Espresso Preparation

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. Espresso stands out from other beverage preparation methods because it uses forced percolation following an increase in water pressure.

As well as water pressure, espresso can differ according to the different grain size of the coffee (normally fine), different dosages (approx. 7g per dose yielding 1 fl. oz.) and a water temperature of 88°C ± 5°C (190 – 200.0 Fahrenheit). Espresso also stands out for the composition of the coffee mix and the roasting curve used and it is essential to start with a suitable blend, processed by a proper grinder and a proper coffee machine operated by a qualified professional, with some important parameters.

The preparation of a good espresso coffee passes through 3 different stages.

  • The first is WETTING (also known as pre-infusion), when the interstitial cavities are filled to prevent the pressurized 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 (40 Lb.) the coffee will take up some 40% of the pod volume.
  • 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.
  • 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.

Authentic espresso preparation parameters:

Necessary portion of fine ground coffee 7 g ± 0,5
Milliliters in the cup (including foam) 25 ml ± 2,5 (0.84 – 0.93 US fluid ounces)
Ceramic cup of 50ml heated up to a core temp of 88°C ± 2°C (190.4 – 194.0 Fahrenheit)
Entry water pressure 9 bar ± 1
Entry temperature of water to brew unit 88°C ± 5°C (190 – 200.0 Fahrenheit)
Exit temperature of water from the unit 88°C ± 2°C (190 – 194.0 Fahrenheit)
Temperature of the drink in the cup 67°C ± 3°C (152.6 – 158.0 Fahrenheit)
Extraction time 25 seconds ± 2,5 seconds
Viscosity at 45°C > 1,5 mPa s
Total fat > 2 mg/ml
Caffeine < 100 mg/cup