To make a good coffee, use soft water (or water that is not too hard) without any traces of chlorine.
The temperature of the water poured over the grind must be roughly 90°C. Boiling water, i.e. over 100°C, destroys the coffee's aromatic molecules.
There are five ways of making coffee, and each one gives a beverage with different organoleptic properties.
Infusion (French press coffee maker)
This method requires the use of a French press. The grind is placed with the water in a glass jug and a plunger equipped with a wire mesh traps the coffee grinds at the bottom of the jug. This method captures the froth, and the emulsion of oils that contain the aromatic molecules.
TERRA KAHWA® prefers this simple method that gives an excellent brew.
Cone-style brewing (filtered coffee)
This is the most common method today. Hot water is passed through a filter filled with ground coffee. The disadvantage of this method is that it traps a number of aromatic molecules in the grind. Furthermore, keeping coffee on a hot plate tends to oxidise the beverage and makes it more acidic.
Percolation (Italian cafetière)
This is lixiviation with pressurised steam. The cafetiere is made up of two compartments separated by a filter holder containing a dose of coffee. When it is heated, the water placed in the tightly closed unit evaporates and then comes up, pushed by the pressurized steam. As it does so, it goes through the coffee and spills over through the funnel and then to the upper chamber. The pot is used for preparing and also for serving the coffee.
The main disadvantage of this method is that it passes extremely hot water (>100°C) through the grind and destroys the aromatic molecules.
Percolation under high pressure (Espresso)
Pressurised percolation is used in making espresso coffee. It is different from the previous method in that the pressure is created by a pumping system. The water does not heat up to 100°C and the aromatic molecules are preserved.
Contrary to what is commonly thought, espresso contains very little caffeine because the water goes very fast through the grind (7 g) and is therefore unable to dissolve it.
Turkish coffee
An extra-fine coffee grind mixed with water and sugar (300 ml of water, 1 cube of sugar and 3 spoons of coffee) is boiled in a container on a stove. This is the oldest method.