Coffee: Green Coffee Defects — SCA Primary and Secondary Classification
SCA defines primary green coffee defects (full black, full sour, pod/cherry, large stone) — each counting as one equivalent defect — and secondary defects (partial black, floater, shell, insect damage) at lower equivalency.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Sample size for defect count | 350 | grams | SCA standard defect analysis sample weight |
| Primary defects allowed (SCA Specialty) | 0 | defect equivalents | Zero primary defects for specialty grade |
| Secondary defects allowed (SCA Specialty) | ≤5 | defect equivalents | Maximum 5 secondary defect equivalents in 350g |
| Full black bean (1 defect equivalent) | 1 | bean = 1 equivalent | |
| Full sour bean (1 defect equivalent) | 1 | bean = 1 equivalent | |
| Insect-damaged bean (minor) | 10 | beans = 1 equivalent | |
| Floater | 5 | beans = 1 equivalent |
Green coffee defect classification is the primary quality-sorting tool used by buyers, Q Graders, and exporters to determine whether a lot qualifies as specialty grade. The SCA Green Coffee Classification System, derived from the earlier SCAA defect guide, provides a standardized vocabulary and equivalency scale for categorizing physical defects found in unroasted coffee.
SCA Grade Definitions
| Grade | Primary Defects | Secondary Defects | Cup Requirements |
|---|---|---|---|
| Specialty (Grade 1) | 0 | ≤5 | No cup defects; clean, sweet |
| Premium (Grade 2) | 0 | ≤8 | No primary cup defects |
| Exchange (Grade 3) | ≤9 | ≤23 | — |
| Below Standard (Grade 4) | 10–23 | 24–86 | — |
| Off Grade (Grade 5) | >23 | >86 | — |
Primary Defects (1 Full Equivalent Each)
Primary defects have severe cup impact — a single occurrence disqualifies a lot from specialty grade.
| Defect | Visual Description | Cup Impact | Cause |
|---|---|---|---|
| Full black bean | Entire bean black, shriveled | Moldy, phenolic, fermented | Disease (CBD), over-fermentation, or dead bean |
| Full sour bean | Tan to brown, hollow shell | Acetic/vinegar, sharp sourness | Internal bacterial fermentation |
| Dried cherry / pod | Intact dried fruit husk on bean | Fermented, astringent | Failed pulping; cherry not removed |
| Large stone | Non-coffee material >5mm | Equipment damage risk | Field or processing contamination |
| Large stick | Woody material >5mm | Equipment damage risk | Harvest contamination |
Secondary Defects and Equivalency Scale
Secondary defects require multiple beans to equal one defect equivalent. Their cup impact varies from negligible to moderate.
| Defect | Equivalency | Visual Description | Cup Impact |
|---|---|---|---|
| Partial black | 3 beans = 1 | Portion of bean is black | Mild ferment/moldy notes |
| Partial sour | 3 beans = 1 | Partial discoloration, hollow | Mild sour/fermented |
| Parchment (in parchment) | 5 beans = 1 | Bean still inside silver skin/parchment | Woody, papery |
| Floater | 5 beans = 1 | Pale, very low density; floats in water | Faded, musty, empty |
| Immature / unripe | 5 beans = 1 | Pale green, wrinkled center cut | Astringent, grassy, salty |
| Withered | 5 beans = 1 | Shriveled lengthwise; drought or disease | Papery, astringent |
| Shell (elephant ear) | 5 beans = 1 | Separated hull fragment from twinned bean | Uneven roasting |
| Broken / chipped | 5 beans = 1 | Mechanical fracture | Scorching; over-extraction |
| Hull / husk | 5 beans = 1 | Dried outer skin fragment | Woody, dry |
| Insect damage (minor) | 10 beans = 1 | 1–3 holes from coffee borer beetle | Slightly fermented |
| Insect damage (major) | 5 beans = 1 | >3 holes, heavily tunneled | Fermented, dirty |
How to Conduct an SCA Defect Count
- Weigh exactly 350 grams of the green coffee sample.
- Sort all beans by defect type, placing each category in a separate pile.
- Count each pile and apply the equivalency multiplier.
- Sum all equivalents for primary defects and secondary defects separately.
- Compare totals against the SCA grade thresholds.
A specialty-grade lot must have zero primary defect equivalents and five or fewer secondary defect equivalents in the 350-gram sample.
The Coffee Borer Beetle (Hypothenemus hampei)
Insect damage in green coffee is predominantly caused by the coffee borer beetle (CBB), which bores into the cherry and coffee bean to lay eggs. Beans show characteristic circular entry holes. CBB is considered the most economically damaging coffee pest worldwide, affecting all major producing regions. At low damage levels (1–2 holes), the cup impact is minor. At high infestation levels, fermentation-adjacent off-flavors from the beetle’s microbial environment permeate the cup.
Floaters: Low Density as a Defect Signal
Floaters — beans with very low density that float during wet processing water flotation — are a key defect category because low density indicates incomplete starch and sugar development inside the bean. This results from under-ripeness, drought stress, or disease. Floaters produce faded, papery, musty cup profiles and are screened during wet milling via density sorting tanks.
Defect Training in Q Grader Certification
The Coffee Quality Institute’s Q Grader program includes mandatory defect identification practical exams. Candidates must correctly classify all primary defects and the majority of secondary defects from a prepared sample. Q Grader certification is valid for three years and requires recalibration, ensuring consistent application of SCA defect standards across the global green coffee trade.