Extraction Rate

Extraction rate (also called extraction yield, or EY) is the percentage of the dry coffee dose that is actually dissolved and carried into the finished brew. Not all of coffee's soluble mass is desirable: the earliest compounds to dissolve are fruity acids and bright sugars, while bitter phenolics and harsh tannins extract last. The SCA's Gold Cup standard places the ideal range at 18–22% for brewed coffee — below 18% produces a sour, thin, underdeveloped cup; above 22% introduces harsh bitterness and astringency. Extraction rate is calculated from a TDS reading taken with a refractometer: EY (%) = (brew weight × TDS%) ÷ dry coffee dose × 100.

Background & Context

Extraction rate (taux d'extraction in French) is the percentage of the coffee's dry mass that dissolves into the brew water during extraction. A 20g dose of coffee grounds contains roughly 28–30% soluble material — the maximum physically extractable. Specialty brewing targets an extraction rate of 18–22% (SCA brewing control chart "ideal" zone): below 18% is under-extraction (sour, thin, underdeveloped); above 22% risks over-extraction (bitter, astringent, hollow). The calculation is straightforward: (brewed beverage weight × TDS%) ÷ dry coffee dose weight × 100. A 300g V60 brew at 1.35% TDS from 20g coffee = (300 × 0.0135) ÷ 20 × 100 = 20.25% EY. Different compounds extract at different rates: acids and sweet compounds first, then body compounds, then bitter compounds — which is why the extraction rate dial is also a flavour balance dial.

Practical Use

In practice, extraction rate is controlled primarily by grind size, water temperature, and brew time. Grind finer → more surface area → faster extraction → higher EY at same brew time. Raise temperature → faster extraction → higher EY. Extend brew time → more contact → higher EY. The challenge is that EY cannot be measured without a refractometer (which measures TDS). Without equipment, experienced tasters use the flavour signature: sourness indicates under-extraction; aggressive bitterness and dryness indicate over-extraction. A TDS/EY reading is the objective tool; tasting is the subjective confirmation. Professional baristas check both.

Related Terms

Related terms: TDS, Extraction yield, Brewing control chart, Under-extraction, Over-extraction.