The Cashew Cooking (Steaming) Process
Commercial plants "cook" raw cashew nuts by steaming them at 3–4 bar for 20–25 minutes before shelling — softening the shell and conditioning the caustic shell liquid so kernels cut cleanly.
In commercial cashew processing, "cooking" almost always means steaming: raw nuts are pressure-steamed at 3–4 bar for about 20–25 minutes before shelling. Steaming softens and loosens the hard shell so cutting blades split it cleanly, and it conditions the caustic cashew nut shell liquid (CNSL) so it is easier and safer to handle. The result is lower kernel breakage and higher whole-kernel yield. Steam is usually raised from the plant’s own shell-fired burner or a biomass boiler.
Steaming is the quietest stage on a cashew line and the one that decides most of the outcome. Get it right and the shell cuts cleanly, kernels come out whole and the CNSL stays where you can collect it. Get it wrong and every machine downstream is working against damaged material it cannot repair.
What happens during cooking
Reception and cleaning
raw nuts arrive, are cleaned of stones and field debris, and graded by size so a single steaming programme suits the whole batch.
Loading
nuts are charged into the steaming vessel — TTQ builds 300, 600, 800 and 1,000 kg batch units, the largest being a vertical steam tower with two wagons.
Steaming
saturated steam at 3–4 bar for 20–25 minutes. Heat and moisture soften the shell and loosen the kernel inside it. That is the cycle on the 600, 800 and 1,000 kg machines; the 300 kg batch design runs 40–60 minutes.
Cooling and rest
nuts come out and are allowed to equalise for 12–24 hours before cutting. Cutting a nut straight out of the steamer gives poorer results than letting it stabilise, and the rest period is free — it costs floor space, not money.
To shelling
the shell is now pliable enough to cut rather than shatter.
Why it matters more than it looks
An unsteamed or under-steamed shell shatters when the blade meets it, and the fragments take kernel with them. An over-steamed nut has a soft kernel that marks and breaks in handling. The window between those two failures is what the equipment is for, and holding it consistently across a batch is what separates a good steamer from a cheap one.
What optimised steaming is worth
| Aspect | Without optimised cooking | With optimised steaming | Effect on profitability |
|---|---|---|---|
| Kernel recovery | 20% | 30% | +50% yield value, about $200 per tonne |
| Breakage rate | 15–20% | Under 3% | +15% premium kernels |
| Processing time | 10 hours per tonne | 6–7 hours per tonne | +40% throughput |
| Waste | High, around 10% | Low, around 3% | Around $30,000 a year saved |
| CNSL revenue | Minimal | $150 per tonne | +10% total income |
Illustrative model, not a quotation or a guarantee — these are the figures the equipment has to justify, on a one-tonne-per-batch basis at indicative kernel and CNSL market prices. Your own numbers will move with RCN cost, grade mix and local energy prices. The largest single line is kernel recovery: the gap between 20% and 30% dwarfs everything else on this table.
How it is done regionally
| Region | Method | Breakage | Uniformity | Profitability gain |
|---|---|---|---|---|
| India | Drum or boiler steaming | 5–8% | High — about 95% uniformity | +20% |
| Africa | Open boiling or steaming | 10–15% | Medium — variable | +15% |
| Brazil | Pressure steaming | 4–6% | High, with an organic focus | +25% |
Reported regional practice, for comparison — the method is what differs, not the physics. TTQ equipment works to one basis regardless of region: 3–4 bar for 20–25 minutes. The African figures are the upgrade opportunity, not a criticism: open boiling is what is available, and moving to controlled steaming is the single highest-return equipment change on that continent.
India (725,000 MT in 2025)
drum steaming and boiler systems dominate, with well-developed operating knowledge and high batch uniformity feeding a strong export trade.
Africa (about 60% of global production; Côte d’Ivoire alone 1.15 million MT)
open boiling remains common, which is why breakage runs 10–15% and consistency varies. Controlled steaming equipment typically pays back faster here than anywhere else.
Brazil (135,000 MT in 2025)
a hybrid of traditional roasting and pressure steaming, with a strong organic and premium market focus that rewards low breakage.
The steam boiler side of it
Steam quality
saturated steam at a stable pressure. Fluctuating supply gives uneven conditioning within a single batch.
Capacity sizing
the boiler serves steaming, drying and often humidification. Size it on total simultaneous demand, not on the steamer alone.
Fuel
cashew shell from your own shelling line is the obvious fuel and closes the loop. Shell-fired boilers need handling and storage but remove a purchased fuel line entirely.
Safety and certification
pressure vessels carry real risk. Insist on proper certification and safety interlocks, not just a pressure gauge.
Batch scheduling
a 500 kg/h shelling line typically needs 2–3 batch steaming units working in rotation so the cutter never waits.
TTQ builds steaming systems, shell-fired boilers and the shelling lines they feed. Capacity figures are quoted per 8-hour shift. See cashew steaming machine for the equipment and cashew shell burner for closing the fuel loop with your own shell.
Why cook (steam) before shelling
- Softens the shell for a clean, low-breakage cut
- Conditions the caustic CNSL for safer handling
- Raises whole-kernel yield
The steaming machine runs timed pressure cycles; heat typically comes from the shell burner.
Some older methods roast or drum-roast raw nuts in shell instead of steaming; steaming is the standard for modern, high-yield lines.
The process, drawn
One steaming batch, start to cutter
The quietest stage on the line and the one that decides most of the outcome.
Every model runs the same 20–25 minutes at 3–4 bar, on boiler steam. The 300 kg batch design is the exception on both counts: 40–60 minutes, and it can be heated by wood, gas, electricity or a burner instead. The rest period costs floor space, not money.
Frequently asked questions
Why are cashews cooked before shelling?
How long are cashews steamed?
Talk to a cashew engineer
Tell us your target capacity, grades and location — we’ll come back with a costed proposal.