Measuring roast colour is important. The type of roast - light, medium or dark - has a definite bearing on quality.
- The darker a roast, the less pronounced the acidity and different flavour aspects (as well as defects) of the liquor, but the heavier the body.
- The lighter a roast, the more pronounced the acidity and flavour (and defects), but the lighter the body.
Different markets roast coffee differently. Exporters should understand the type of roast their buyers need. But 'light, medium and dark' mean different things to different people: they are subjective terms. See also also 12.09.01 on roast and 12.09.04 on tasting - traditional versus espresso.
The Specialty Coffee Association of America (SCAA) has developed a points system to classify the degree - the colour - of different roast types. The system consists of eight numbered colour disks against which one matches a sample of finely ground, roasted coffee, usually pressed into a laboratory petri dish. In this way one assigns the roast an approximate number on what is commonly called the Agtron Gourmet Scale, ranging from #95 (lightest roast) at intervals of 10 down to #25 (the darkest common roast).
This helpful tool enables producers and roasters to speak the same language when discussing 'the roast' of a coffee. (It is available from the SCAA's resource centre in Long Beach, California - see www.scaa.org.)