EBF : Espresso Brewing Formula
Measuring coffee by volume is inconsistent because as coffee ages, the amount of crema also varies. Typically we define an extraction by saying something like 30 mL in 25 seconds or 30 mL in 20 seconds.
Scientifically, this is known as a volumetric flow rate, i.e. change in volume over changes in time.
For espresso, the units would be in mL/s. This is highly inaccurate due to the fact that a volume reading is typically done by eyeballing in a graduated shot glass, which is inaccurate by its very nature.
Mass is a much more reliable unit to measure our extractions. We could perhaps use a mass flow rate, i.e. change in mass over changes in time for the espresso in our demitasses, leading to a measurement in grams/s. However, volumetric flow rates and mass flow rates don’t give us much insight to the extraction were trying to describe. We need other pieces of key information such as dosage and espresso mass. In other words, describing our espresso in terms of flow rates is useless.
Enter the Espresso Brewing Formula or EBF.
The Espresso Brew Formula or EBF is a ratio of the mass of ground coffee to the mass of the brewed espresso.
EBF (%) = (dosage in grams)/(espresso mass in grams) * 100
What the EBF does not specify is grind setting and hence extraction time, like the volumetric flow rate.
However, this can be rectified by appending such information on top of the EBF.
In order to replicate an espresso between colleagues, write your recipe this way.
eg: EBF (%) = 60 % – 18 gram dose, 30 gram espresso, 22 second extraction, 92 C°.
Now, another person trying to replicate your extraction has almost all the information needed to achieve a similar extraction.
If your extraction is 65% and above is ristretto range – underextracted sour coffee.