Modern Rice Milling

1
Modern Rice Milling

• Agricultural Engineering Unit
• International Rice Research Institute

2
The Aim of Rice Milling

• To attain the highest yield of white rice
• With the best quality
• Remove least amount of hull and bran
• Minimum brokens
• Little foreign matter

3
The Process
4
Paddy Intake

• Quality input quality output
• Garbage in garbage out!

5
Paddy Cleaning

• After harvest, foreign matter can be as high as
  5-10

6
Hulling the Paddy

• Husks account for 20 of paddy weight
• Rubber roller huskers are widely used

Rice Huller
Rollers
7
Rice Hull Storage
8
Paddy Separation

• Removal of paddy and husk from brown rice
• Sieve or gravity separator

Paddy separator
Separator tray
9
De-stoning

• Paddy will contain small stones and debris
• Debris must be removed before polishing

De-stoner
10
Polishing

• Removes bran layer to produce white rice.
• Amount of bran removed (usually 8-12) is called
  Milling Degree.

11
Sifting or Separation of White Rice

• After polishing, white rice contains
• Head rice
• Large brokens
• Small brokens
• The white rice is separated using a Sifter

12
Grading or Length Separation

• After polishing, white rice contains
• Head rice (75 of whole kernel is present)
• Large brokens
• Small brokens

13
Rice Mixing

• An efficient rice mill will produce
• 50 head rice (whole kernels)
• 5-15 large broken and
• 5-15 small broken kernels
• Depending on the countrys standards, rice grades
  in the market will contain from 5-25 broken
  kernels.

14
Rice Mixing
Large brokens
Small brokens
Whole kernels
15
Mist Polishing

• Adds luster, or polished appearance.

16
Rice Weighing

• Rice is normally sold in 50 kg sacks which must
  be accurately weighed and labeled.