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 chute Paddy Intake • Quality input = quality output • Garbage in = garbage out!

5. Rice pre-cleaner 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. Removed debris 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. Rotary Seiver 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. Rotary sieves 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 country’s standards, rice grades in the market will contain from 5-25% broken kernels.

14. Variable speed motors allow the mill operator to mix the appropriate amount of whole kernels with large and small brokens. Rice Mixing Small brokens Large brokens Whole kernels

15. Mist Polisher (Water) Mist Polishing • Adds luster, or polished appearance.

16. scales Bag filler and weighing Rice Weighing • Rice is normally sold in 50 kg sacks which must be accurately weighed and labeled.