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Last active November 6, 2023 19:00
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Intuition for espresso recipes
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espresso.md

Variables that make up the espresso puck

  • Coffee bean solubility (roast level / altitude grown / type of bean)
  • Coffee dose / Head space
  • Grind size
  • Uniformity (puck preparation)
  • Tamp pressure

What makes an espresso

  • All these variables must yield a puck that in contact with water creates some "integrity" - this integrity creates the resistance to water necessary for extraction under pressure.
  • Integrity always increases with these variables.

The recipe

  • The puck
  • Water temperature
  • Pre-infusion (time, pressure / flow-rate, temperature)
  • Infusion (time, pressure / flow-rate, temperature)
  • Yield amount

Goal of a recipe

  • Enhance the extraction of desired flavor compounds to archive specific tasting notes.
  • Hide bean defects.
  • Balanced extraction for the desired drink: milk drinks prefer less acidic and more chocolatey notes.

Overall characteristics of a espresso

  • Body: greater body caused by short head space (high dose) and low yield.
  • Fruitiness / Clarity: Higher flow rate increase fruitiness and lowers the chocolate notes, greater clarity is more likely to show defects on highly soluble beans.
  • Astringency: High pressure causes more astringency and chocolate notes, lower clarity.
  • Overall extraction: Bitterness caused by over-extraction, sourness caused by under-extraction. A mix of both is an unbalanced espresso - caused by over-extraction / loss of puck integrity.

Principles of extraction

  • Extraction does not relate directly with: shot time, flow, grind, yield. Extraction is only about water contact / pressure and temperature!
  • Extraction is a process - different flavor compounds are extracted at different rates: pressure, temperature and flow rate are a function of time and are part of the recipe (flow profile, pressure profile, temperature profile).
  • Puck loses integrity with extraction. Pre-infusion preserves more integrity than infusion.
  • Over-extraction is extracting after the puck has lost integrity. Sometimes this integrity is broken at the start of the shot (channeling). There is no difference between a channeled shot and an overextracted shot.
  • Over time, the puck always tends towards losing integrity, and the lesser the integrity, the more easily it tens to disintegrate more. Slight decrease in presssure can recover some of this.

Developing the recipe

  • Design the recipe so that you can extract desired compounds while the puck keeps its integrity.
  • Keep updating the puck recipe in such a way that you have the desired integrity for your pressure / temperature / flow profile.
  • There is no clear relationship between flow and extraction, but pressure directly affects integrity. Pressure can compact a puck and lead to a stable extraction, or break the puck and generate channeling.
  • Diagnose pucks with broken integrity with open portafilter (non uniform color or extra yellow / watery), jumps in pressure or flow, dark spots in the puck.
  • Example: extraction converges to very pale yellow only after 5 seconds (puck rapidly loosing integrety). Solution 1: Decrease pressure/flow to maintain integrity for longer. Solution 2: Increase puck integrity by changing any puck input variables (grind size...).
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