Coffee-grinding is a vitally
important factor of excellence. Inappropriate
coffee-grinding may mean that an otherwise excellent
product is burnt while the coffee is being made.
If the ground coffee is too coarse, it loses solubility,
which means the water can flow off without fully
extracting the aroma and flavour. If too fine,
the beverage is too strong and occasionally acquires
the flavour of burnt coffee.
For an excellent cup of espresso coffee
the ground coffee must produce 25 ml (±
2.5 ml) of beverage in 25 seconds (± 2.5
If making the coffee takes more than 30 seconds
(over extracted coffee), a coarser texture of
ground coffee is required. If it takes less than
30 seconds (under extracted coffee), a finer ground
coffee is required, to slow down the flow of water
through the coffee.
The quantity of ground coffee per shot must range
from 6.5 to 7.5 grams. The hopper and doser must
be periodically cleaned. Clogging of coffee on
the doser blade may affect dosing. Fatty clogging
of the hopper or doser will make for rancid coffee.
The ground coffee should be consumed rapidly following
grinding (max. 1 hour).