he rules for making espresso are rather strict because of the technology involved. The quality of a cup of espresso depends on three factors: the blend of coffee, the grinding and the espresso maker.
The Blend
The key here is to know how to blend various coffee types in order to get the desired aroma, taste and body, and to maintain the quality of that blend over time.
Generally speaking, the more complex the blend is (usually between five and eight different varieties of coffee can be used), the easier it is to maintain its quality over time. This is especially true because as some plants grow old and are replaced with younger ones with more marked characteristics, the other varieties help keep the general characteristics of the blend
unaltered.
The Grinding
The heat-producing grinding process is a delicate one. Just one mistake can turn a promising blend into burnt powder. If ground too coarse, coffee becomes less soluble and does not release its aroma and taste into the water. If ground too fine, it yields an excessively strong beverage that tastes very bitter.
The Espresso Maker
The quality of the espresso depends on how well the espresso maker has been calibrated. Each machine must be calibrated in a different way, but there are some parameters that are the same for all espresso makers:
- The temperature of the water must be between 185 and 197F.
- The boiler pressure must be between 1.2 and 1.4 bars in hydraulic or continuous dispensation espresso makers.
- The pressure of the centrifuge pump must be set at 9.2 bars.
- A minimum quantity of 1/4 oz. of coffee must be used per cup.
- Coffee must be pressed into the filter at a pressure of between 44 lbs and 55 lbs.
- Brewing time for 1 oz. of coffee must be between 25 and 32 seconds.
- The temperature of the coffee in the cup, immediately after brewing, must be about 150F.