Quality Control

Green Coffee Defects & Grading

Defect counts tell you what's wrong with a coffee before you roast it. Understanding grading standards helps you buy confidently—and know when "Grade 1" actually means something versus when it's marketing.

By Samuel Demisse — 3× U.S. Coffee Tasters Champion, Q-Grader, 34 years in specialty coffee

Primary defects Secondary defects Grade standards SCA protocol

TL;DR for Roasters

What defect counts mean for your roast

Defects show up in the cup. Some ruin individual cups (stinkers). Some drag down the whole batch (quakers). Here's what to watch for.

Primary defects (severe): Black beans, sour beans, foreign matter, fungus damage. One primary defect = one full defect.
Secondary defects (less severe): Broken beans, insect damage, partial quakers. Multiple secondaries = one full defect.
Roast implications: Quakers stay pale and taste papery. Blacks/sours taint multiple cups. Foreign matter = safety risk.

SCA specialty standard

  • 1 Sample size: 300 grams (about 1,200 beans depending on screen size).
  • 2 Grade 1: ≤3 full defects, no primary defects, no quakers.
  • 3 Grade 2: ≤8 full defects. Still specialty eligible if cup score hits 80+.
  • 4 Cup score: 80+ required for specialty regardless of visual grade.

We provide full defect counts on every lot. Request samples →

Category 1

Primary defects (severe)

Full black

Bean is entirely black. Caused by over-fermentation or severe disease.

Cup impact: Fermented, rotten, ruins multiple cups.

Full sour

Yellowish-brown, often with wrinkled surface. Over-fermented or picked overripe.

Cup impact: Vinegar, sour, off-putting acidity.

Fungus damage

Yellow or reddish-brown spots. Mold growth during processing or storage.

Cup impact: Musty, moldy, potential health risk.

Foreign matter

Stones, sticks, nails, glass. Contamination during processing.

Cup impact: Safety hazard. Grinder damage.

Dried cherry (pod)

Entire cherry that wasn't depulped. Common in dry process with poor sorting.

Cup impact: Fermented, dirty notes.

Severe insect damage

3+ holes or tunneling through bean. Coffee borer beetle is common cause.

Cup impact: Dirty, thin, papery.

Category 2

Secondary defects (less severe)

Partial black

Part of bean is black. Same causes as full black, less severe.

Count: 3 partial blacks = 1 full defect

Partial sour

Part of bean shows sour characteristics. Less impact than full sour.

Count: 3 partial sours = 1 full defect

Quaker (immature)

Light-colored, low density. Picked before fully ripe.

Count: 5 quakers = 1 full defect

Broken/chipped

Mechanical damage during milling. Fragment is less than half a bean.

Count: 5 brokens = 1 full defect

Shell (elephant ear)

Malformed bean—outer layer only. Genetic or processing cause.

Count: 5 shells = 1 full defect

Slight insect damage

1–2 holes. Less severe than full insect damage.

Count: 10 slight insect = 1 full defect

Ethiopia Specific

Ethiopia's grading system

Ethiopia uses its own grading scale (Grades 1–9) based on defect count, screen size, and cup quality. Understanding what these grades mean helps you buy better.

Washed grades

G1

Grade 1: ≤3 defects per 300g. Highest quality washed.

G2

Grade 2: 4–12 defects per 300g. Still specialty-eligible.

Natural grades

G1

Grade 1: ≤15 defects per 300g. Highest quality natural.

G3

Grade 3: 16–45 defects. Common commercial natural.

G4

Grade 4: 46–100 defects. "Blender grade"—not for single origin.

Our standard: We focus on Grade 1 and Grade 2 washed, Grade 1 naturals. Our YirgZ trademark goes beyond Grade 1 to "zero defect"—no primary defects at all. Learn about YirgZ →

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