WHAT IS THE OPTIMUM ROASTING TEMPERATURE OF COFFEE?
There is no straight answer to this question. Each level of roast like Light (Cinnamon), Medium (American/City) or Dark (Full City/City+/French) has their own desired optimum roasting temperature. Another important aspect on roasting coffee is time, air pressure (profiling) inside the roasting drum (perhaps at a different altitude of roasting place! more research needed…) that determines the taste and flavor of coffee. Let me put this in another way – two batches of same coffee roasted to exactly the same temperature but with a different air pressure inside the roasting drum will result in a dramatically different taste.
There is no optimum temperature for coffee roasting. Large European roasters use hot air roasters (Neuhaus Neotec) and are able to roast 120 kg in 2 minutes! Roast temp around 400/500C. Other large roasters do not need more than 5 to 7 minutes to roast large quantities like 240 kg and more.
If you look at Austria and Turkey, they want at least a roast cycle of 20 minutes, they us relatively low temperatures like 170 or 180C.
I like to roast in cycles of about 13/15 minutes – thermostat at 180C, measuring in the out going air.
In my other roaster (5 kg) temp is measured inside the roast chamber, no thermostat, cycle of about 14 minutes, I dumb the coffee at start of 2nd crack, temp showing around 190C”
– Mr. Ivo van der Putten, The Netherlands, Craft Roaster 30+ years
ROASTING COFFEE: ART OR SCIENCE?
There are generally two roasting cultures. As art, typically referred as Craft Roasters with the years of experience on roasting who relies on their ear (cracking sound), eyes (changing color of beans) and nose (smell on various level as roasting going on) and Technical Roasters who uses roasting profile system and depends mainly on the variables like time, temperature and velocity of the air inside the drum.
Having said above, it is not necessary that craft roast is better than technical or vice-versa. Neither craft roasters with their experience nor technical roasters with technical profiling necessarily produce better roast compared to each other.
Because the craft roasting needs a long experience and may widely rely on particular machines, I would like to share a general guideline of roasting temperature for newcomers on technical roasting.