Cashew Nut Processing: The Complete Process
Raw nut to premium kernel, stage by stage
Cashew nut processing converts raw in-shell nuts into clean, graded kernels through eight core stages — calibration, steaming, shelling, borma drying, humidification, peeling, grading and colour sorting, and packing with metal detection.
Cashew nut processing is the sequence that turns raw cashew nuts (RCN) into edible, export-ready kernels. The eight core stages are calibrating raw nuts by size, steaming at 3–4 bar to soften the shell, shelling (cutting) to release the kernel, borma drying to take the kernel down to 3–4% so the testa turns brittle, humidification back to about 5–6% at the surface, peeling off the testa, grading and colour-sorting the kernels, and packing with metal detection. Modern plants run these as one PLC-automated line to maximise whole-kernel yield and minimise labour.
Conditioning: roasting vs steaming
| Roasting | Steaming | |
|---|---|---|
| Method | Rotating drums, 180–200°C | High-pressure steam, 3–4 bar |
| Time | 8–12 minutes | 20–25 minutes |
| CNSL | Partially liquefies / burns off | Softens shell, does not fully remove CNSL |
| Common in | Many African processors | Most Asian facilities |
Both weaken the shell without damaging the kernel. Capacity decides batch vs continuous: a 500 kg/h line typically needs 2–3 batch steaming units working in rotation.
Shelling: how the machines differ
Cutting machines
the modern standard. Calibrated blades cut the shell at a precise depth: deep enough to penetrate the shell, shallow enough to miss the kernel. TTQ uses a dual-blade system making two cuts so the shell splits open and the kernel stays whole. The specification that matters is whole-kernel recovery, and good machines hold 85–90%.
Centrifugal shelling
spins nuts against a hard surface, cracking the shell by impact. Useful for specific nut sizes but generally higher breakage.
CNSL collection
shelling machines should capture the shell liquid rather than waste it. It has industrial uses in resins and friction materials, so collecting it offsets processing cost.
Raw-nut grading and drying, sized properly
- Grading — raw nut graders sort into five size grades, A+ to D, 500 kg/h for small operations up to 2,000+ kg/h industrial. Mixed sizes mean either under-processed large nuts or broken small ones.
- Borma drying — kernels leave shelling at 9–12% moisture and must reach 3–4% before peeling, on a 13–14 hour batch cycle in the borma oven. Under-dried kernels peel poorly; over-dried kernels turn brittle and break. Size the dryer to the day: a 300 kg/h shelling line over 8 hours needs roughly 2,000–2,500 kg of dryer capacity, which is a 2 T or 4.5 T chamber.
The humidification step — where processors separate
After borma drying to 3–4%, kernels move to the humidifier room — Stage 09, a separate chamber from the dryer, built on the same platform at half the fan power. Saturated steam raises surface moisture to 5–6% while the core stays at 3–4%; TTQ chambers run 5–6 hours on a 0.5 T batch, 5–7 hours at 1–1.5 T and 3–5 hours at 2–4.5 T. That moisture gradient softens the testa while keeping the kernel firm.
Timing matters enormously: peel within 2–4 hours of leaving the humidifier. Leave it too long and the moisture redistributes, losing the gradient. Rush it and the surface moisture has not penetrated enough.
TTQ works to an average of 35 kg/h per cutting head on Size A. A 10-head line therefore runs about 350 kg/h (410 kg/h on Size A+), and a 16-head line about 560 kg/h. Knife-configured machines run a little higher per station — a 16-knife machine reaches about 700 kg/h on Size A. Older published figures of 60–80 kg/h for a single head do not reflect this standard and have been corrected. All capacities are quoted per 8-hour shift.
The eight core stages
- Calibration — size raw nuts so they shell evenly
- Steaming — 3–4 bar for 20–25 min softens the shell for a clean cut
- Shelling / cutting — split the shell, release the kernel
- Borma drying — 13–14 h to 3–4%, which makes the testa brittle
- Humidification — surface back to 5–6% so the testa lets go
- Peeling — remove the skin, dry method
- Grading & colour sorting — W-grades, then optical defect removal
- Packing & metal detection — vacuum sealed, checked before dispatch
On this site borma always means the kernel drying oven, Stage 08 — the chamber that takes kernels down to 3–4%. Rewetting is a separate stage in a separate room (Stage 09, the humidifier). Some published sources use "borma" for the rewetting step instead; if you are comparing specifications between suppliers, check which stage the word is being applied to before comparing cycle times.
Manual, semi-automatic or fully automatic
The same eight stages can be run by hand, semi-automatically, or as a fully automatic plant. More automation means higher whole-kernel yield and lower labour per tonne.
Every machine on the line
Automatic Raw Cashew Nut Grading Machine
Size before you shell
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Cashew Nut Shelling Machine
Crack the shell, keep the kernel
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Cashew Nut Cutting Machine
Clean, consistent kernel separation
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Cashew Dryer Machine (Borma)
Controlled borma drying
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Cashew Peeling Machine
High whole-kernel yield, dry-peeled
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Cashew Grading & Sorting Machine
W180 to W450, sorted by size and colour
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Cashew Vacuum Packing Machine
Nitrogen-flush, export shelf life
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Cashew Vacuum Packing Machine
Nitrogen-flush, export shelf life
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Cashew Steaming Machine
Soften shells, protect kernels
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Automatic Cashew Shelling Machine
Fully automatic, minimal hands
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Cashew Scooping Machine
Extract the kernel, whole
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Cashew Kernel Humidification Chamber
Condition moisture for clean peeling
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Automatic Cashew Peeling Machine
Automatic dry-peeling at volume
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Cashew Pouch Packing Machine
How retail pouch packing works — and who supplies it
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Cashew Nut Roasting Machine
Even roast, edge to edge
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Cashew Sugar Coating Machine
Glaze, coat, candy
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Cashew Dicing Machine
Splits, pieces and dice
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Cashew Color Sorter
CCD optics catch every off-colour
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Cashew Metal Detector
Catch metal before it ships
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Cashew Moisture Meter
Know the moisture, hit the grade
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Cashew Shell Burner
Turn shell waste into heat
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Wood Chip Boiler
Biomass steam for the line
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Air Compressor
Clean air for every actuator
Open →The process, drawn
The eight core stages
Raw cashew nut in at one end, packed export kernel out at the other. Moisture is the thread: every stage either takes it out or puts a controlled amount back.
Capacities and cycles are Size A basis, per 8-hour shift. Stages 04 and 05 are separate machines in separate rooms — the borma oven dries, the humidifier puts moisture back.
The moisture ladder
Every number a cashew plant lives or dies by is a moisture number. Read left to right — this is the same journey as the eight stages, seen through water content.
Stages 03 and 04 look contradictory and are not. Drying makes the skin brittle; humidification softens only the outer surface so the skin lets go without the kernel softening with it.
Where the raw nut actually goes
One tonne of RCN leaves the plant as three streams, not one. The kernel pays the wages; the shell pays the fuel bill.
The testa is the thin brown skin taken off at peeling. CNSL comes from the SHELL, not from the testa or the husk — a distinction worth holding onto when reading supplier literature.
Frequently asked questions
What are the stages of cashew processing?
Can cashew processing be fully automated?
Related reading & machines
Fully Automatic Cashew Processing Plant
From raw nut to sealed kernel — one automated line
Open →Cashew Processing Steps (Step by Step)
Walk the line, one step at a time
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Cashew Processing Flow Chart
A flow chart of cashew processing showing the input, output and machine at each stage — from raw cashew nut in to sealed kernel out.
Open →Cashew Nut Machine: The Complete Range
A "cashew nut machine" can mean any stage of the line — shelling, peeling, grading, packing and more. Here’s the full range and how the machines fit together.
Open →
Cashew Harvesting Machine
Cashew harvesting is still largely manual. Mechanised aids exist for collection and de-appling, but full mechanical harvesting of cashew remains limited.
Open →Talk to a cashew engineer
Tell us your target capacity, grades and location — we’ll come back with a costed proposal.