Coffee Extraction Science: Why 18-22% Changes Everything

Only 30% of a coffee cherry is soluble in water, and the target extraction range hasn’t changed since the 1960s — so why does everyone still measure coffee with a scoop?

Brewing Science

• Coffee bean is mostly cellulose (insoluble); ~30% of a roasted bean is soluble in water
• Target extraction: 18-22% of the ground coffee by weight — the ‘sweet spot’
• Under-extraction (<18%): sour, thin, astringent — not enough good stuff dissolved
• Over-extraction (>22%): bitter, harsh, ashy — too much bad stuff dissolved
• Strength ≠ roast level: strength = concentration of dissolved coffee in water
• Recommended starting ratio: 60g coffee per liter of water
• Variables: grind size, water temperature, contact time, agitation — all interrelated

In this episode

0:00 Coffee is mostly insoluble — extraction is the goal
0:24 The 18-22% target, and what under/over-extraction tastes like
1:57 Myth-busting: strength does not equal roast level
3:10 Why metric measurement and weight (not volume) matter

Watch the series: https://www.youtube.com/playlist?list=PLX4SK1C49ZWA
(This episode goes live in the playlist on its release date.)
Free guided tasting sheet: https://gillespie.coffee/pages/guided-tasting-sheet
Coffees: https://gillespie.coffee — viewers get 10% with FEARLESS10

Coffee by Gillespie · Fearlessly Roasted