Beverage & Wine

Extraction (Coffee)

Also: coffee extraction, percent extraction, extraction yield

The percentage of soluble compounds dissolved from coffee grounds into brew water, determining whether a cup tastes under-, over-, or optimally extracted.

From Latin extractio, 'a drawing out'; applied to coffee science in the mid-20th century by researchers at the Coffee Brewing Center (Massachusetts Institute of Technology, 1950s) and codified by Lockhart's 1957 Coffee Brewing Research.

Definition

Extraction is the process by which hot water dissolves soluble compounds — acids, sugars, lipids, Maillard-reaction products, and bitter melanoidins — from roasted coffee grounds. Extraction yield is expressed as a percentage of the dry coffee mass that ends up dissolved in the final brew. The Specialty Coffee Association (SCA) identifies an optimal extraction window of 18–22%, with anything below feeling sour, thin, and underdeveloped (under-extraction) and anything above turning harsh, drying, and astringent (over-extraction). Extraction rate is governed by four interlocking variables: grind size (surface area), water temperature (solubility of compounds), contact time (how long water touches grounds), and agitation or turbulence. Finely ground coffee extracted at 93 °C for a longer dwell extracts more than coarsely ground coffee at the same temperature. Because different flavor compounds dissolve at different rates — acids first, sugars in the middle, bitter compounds last — a brewer can target a specific slice of the extraction curve by manipulating these levers. Measuring extraction requires a refractometer to read total dissolved solids (TDS) in the brew, then back-calculating against the brew ratio. Light roasts are denser and resist extraction, often requiring finer grinds or higher temperatures to reach the same yield as a dark roast.

In use

“The barista tasted sharp citric acidity and a hollow finish, telltale signs of under-extraction, so she tightened the grind to increase extraction yield into the 20% sweet spot.”

Related terms

Brew Ratio & TDS Dialing In (Espresso)Total Dissolved SolidsGrind SizeChannelingBloomContact Time

References

1.The Coffee Brewing Handbook — Ted Lingle (SCAA, 1996)
2.The World Atlas of Coffee — James Hoffmann (Mitchell Beazley, 2014)
3.Coffee Flavor Chemistry — Ivon Flament (Wiley, 2002)
4.SCA Water Quality Handbook — Specialty Coffee Association (2018)

Confidence: high

Notes

The Extraction Curve

Flavor compounds do not dissolve simultaneously. Fruit acids and chlorogenic acids extract first (lending brightness), followed by sucrose-derived sweetness, and finally high-molecular-weight melanoidins that contribute body and, in excess, bitter dryness. A skilled brewer can stop or manipulate extraction to capture a chosen bandwidth of the curve.

Measuring with a Refractometer

A digital refractometer reads the refractive index of brewed coffee in Brix, which software converts to TDS percentage. Extraction yield is then calculated: Extraction % = (TDS% × brew weight) ÷ dry dose weight. Without this tool, extraction is judged by taste alone — valid but imprecise.