After upgrading from savage methods like a pan or an oven I can finally record my temperature and RoR properly and start learning. Few days ago I roasted some Costa Rican washed beans using the new setup (it's a Hottop) and yesterday I finally brewed this coffee. The cup quality is definitely better than what I was able to achieve in the oven or with the pan but it definitely might be better. I was aiming for a rather light roast (New England?).

The complaints I have:
1) Even though the roast reached only 184C (363F) it seems darker than I'd expect so maybe my thermocouple is a bit off
2) The flavour reminds me mostly of almond, nougat, bread crust but it's a bit flat and dull. I'd like it brighter, crispier, juicier

The questions I have:

1) It's often said that the RoR should be going down steadily after peaking during drying phase. It's not the case for my roast as you can see so I ask - what are the benefits of such RoR? Is it crucial?
2) If I wanted my roast to be a bit lighter should I develop shorter or leave it be around 20% but try to flatten the temperature curve there so that the final temp is lower? What is the impact of both?
3) What's the best way of preserving the acidic notes? During which stage did I lose them? Should I just aim for lower end temp or is it rather about the temp dynamics throughout the roast (like coming to the FC faster so that the acidic compounds are preserved)?

As you can see on the graph I charged with the burner turned off and set it to 100% on turning point. The temperature recovered very slowly though so I did not achieve RoR peak anywhere near this place. Is it because of the inertia of the electric burner and I should perform any changes in advance?

These are the curves:

IMO your numbers look very good as far as percentages go in the 3 phases. I'm going to say your BT thermocouple placement needs to be looked at..

pralat wrote: The complaints I have:
1) Even though the roast reached only 184C (363F) it seems darker than I'd expect so maybe my thermocouple is a bit off

Can you remove your thermocouples and test their readings in ice water and boiling water to see if they read correctly? You could add calibration adjustments in Artisan for this.

pralat wrote: 1) It's often said that the RoR should be going down steadily after peaking during drying phase. It's not the case for my roast as you can see so I ask - what are the benefits of such RoR? Is it crucial?
2) If I wanted my roast to be a bit lighter should I develop shorter or leave it be around 20% but try to flatten the temperature curve there so that the final temp is lower? What is the impact of both?
3) What's the best way of preserving the acidic notes? During which stage did I lose them? Should I just aim for lower end temp or is it rather about the temp dynamics throughout the roast (like coming to the FC faster so that the acidic compounds are preserved)?

It's generally accepted that a smoothly declining RoR curve will result in fewer roast defects. For more info on this, I suggest Scott Rao's latest book, "Coffee Roasting Best Practices". As for the effects of various roasting techniques on flavor, I also suggest Rob Hoos book, "Modulating the Flavor Profile of Coffee". You may also want to use the search feature of this forum which will provide information on your questions.

pralat wrote: These are the curves:

Re: the BT RoR curve: I will echo that you should look at your BT probe placement, determine if it's reading accurately, and also ensure you had an adequate charge weight so the probe was covered by the bean mass. Also, you may wish to make fewer fan changes during a roast, but I defer to those with HotTop expertise whether that's true on your roaster.

mkane wrote:IMO your numbers look very good as far as percentages go in the 3 phases. I'm going to say your BT thermocouple placement needs to be looked at..

I came up with an idea. It's a hottop, so the BT probe is not touching the beans anyhow - it's just another probe like the ET one but placed away from the burner so the real BT might be higher than the one measured - can any Hottop user confirm this?

Another thing. The coffee I've been roasting is extremely nonuniform in regards of bean size (and so is my resulting roast level because of this). I guess the moment I marked the FC is the moment when the softest (or smallest?) beans started popping while the denser ones were still warming up before the crack and thus the low BT probe reading. Is this thinking anyhow reasonable?

pralat wrote:I came up with an idea. It's a hottop, so the BT probe is not touching the beans anyhow - it's just another probe like the ET one but placed away from the burner so the real BT might be higher than the one measured - can any Hottop user confirm this?

Yes, it is. In my hottop2k+, 1C starts at around 180-186ºC BT, while it is well known that 1c starts at approximately ~195ºC

While I do not have a Hottop, if I were given this machine and this roast curve result I would do the following for starters (then adjust more based on results):

• Eliminate the soak. Your turning point marked at 1:40 suggests your T/C is slow to respond and 1:40 into the roast has put your ET to close to your BT. This results in a low initial ROR and the need to catch up by applying heat more aggressively leading to an increase in ROR. This aggressive heat application mid roast sets your Environment Temp (ET) to be a bit high entering first crack which carries your finish temperature higher than what you are looking to achieve.

• For your purposes, ignore the 20-25% development time rule of thumb for now and cut your development time to ~1:20. We can adjust from here based on what you want to achieve.

• Shoot for total roast time of ~9:20. This will put you at FC at around 8:00 then 1:20 development to get to 9:20. IMHO this will give you a bit more acidity than your 10:10 roast but not put you at too much risk of underdevelopment. A faster roast time will preserve acidity. You can get too fast though so this time provides some margin to be more aggressive while still preserving more acidity than your displayed roast.

• Cut your heat in a similar manner to what you did in your roast trying to hit Dry End between 4-5 minutes and FC at 8:00 (as targets for this attempt)

• You have an electric roaster. The time delay between when you make an adjustment and when you see the impact in ET and BT should be noted. You may not see adjustments for 45 seconds which means you need to learn to anticipate.

In regards to your questions, I will give you my opinions on a very complex topic and hopefully others will weigh in with more opinions:

1.) Is it crucial, no, does it matter yes. I know opinions vary somewhat on this, but I would recommend trying to get your roast to that general declining ROR look first, then experiment from there to see in which camp you fall.
2.) The short answer is you want to balance both time and temperature. Think about roasting meat. If the meat is put into a very hot environment, you can sear the outside while preserving rare in the middle or you can sous vide at low temperatures for long periods of time to achieve the exact temperature throughout. For coffee, we do not want raw in the middle so we don't want too high of an ET at the end (especially after the moisture is released in FC) or the coffee will taste roasty. On the flip side, if we take too long, our acids are breaking down and we not only lose acidity but we are actively creating bitter compounds from the break down of chlorogenic acid. So there's a window in which we are working. Within that window, it comes down to preference.
3.) The acidic break down increases with temperature and time. The longer the roast, the more acidity will be lost. The hotter the temperature, to faster acidity will be lost. In other words, two roast that finish in 10 minutes with roast A finishing at 420 deg F and roast B finishing at 405 deg F, one would expect roast B to be slightly higher in acidity. If roast C finished in 9 minutes at 405 deg F, roast C would be expected to be slightly more acidic than roast B.

Please understand that there are many methods to roasting and I don't claim this to be THE answer. These are merely the adjustments that I would start with to move the needle in the direction you say you want to go. I would caution you not to change too many things at one time, it will muddle the impact of each change. Hope this helps!

I wouldn't advise doing a soak on the HotTop as the electric element isn't likely to be able to fire up your RoR again in a suitable time frame. Typically soak works for high preheat and back to back on gas roasters from my reading up on it. Your mention of "bread like" suggests "baking" which can be a symptom of the level vs declining RoR you see. I would try another run with no soak and see how that changes things from a curve and taste perspective and go from there...

CrabApplesSix wrote:Hope this helps!

Totally! Thanks a lot for such insightful advice. Can't wait to give it another try

@crabapplesix very good post thanks for sharing that.

I finally started getting some curves and roasting times I'm happy about. Now I struggle to overcome this massive drop in my RoR followed by an instant flick and crash around 4min. Might be helpful to know what's the reason for that - is it the fact that the moist beans are absorbing heat on a very high rate and later when they're dry they start to give the heat back to the drum? Should I even bother to smooth this curve? What's the potential benefit? These were quite dense washed Ethiopian Yirgacheffe beans BTW.