topbanner.gif
Login
Username

Password




Not a member yet?
Click here to register.

Forgotten your password?
Request a new one here.
Shoutbox
You must login to post a message.

10/19/2021 6:22 AM
Welcome tarunk!

10/17/2021 12:40 PM
Ploni and nader fouad, Welcome!

10/15/2021 2:19 AM
merlot85, maycondelpiero and hoeltz, Welcome !

10/14/2021 10:06 AM
Thanks for the addition to the group. Seriously considering building a drum roaster along the lines of oldgrumpus's. Love the design and craftsmanship.

10/14/2021 4:00 AM
Morning, ar3mia ! and... coffee drink

In Memory Of Ginny
Donations

Latest Donations
JackH - 25.00
snwcmpr - 10.00
Anonymous - 2.00
Anonymous - 5.00
Anonymous - 5.00
Users Online
Guests Online: 19

Members Online: 0

Total Members: 7,363
Newest Member: tarunk

View Thread

Who is here? 1 guest(s)
 Print Thread
The steadily-declining RoR
Barrie
In his new book The Coffee Roaster's Companion Scott Rao recommends three aspects of a roast that he considers very important. Ignoring any one of them leads to inferior-tasting coffee, he suggests. They are
1. Apply enough heat at the beginning of the roast in order not to spend too long drying the center of the bean, i.e. outside-to-inside heat gradient is all-important.
2. The Delta BT curve (R0R) should decrease throughout the roast. He says If the ROR is constant or horizontal, even for just 1 minute, it will also destroy sweetness and create "flat" flavors reminiscent of paper, cardboard, dry cereal or straw
3. 1st crack should begin at 75-80% of total roast time.

This has been the basis of considerable challenge, particularly on the HB forum, but I do not have the expertise to participate in that. Nevertheless, I decided to see what I could do with the HT to produce a steadily declining RoR. At Miroslav's suggestion I am posting some of my experience. The third image is of a roast of an SM staple, where these issues were not in my mind. The second is of a more recent roast of the SM Finca Rosma bean where I tried to get rid of the plunge in RoR at the start of 1st crack, due to evaporative cooling (quoting Rao), and then the subsequent reacceleration. The first is the alarm list for the Finca Rosma
Barrie attached the following images:
alarms.jpg guat_sm_huehuetenango_finca_rosma-14-09-25.png sm_monkey_blend_14-01-13_1621.png

Barrie (San Diego, CA)
"So much to learn, so little time."
Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).
Omega
Thanks for the great information. This will help me out, I'm sure!

Barry
smico
Thank you Barrie. Have you tried to attach .alog file for lazy people like me?
Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario
JackH
Barrie, I think that information is a good general guide.

I follow one other thing which seems to allow me to have the proper timing of the roast. I also watch the ET and adjust the heat up or down never allowing ET to exceed 500F (260C). It seems when I do that, the timing of backing off on the heat is at the proper time before first crack and better RoR control at the end of the roast as needed. I am able to dial down the heat easier at the end.

My roaster is all manual control and the above may only apply to the roaster design, but it works for me.

I have read somewhere that enviroment temperatures above 500F are not good for control in coffee roasting. I think this came from some coffee industry study. Roast times exceeding 15-16 minutes are also undesirable.
---Jack

KKTO Roaster.
Ringo
Did you try the coffee? This is very interesting to me, I love a new idea to try with my roasting. I find on my drum the natural tendency is for the rate of rise to slow. I think its just harder to get the heat in the beans. The only difference in what I am doing now is I push the beans between 300 Deg F and 340 deg F then I slow when I get to 340. I will test this the next time I roast. I need to get this book seems like a lot of info that I agree with and somethings to be learned.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
Barrie

Quote

Ringo wrote:

Did you try the coffee?


Yes, I did and I am quite impressed with the result. However, I claim no expertise at cupping.
Barrie (San Diego, CA)
"So much to learn, so little time."
Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).
oldgearhead
The steadily-declining RoR is unavoidable in fluid-bed roasting if you maintain a constant process-variable temperature, because the beans are losing their mass as they roast. The trick is to control the air flow to produce the RoR desired.

This month I'm roasting some pretty generic (Costa Rica Tarrazu) Central American beans. First I set the roasting temperature (ET, process-variable)
to 1038.5 watts. Flow-meter tests have confirmed this to be 490?F air delivered to the RC.
T= 0 - Start roast with a nice center-spouting bean mass
T= 3min - Reduce air flow to maintain the same center-spouting bean mass
T= 6min - Reduce air flow to absolute minimum that will allow bean circulation. RoR 2?F/5 second.
T= 9min - Adjust air flow to produce a RoR of 1?F/ 5 second.
T= 10min - First crack
T= 12min - Start cooling.

Notes:
1) If I don't pre-warm the RC the first batch will take 13 minutes instead of 12.
2) I really don't worry too much about air flow and heat during the first few minutes of the roast because my commercial grain-drying experience tells me that as long as the air temperature is above 100?C drying will take place.
3) This batch of greens tested 14% moisture on the Wheat scale of my corn tester.

I think Michael Sivitz favored 500?F roasting air temperature.
"..as fast as possible with the lowest temperature."
Jump to Forum:

Similar Threads

Thread Forum Replies Last Post
Declining RoR on SR500? Fresh Roast 8 and NEW SR 500 3 02/16/2020 1:02 PM
Declining ROR on Quest M3 Quest M3 Roaster 12 01/29/2016 8:20 AM
Homeroasters Association Logo, and all Content, Images, and Icons © 2005-2016 Homeroasters Association - Logos are the property of their respective owners.
Powered by PHP-Fusion Copyright © 2021 PHP-Fusion Inc
Released as free software without warranties under GNU Affero GPL v3
Designed with by NetriX