☕ Coffee Brewing

What Is Coffee Extraction?

Brewing is controlled extraction: dissolving desirable compounds from ground coffee into water.

Key groups:

• Acids: bright, fruity
• Sugars: sweetness, body
• Bitter compounds: balance, dryness

Aim: high flavor, low defect.

Under-extraction → sour, thin. Over-extraction → harsh, dry. Mastering extraction means learning to steer between these extremes using grind, time, and temperature.

Extraction Yield vs Strength

Two distinct ideas:

• Strength (TDS): percentage of dissolved solids in the cup; how intense it tastes.
• Extraction yield: percentage of the dry coffee mass dissolved.

You can have strong yet under-extracted coffee (too concentrated, still sour) or weak but over-extracted coffee (dilute, bitter). Serious brewing targets both simultaneously.

The Ideal Extraction Window

Empirically, many specialty roasts taste best around:

• 18–22% extraction yield
• 1.15–1.45% TDS for filter coffee

Outside this “window,” defects dominate: vegetal sourness at low extraction, woody bitterness at high extraction.

These are guidelines, not rigid laws. Light roasts often prefer slightly higher extraction; darker roasts slightly lower.

Under-Extraction: Sensory Markers

Signs your brew is under-extracted:

• Sharp, lemony or vinegar-like acidity
• Dominant saltiness or vegetal notes
• Thin, abrupt finish

Typical causes:

• Grind too coarse
• Too little contact time
• Water too cool
• Insufficient agitation

Diagnosis starts with taste: prioritize recalibrating grind and time before changing everything at once.

Over-Extraction: Sensory Markers

Over-extracted coffee often shows:

• Lingering harsh bitterness
• Dry, astringent mouthfeel (fuzzy tongue)
• Hollow, woody aftertaste

Likely causes:

• Grind too fine
• Excessive contact time
• Water overly hot
• Very high turbulence

Correct by coarsening grind, shortening time, or lowering temperature, one variable at a time.