What Is Kaju Chhilka — and Why It Makes Excellent Kattha
Kaju chhilka is the thin red-brown skin (testa) that separates from the cashew nut kernel during roasting and peeling at cashew processing factories. In most factories today, it is either burned as fuel or sold for a few rupees per kilogram. That is a significant missed opportunity.
Chemically, kaju chhilka (cashew peel / cashew testa) is one of the richest natural sources of catechin and epicatechin outside of Khair heartwood — the same bioactives that define premium Kattha:
| Total polyphenols | ~32% by dry weight |
|---|---|
| Catechin + Epicatechin fraction | >40% of polyphenol fraction = 12–15% of dry kaju chhilka weight |
| Water extraction yield | 151.2 mg (+)-catechin per gram of extract + 85.2 mg (−)-epicatechin per gram |
| After ethyl acetate purification | 219.4 mg catechin/g + 123.6 mg epicatechin/g |
| IS 4359:1967 compliance | AN-Catechu from cashew peel validated at 30%+ catechin (Indian patent) |
| Market price of kaju chhilka | ₹50–60/kg — an industrial by-product, currently deeply undervalued |
Compare this to Khair heartwood at ₹80–150/kg — with forest felling permits, seasonal supply constraints and lower achievable catechin purity. Kaju chhilka is available year-round, directly inside cashew factories, with no permits required.
Why Kaju Chhilka Is a Better Raw Material Than Khair Wood
- No forest permit required — kaju chhilka is generated entirely as waste inside cashew processing factories; no regulatory or seasonal supply risk.
- Year-round availability — major cashew belts in Kerala, Goa, Maharashtra, Tamil Nadu, Karnataka and Andhra Pradesh process cashew continuously; testa is always available.
- Lower raw-material cost — ₹50–60/kg vs ₹80–150/kg for Khair heartwood chips (2025–26 market rates).
- Higher purity potential — solvent extraction of kaju chhilka with fractional purification achieves 50–70%+ catechin purity, which is impossible with conventional Khair water-boiling processes (30–40% maximum).
- Better product colour — with proper FFE-based solvent recovery at sub-55°C, the Kattha produced is pale amber to near-white — commanding premium prices in pharma, nutraceutical and cosmetic markets.
The 8-Step Process: Kaju Chhilka to Kattha
The following process is used by SS Fabrication's turnkey Kattha plants. Each step is critical — skipping or under-engineering any one of them (particularly defatting — see below) directly degrades product quality.
| Step 1 — Raw Material Preparation | Incoming kaju chhilka is moisture-checked and inspected for contamination. Dried to target moisture before grinding. Hammer mill or pulveriser grinds to fine powder (200–400 micron) to maximise extraction surface area and yield. |
|---|---|
| Step 2 — Defatting ★ Critical | Cashew peel contains 3–8% co-extractable oils and lipids. If not removed before extraction, these oils cause sticky, clumping Kattha with off-odour and short shelf life — and will cause pharma buyers to fail the product on peroxide value tests. SS Fabrication integrates a single-skid hexane or isopropanol defatting unit inline with the extraction process. See the defatting section below. |
| Step 3 — Solvent Extraction | Defatted kaju chhilka powder is loaded into jacketed SS316 extractors with agitators. Ethanol or ethyl acetate dissolves catechin, epicatechin, tannins and polyphenols into the miscella (solvent + extract solution). Counter-current extraction with 2–3 extraction stages maximises yield. |
| Step 4 — Solid–Liquid Separation | Spent kaju chhilka marc is separated from the catechin-rich miscella using a plate-and-frame filter press or centrifuge. The exhausted marc can be sold as animal feed or composted. |
| Step 5 — FFE Solvent Recovery ★ Key Differentiator | SS Fabrication's continuous falling film evaporator (FFE) recovers solvent from the miscella at 45–55°C under vacuum (−0.08 MPa) — 20°C+ lower than a conventional batch distillation still. This prevents all thermal degradation and browning of catechin. Solvent recovery: 82–90% per pass. The concentrated aqueous extract proceeds to crystallisation. |
| Step 6 — Crystallisation | The concentrated extract is transferred to jacketed crystallisation tanks and cooled slowly with stirring. Catechin (Kattha) crystallises out of solution as white to pale amber crystals. The tannin-rich mother liquor separates for independent processing. |
| Step 7 — Filter Press & Washing | Crystallised Kattha cake is separated in a plate-and-frame filter press. Multiple cold-water wash cycles improve whiteness, remove residual tannins and improve paste value. Washing cycles directly control final catechin purity (30–70%+ depending on grade required). |
| Step 8 — Drying & Finishing | Kattha cake is dried in a vacuum tray dryer to final target moisture, then ambient-cured. Finished product is moulded into traditional blocks or spray-dried to fine powder for pharmaceutical and nutraceutical applications. Packed and labelled per buyer specification. |
Expected Yield: How Much Kattha from 100 kg Kaju Chhilka?
With SS Fabrication's FFE-based process: 100 kg of well-prepared kaju chhilka yields 8–10 kg of dry Kattha.
Conventional batch-still plants typically achieve only 6–8 kg per 100 kg — a 25–40% yield penalty due to thermal catechin degradation during solvent recovery at 78°C+.
The Defatting Step — Why Most Plants Skip It (and Why That's a Mistake)
Most kaju chhilka Kattha plant designs focus only on catechin content and treat everything else as inert filler. This is the root cause of product quality failures in the field. Cashew peel is not a simple polyphenol carrier — it is a complex biological matrix with multiple co-extractable fractions.
Without defatting, kaju chhilka oil causes serious quality problems:
- Sticky, clumping Kattha — absorbs humidity, poor shelf life, packaging failures.
- Rancid off-odour within 3–6 months — linoleic acid in the oil oxidises into hexanal and nonanal; the paan market detects a 'kaccha' (raw/oily) off-taste instead of clean astringency.
- Pharma rejection — nutraceutical and pharmaceutical buyers test peroxide value and free fatty acid; un-defatted Kattha fails consistently.
- Cosmetic rejection — rancidity makes the product unsuitable for skincare formulations.
SS Fabrication's solution: A single-skid defatting unit that installs inline adjacent to the main extraction process. Hexane or isopropanol pre-wash of the ground kaju chhilka removes 80–95% of co-extractable oils before the main catechin extraction begins. Result: clean, shelf-stable, pharma-grade acceptable Kattha from the first batch.
Equipment in a Kaju Chhilka Kattha Plant
- Hammer mill / pulveriser — 500 to 2,000 kg/hr kaju chhilka grinding
- Defatting skid — hexane or IPA pre-wash system, single-skid, inline
- SS316 jacketed solvent extractors — 2,000 to 20,000 L with agitators
- Miscella tanks, membrane filters and plate-and-frame filter presses
- SS316 falling film evaporator (FFE) or WVR unit — plus condensers, receivers and vacuum system
- Crystallisation tanks with cooling coils
- Vacuum tray dryer and optional spray dryer for catechin powder grade
- Explosion-proof ATEX/PESO Zone 1 electrical panels, solvent storage, chiller and scrubber
Frequently Asked Questions
Is kaju chhilka (cashew peel) Kattha accepted under IS 4359:1967?
Yes. AN-Catechu (Acacia Nut Catechu) produced from cashew testa has been validated at 30%+ catechin content in Indian patent literature and meets the IS 4359:1967 specification for commercial Kattha. With SS Fabrication's FFE process, 50–70%+ catechin purity is achievable — exceeding IS standards.
How much kaju chhilka does a typical cashew factory generate?
A medium-scale cashew factory processing 10 MT of raw cashew per day typically generates 300–500 kg of kaju chhilka. A large plant at 30 MT/day generates 1–1.5 MT of testa daily — enough feedstock for a 100–150 kg Kattha/day plant.
What is the minimum viable plant size?
SS Fabrication supplies plants from 50 kg Kattha/day (pilot / proof-of-concept scale) through to 500+ kg/day commercial lines. A feasibility assessment based on your testa availability is free — see the CTA below.
Can I add a Kattha module to my existing cashew factory?
Yes. This is the most common project type. SS Fabrication designs the extraction module to fit within existing factory space and utility infrastructure. Timeline: 4–8 months from concept to first production batch for a typical add-on module.
Free feasibility assessment — 24-hour response.
Tell us your daily cashew input (kg), estimated testa availability, target product grade (paan / pharma / cosmetic) and location. Our engineering team will respond within 24 hours with a feasibility note and indicative plant layout.