What are primary defects in green coffee?

Primary defects in green coffee are the most serious imperfections identified in a batch of green beans before roasting. The SCA defines five main categories: full black bean, full sour bean, dried cherry, foreign matter (husks, foreign seeds), and fungus-damaged beans. Each defect corresponds to a severe sensory impact in the cup.

The SCA Arabica green coffee defect classification distinguishes primary from secondary defects based on their cup impact. A single full black bean in a 350 g sample constitutes one complete defect — one bean is enough to potentially disqualify a lot. Each type of primary defect has a specific origin and sensory profile.

The full black bean results from harvesting overripe cherries that have fallen to the ground, or from Erwinia bacterial infection. In the cup it generates phenolic, medicinal, or burnt leather flavours. The full sour bean comes from excessively long uncontrolled fermentation — the bean has fully fermented before or during depulping. It produces a pronounced vinegar taste in the cup, sometimes with an alcoholic note. Dried cherries are whole cherries that the depulping process failed to remove; during roasting they generate an over-fermented cherry flavour and can create uneven burning spots in the drum. Foreign matter (stones, twigs, seeds of other species) has no direct aromatic impact but poses a mechanical risk to roasting and grinding equipment.

Fungal damage (green beans with visible moulds or mycotoxins) is arguably the most serious defect — not in terms of taste but food safety: certain moulds produce ochratoxin A, regulated by the European Union since 2005 in roasted coffee (maximum 10 µg/kg). A fact worth knowing: ochratoxin A is heat-stable — it does not break down during roasting. This is why specialty coffee insists on impeccable drying of green beans to a residual moisture of 10-12 %: below this threshold, moulds cannot develop.

The 5 SCA primary defects in green Arabica coffee