Philip P. Ide

Author, programmer, science enthusiast, half-wit.
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blog:coffee_blog:2022-07-31

Coffee Blog: 2022-07-31

Yesterday, I roasted Profile I, which I'd come up with after sampling Profile H. I did two loads, each of 200g.

Profile I
Load 200g End (mins)
Pre-heat 200°C
Stage 1 (to yellow) Drying 200°C 6:00
Stage 2 (to 1st crack) Caramelising 250°C 10:30
Stage 3 Development 240°C 16:30
Ambient Temp 25.8°C
RH 49%
Coffee Columbian - El Carmen

The first load, I forgot to set the stopwatch because I was disturbed by visitors. However, I started the timing once the beans had reached the end of the first stage and turned yellow, which experience told me would be about 6 minutes in. So for the first load, the times for Stage 2 were 4:15 and Stage 3 at 10:30.

Before loading the second load, I had to put the machine into cool-down (start machine up, press red button until it enters cool-down mode), to get the exhaust temperature below 200(^C). Then stop and preheat to 200°C. The second load followed the first so exactly it was beautiful to see - and confirmed my estimate that I had reached the yellow stage at 6 minutes in the first load.

I used some shop-bought medium-to-dark Italian-style roasted beans as a guide for colour. When I stopped the machine, as usual I put it into emergency stop mode, then put the beans into a cooler. I put the drum back in the roaster and start it up again and immediately put it into cool-down mode, then start stirring the beans in the cooler. It takes about 90 secs for the beans to cool down this way.

Both loads were so similar in colour it was impossible to tell them apart, which after considering the similar timing and heat profile means they are, to all intents and purposes, the same.

Testing

As I've said before, grinding and drinking a sample straight after roasting carries some issues. There is a slight burnt taste you have to learn to ignore. Over the next week there will be chemical reactions taking place, one of which is oxidisation. You hear a lot about how this is a bad thing for coffee, but certainly for the first three days it's a good thing. A by-product of this process is CO2, which outgasses, removing a lot of the carbon and taking away that burnt taste.

There may also be a bit of astringency - sourness - which will also fade over the next few days. A lot of the flavours will also develop as part of this process, so what you taste now is only a phantom of what it will be like in a week's time. However, tasting immediately after roasting will reveal whether it is a duffer or not.

I made a double-shot of espresso in my Rok, and man, was that smooth! Ok, things are looking good so far, let's make a mugful in a French press. As expected, there was a hint of burnt flavour, and an equal amount of sour after-taste. What was interesting though, was the amount of flavours in the coffee - so many of them - and this had a week to mature so overall I am very pleased with the result.

Improving The Recipe

So, what can I do to improve the recipe? The yellowing stage ought to be 50% of the process, browning 30% and development 20%.

Looking at the profile above, I see the following:

Stage Actual % Target %
Yellow 36.3% 50%
Browning 27.2% 30%
Development 36.6% 20%

I can slow the yellowing stage down by dropping the temperature, but by lengthening the yellowing stage, all the other values change. Also, it is crucial to go from yellow to first crack in ~30% of the overall time, and currently I'm almost doing that. As it stands, I can drop the temperature slightly in the second stage to get me to 30%, but if I extend the time of the yellowing stage, I also need to extend the time of the browning phase. Whatever happens, the development phase is currently way too long but I can only raise the temperature a small amount. Remember though, that if I extend the yellowing phase to ten minutes, the development phase is currently almost right.

The danger of a twenty minute roast, is that it turns roasting into baking. However once achieved, a twenty-minute roast/bake will give the correct proportions to each stage, which can then be brought down (in total time) simply by adjusting all the temperatures upward (if there is room to move).

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blog/coffee_blog/2022-07-31.txt · Last modified: 2022/07/31 10:25 by Phil Ide

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