Parboiled rice is paddy that has been soaked, steamed and dried before it is milled. Those three steps happen while the husk is still on the grain, and they set most of what a buyer later judges in the bag: colour, hardness, broken percentage and how the rice cooks. This guide follows the sequence used at the SONIK mill in Ghentugachhi, Chakdaha, and explains what each stage controls.
Key takeaways
- Parboiling is done on paddy, not on milled rice: soak, steam and dry first, then husk and mill.
- Soaking and steaming set the colour and hardness. Heavier treatment gives a darker, harder grain.
- Drying decides how much of that hardness survives. Fast or uneven drying cracks the grain and raises brokens.
- “Parboiled” on its own is not a specification. State the colour range, maximum brokens, moisture, polish and whether the rice should be colour sorted.
In this guide
The sequence at a glance
The mill runs twelve stages from paddy intake to dispatch. The table shows what happens at each one and what it changes in the rice you receive. Equipment details are on the Process & Infrastructure page.
| Stage | What happens | What it affects for the buyer |
|---|---|---|
| 1. Receiving | Paddy is weighed in over the weighbridge. | Quantity records for each intake. |
| 2. Lot identification | Each intake is identified lot-wise. | Traceability through processing. |
| 3. Incoming inspection | Paddy is assessed on arrival before it goes into process. | The paddy’s own quality sets the ceiling for the finished rice. |
| 4. Pre-cleaning | Straw, dust and foreign matter are separated. | Fewer impurities left for later stages to remove. |
| 5. Soaking | Paddy takes up water through the husk on the INDUSS system. | How evenly the grain parboils; colour. |
| 6. Steaming | Heat gelatinises the starch inside the grain. | Hardness, translucency, colour depth. |
| 7. Controlled drying | Moisture is brought back down to milling condition. | Cracked grains and broken percentage. |
| 8. Husking and milling | The husk is removed on the Satake line. | Husk is used as boiler fuel. |
| 9. Whitening and polishing | Bran layers are removed to the required degree. | Whiteness, gloss and surface bran. |
| 10. Grading and colour sorting | Size grading, then optical colour sorting. | Broken percentage and visual uniformity. |
| 11. Final checks and packing | Milled rice is checked, then packed to the confirmed requirement. | Packing and marking for your order. |
| 12. Storage and dispatch | Stored and loaded against confirmed orders. | Delivery schedule. |
Intake, inspection and pre-cleaning
Every intake of paddy is weighed over the mill weighbridge, identified lot-wise and assessed before it is taken into process. Parboiling cannot improve paddy that arrives immature, mixed or damaged, so this is where finished quality is first decided.
Pre-cleaning then removes straw, dust and other foreign matter. Cleaning before soaking matters more than it sounds: anything left in the paddy takes up water and heat, and what survives to the end of the line has to be caught by the colour sorter.
Soaking
Cleaned paddy is soaked on the INDUSS parboiling system. The grain takes up water through the intact husk until the kernel is evenly hydrated. Traditional parboiling soaked paddy overnight in water at ambient temperature; the hot-water soak used in modern plants is held below the temperature at which starch gelatinises and takes a few hours instead (FAO, Rice in human nutrition).
Soaking time and water temperature are the first variables that move the finished colour. Uneven soaking shows up later as grains with a chalky white core, which FAO describes as a sign of incomplete parboiling. Sound paddy and clean soak water also matter: FAO notes that recycling soak water can make existing contamination worse.
Steaming
Soaked paddy is steamed. The heat gelatinises the starch inside the kernel while the husk holds the grain together. When it cools and dries, the kernel is harder and more translucent than raw rice. Done properly, parboiling substantially reduces the number of grains that break in milling (Buggenhout and others, 2013).
Steaming also changes colour and nutrition. Parboiled rice ranges from cream to yellow depending on how intense the heat treatment is, and water-soluble vitamins move from the bran layers into the kernel, so more of them remain after milling (FAO). A lighter parboil gives a paler grain; a heavier one gives a harder, darker grain.
Drying
Steamed paddy is far too wet to mill, so it is dried back to milling condition under control. Drying is where much of the yield advantage of parboiling is kept or lost. FAO notes that parboiled grains can fissure during drying, especially as moisture falls below about 18%, and a fissured grain breaks in the huller or the whitener.
Final moisture also matters for storage. FAO gives about 14% as generally safe for storage in tropical conditions, and the Codex standard for rice sets 15% as the maximum. If your market or your storage needs a tighter limit, put it in the specification.
Husking, whitening and polishing
Only now does the paddy reach the Satake milling line. The husk is removed first; it goes to the boiler as fuel. Whitening then removes the bran layers to the degree of milling required, and polishing finishes the surface. The degree of milling changes whiteness and gloss, and how much bran is left on the grain.
Parboiled grain is harder than raw grain, so it needs more milling pressure, and its bran tends to clump (FAO). The bran from parboiled paddy is also richer in oil than raw bran, which is one reason it is sold separately as rice bran.
Grading, colour sorting and packing
Milled rice is size graded to separate whole grains from broken pieces, then passed through an optical colour sorter to remove discoloured grains and remaining foreign matter. Both steps run on Satake equipment. The broken fractions and the sorter’s rejects become products of their own, such as grader rice, khud and rice cuts and rejection rice. Our guide to Sortex, grading and polishing explains each step.
Milled rice is checked before packing, and packing and marking are checked against the requirement confirmed for the order. See rice packing requirements for the choices involved.
What to specify
Because soaking, steaming and drying all move colour and hardness, ask for parboiled rice by its result rather than the word alone. Include:
- Variety, for example Swarna, Miniket or Ratna (see products).
- Colour range your market accepts, ideally against an approved sample.
- Maximum broken percentage and maximum moisture.
- Finish: degree of polish (silky or non-silky) and whether the rice should be colour sorted.
- Packing, quantity and destination, so the quotation is complete.
Our bulk order checklist sets this out in a form you can copy. The specification is confirmed in writing before production is scheduled.
Frequently asked questions
Is parboiled rice the same as “boiled rice”?
Yes. In Bengal the trade often calls parboiled rice siddha or boiled rice, and raw rice atap rice. Both describe what happens to the paddy before milling, not how the rice is cooked at home.
Why does parboiled rice take longer to cook?
The gelatinised, harder kernel takes up water more slowly. FAO notes that parboiled rice takes longer to cook than raw rice and that soaking before cooking shortens the time. The cooked grains are firmer and less sticky.
Can the same variety be supplied raw or parboiled?
Often, yes. SONIK lists both Swarna parboiled rice and Swarna raw rice. Our comparison of parboiled and raw rice explains how to choose.
Can I see a sample before ordering?
Samples are reviewed individually where requested. Mention it in your bulk enquiry, and agree the approved sample as the reference for the order.
Sources
- FAO (1993). Rice in human nutrition, chapter 5: Rice post-harvest processing, parboiling and home preparation.
- Buggenhout, J., Brijs, K., Celus, I. and Delcour, J.A. (2013). The breakage susceptibility of raw and parboiled rice: a review. Journal of Food Engineering 117(3), 304–315.
- Codex Alimentarius. Standard for Rice (CXS 198-1995).
- SONIK INDUSTRIES LLP. Process & Infrastructure.
