13. 6. Saccharification, Fermentation,
Distillation, and Dehydration
 The starch suspension is treated with acid and enzymes to
break down the starch into dextrin, which are further broken
down into glucose
 Yeast fermentation then converts the glucose into ethanol
 The ethanol is distilled to concentrate the alcohol content
 Remaining water is removed via molecular sieve, and the
product is denatured prior to shipment

14. By Product Processing

15. 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

16. 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