What to look for in a roast profile

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
eltakeiteasy

Postby eltakeiteasy » Feb 18, 2019, 5:03 pm

Hey all,

I have only been roasting for a short amount of time so I am looking to the pros for some insights. Here's a bit of background on my journey thus far:

Since I was looking to only roast about half a pound a week I decided to use a FreshRoast SR700 as the base for this project.

In order to accomplish my desired charge rate I had to modify the following:

Fan- The stock fan only allowed for a setting of 1-9. This was not ideal as each jump from each step was too large. In order to help create a stepless fan for better control and incremental options which helps create a smooth ROR.

Heating element- The stock heating element configuration was not able to heat the additional load quickly enough so my initial roast was very long or very quick to start and long to finish due to the fan settings needing to be lower to get the heat rising faster. Less airflow was giving me the temperature I needed but I was sacrificing the ability for a high fan setting at the beginning of the roast to extend my DE. I just recently figured out a few solutions to this issue this weekend. After some experimenting, I realized that by removing the built-in fuse and the bi-metallic switch combined with disconnecting the heater coil from the fan, (which was then re-routed back to the primary heater coil) so they can now both run at the same time. By doing so, I was able to increase output from 1520 watts (with major oscillations) up to 1580 at high and full fan before bypassing the controls. Now at 100%, I was able to get a higher range of 1600 to 1750 watts (with little to no oscillations). This modification was key to allowing me to extend my DE and increase the heat on demand when needed for FC. The issue now was that the stock BT temperature that the machine was outputting was so far off I needed another solution to control the temperature accurately.

Phidget setup- By using a Phidget hub (HUB0000_0 - VINT Hub Phidget), TMP1101_0 - 4x Thermocouple Phidget and TMP1000_0 - Temperature Phidget I was now able to get an accurate reading of the BT and the ambient temperature of my roasting environment. I could now use the roasters heating element "BT" (stock BT reading from the FreshRoast) and set that as my ET via Artisan. By doing so I am now able to use the ET curve to build a BT curve via the derivative of those functions in real-time (more to come on this below).

Roast chamber- The stock roast chamber allows for ~80g roast with a 90g max depending on how dense the bean and how long you want to roast. By adding a longer glass insert into the stock glass roast chamber I was able to roast 160g consistently with the modifications above and now with the proper airflow.

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I am having a larger 500mm glass roast chamber made for me at the moment but I am currently using a few 3D printed parts to allow for up to ~350g roast with 260g being the sweet spot. This nets ~.5lb per roast after the weight loss. The issue now was the stock chaff collector top cap could not handle all the additional chaff.

External chaff collector- By adding a cyclone and a few 3D printed parts for high temp I was able to build an external chaff collector system that has removed close to 100% of the chaff during the roasting:

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The cyclone on top of the roaster has been cut in half to become a "top" for the 3D printed part. This allows me to use the same connection on both sides and not have to fabricate another connecting piece:
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I was able to start to produce some really great tasting roast with this setup. Now that I have had some time to roast more and read a few books I have been looking to see what makes one profile taste better than another (similar) profile.

My first few profiles were short to start and long to finish so I have adjusted the phases of the roast via software and some server-side processing on my local machine to help to automate the process of alarms. A combination of alarms (milestones) with log10/20 math for curve targeting has allowed me to plot points on a graph and see a theoretical curve of based on all the roast factors.

It's currenlty theoretical and not 100% accurate as of yet. This is mostly because the program is modulating heater output and the fan speed together in real time which then adjusts the Phidget BT temp that is needed, to the time of the total roast to achieve the desired RoR.

There's a lot more going on here to get all this setup and working correctly but for the sake of this post I wanted to give some contextual background so hopefully, now we can focus on the profiles and less on the modifications for the SR700. That will be another thread once I get everything dialed in 100%. If you have any questions about trying to modify an SR700 please PM me and keep this thread for general roast discussion.

Here's an example from a roast yesterday:

One-second sample time, zero smoothing:

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With optimized smoothing:

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Here are a few of my initial questions:
1. Most say a 45/35/20 split for phase % is perfect. Why is this?
2. What is an acceptable RoR max?
3. What do the evaluation stats mean? Leathery, Grassy, Toasty, Acidic OK, etc..
4. Most say the last 20% of the roast should be 2.5 mins after the first crack why is this?
5. If you could design a perfect profile what would it look like?
★ Helpful

happycat

Postby happycat » Feb 18, 2019, 6:27 pm

Impressive work!

Is the glass heat resistant?

I wonder how hotrodding the elememt will affect its life especially for long roasts. I burned out a popper doing 70-90g roasts regularly.

I'm not familiar with the roast breakdown you share. Who is promoting it?

FYI Rao curves hit hard with high charge temps to provide energy through the roast and have 25% time post 1c. He wants to get internal dev going fast and produce enough development to both produce acidity and temper it with sweetness and not go roasty.

that's for drum roasters though. You seem to already know about extending dry times to tame natural process funk.

The descriptive words relate to projected tastes if you dropped during that period of the roast, I believe.
LMWDP #603

EddyQ

Postby EddyQ » Feb 18, 2019, 11:39 pm

eltakeiteasy wrote: Here are a few of my initial questions:
1. Most say a 45/35/20 split for phase % is perfect. Why is this?
2. What is an acceptable RoR max?
3. What do the evaluation stats mean? Leathery, Grassy, Toasty, Acidic OK, etc..
4. Most say the last 20% of the roast should be 2.5 mins after the first crack why is this?
5. If you could design a perfect profile what would it look like?


Rather impressive work you got there! You have come a long way! Your profile is looking reasonable. Time to roast and taste coffee.

Unfortunately, there is no ideal profile. Mainly because different beans react with different to heat which is different with every roaster. Some beans would burn, scorch and tip with the perfect profile for another bean. I notice you are roasting an dry processed Ethiopian. This is a natural processed bean, which often is best to keep the peaky RoR down a bit. How much?? Your roaster is likely way different than my drum. With my drum, I'd worry with it at above 50. But taste is king. If it is roasted very light, but tastes burnt it probably is burnt. There are a lot of rules. 45/35/20 is just a rule/guide for beginners IMO. Play with it and taste the difference.

Don't believe anyone who says the last 20% should be 2.5min after FCs. I've roasted many roasts only 1 - 1:30min past FCs. And others 3-4min. Again, taste should guide you.

Many beginners and seasoned professionals follow Scott Rao's linearly declining RoR curve. It pretty reliably produces good coffee. It is my go-to profile for a new bean and I work it from there based on taste.

eltakeiteasy

Postby eltakeiteasy » Feb 19, 2019, 12:21 am

happycat wrote:Impressive work!

Is the glass heat resistant?

I wonder how hotrodding the elememt will affect its life especially for long roasts. I burned out a popper doing 70-90g roasts regularly.

I'm not familiar with the roast breakdown you share. Who is promoting it?

FYI Rao curves hit hard with high charge temps to provide energy through the roast and have 25% time post 1c. He wants to get internal dev going fast and produce enough development to both produce acidity and temper it with sweetness and not go roasty.

that's for drum roasters though. You seem to already know about extending dry times to tame natural process funk.

The descriptive words relate to projected tastes if you dropped during that period of the roast, I believe.


Hi David,

Thank you for taking the time to reply! Yes, the glass is heat resistant (operational) up to ~1200℃ if I remember correctly. I am sure the modifications will cause a faster wearing cycle than not having the heating element modified but only time will tell. Luckily it's cheap to replace if needed.

I have had many promote it but do not want to call them out. Perhaps they will chime in and talk a bit about their reasoning. I think it is probably just a pretty 'safe' % that could produce decent enough coffee without too much thought.

Looking forward to getting more feedback!

eltakeiteasy

Postby eltakeiteasy » Feb 19, 2019, 12:24 am

EddyQ wrote:Rather impressive work you got there! You have come a long way! Your profile is looking reasonable. Time to roast and taste coffee.

Unfortunately, there is no ideal profile. Mainly because different beans react with different to heat which is different with every roaster. Some beans would burn, scorch and tip with the perfect profile for another bean. I notice you are roasting an dry processed Ethiopian. This is a natural processed bean, which often is best to keep the peaky RoR down a bit. How much?? Your roaster is likely way different than my drum. With my drum, I'd worry with it at above 50. But taste is king. If it is roasted very light, but tastes burnt it probably is burnt. There are a lot of rules. 45/35/20 is just a rule/guide for beginners IMO. Play with it and taste the difference.

Don't believe anyone who says the last 20% should be 2.5min after FCs. I've roasted many roasts only 1 - 1:30min past FCs. And others 3-4min. Again, taste should guide you.

Many beginners and seasoned professionals follow Scott Rao's linearly declining RoR curve. It pretty reliably produces good coffee. It is my go-to profile for a new bean and I work it from there based on taste.


Hi Ed,

Thanks for the response! When you say the profile is looking reasonable would you mind expanding a bit on what criteria you look at to determine that. It would really help me to know the thought process of a pro to understand how I should be evaluating each roast.

Thanks for the feedback on the FC stats. That makes total sense! From your experience is there a safe % of the roast that you would say is a good starting point for FC to drop? I am looking to add that into my process to help automate the baseline (although I am sure manual adjustments will need to be made during the roast).

EddyQ

Postby EddyQ » Feb 19, 2019, 10:59 pm

eltakeiteasy wrote:When you say the profile is looking reasonable would you mind expanding a bit on what criteria you look at to determine that. It would really help me to know the thought process of a pro to understand how I should be evaluating each roast.


Oh I am not a pro. What I liked about your profile is the total roast time was less than 14min. Longer than that tends to roast out some goodness IMO. Your RoR was constantly declining. No stalling or constant baking going on. But best of all, it looks like you have some control of your profile. I bet you could duplicate that roast rather precisely. This ability allows you to "tweak" the profile in one particular area while keeping the rest constant. A nice exercise would be to do three identical roasts and vary your development %. Try 20%, 25% and 30% keeping all else constant (or better yet end at same end temp). Does your roaster allow you to roast small batches? Doing three or four small batches would help answer your questions and not use many beans.

devlin2427

Postby devlin2427 » Feb 20, 2019, 9:36 am

1. Your BT reading is about 20C above what it should be. That means you picking up too much air with it. I would pull it back a few millimeters.

2. I would decrease the batch weight to the point where I can comfortably get a 4 minute dry and 4 minute maillard. The development is up to you.

3. The bean holder/chamber glass should have a reversed milk bottle shape. Or even like an old gas lamp.

Birdcollin

Postby Birdcollin » Feb 20, 2019, 11:22 am

EddyQ wrote:Oh I am not a pro. What I liked about your profile is the total roast time was less than 14min. Longer than that tends to roast out some goodness IMO. Your RoR was constantly declining. No stalling or constant baking going on. But best of all, it looks like you have some control of your profile. I bet you could duplicate that roast rather precisely. This ability allows you to "tweak" the profile in one particular area while keeping the rest constant. A nice exercise would be to do three identical roasts and vary your development %. Try 20%, 25% and 30% keeping all else constant (or better yet end at same end temp). Does your roaster allow you to roast small batches? Doing three or four small batches would help answer your questions and not use many beans.

The varying DT% is an exercise that I'm currently learning to execute. How do you stretch your development without stretching the middle phase? If I want to hit the same end temp but stretch the time to get there, I have to enter 1C a bit slower which also stretches the Maillard phase as well. Any suggestions?

eltakeiteasy

Postby eltakeiteasy » Feb 20, 2019, 3:12 pm

EddyQ wrote:Oh I am not a pro. What I liked about your profile is the total roast time was less than 14min. Longer than that tends to roast out some goodness IMO. Your RoR was constantly declining. No stalling or constant baking going on. But best of all, it looks like you have some control of your profile. I bet you could duplicate that roast rather precisely. This ability allows you to "tweak" the profile in one particular area while keeping the rest constant. A nice exercise would be to do three identical roasts and vary your development %. Try 20%, 25% and 30% keeping all else constant (or better yet end at same end temp). Does your roaster allow you to roast small batches? Doing three or four small batches would help answer your questions and not use many beans.


Thanks for the additional info, Ed! I have read that no less than 7 and no more than 14 roast times seem to be the best tasting. I can absolutely replicate this roast as I have roasted it a few times now :) I will be sure to try 20,25 and 30% development and see how that taste. I have only been changing one variable at a time to make it easier to see the direct correlation of that change.

I can take out the glass insert and roast 80g batches which may be where I am at now that I have all the roasting factors in a decent baseline.

Really appreciate all the feedback and thoughts!

eltakeiteasy

Postby eltakeiteasy » Feb 20, 2019, 3:22 pm

devlin2427 wrote:1. Your BT reading is about 20C above what it should be. That means you picking up too much air with it. I would pull it back a few millimeters.

2. I would decrease the batch weight to the point where I can comfortably get a 4 minute dry and 4 minute maillard. The development is up to you.

3. The bean holder/chamber glass should have a reversed milk bottle shape. Or even like an old gas lamp.


Hi Devlin,

I hope all is well. Thanks for taking the time to give some feedback. Would you mind expanding on these items?

1. Your BT reading is about 20C above what it should be. That means you picking up too much air with it. I would pull it back a few millimeters.

I am not sure what you mean by my BT being 68F (20C) above where it should be? When you say it's picking too much air and you would pull it back a few millimeters what are you referring to?

2. I would decrease the batch weight to the point where I can comfortably get a 4 minute dry and 4 minute maillard. The development is up to you.

I can change my curve and hit 4-minute mallard, but I wanted to try to hit the baseline of 45/35/20% as close as possible before making too many changes. I have been reading Robert Hoos book and I was mainly focusing on page 40 as I have been developing my different phases %. One thing that I was completely intrigued with was the part on page 38 about Time Relative to Baseline with the Flavor Profile. Really cool stuff! I was going to post the excerpts but I figured people could buy the book if they want the info, as I don't want to take money away from Robert.

3. The bean holder/chamber glass should have a reversed milk bottle shape. Or even like an old gas lamp.[/quote]

It does, but many fluid-bed roasters do not. What the rationalizing behind this? The insert sits inside the stock glass chamber like so:

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