Level of Extraction

Principle #2 of making good coffee – Managing the level of extraction

When one first get introduced to making your own coffee, or when you are introduced to a new way of making coffee.  There is some questions that people ask me often like: “how fine should I grind my coffee?”.  Most of the answers on these questions will affect extraction, so I decided to have a post about extraction.

Principle#2 in making good coffee is managing the level of your coffee extraction.

Managing extraction is super important since incorrect extraction will lead to either over or under extraction.  As a rule of thumb, under extraction will lead to sour or acidic tasking coffee, but you can also get salty tasting coffee.  Over extraction can be recognised by a bitter, but tasteless or hollow tasting coffee.  Only when you hit the sweet spot in-between, will your coffee hit the spot with intensity of flavour, balance and lingering pleasant aftertaste.

Extraction level can become very scientific by the use of a refractometer, which is a device often used by especially fruit farmers.  This device can measure level of refraction and since light refract more when traveling through suspended solids it can measure percentage of solids within any liquid.  Because of this, it can also measure extraction level of coffee!

We will try and keep things simpler here 🙂

The following will affect extraction, separated by brewing category as described in Brewing Methods:

Extraction factors for all methods:

  1. Grind size
  2. Water temperature
  3. Brew ratio

Extraction factors for steeping methods

  1. Agitation
  2. Steeping time

Extraction factors for drip or pour over methods

  1. Pouring technique

Extraction factors for pressure or vacuum methods

  1. Pressure applied
  2. Compaction
  3. Distribution

Let us expand just a little into each of these, but play around with all the variables and have fun!  Coffee making is a science for sure but also an art form, so do not let these factors steal your coffee joy.

  1. Grind size: this will affect extraction for all methods, since smaller particle size makes for bigger surface area, so finer grind = quicker extraction.  Various methods also require different grind sizes although some methods can be used with various grind size such as the Aeropress.  Here are general grind sizes per preparation method as a rule of thumb:
    • Super Fine: Turkish Coffee
    • Very fine: Espresso
    • Fine: Mocha Pot like Biatelli
    • Medium to fine: Pour over like V60, Chemex or other cone filter equipment as well as Aeropress
    • Medium: auto drip machines
    • Medium to coarse: Vacuum pots
    • Coarse: French press
  2. Water temperature: Water should not be too hot, else you will get over extraction.  The ideal temperature is between 91-96 degrees Celsius (195F-205F).  Closer to upper level is optimal, but never over.
  3.  Brew Ratio: This is the ratio in grams between the coffee and the water used.  The rule of thumb is 1:15-1:18, where 1:15 is stronger ratio since only 15g of water is used for every gram of coffee.  Note, this is only a rule of thumb as the other factors come into play, but it is a good starting point for your experimentation!
  4. Agitation (for steeping methods): The more you agitate or stir the coffee wile steeping, the more extraction you will get in a shorter time.  Since even coffee allowed to bloom first, will rise to the top of the water, agitation is needed for optimal extraction.  Blooming is the practice of adding just a little water initially and waiting for about 30 seconds before adding the rest of the water, allowing gasses trapped in the coffee to escape and the coffee to get saturated.  I recommend an initial gentle but firm agitation and then letting the coffee steep.
  5. Steeping time (for steeping methods):  You should allow optimal steeping time before you plunge if you are using a French press or filter out grounds in any other way.  If you are using a French Press, pour straight after plunging or decant, else extraction will continue.  The amount of time will vary from 4 minutes for French press to 24 hours for cold brew!
  6. Pouring technique (Pour over methods): A lot has been written on pour over technique.  The height, the number and duration of pours etc.  as it has the same effect as agitation in point 4 above.  I like to keep it simple.  After allowing for blooming as described before, I like to do around 5 pours to reach the desired ratio of water to my coffee, done in such a way where I do not let grounds go dry at any time and when I pour, I do it slowly and as stated in the Stumptown video, always aim for the dark spots, never for the light spots, in concentric circles.
  7. Pressure applied (Espresso and Aeropress)  Although most espresso machines have a fixed pressure, it does have an effect on extraction.  with Aeropress you can manage pressure your self and I have seen posts where people tray and achieve espresso from an Aeropress and going to lengths like creating a lever system to allow for increased pressure!  The general rule for the Aeropress is a gentle but firm, even pressure.
  8. Compaction (espresso): a lot, as always, have been said about pressure and how many pounds of pressure.  More important than this though will be to always tamp with a consistent pressure.  I apply pressure until the coffee grounds resist further compaction.  When you start tamping, the coffee will give way easily, but soon it start to resist.  I stop at my known point of resistance.  You should do the same and modify pressure if coffee either flows out like an open tap by increasing tamp pressure or fineness of the grind.  The opposite should apply if you get drop by drop espresso being extracted.  Compaction should of course leave you with a level bed of coffee.
  9. Distribution (espresso): The even distribution of the coffee in the portafilter before tamping will allow for optimal extraction.  Since water will always find the way of least resistance, we want to create even resistance to water penetration throughout.  There al lots of methods, but I use the ONA OCD distribution tool and swear by it!  Distribution is now less of an art, but I get super consistent distribution from using this tool.

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