Basic roasting profile
S SHOUT
The curve generally takes place over a time frame of 14 to 15 minutes. It looks at temperature and time, the two main variables. The first crack occurs about 12 minutes after the start of the roasting process. Dismas Smith, a contributor to the Perfect Daily Grid advises to stop roasting 1 to 2 minutes after the first crack, when you will be sure there is less than 1℃ to the second crack. This "window" is large enough to allow the coffee to develop its flavor and aromatic qualities perfectly without unpleasant acidity when the coffee is under-roasted or oily flavors when the coffee is over-roasted.
It's not about setting the S curve on your roaster, throwing in the beans and waiting to see what happens. Roasting requires your activity at least at the points that the S curve indicates.
Study the S curves of other roasters and roasters and draw on their experience.
START: STARTING TEMPERATURE
The temperature at the second crack can be a guide for setting the starting temperature. Set this on your roaster and then adjust the temperature as the roast progresses. Do not increase the temperature suddenly, but allow the beans to warm up gradually. The air in the roaster cools down as the beans are thrown in, you can see this on the curve, but they start to warm up very quickly and the temperature will equal the set values and soon exceed them. At this point, beware, the Turning Point is coming!
TURNING POINT
The turning point occurs when the grains have absorbed enough heat. Thetemperature starts to rise again. Now it is important to heat the grains to the maximum. Increase the temperature roughly so that it reaches an increase of 10℃ in 1 minute. Until the first crack.
FIRST CRACK
Can you hear the crackle? This is when the grains have reached the first crack, when the gases and moisture inside the grains have started to be released and the Maillard reaction has been activated. Atthis point, the temperature should be lowered or the heating turned off completely, because the first crack takes place very quickly and the grains could easily burn due to the rising temperature. If you have turned off the heat, allow the beans to crack for a period of time to allow the desired flavour characteristics to develop sufficiently.
DEVELOPMENT TIME
Theflavour characteristics of the coffee develop throughout the roasting process, but it is during this time that the overall flavour quality of the roasted coffee will be decided. Its acidity and body. If the Development Time is longer, the acidity will be lost and the body (i.e. the density, fullness of flavours and aromas) will become more important. The coffee will be sweeter. If you want to retain the light acidity likened to the fruity notes in coffee, shorten this time. It is then up to you what you want to get out of the roast. The temperature should be stable at this stage, rising no more than 6℃ and should not drop unnecessarily.
END OF ROAST
Thetemperature should be sensitively increased at the end to allow the beans to finish roasting without complications. At this stage, they have gained a little more volume and their surface is smooth and darker. After cracking, the grains should be uniform in colour. Beginners, to avoid undercooked grains, can let the grains roast just before the second crack, when the grains darken considerably.
Roasting is a joy, so don't be afraid of it and study its laws with enthusiasm!