Cashew processing
Turning raw cashew nut (RCN) into the smooth, kidney-shaped kernels on retail shelves is one of the most labour-intensive jobs in the food industry. Eight steps, careful chemistry, and a by-product (CNSL) that's almost as valuable as the kernel itself.
- 01
Reception & moisture
RCN sampled for KOR, defective count, moisture. Moisture adjusted to ~9% via drying.
- 02
Steaming
100°C for 20–30 min. Softens shell, neutralizes CNSL phenolic toxicity.
- 03
Shelling
Manual or mechanical cracking. Manual preserves whole-kernel ratio; mechanical is faster.
- 04
Kernel drying
Conditioned-air dryers reduce moisture to ~5% over 8–12 hours.
- 05
Peeling
Reddish testa skin removed by mechanical peelers or hand-rubbing.
- 06
Grading
Sorted by size (W180–W500), colour, integrity (whole vs pieces). Optical sorters + hand-grade.
- 07
Quality testing
Aflatoxin, moisture, foreign matter, defect ratio. Certificates per lot.
- 08
Packing
22.68 kg vacuum tins, CO₂ or N₂ flushed, in 25 kg cartons.
Why processing economics matter
A kilogram of raw cashew nut yields roughly 220–270 grams of edible kernel — a "kernel out-turn ratio" (KOR) of 22–27%. The rest is shell (sold as fuel or biomass), testa (animal feed), and CNSL. For a 12,000 MT-capacity processing facility, even a 1% KOR improvement is worth $1–2 million per year. This is why processors obsess over RCN quality at intake and why African-origin RCN with KOR >50 lbs/80kg bag commands premiums.
The CNSL story
Cashew nut shell liquid is recovered during steaming and roasting and refined into a feedstock for industrial chemicals. Distilled cardanol is used in friction linings, paints, varnishes, and electronic resins. Most large processors operate a CNSL recovery line as a parallel revenue stream — globally, the CNSL trade is worth ~$300 million annually, on top of the kernel trade.
Manual vs mechanical processing
- Manual shelling and peeling — historically the dominant Indian model. Preserves whole-kernel ratios (W180/W210 yields are higher), but labour costs and worker-safety questions have driven a shift.
- Mechanical shelling and peeling — Vietnamese-led innovation. Higher throughput, lower unit cost, but breakage ratios push more product into LWP/SWP grades.
- Hybrid lines — increasingly common — mechanical shelling, mechanical peeling, hand-grading for premium grades.
Sustainability and worker safety
CNSL is caustic. Direct skin contact during manual processing causes burns; long-term exposure has serious health effects. Modern processing facilities use PPE (gloves, masks), exhaust ventilation, and increasingly mechanical alternatives to reduce exposure. Buyers increasingly screen suppliers for SMETA, Fair-trade, or BSCI audits on worker safety in addition to BRC/HACCP for food safety.