The objective of roasting
espresso is to maximize the sweetness and aroma of the
coffee while minimizing the bitterness and acidity.
Most people focus on trying to reduce the acidity by
roasting the coffee extremely dark. This also removes all the
wonderful aroma and sweetness of a coffee, making the espresso less palatable. This explains the unpopularity
of straight espresso and the popularity of espresso based
drinks where either milk or other flavors are added to replace
the sweetness that was lost by roasting darkly.
170-200°C the sugars in coffee begin to caramelize.
From tasting pure sugar versus its caramelized component
it is evident that uncaramelized sugar is much sweeter.
The dark color of coffee is directly related to the caramelization
of the sucrose in coffee. Therefore, to maximize sweetness
you want to minimize the carmelization of sucrose, yet you
do not want to roast too lightly or bitter tasting compounds
will not thermally degrade. When roasting espresso, stop the roast somewhere
between the end of the first crack and less than half way
through the second crack. Do not roast well into or
past the second crack. We recommend a roasting chamber
temperature somewhere between 205-215°C. Realizing
the danger of the following suggestion we might recommend
a color similar to the one below. Note: All monitors,
computers, and internet browsers will display the color
slightly different. This is only a recommendation
to point out that this color is preferable to the almost
black color you will frequently observe for espresso.
To get a better idea of coffee roasting colors order the Agtron
roasting classification kit from the SCAA.
See the article written by
Carl Staub of Agtron on coffee roasting
and chemical reactions for more information.