Green Coffee Grading and Defect Identification
What you must know
Green grading is a counting exercise with a strict discipline. A 350 g sample is spread in a single, even layer on a black tray under consistent, neutral light, and every bean is examined. Defects are split into two tiers. Category 1 (primary) defects are disqualifying: full black, full sour, fungus damage, foreign matter, and severe insect damage. Category 2 (secondary) defects are tolerated in small numbers: partial black, partial sour, floater, immature/unripe, withered, shell, broken/chipped, hull/husk, pulp, and slight insect damage.
Category 2 beans are converted to full-defect equivalents: one full black or full sour bean counts as one defect on its own, while three partial blacks or three partial sours equal one full defect, and five floaters, immatures, shells, wits, or broken beans equal one. Specialty grade requires zero Category 1 defects and no more than five Category 2 full defects in the 350 g sample.
Graders also record moisture (roughly 10–12%), water activity (generally below 0.60), bean density, and screen size, since these predict stability and roast behaviour.
Traps
- Counting the same bean twice. A black, broken, insect-damaged bean is counted once, under the most severe defect it shows.
- Treating quakers as green defects. Quakers are pale, unripe beans visible only after roasting.
- Confusing floaters (light, hollow, pale) with immatures (thin, wrinkled, grey-green).
- Classifying husk or pulp as foreign matter. Foreign matter means sticks, stones, glass, metal, or other non-coffee material.
Rule of thumb
Sort first, count second. Physically separate suspect beans into piles, then weigh each pile against the equivalence table before totalling.