tags: [] - coffee/green-beans - coffee/tasting - coffee/roasting aliases: - Coffee defects - Green coffee faults - Roast defects - Cup faults

Defects & Faults¶

Tags: #coffee/green-beans #coffee/tasting #coffee/roasting Aliases: Coffee defects, Green coffee faults, Roast defects, Cup faults Related: Green Coffee | Cupping | SCA Flavour Wheel | Roast Profile | Processing | Coffee Tasting MOC Status: ✅ Complete

Overview¶

Defects and faults in coffee refer to physical flaws in green or roasted beans and the sensory imperfections they produce in the cup. Defects arise from problems at any stage of the coffee supply chain — agricultural (disease, insect damage, poor harvesting), processing (fermentation errors, drying problems), green storage (mould, moisture), roasting (inconsistent heat application, equipment malfunction), or preparation (under/over-extraction, stale coffee). The Specialty Coffee Association (SCA) and the New York Green Coffee Association (NYGCA) maintain classification systems for green coffee defects. Understanding defects enables producers to improve quality, buyers to evaluate green coffee samples accurately, and roasters to identify and minimise quality problems.

Green Coffee Defects (Primary and Secondary)¶

The SCA classifies green coffee defects into primary (severe, heavily penalised) and secondary (less severe) categories:

Primary Defects (Category 1)¶

Defect	Description	Cup impact
Full black bean	Entire bean surface is black; dead bean; over-fermented or disease-affected	Sour, fermented, phenolic; severe quality impact
Full sour bean	Bean is brown-yellow and has a sour fermentation odour	Vinegary, fermented, unpleasant sour
Dried cherry / pod	Whole undehulled cherry or pod in the green lot	Fermented notes; husk material
Fungal damage	Bean shows mould growth; greenish-blue, white, or grey patches	Musty, mouldy, medicinal; earthy defect
Severe insect damage (>3 holes)	Extensive borer damage from Hypothenemus hampei (coffee berry borer / CBB)	Woody, fermented, musty
Foreign matter	Sticks, stones, metal — not technically a bean defect but a processing failure	Physical contamination; equipment damage risk

Secondary Defects (Category 2)¶

Defect	Description	Cup impact
Partial black bean	Part of bean is black	Milder version of full black — sour, fermented
Partial sour bean	Portion of bean shows sour fermentation	Mild sour notes
Floater	Low-density bean that floats in water; underdeveloped	Hollow, papery, cereal flavour
Immature/unripe bean	Green, grassy, underdeveloped	Grassy, astringent, sour
Withered/shrivelled bean	Desiccated; small and wrinkled	Straw, hay, thin body
Shell / broken bean	Bean separated into two shells or broken	Uneven roasting; scorching risk
Slight insect damage (1–3 holes)	Minor borer damage	Mild woody/fermented notes
Hull/husk	Residual parchment or cherry skin	Papery notes in cup

Roast Defects¶

Defects introduced during roasting affect the entire batch:

Defect	Cause	Cup impact
Tipping	Bean tips scorched by drum surface contact; too high charge temperature	Burnt, ashy notes at high concentration
Scorching	Large bean surface area scorched; conductive heat excess	Harsh burnt/bitter notes
Baked	Insufficient heat during the Maillard phase; flat Rate of Rise for extended period	Flat, bread-like, low complexity; "bready" aroma
Quakers	Underdeveloped, unripe beans that remain light-coloured even after roasting	Peanut, hay, papery; must be sorted post-roast
Underdevelopment	First crack not reached in significant proportion of beans	Grassy, sour, astringent
Over-development	Extended time after first crack; dark roast pushed too far	Harsh bitterness; loss of origin character; carbonised notes

Cup Faults¶

Sensory faults detected in the brewed cup that may originate from green, roast, or preparation defects:

Fault	Typical origin
Fermented / sour	Full sour green beans; processing fermentation error
Musty / earthy	Fungal-damaged beans; improper storage
Phenolic / medicinal	Bacterial contamination during fermentation; chlorinated water
Rubbery	Canephora (Robusta) content; certain fermentation faults
Papery / stale	Stale green or roasted coffee; old crop; paper filter taste
Grassy	Underdeveloped (unripe) beans; insufficient drying
Rancid	Old coffee oils; poorly cleaned equipment
Metallic	Water chemistry issues; old equipment; some defect beans

SCA Defect Tolerance in Grading¶

In the SCA Specialty Grade classification: - Specialty Grade (80+ points): Zero primary defects; maximum five secondary defects per 350 g sample; no quakers allowed in the roasted sample - Premium Grade (75–80 points): Some primary defects tolerated; higher secondary defect count allowed - Commodity Grade: Defects are counted but tolerated within limits set by exchange standards (New York C contract, London LIFFE)

Key Facts¶

Defects arise at any stage: agricultural, processing, storage, roasting, or preparation
Primary (Category 1) defects — full black, full sour, fungal damage — have severe cup impact; must be zero for SCA Specialty Grade
Secondary (Category 2) defects include floaters, immature beans, shells, and minor insect damage; maximum five per 350 g sample for Specialty Grade
Roast defects (tipping, scorching, baked, quakers) are introduced by improper heat application — separate from green defects
Cup faults (fermented, musty, phenolic, grassy) are the sensory evidence of defects; allow reverse diagnosis of their cause
Quakers — underdeveloped beans that roast lighter than the rest — must be physically removed from specialty roasted lots

References¶

Changelog¶

Date	Change
2026-04-28	Note created

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