The current roast doesn’t necessarily respond the same way to power and fan settings as a previous roast. And the roasting proces is slow to respond on changes so you have to make changes in advance – its like sailing a ship.
So I wanted to find control points along the roast that tells me where the roast is headed – so I can adjust the heat in time. Me = Therese.
I first wrote about adjusting by control points in November 2016. Since I have continued to develop my strategy.
Update October 2017
After having been focusing for a year on the bean temperature profile and ROR – I have now moved it to a secondary position. Because it didn’t really help me make good coffee. And because what happens in the bean probe is not exactly the same as what happens in the beans, see Bean probe sensitivity.
But I still use the BT and ROR as input to how I manage the roast.
In the beginning of the roast I look at these parameters to see how quick the roast got started:
Temperature of turning point (TP)
The ROR peak level
Time when bean temperature (BT) reaches 115 C.
If the roast is going too slow for what I want → I will use more heat (P). If it goes too fast → I will use less heat.
What happens in the beginning of the roast very much determines the direction of the rest of the roast – and more so the larger the batch is. It is very difficult to change direction later on.
From there on I note the physical change: color and start of First Crack.
Time of yellow point – and note temp and ROR
Time of medium brown – and note temp and ROR
Time of start dark brown – and note temp and ROR
Time of First Crack start – and note temp and ROR
I have in mind approximately how fast I want to reach First Crack, the length of the middle phase (=from yellow to first crack, MAI) and the ROR level around first crack. I adjust the heat according to how the roast is progressing and how I know the roast behave in the different stages.
To stop the roast I go by time: counting seconds from first crack start.
I don’t worry about getting the exact same BT and ROR curves as an earlier good roast of the same bean. I don’t worry about have a perfectly nice declining ROR curve.
My earlier approach:
Post from November 2016
I have found a new approach to decide adjusting power and fan during the roast on the Bullet R1. Until now I have just tried to do what worked earlier. And then hoping it was right for the current roast.
When it didn’t work out, it was too late to do anything about it. Like a ship the roast takes time to change direction.
How the batch develops from a given setting is much affected by type of bean, batch size, ambient temperature, how clean the filter is and so on.
My hopes for this roaster were to be able to design the profile: ROR levels, time of 1st crack (FC), yellowing and so on … And to know what I am doing during the roast. Not having to repeat the same roast many times before I get to where I want.
So I got the idea to find control points that tells me where the roast is headed. So I can adjust the heat in time.
When the roast has reached BT= 115 C at a certain time, I know if its on time or ahead or behind – and I can adjust the heat to regulate.
ROR levels are the speed of the roast and predict the time to reach FC start and so on.
I analyzed a bunch of my previous roasts. Both the successful ones and the unsuccessful (acording to how I want to roast).
Successful ones = when FC start around 7-8 minutes
Unsuccessful = FC starts later than 10,5 minutes
I picked milestones along the roast: bean temperature and yellowing and FC. Then noted the time and ROR.
There was a clear pattern. The unsuccessful roasts had lower ROR, naturally. Not so clear at 115 C. But from 130 C and onwards.
With this list I then roasted 3 batches. What a difference it made! Now I had the feeling of knowing where I was headed and could adjust heating in time.
All 3 batches got a FC on 8-9 minutes. I got the ROR levels more where I wanted them.
I am thrilled :-D
I have posted my list under Roast Profiles. But its only a start. Surely it will be developed as I go.
Be aware: Our bean probes are different: so you can’t use my list if your FC onset isn’t around 170 C. Make your own list.
UPDATE JUNE 2017
My strategy has developed since I started my control point guide in November 2016, see http://coffeenavigated.net/roast-by-control-points/
This is for high-density beans = high grown (I haven’t investigated the threshold for this, but something like above 1.500 meters) and a light roast.
My bean probe may be different than yours, so you cant use the degrees directly – but this can serve for inspiration to make your own guidelines.
A high heat start → higher preheat than earlier
To prevent to big a drop in ROR after the initial peak (at somewhere around 1-3 minutes), increase heat at this point
Already at 150°C; aim for ROR level around 3-5 at FC start (typical around 170°C with my bean probe) by slowly decreasing Power
Preheat for 400 grams: 185°C – but if its the first batch 190°C
Start at P6. At turning point go to P7. During the ROR peak rise to P8. Exactly how this is done depends on Turning point temperature, the ROR-level of the peak and the time for reaching 115°C and 125°C
Fan at P2 until yellowing point or just as browning starts then F3.
After yellowing point, around 150°C decrease power step by step. I adjust this according to:
Aim for ROR around 10 at 150°C . And at 160°C ROR at 8 and power stepped down to P4.
At First Crack start have power at P2 and have ROR around 5. During FC the ROR has a tendency to drop. Don’t worry too much about it. But try and keep ROR between 2 and 4. If ROR is to high try with fan at F5 or even F6.
If ROR is higher than 5 after FC start, then do a shorter time to drop.
400 grams ethiopean (Homa)