Coffee Defect Identification — Primary & Secondary
The SCA's defect taxonomy and how to spot problems before they reach the cup.
Why this matters for professionals
Specialty grade coffee is defined by the SCA as having zero Category 1 (primary) defects and a maximum of 5 Category 2 (secondary) defects per 350 g sample. This standard separates specialty from commercial grade. A roaster who cannot identify a quaker before it goes into a blend, or a Q grader who cannot distinguish ferment from phenol in the cup, cannot do the job.
This article catalogs the SCA-defined defects, both visual (in the green coffee) and sensory (in the brewed cup), with the cup characteristics and the likely origin of each.
SCA Defect Classification
The SCA Green Coffee Defect Handbook organizes defects into two categories based on severity:
Category 1 (Primary) Defects
| Defect | Visual | Cup Impact | Cause |
|---|---|---|---|
| Full black | Entirely black bean | Rancid, dirty | Severe over-fermentation |
| Full sour | Reddish-brown, opaque | Vinegar, fermented | Contaminated water, prolonged ferment |
| Pod / Cherry | Dried whole cherry | Funky, off | Insufficient hulling |
| Fungus damaged | Yellow/brown stains | Moldy, musty | Storage in humid conditions |
| Foreign matter | Sticks, stones | Mechanical risk to grinder | Poor sorting |
| Severe insect damage | 3+ borer holes | Dirty, papery | Coffee berry borer beetle |
Category 2 (Secondary) Defects
| Defect | Visual | Cup Impact |
|---|---|---|
| Partial black | Less than 50% black | Mild rancid note |
| Partial sour | Less than 50% sour | Mild ferment |
| Parchment | Husk still attached | Astringent |
| Floater | Pale, low density | Underdeveloped |
| Immature / Quaker | Pale, wrinkled (visible after roast) | Peanutty, papery |
| Withered | Shriveled, light | Grassy, woody |
| Shell | Hollow malformation | Burns easily, harsh |
| Broken / Chipped | Fragmented beans | Over-extraction risk |
| Hull / Husk | Fragments of parchment | Astringent |
| Slight insect damage | 1-2 borer holes | Subtle muted character |
The Critical Sensory Defects
Some defects show in the cup more reliably than in the green:
Phenolic (Phenol). Medicinal, plastic, band-aid character. Caused by certain bacteria or chemical contamination. Rare but devastating; one phenolic bean per 100 g can ruin a roast.
Stinker / Foxy. Heavy ferment, almost rotten character. Comes from over-fermentation or poor drying conditions.
Rio (Iodine). Iodine, medicinal, often associated with Brazilian washed coffees that have been processed poorly. Distinct smell of seawater.
Earthy / Musty. Storage defect. Coffee absorbs cellar or warehouse odors.
Baked. A roast defect rather than a green defect — flat, dull, no acidity. Caused by stalled rate of rise during development.
Tipping / Scorching. Black spots on bean tips, caused by aggressive heat application during roasting. Burnt, ashy notes.
The Procedure
For SCA grading, take a 350 g sample. Spread on a sorting tray under daylight or daylight-equivalent lighting. Sort by visual inspection. Count and record each defect. Apply the SCA equivalence chart to convert defects into full defect counts (1 full black = 1 full defect; 5 parchments = 1 full defect, etc.). Specialty grade allows zero Category 1 and a maximum of 5 full defects in Category 2.
Common Mistakes
- Skipping the green sort. Some defects only appear after roasting (quakers), but most are visible in the green.
- Insufficient lighting. Subtle color variations require daylight-spec LEDs minimum.
- Not weighing the sample. Defect counts are relative to 350 g. Smaller samples need proportional adjustment.
- Mistaking processing artifacts for defects. Honey-processed beans have residual mucilage color; not a defect.
- Roasting defective lots blindly. One phenol bean per 500 g can ruin a 25 kg batch.
Further Reading
The SCA Green Coffee Defect Handbook is the canonical visual reference. The Coffee Quality Institute (CQI) Q Grader program is the most rigorous formal training. Sweet Maria's defect identification photos are freely available online. Coffee Quality Institute's Arabica Q Grader exam includes a defect identification component.
Defect-free lots
Seelaz curates specialty-grade coffees with full traceability and defect screening. Browse the collection.
ملخص بالعربية
عيوب البن تصنّفها SCA إلى فئتين: أولية وثانوية. الأولية الأشد ضرراً: الحبة السوداء الكاملة (تخمير مفرط)، الحبة الحامضة الكاملة، التلف الفطري، الثمرة الكاملة، والأضرار الحشرية الشديدة. الثانوية أخف: جزئية السواد، جزئية الحموضة، الورق العالق، الحبب العائمة (فلوتر)، والحبت غير الناضجة (كويكر) التي تظهر بعد التحميص. الدرجة التخصصية (specialty) تسمح بصفر عيوب أولية وحد أقصى 5 عيوب ثانوية لكل عينة 350 جرام، مع درجة تذوق 80+ للحصول على تصنيف تخصصي. العيوب التي تظهر في الفنجان فقط: الفينول (طعم دوائي)، الريو (يودي)، والتخمير المفرط. تدريب التعرف على العيوب جزء أساسي من برنامج Q Grader.
