Cashew Nut Processing : Modern Equipment Solutions for Commercial Operations

The cashew nut processing sequence follows a logical pattern, though the equipment complexity varies significantly based on production scale and automation level.

Raw Material Reception and Storage

Before actual processing begins, raw cashew nuts need proper handling. Most facilities receive raw nuts at 8-10% moisture content after initial farm-level drying. Storage in moisture-controlled warehouses prevents mold growth and maintains processability.

Equipment considerations: Moisture meters for incoming quality checks, adequate storage bins with ventilation, material handling conveyors or loaders for moving raw nuts to processing lines.

Pre-Processing: Cleaning and Grading

Raw cashews arrive with debris, damaged nuts, and significant size variation. The first processing step separates foreign material and sorts nuts by size.

Cleaning systems use vibrating screens or aspiration channels to remove leaves, twigs, and undersized nuts. This prevents downstream equipment damage and improves processing efficiency.

Raw nut grading machines sort cashews into 3-5 size categories. Why does this matter? Different sizes require different cutting and shelling parameters. Processing mixed sizes together results in either under-processed large nuts or over-processed small ones that break.

Modern automatic raw cashew nut grading machines use vibrating screen decks with progressively smaller openings. Nuts cascade over each screen, falling through when they reach their size category. Throughput ranges from 500 kg/h for small operations to 2,000+ kg/h for industrial facilities.

Conditioning: Roasting or Steaming

Raw cashew shells are extremely hard. The conditioning step weakens the shell structure while avoiding damage to the kernel inside. Two methods dominate commercial processing:

Roasting method: Traditional approach where raw nuts roast in rotating drums at 180-200°C for 8-12 minutes. The heat makes shells brittle and partially liquefies the CNSL (cashew nut shell liquid), making subsequent shelling easier. Many African processors prefer this method.

Steaming method: More common in Asian processing facilities, steaming exposes raw nuts to high-pressure steam (3-4 bar) for 10-15 minutes. Steaming doesn’t fully remove CNSL but softens shells enough for shelling machines.

Equipment options: Cashew steaming machines (pressure vessels with steam injection) or roasting drums with gas or wood-fired heating. Capacity requirements determine whether batch or continuous systems make more sense. A 500 kg/h processing line typically needs 2-3 batch steaming units operating in rotation.

Shelling: The Critical Step

Shelling represents the most technically challenging step in cashew nut processing. The shell must break without damaging the fragile kernel inside. Manual shelling by skilled workers remains common in some regions, but mechanization offers clear advantages in consistency, safety, and labor costs.

Cashew nut shelling machines work on several principles:

Cutting machines: Most common in modern facilities. These machines use calibrated blades that cut the shell at precise depth—deep enough to penetrate the shell but shallow enough to avoid the kernel. The TTQ cutting machine employs dual-blade systems that make two cuts, allowing the shell to split open while the kernel remains intact.

Capacities range from 60-80 kg/h for single-head machines to 400+ kg/h for multi-head configurations. The key specification is whole kernel recovery rate—good machines achieve 85-90% whole kernels versus broken pieces.

Centrifugal shelling: Less common but useful for specific nut sizes. These machines spin nuts against a hard surface at calculated speeds, cracking shells through impact force. Works well but can have higher breakage rates.

CNSL collection: Shelling machines should incorporate CNSL collection systems. This toxic liquid has industrial applications (resins, friction materials) that offset processing costs when captured rather than wasted.

Kernel Drying

After shelling, kernels contain 8-12% moisture. Before peeling, they need drying to 3-4% moisture. This specific range is not arbitrary—it affects peeling success rates significantly.

Cashew dryer machines circulate hot air (60-70°C) through kernels spread on trays or moving through tunnel dryers. Forced-air circulation ensures even drying. Under-dried kernels peel poorly; over-dried kernels become brittle and break during peeling.

Processing facilities typically install dryers sized for 8-12 hour batch cycles, matching shelling output. For a 300 kg/h shelling line running 8 hours daily, dryer capacity needs to be around 2,000-2,500 kg to handle the day’s production.

Kernel Conditioning: The Borma Process

This step separates successful processors from struggling ones. After drying to 3-4% moisture, kernels undergo brief rewetting called “borma” in India or humidification elsewhere.

Cashew kernel humidification chambers expose dried kernels to steam or water spray for 30-90 seconds, raising surface moisture to 5-6% while the core remains at 3-4%. This moisture gradient softens the testa (skin) while keeping the kernel firm.

Timing matters enormously. Process kernels 2-4 hours after borma for optimal results. Wait too long, moisture redistributes and you lose the advantage. Rush it, and surface moisture hasn’t penetrated enough.

Peeling: Removing the Testa

The thin brown skin (testa) covering shelled kernels must be removed to produce the white/cream cashews consumers expect. Multiple peeling approaches exist:

Manual peeling: Workers use small knives to scrape away the testa. Labor-intensive but provides employment in developing regions. Skilled workers achieve 3-5 kg per person per day.

Mechanical peeling: Specialized equipment uses rotating drums lined with abrasive surfaces to scrub away the testa through gentle friction. Modern machines combine mechanical action with pneumatic peeling.

Cashew peeling machines from manufacturers like TTQ use a two-stage approach. First, rotating cages with brushes mechanically loosen the testa. Second, high-pressure air jets blast away the loosened skin. This combination achieves 80-85% whole kernel recovery—much better than purely mechanical methods.

Machine capacities: Single-head peelers process 120-180 kg/h, while four-head systems handle 420-480 kg/h. The machines require substantial compressed air (30-100 HP compressors depending on configuration), making air compressor selection a key infrastructure decision.

Grading and Sorting

Peeled kernels get classified into grades based on size, color, and wholeness. International standards define 26+ grades from W180 (largest wholes, 180 kernels per pound) to W450 and broken grades.

Cashew grading machines use multiple approaches:

Size grading: Vibrating screens with standard opening sizes separate kernels into size categories. Relatively simple technology but requires regular screen maintenance.

Color sorting: Advanced machines use optical sensors to identify and reject kernels with dark spots, discoloration, or remaining testa patches. These cashew nut color sorters improve final product consistency significantly but represent major capital investment (₹15-25 lakh for commercial units).

Manual sorting: Final quality check where workers remove any defective kernels that automated systems missed. Even highly automated facilities maintain manual inspection stations.

Roasting and Flavor Development

Many processors sell raw cashew kernels to traders or roasters. However, adding a roasting step captures additional margin by moving closer to the consumer product.

Cashew nut roasting machines use several technologies:

Drum roasting: Kernels tumble in rotating drums with heated salt (1:1 or 1:2 ratio). The salt acts as a heat transfer medium, preventing direct contact with hot metal that causes burn spots. Produces evenly roasted nuts with consistent color. Typical batch size: 50 kg roasted in 10-15 minutes.

Oil roasting: Less common in modern facilities due to added fat content and cleanup requirements. Still used for certain premium products.

Dry roasting in ovens: Some operations use tunnel or conveyor ovens. Generally less even than drum roasting and higher energy consumption.

Roasting equipment selection depends on whether you’re producing plain roasted, salted, flavored, or specialty products. Each requires slightly different parameters.

Packaging

The final step protects processed kernels from moisture absorption, oxidation, and contamination during distribution.

Vacuum packing machines remain the choice for premium whole kernels destined for export markets. Removing air extends shelf life significantly while preventing kernel breakage during shipping.

Nitrogen flushing systems replace air with inert nitrogen gas, preventing oxidation without vacuum compression. Useful for products where appearance matters more than density.

Standard pouch packing machines handle retail-sized packages for domestic markets. Many include weighing systems ensuring accurate fill weights that meet regulatory requirements.

Packaging speeds need to match upstream processing capacity. A facility processing 500 kg/day of finished kernels needs packaging capacity of 60-80 kg/h to complete packing in a single shift.