Every coffee has unique characteristics that affect the way beans are roasted.
Moisture levels, bean size, processing method, and varietal are just a handful of the variables that dictate our coffee roasting process. Developing a “roast profile” that is unique to each coffee highlights the flavour characteristics that we look for when we select our coffee beans. It’s not a bad idea to get used to the jargon of coffee roasting. When preparing a coffee for its first go through the roaster, there are a few important things to consider:
Moisture content -% moisture in the coffee beans (usually 11-12%)
Screen size – the physical dimensions of the bean
Bean density – compactness or mass of a volume of coffee
Processing method – how the coffee was prepared for market post harvest
Varietal – the specific species of coffee tree that our coffee was harvested from
With all the info at hand, we consider how the coffee will be served, and plan a roast profile accordingly. Read about serving style roasting here!
A roast profile is basically a set of instructions for repeatable coffee roasting. The variables in the instructions:
Charge temp – the temperature at which beans are loaded into the roaster
Soak time – time at the start of the roast where little to no energy is introduced
Batch size – quantity of green beans, usually measured in kg/lb
Burner % – gas burner setting/electrical heating element setting, usually 0-100%
Air % – air flow setting, usually 0-100%
Drum speed – the RPM of the roasting drum, or how fast the drum is spinning
By now, the coffee beans are loaded into a clean bucket, ready to charge into the roaster that has gone through a preheating procedure. We set the roast profile and charge the drum/heating chamber. Immediately, the coffee absorbs the heat in the drum, and our clever coffee profile software draws nice little graphs for us. Not everyone uses software for roasting, and some prefer the subtle art of sensory roasting and that’s pretty awesome too.
The roast has begun, and as variables are adjusted, measurements of the coffee and roasting environment are taken and analysed
Bean temperature – the temperature of the bean mass as it is agitated in the drum
Environment temperature – the temperature of the air inside the roaster
Rate of Rise – temperature change divide by time
Throughout the roast, there are a few key events that are important indicators in how the coffee is progressing, and what the roasters’ next step should be.
Turning point – this is the time or temperature that the green bean temp reaches equilibrium with the roasting environment temperature.
Drying phase completion – the time at which the 10-12% moisture content of the green coffee has reduced to around 2%
Browning / maillard reaction – the time between completion of drying and beginning of first crack
First crack – when the moisture remaining in coffee beans expands rapidly and causes the coffee b to crack open similar to how corn pops.
Drop temp/time – the time and temperature readings when the roast is completed and dropped from the drum into the cooling tray
Development time – the time measured between first crack (measured or assumed), to the drop temp
Development time percentage – a measure of the development time as a percentage of the entire roast time
The result: an intentionally roasted coffee. What does that mean? The coffee has been carefully roasted to suit the exact purpose it was purchased for: to delight and add value to the coffee experience of Brightside buddies.