It is all about what do you want to get from your coffee beans.
Understanding the nature of your coffee and your roaster are the essential keys to reach your goal.
I will explain few things related to green coffee beans may help you to improve roast profiling.
Density : beans with high density absorb energy quicker than lower density, thats why its better to be charged on higher temp than lower density beans. If you don’t have density analyzing tool, you can kind of rely on altitude, higher altitude beans normally are more dens than lower altitude due to cold weather, which allows the coffee cherry to mature slower and be more dens.
Thats why i charge the Ethiopian beans somewhere between 195-205 C degrees for 800g batches, while I charge the Brazilian 800g batch between 180-185 C (I am using humidity and density analyzer).
I charge the beans, let it soak for a minute at least (normally turning point would be around 1:05 and 1:10 minuets ). I prefer applying heat after the bean obserb the heat to the core to avoid roasting from outside.
My advise is you should preheat your roaster well, to make sure the locked energy goes to the bean, if the roaster was not ready, you will waste some of your energy source on heating both the beans and the roaster itself. But if you preheated your roaster as you should, all the energy will go to the beans.
Maintaining the momentum of the heat is mandatory during the dry phase. Thus I prefer to do not go higher than F2 during the drying phase ( between charge and yellow point). But after the yellow point, and during the milard phase, we better increase the fan to be F4 for 600g batches and F5 for 800g batches, to increase the conviction and rely less on the conduction, that may affect the momentum, because we are blowing some of the energy we were maintaining during the dry phase, but it will increase the clarity in our cup.
Yet, we will increase the fan speed one more time ahead of the first crack point, to blow the traped somke out of the roaster and get a cleaner cup. I go for F6 for the 600g batch and F7 for the 800g batch.
I advise to depend on Bean pulp temp all the during roast phases,
If we had 2 roasts for the same batch ended on 220C degrees, first one ended in9 minutes while the second one ended in 11 minutes. The first one will be with higher acidity less body and higher clarity, while the second one will has a richer body, more bitter, less acidity and clarity.
If I want to roast a fruity notes coffee, I will hunt for a quicker roast time. But that greedy desire may lead to underdeveloped roast with greens and grassy notes, if you noticed these notes in your cupping, thats mean it was dried from outside, but was not dried enough in the core. Better to adjust the profile to increase the span of the drying phase.
If you noticed chocolate, brown sugar and nuts in a profile designed for a fruity flowery beans, thats mean your milard phase had taken longer time, push more energy between yellow point and first crack to shorten the the middle phase (aka : caramelization / milard).
Please, keep in mind, there is no one correct way to do anything including roasting, roasting is all about choices we make to achieve what we like.
I hope these notes may be helpful for you. Thank your for taking time reading my article, and I am open for any comments.
Have a good roasts.
Majid
SCA Certified Intermediate Roaster
Diploma In Coffee Roasting & Blending from Espresso. Academy - Firenze, Italy
I’m thinking of making one or two more tweaks the next time I roast and see how it turns out.