In Italy there is a traditional rule, known as the five M’s, which all must be achieved to make great espresso.
1. Miscela (Espresso Blend)
Espresso is rarely ever made with a single-origin coffee. As espresso intensifies the flavour, it is found that single-origin coffees lack balance because the espresso highlights one particular characteristic. To give an espresso complexity and balance a blend of coffees from different regions is required.
The number of coffees in an espresso blend varies from roaster to roaster. Many small scale roasters will concentrate on between 3 or 4, so as to allow each coffee to add their individual character to the blend. But large scale roasters may use as many as 12 different coffees, so each is less distinctive, to minimise the variation in taste from season to season.
The exact espresso blend you choose is purely down to personal taste, but you should use coffee which is:
a. fresh and;
b. of high quality.
The freshness of coffee is vital for making great espresso. Ideally your espresso blend should be between 2-10 days old (after roasting). Coffee younger than this can contain too much CO2 (leftover from the roasting process) and produce a shot with excessive amounts of crema that quickly dissipates. Coffee older then this may taste flat and have little or not crema.
The espresso blend you choose should use high quality coffee beans. However, this does not necessarily mean that the blend needs to be 100% Arabica. Used sparingly, Robusta beans can add a further dimension to an espresso blend, giving it that extra zing. The use of Robusta in espresso blends is a hotly debated topic with many arguing that it takes away more than it adds. However, it is a traditional ingredient of espresso blends from Northern Italy and so whether you choose a blend with or without Robusta is down to your own personal preference.
2. Macinadosatore (Coffee Grinder)
The optimum time (flow rate) to brew an espresso is between 25 and 30 seconds. This is the period when the majority of the flavour has been extracted from the coffee grounds but before the bitter compounds and excessive caffeine are released. In the process of making espresso, it is the coffee grinder’s role to control the flow rate.