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Espresso

The espresso system is the result of a need to obtain coffee within a short time and to make the preparation stage simultaneous with consumption: the word "ESPRESSO" in Italian means fast, at the moment.
From a purely physical viewpoint, espresso stands out from other beverages because it uses forced percolation following an increase in water pressure.
Thanks to the different systems to increase water pressure, such as the use of steam pressure on early machines, or the pressure of a spring on a piston in the case of lever-operated machines, or the pressure multiplier in case of machines with hydraulic units or lastly, the use of a pump in modern machines, preparation times are now less than 30".
As well as water pressure, espresso can differ according to the different grain size of the coffee (normally fine), different dosages (approx. 7 g per dose) and a water temperature of around 90° C. Espresso also stands out for the composition of the coffee mix and the roasting curve used.
The 3 extraction stages of espresso
The preparation of a good espresso coffee passes through 3 different stages.
  1. The first is WETTING (also known as pre-infusion), when the interstitial cavities are filled to prevent the pressurised water jet attacking the surface of the layer. To this end, it is useful to know that in a coffee pod ready for extraction of an Italian espresso (and therefore, with a correct grinding fineness and pressing level of 22 kg) the coffee will take up some 40% of the pod volume.
  2. With the second stage, EXTRACTION, water passes through the layer of coffee powder in the filter at a constant temperature and pressure. The extraction process is extremely complex and involves different chemical and physical phenomena.
  3. Finally, the extraction process concludes with the process of EMULSION of the oils extracted in the previous stage and through which the beverage takes on the creamy appearance for which it is so well known.