AUTHOR: Daniel Moranville, KOHI
Because each coffee doesn't have the same solubility in water, whether due to the degree of roasting or the origin of the bean, the coffee / water ratio must be continuously adjusted to bring out the best in each bean. Since an espresso is subjected to about 9 bars of pressure, a small change can have a big impact. We will try here to reduce the number of trials / errors in your process.
You will need a scale and a stopwatch for the purposes of the case. Since we must have a starting point, as in every experimentation process, the ratio that is often used for an espresso is 1: 2 (1 part coffee for 2 parts water). So, if 18g of coffee is ground in my filter holder (what your machine's double filter should contain), I will extract 36g of espresso in my cup. Simple, right?
Indeed, it is not very rocket science as a formula, but what comes to confuse the cards? Time ... 1: 2 is alright, but how long does 18g of coffee take to turn into 36g of espresso? Aim for an extraction between 25 and 35 seconds to begin. Some coffees will be enhanced with faster extraction and others with slower extraction.
To lengthen the extraction = finer grinding (the water will take longer to pass through the coffee)
To shorten the extraction = coarser grind
Forget the numbers and calculations for a moment ...
Before throwing an espresso because according to your data it is not successful, TASTE IT! In all situations, it is possible that the parameters of your last extraction are the best for this coffee, or above all, for your tastes.
Then, the changes you make to all of the variables in these extractions will be related to your preferences. In all cases, trust your taste buds and not the scientific graph of your extraction.
To guide you on how to modify the variables, here are a few tips:
The espresso is too acidic, even safe: extend the extraction time by reducing the grind.
The espresso is bitter, lacking in clarity and acidity: increase the ratio.
Once diluted in milk, the espresso loses its presence: reduce the ratio and lengthen the extraction time.
These are just some examples of what can be done to change the end result in the cup. Do not be afraid to change the extraction parameters from one coffee to another to be able to find the combination that will be ideal. Just because the new bag you just bought does not satisfy you with the first espresso does not mean that it will not surpass those from before after a few small adjustments ...