Quick answer: A cacao cut test involves slicing a representative sample of 100 dry beans lengthwise and counting beans by internal colour: well-fermented beans are brown throughout; under-fermented beans show purple; slaty beans indicate no fermentation at all; mouldy beans are an automatic defect. ICCO and ISO 2451 set maximum thresholds for each defect category, and most European buyers reject any lot where slaty or mouldy counts exceed those limits — making the cut test the single most reliable pre-shipment quality gate available without laboratory equipment.
Fermentation is the step that determines whether your cacao will produce complex chocolate or flat, astringent bitterness. Yet fermentation is invisible from the outside of a dried bean. Two bags from the same origin, the same harvest window, and the same quoted grade can taste entirely different if one was fermented for four days and the other for two. The cut test is the industry's standard answer to that problem: a rapid, low-cost internal inspection that takes roughly twenty minutes and requires nothing more than a sharp knife, a clean board, and a reference card.
For wholesale importers, confectionery manufacturers and private-label chocolate brands sourcing Indonesian cacao, understanding how to commission, read, and act on a cut test result is not optional — it is the first line of defence against receiving material that fails your production specifications. This article walks through every step: correct sampling, the cutting method, the four-category classification system, internationally recognised thresholds, and how cut test results map to expected flavour outcomes.
Why the cut test matters more than certificate claims
Export certificates and phytosanitary documents confirm moisture and pest compliance. Grade marks on a bag confirm physical bean size and basic defect limits for the export market of origin. Neither document tells you what happened inside the fermentation box. A shipment can pass Indonesian SNI (Standar Nasional Indonesia) grade A requirements and still contain 25–30% purple or slaty beans — well above thresholds most European buyers accept for fine flavour production.
The cut test, standardised under ISO 2451:2017 (Cocoa beans — Specification) and referenced by the ICCO Quality Manual, is the only pre-shipment test that directly measures fermentation completion at the bean interior. It is accepted as evidence by trade arbitration bodies, used by independent pre-shipment inspectors, and cited in most quality-floor contracts. Running it on a representative sample before accepting a lot — or commissioning it through a third-party inspector — is standard practice among experienced cocoa traders.
Sampling correctly: the foundation of a valid result
A cut test result is only as reliable as the sample drawn from the lot. Biased sampling is the most common source of buyer disputes over quality.
Sample size and drawing method
The working sample for a cut test is 100 beans. ISO 2451 specifies this number because it makes percentage calculations direct (one defect bean = 1%) without requiring decimal arithmetic in the field. The 100 beans must, however, be drawn from a bulk sample that is itself representative of the full lot.
- For a 1 MT lot, draw sub-samples from at least 10 different bags using a bean trier or grain probe, then combine and reduce to 100 beans using the quartering method (pile, cross-split, discard two opposite quarters, repeat until you reach your working sample size).
- For a full 20 ft container (~18–19 MT), draw from at least one bag per every two tonnes — a minimum of 9–10 bags — across different positions in the container (front, middle, rear).
- Reject beans that are cracked, broken or hollow before starting; these are recorded separately as physical defects, not included in the fermentation count.
Moisture check before cutting
Beans above 7.5% moisture (the ISO 2451 maximum for trade) will not cut cleanly and may show mould or colour distortion attributable to inadequate drying rather than failed fermentation. Always check moisture with a calibrated meter on the bulk sample before proceeding. If moisture is borderline (7.0–7.5%), note this alongside your cut test result — it may indicate the lot needs further conditioning before shipment.
The cutting procedure
Arrange the 100 beans on a flat, clean cutting board in a 10-by-10 grid. Using a sharp, straight-edged blade (a dedicated cocoa cutting board with a hinged blade is standard for high-volume inspection; a firm cook's knife works for field testing), cut each bean lengthwise through the centre — not across the width. A lengthwise cut bisects the two cotyledons and exposes the full internal cross-section. A transverse cut shows only one layer of the internal structure and makes colour assessment unreliable.
Cut all 100 beans before classifying any of them, to prevent observer bias from influencing subsequent readings. Once all beans are open, examine them under consistent natural light or a neutral-white lamp. Record counts for each of the four categories described below.
The four-category classification system
Every cut bean is assigned to exactly one of four categories based on the predominant colour and internal structure of the cotyledon cross-section.
Brown (fully fermented)
The interior shows a rich chestnut to dark brown colour throughout the cotyledon. The cell structure appears swollen and porous rather than compact. Death of the seed embryo during fermentation triggers oxidation of polyphenols (primarily anthocyanins and tannins), converting the purple pigment to brown. A good ferment produces 85% or more brown beans. This category is the target and contributes the bulk of the Maillard and caramelisation precursors that generate chocolate flavour during roasting.
Purple (under-fermented)
The cotyledon cross-section is wholly or predominantly purple or violet. Anthocyanins have not been fully oxidised, indicating that fermentation was too short, bean mass was too small (insufficient heat retention), or the pile was turned too early. Purple beans contribute astringency and a slightly acrid, raw note that survives roasting. A small proportion — typically up to 10% — is tolerated in bulk-grade contracts. Specialty and fine flavour buyers generally accept no more than 5%.
Slaty
The interior is grey-blue to slate-coloured, hard, and compact with a glassy texture. Slaty beans have undergone little to no fermentation: the biochemical cascade that breaks down proteins into amino acids (roasting precursors) and oxidises tannins simply did not occur. Slaty beans are often associated with beans harvested from the placenta without sufficient mucilage separation, or from lots dried without any fermentation phase at all. They produce a harsh, unpleasant astringency that cannot be roasted out and will noticeably degrade a chocolate batch even at modest concentrations. ICCO guidance and most buyer specifications treat slaty beans as a major defect.
Mouldy
Visible fungal growth, white mycelium, or black discolouration penetrating the cotyledon. Mould can originate from inadequate drying, storage above 8% moisture, or pest damage that allowed moisture ingress during transit. Mouldy beans present food safety concerns (mycotoxin risk, particularly from Aspergillus and Fusarium species) in addition to flavour faults. Any visible internal mould is classified here regardless of percentage; European importers subject to EU Regulation 1881/2006 on contaminants must apply strict ochratoxin A limits (maximum 3 µg/kg in cocoa), and mouldy beans significantly increase the risk of exceeding this threshold.
ICCO and ISO grading thresholds
The table below summarises the cut test acceptance limits referenced in ISO 2451:2017, the ICCO quality framework, and typical European buyer contract floors. "Fine flavour" limits reflect the more stringent specifications used by bean-to-bar and high-percentage couverture manufacturers.
| Defect category | ISO 2451 Grade 1 | ISO 2451 Grade 2 | ICCO bulk trade guidance | Fine / specialty buyer typical floor |
|---|---|---|---|---|
| Purple (under-fermented) | Max 10 | Max 20 | Max 15 | Max 5 |
| Slaty | Max 8 | Max 8 | Max 8 | Max 3 |
| Mouldy (internal) | Max 3 | Max 4 | Max 3 | Max 1 |
| Insect-damaged (visible interior) | Max 3 | Max 6 | Max 3 | Max 1 |
| Brown (target minimum) | Min 85 | Min 75 | Min 75 | Min 90–95 |
Note that defect categories are counted independently. A lot could technically pass the slaty limit (8 beans) and the mould limit (3 beans) while failing on purple count (22 beans) against an ISO Grade 1 contract. Always verify that your contract specifies which ISO grade applies and whether combined defect totals are capped.
How cut test results predict flavour
The correlation between cut test categories and cup or flavour profile is well-established in published cocoa science and is directly relevant to production planning.
- High brown count (90%+): Expect full development of chocolate, fruity, and nutty notes during roasting. Fermentation has produced sufficient acetic acid to kill the seed and sufficient amino acid liberation for Maillard reaction. Bean-to-bar producers should target this range for origin-flavour expression.
- Elevated purple (10–20%): Expect residual astringency and a flatter, more one-dimensional profile. Acceptable for industrial cocoa liquor or powder destined for products where sugar, milk powder, or vanilla will mask astringency. Not acceptable for dark chocolate above 70% cocoa solids.
- Any slaty beans above 5%: Expect a harsh, uncooked, almost raw-peanut bitterness that does not dissipate during roasting. Cocoa butter pressed from such beans may carry off-flavours that affect couverture texture perception.
- Mouldy beans at any meaningful level: Risk of flavour taints (mushroom, earthy, medicinal) and potential regulatory non-compliance on ochratoxin A. Reject or request independent mycotoxin testing before accepting.
For a deeper discussion of how fermentation duration and turning schedules drive these outcomes, see our companion article on Indonesian cacao fermentation methods and how they affect flavour.
Conducting or commissioning the test before shipment
Buyers sourcing from Indonesia have three practical options for obtaining a reliable cut test result prior to shipment:
- Supplier-conducted test with photographic documentation. The fastest and lowest-cost option. Request that your supplier photograph the 100-bean grid immediately after cutting, with each category colour-coded or circled, alongside a label showing lot number and date. Useful as a screening tool but lacks independent verification.
- Independent pre-shipment inspection. A third-party inspection body (SGS, Bureau Veritas, Sucofindo in Indonesia, or equivalent) attends the warehouse, draws the sample, and issues a certificate of quality that includes the cut test result. This is the gold standard for high-value or high-volume contracts and is required by most Letter of Credit terms that reference quality inspection. Cakglo can coordinate independent pre-shipment inspection as part of our supplier survey and inspection service.
- Buyer inspection of pre-shipment sample. A 250–500 g representative sample is dispatched to the buyer before the full shipment is released. The buyer runs the cut test in-house and approves or rejects within an agreed window. This is Cakglo's standard sample protocol for cacao and vanilla orders; turnaround from sample dispatch to buyer receipt is typically 5–7 business days.
Whatever method you choose, ensure that the sample used for the cut test is drawn from the same physical lot — same bags, same warehouse position — as the material that will be shipped. A "reference sample" drawn from a different lot or an earlier delivery is not a valid quality gate.
Accept, reject, or renegotiate: applying the result commercially
Once you have your 100-bean counts, decision logic is straightforward:
- Accept: All four defect categories fall within the limits specified in your contract grade. Issue a release instruction and proceed to shipping documentation.
- Conditional acceptance with price adjustment: One or more defect categories exceed Grade 1 limits but fall within Grade 2, and the material is suitable for your intended use (e.g., bulk cocoa powder production). Renegotiate price per MT downward to reflect the lower grade. Document the agreed adjustment against the cut test certificate.
- Hold for re-inspection: Results are borderline and the sampling method is questioned. Commission an independent inspection using a fresh bulk sample from multiple bag positions.
- Reject: Slaty count above 8, mould count above 3, or combined defects create a lot unsuitable for your production standards. Issue a formal notice of rejection citing the specific ISO 2451 clause and attach the cut test documentation. If CIF or DAP Incoterms apply, consult your insurer before accepting the lot into your warehouse.
Buyers working with Cakglo on Indonesian cacao procurement have the option of specifying minimum cut test thresholds in the purchase order, with shipment contingent on independent certification of those thresholds. Contact us via our enquiry form to discuss how quality gates can be built into your sourcing contract.
Frequently asked questions
How many beans do I need for a valid cacao cut test, and does sample size affect accuracy?
The internationally recognised working sample is 100 beans, as specified in ISO 2451:2017. This number makes defect percentages directly readable (each bean = 1%) and is considered statistically sufficient for lot-level decisions when drawn correctly from a representative bulk sample. Smaller samples — 50 beans, for example — introduce considerably more variance; a single extra mouldy bean shifts the percentage by 2 points rather than 1. Larger samples (200 beans) improve precision marginally but add time without proportionate benefit for routine trade decisions. The critical factor is not sample size but correct bulk-sample drawing: sub-samples must be taken from multiple bags across the full lot, then quartered down to 100.
What is the difference between a purple bean and a slaty bean, and why does it matter commercially?
Both indicate incomplete fermentation, but the degree and commercial impact differ significantly. Purple beans have begun fermenting — some biochemical conversion has occurred, anthocyanins are partially oxidised, and the internal colour ranges from violet to dark purple — but fermentation was cut short. They retain elevated tannin levels and produce astringency in the cup, but they can still contribute some chocolate character. Slaty beans have undergone virtually no fermentation: the cotyledon interior is a hard, blue-grey or grey-green colour with a dense, unswollen cell structure. No amino acid liberation has occurred, meaning roasting cannot generate the Maillard-reaction compounds that produce chocolate flavour. The practical consequence is that even 5–8% slaty beans in a blend will noticeably flatten and harshen the flavour profile in ways that roasting adjustments cannot correct. Most fine-flavour contracts set slaty limits at 3% or below for this reason.
Can I rely solely on a supplier-provided cut test result, or is independent inspection always necessary?
Supplier-provided cut test results with photographic documentation are a useful and practical screening tool, particularly for established sourcing relationships. However, they cannot substitute for independent inspection in contracts above a certain value threshold or in contexts where Letters of Credit or trade finance are involved, because a bank or insurer will require a certificate issued by a recognised inspection body. For new supplier relationships, the first one or two shipments should always be verified by an independent inspector — SGS, Bureau Veritas, Sucofindo, or equivalent — regardless of the quality of the supplier's own documentation. For ongoing relationships with a proven track record, alternating between independent inspection and approved supplier self-certification (with documentary evidence) is a reasonable cost-efficiency measure.
Conclusion
The cut test is a twenty-minute procedure that can save a production batch, protect a letter of credit dispute, and define the quality floor for every cacao lot you source. Understanding the brown-purple-slaty-mouldy scale, the ISO 2451 thresholds, and the commercial decision logic that follows from each result is foundational knowledge for any serious importer or manufacturer working with origin Indonesian cacao. Cakglo offers representative pre-shipment samples (250–500 g, dispatched within 5–7 business days) from our cacao and vanilla product range, and we can coordinate independent pre-shipment inspection through our inspection and supplier survey service. To discuss your next order or to receive a sample of our current cacao lots, reach out directly via our wholesale enquiry form.