tags: [] - coffee/roasting - coffee/roasting/quality aliases: - Identifying roast defects - Roasting defects

Roast Defect Identification¶

Tags: #coffee/roasting #coffee/roasting/quality Aliases: Identifying roast defects, Roasting defects Related: Roasting MOC | Quakers | Scorched Roasts | Tipped Beans | Baked Roasts Status: ✅ Complete

Overview¶

Roast defect identification is the practice of recognising physical and cup-quality problems caused by errors in the roasting process or the quality of the green coffee. Roast defects are distinct from green coffee defects — the latter originate in the field or processing, while roast defects arise during roasting. Effective defect identification requires both visual assessment of the roasted bean and sensory evaluation of the cup, since some defects are clearly visible in the finished bean and others are only apparent through tasting. Identifying roast defects accurately is a prerequisite for diagnosing root causes and correcting profiles.

Categories of Roast Defects¶

Visual / Physical Defects¶

Quakers: Under-ripe (immature) beans that fail to develop colour during roasting; they remain pale yellow or tan against a batch of normally coloured beans. Quakers arise from green coffee quality (immature cherry at harvest, inadequate sorting), not from roasting errors. They produce a peanut-like, sour, or raw flavour in the cup and are classified as an SCA primary defect. See Quakers.

Scorched beans: Dark patches on the flat faces of beans, caused by prolonged or excessive contact with a hot drum surface. Scorching is more common at very high charge temperatures, with large batches, or slow drum rotation. The scorched surface produces bitter, rubber, or acrid flavour in the cup. See Scorched Roasts.

Tipped beans: Darkening or blackening of the bean tips (the pointed ends), caused by thermal concentration at the tips from radiation and conduction. Distinct from scorching (which affects flat faces). Produces bitter, roasty notes disproportionate to the overall roast level. See Tipped Beans.

Uneven roast colour: Significant variation in colour across a batch, from pale to dark, indicates poor agitation, inconsistent batch size, or screen-size variation in the green coffee. Produces uneven extraction and a blend of underdeveloped and overdeveloped flavour in the cup.

Profile-Derived Defects¶

Underdevelopment: Insufficient drop temperature or DTR; the roast lacks the Maillard and caramelisation development needed for sweetness. Cup: sharp, harsh, astringent, raw grain or cereal, sour without balance. See Underdevelopment.

Overdevelopment: Excessive drop temperature or DTR; Maillard reactions have advanced too far. Cup: smoky, ashy, bitter, muted acidity, suppressed origin character. See Overdevelopment.

Baked roast: Flat or stalling RoR through browning or development; beans were held at low-to-moderate temperatures for too long without adequate energy to drive final aromatic formation. Cup: flat, bread-like, dull, absent sweetness and brightness despite adequate colour. Distinct from underdevelopment. See Baked Roasts.

Crash-and-flick (RoR defect): The RoR drops sharply before first crack (crash) and then rises (flick) in the development phase. Caused by reactive burner reduction too early followed by over-correction. Produces uneven development; cups may have a combination of baked and harsh notes. See Crash and Flick.

Visual Inspection Method¶

A systematic visual inspection of a roasted batch:

Spread a sample (50–100 g) on a white tray or cupping plate under consistent lighting
Assess overall colour uniformity: Are beans within a consistent colour range, or is there significant lighter-to-darker variation?
Look for quakers: Identify any beans significantly lighter (pale yellow/tan) than the batch average
Inspect bean faces for scorching: Look for irregular dark patches on flat surfaces
Inspect bean tips for tipping: Check whether tips are darker than the flat surfaces in a pattern consistent with tipping
Assess bean surface for oil: Is oil present? At what level? Oil at Full City or lighter indicates overdevelopment or very dark roasting
Note any irregular shapes or cracked beans: Very high drop temperatures can produce cracked or split beans beyond first crack's normal pop

Cup Defect Identification¶

Cup defects from roasting are assessed through standard cupping or brewing:

Cup note	Likely roast defect
Raw, harsh, cereal, sour	Underdevelopment
Flat, bread-like, dull, no sweetness	Baking
Smoky, ashy, bitter	Overdevelopment
Bitter, rubber, acrid	Scorching
Peanut, sour (distinct beans in cup)	Quakers
Bright-baked combination	Crash-and-flick RoR

Key Facts¶

Roast defects are caused by errors in the roasting process, not the green coffee (except quakers, which originate in green coffee quality)
Primary visual defects: quakers (pale, immature beans), scorching (dark face patches), tipping (dark tips), uneven colour
Profile-derived defects: underdevelopment (harsh, raw), overdevelopment (smoky, bitter), baking (flat, dull), crash-and-flick (mixed)
Cup defect identification requires cupping or careful brewing; profile data (RoR, DTR, drop temperature) provides the diagnostic framework
Systematic visual inspection of a spread sample is a basic production QC step for every batch

References¶

Changelog¶

Date	Change
2026-04-27	Note created

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