tags: [] - coffee/tasting - coffee/quality-control aliases: - Coffee defect categories - Defect classification coffee - Supply chain defect origins

Defect Categorisation¶

Tags: #coffee/tasting #coffee/quality-control Aliases: Coffee defect categories, Defect classification coffee, Supply chain defect origins Related: Quality Control MOC | Defect Grading | Defect Recognition | Defect Recognition Training | Cupping Status: ✅ Complete

Overview¶

Defect categorisation is the systematic classification of coffee quality problems by type, origin point in the supply chain, and severity. At an advanced level it moves beyond identifying that something is wrong — as covered in Defect Recognition — to precisely naming defect types, identifying where in the supply chain they originated, and assessing their severity relative to quality standards. This is the sensory skill underlying quality control, green buying, and the training of other evaluators.

The Three Defect Categories¶

Defects in the cup can be traced to one of three origin points in the supply chain: the green coffee stage, the roasting stage, or the preparation stage. Effective categorisation identifies the correct origin point, because corrective action differs fundamentally for each.

Category 1: Green Defects¶

Originating in the cherry, processing, sorting, or storage of the green coffee before roasting.

Fermentation defects: Over-fermentation during wet processing or natural drying produces acetic, butyric, or propionic acids that create strong, unpleasant sourness, vinegar character, or a rotten note. Even small quantities of fermented beans can contaminate a batch.

Defect name	Cup character	Cause
Over-fermented	Vinegary, harsh, putrid	Extended or uncontrolled fermentation
Sour / Rio	Strong, medicinal, iodine-like	Bacterial infection; particular to certain origins
Potato defect	Raw potato, starchy	Antestia bug damage (East Africa)
Phenolic	Medicinal, antiseptic	Bacterial contamination
Musty / earthy	Damp earth, mould	Improper storage; high moisture during drying

Unripe / immature defects: Unripe cherries produce astringent, harsh, grassy, or green notes. Under-ripe green beans are often whiter and harder than ripe beans.

Defect name	Cup character	Cause
Grassy / hay	Raw, vegetal, fresh-cut grass	Immature coffee; very light roasting
Astringent	Dry, puckering, mouth-coating	Immature beans; incomplete development
Starchy	Bread-like, flat	Immature; under-developed processing

Insect and physical damage: Physical damage to the bean allows oxidation or bacterial entry, creating woody, phenolic, or musty notes.

Category 2: Roasting Defects¶

Occurring during or immediately after roasting when profiles are inappropriate for the green coffee's properties.

Defect name	Cup character	Cause
Underdeveloped	Grassy, raw, baked bread	Insufficient time at development stage
Baked	Flat, bread-like, no sweetness or brightness	Too slow a roast; excessive drying phase
Scorched	Harsh, acrid burning note	Too fast initial heat; direct contact with hot drum
Tipped	Hollow, papery, bitter	High charge temperature causing surface burning
Carbonised	Tobacco, ash, intense bitterness	Over-roasted
Uneven development	Mixed — simultaneously grassy and bitter	Inconsistent bean sorting; mixed screen sizes

Category 3: Preparation Defects¶

Occurring at the bar through extraction, milk handling, equipment condition, or contamination. These are the defects most directly within barista control and are covered in detail in Defect Recognition.

Defect name	Cup character	Cause
Under-extraction	Sour, harsh acidity, thin	Grind too coarse; short yield; low temperature
Over-extraction	Bitter, astringent, drying	Grind too fine; long yield; high temperature
Channelling	Simultaneous sour and bitter	Poor distribution or tamping
Rancid oils	Rubber, rancid, intense bitter	Unclean equipment
Stale	Flat, papery, cardboard	Coffee past optimal age
Contamination	Chemical, detergent, foreign odour	Inadequate rinsing; incorrect storage near aromatics

Severity Assessment¶

Not all defects have equal impact on the cup. Severity is assessed across two dimensions:

Intensity: How strongly the defect note appears in the cup: - Trace: Present but in the background; does not disturb balance - Mild: Noticeable; affects the cup but does not dominate - Pronounced: Clearly dominant; fundamentally changes the cup character - Severe: The cup is undrinkable or professionally unacceptable

Pervasiveness: Whether the defect is present in all cups in the flight or only in some. In SCA cupping, uniformity and clean cup scores capture per-cup defect pervasiveness. A defect present in one of five cups is less severe than one present in all five.

Categorisation in Practice¶

A systematic assessment workflow involves:

Characterise the flavour: "Vinegary sourness," "musty earthiness," "harsh bitterness," etc.
Assign a category: Is this a green, roasting, or preparation defect?
Assess severity: Is it trace, mild, pronounced, or severe?
Determine the corrective action:
Green defect → flag to roaster or green buyer; cannot be corrected at bar
Roasting defect → flag to roaster; adjust brewing parameters to minimise (some roasting defects can be partially masked by extraction adjustment)
Preparation defect → correct immediately at bar

Documentation¶

At advanced level, defect findings should be documented with: - Date and time - Coffee details (origin, roaster, batch, roast date) - Defect name and category - Severity - Action taken and outcome

This creates a quality control record supporting stock decisions, roaster conversations, and staff training.

Key Facts¶

Three origin categories: green coffee defects, roasting defects, preparation defects
Green defects include over-fermentation, potato defect, phenolic contamination, and immature cherry character — cannot be corrected at bar
Roasting defects include underdevelopment, baking, scorching, and carbonisation — flagged to the roaster
Preparation defects (under/over-extraction, channelling, stale coffee, rancid equipment) are correctable at the bar
Severity is assessed on two axes: intensity (trace to severe) and pervasiveness (proportion of cups affected)

References¶

Changelog¶

Date	Change
2026-05-02	Compliance review: full rewrite — added frontmatter and metadata block; removed `../` wikilinks (Extraction Tasting, Quality Scoring, Palate Calibration); removed `05_PUBLISHING/Homepage/Coffeepedia` footer; converted second-person instructional sequence to third-person encyclopedic workflow; aligned defect tables with standard markdown; added References, Changelog, copyright

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