Although studies circulate that the bitter taste of coffee is related to the level of stress, the reason is really much simpler: you don’t prepare it well. As nobody said that making coffee at home with a manual preparation method was going to be easy, we have tried to gut the most important factors that influence the more or less acidic, or more or less bitter taste of our coffees.
Sub-extraction vs over-extraction of coffee
When we talk about extraction, we mean the process by which water soaks the ground coffee particles by dissolving all its components to a greater or lesser extent. If we do it well, and we reach the optimum extraction point, our coffee will have a sweet and pleasant taste with a balanced acidity note.
If, on the other hand, the taste does not seem appropriate, one of the following phenomena has occurred: under-extraction or over-extraction of coffee.
As the specialist explains, under-extraction occurs when the water has failed to extract enough flavour from our coffee. Normally this happens because the extraction has been of short duration or the grinding too coarse, causing the water to take longer to emulsify the ground coffee.
When this occurs, the coffee leaves in our mouth an unpleasant acid aftertaste with salty notes — nothing to do with the pleasant acidity point we want to get in our coffee preparations.
Over-extraction, on the contrary, usually occurs because the grinding is very fine or the total extraction time is longer than it should. The coffee has in these cases a bitter aftertaste (as if burned) because the water has been infused too long taking unwanted flavours of the soluble elements that make up the coffee.
One of the most determining factors for your coffee to come out round is the grinding. If you buy the coffee already ground, warn your local barista about the type of coffee maker you use to adjust the grinding properly.
If instead, you have a grinder at home, you should regulate it until you find the ideal ground coffee. Keep in mind that the size of the ground coffee particles will influence your contact with water. The smaller these are, the contact with the water will be greater and, as a consequence, the faster the extraction because the coffee dissolves earlier.
As a general rule, the longer the water needs to remain to infuse the ground coffee (methods of preparation by immersion and dripping), the thicker the grinding should be to avoid over-extraction of the coffee.
The proportion of coffee and water
Surely when you make a cake at home, you put the amount of flour, milk or sugar that you put in the recipe. More of the same happens with coffee: you have to take out the calculator and measure the exact amounts so that the coffee does not spoil us.
The best thing you can do is keep the proportion of water and coffee always constant. To accomplish this mission, invest in a digital kitchen scale. They are available at affordable prices, are easy to use and will let you know precisely how much coffee and water you use at any time.