Roasting Dry Processed Coffees

#1: Post by **pShoe** » February 25th, 2014, 6:42 pm

Lets talk about roasting dry processed coffees. What are some tips or approaches?

Here is my recent experience with Roast Master's Ethiopia Kebel Aricha Natural.

I'm roasting on a Quest M3 with EricS probes. I used a reasonably low batch size (112g) to keep MET on the low side. I have read many times that roasting DP has to be gentle, and the best way I know how to accomplish that is roasting smaller batches and keeping the heat low.

Roast 1: I kept MET low during the entire roast, and was shooting for a 6:00 drying time. After drying, I turned up heat and fan to about 80-90% for the ramp to first crack. For development I returned to my drying phase heat setting and used the fan to control the RoR during the finial stage. I ended the roast when I stopped smelling strong vinegary notes coming from the exhaust.

Roast 2: I wanted a shorter drying phase and a quicker ramp to 1C, and a long development. I always use minimum fan during drying but I used a slightly lower setting than normal to let the MET creep up during. I figured the coffee could take a little more heat in the early stages. It didn't help the ramp (which I thought it would), and the cup suffered from the higher MET (even at the early stages of the roast).

Cup 1 - Roast 1
Cup 2 - Roast 2

Double blind testing protocols. I basically ID the roasts immediately just by smelling the coffees. Cup 2 had a rather strong aroma of ash, while cup 1 had a pleasing sweetness. I knew there couldn't be ash in roast 1. It is still interesting because roast 2 beans' do not have an ashy smell. Anyway, Cup 1 had an incredibly syrupy body, the fruit flavors were not as apparent as other DP Ethiopians I've tasted. It was also a little less clean than other DP Ethiopians I've had in the past, but not in a displeasing way. Cup 1 held up very well all the way to room temperature where is actually improved. The fruit flavors really came through at room temp. Cup 2 tasted like it smelled, all ashy. It made it really hard to taste anything else.

Update 2/27: Coffee from roast 1 is really good. Juicy body, leather and tobacco stand out but it finishes into strawberry that lingers. It lost its citrus finish it had a couple days ago.

Roast 1 Update: Linked to a new app that turns Artisan files into a viewable website. I think it is really cool. Please check it out and contribute. Kudos to Nicholas for creating it.

Roast 2

#2: Post by **Italyhound** » February 25th, 2014, 7:12 pm

The graphs are hard to read.

I like the discussion, since I am not big on DP coffee roasts.

I would be interested in a roast 3. Which is roast 2 with a shorter development after 1C and keeping the MET lower in that range too. Did you brew this or pull shots - to me that's a long development for brew.

In my experience, and I use the same probes as you, the MET spike where you have it at the end of drying doesn't harm the beans. Still, they are DP and may be more vulnerable, but my historical MET problems manifested toward the end of the profile rather than the earlier phases.

Roast 3 may pinpont better the source of the ashiness.

#3: Post by **another_jim** » February 25th, 2014, 7:14 pm

Ditto on low MET. I run high grown wet process coffees at 525F and low grow or naturals at 475F. If you run too hot, there's a risk of getting a charred note from the deposited sugars.

February 25th, 2014, 7:31 pm

Italyhound wrote:The graphs are hard to read.

I like the discussion, since I am not big on DP coffee roasts.

I would be interested in a roast 3. Which is roast 2 with a shorter development after 1C and keeping the MET lower in that range too. Did you brew this or pull shots - to me that's a long development for brew.

In my experience, and I use the same probes as you, the MET spike where you have it at the end of drying doesn't harm the beans. Still, they are DP and may be more vulnerable, but my historical MET problems manifested toward the end of the profile rather than the earlier phases.

Roast 3 may tease the source of the ashiness out.

The graphs are hard to read. I included a link to roast 2 through an new website http://homeroasts.appspot.com/. It is a really cool new project that I think will really improve profile sharing. The creator is working out some bugs, which is why I don't have a working link to roast 1. I will update when I get a working link for roast 1.

I have definitely had higher initial MET work with WP coffees, but it manifested itself very badly for this coffee. It could have been the longer development, but until further testing I'm pinning it on the high MET.

I brewed them with a Clever. Roast 2 was a very long development time, but I really want to see the differences between the two. I plan to do further profile experimenting with this coffee including one you are talking about. I plan on reporting my progression roasting DP coffee here. I'd like to welcome others to talk about their experiences with roasting DP coffees too. I'm kinda new to roasting DP compared to WP. I'll be pulling shots soon, but it won't be as ease to do a blind tastings, but I'll do my best.

Thanks for the numbers, Jim. I think I could run slightly lower MET easily. I let it get a little higher then I would have liked around 1C on roast 1.

#5: Post by **dogjamboree** » February 25th, 2014, 8:23 pm

Are there any similar guidelines for maximum ET as measured in the drum on dry process coffees (or washed for that matter)? I felt I was pretty in tune with the Quest, but now I'm learning again on the Revolution 500. I know I'll eventually find some numbers that work for me through trial and error, and lots of cupping, but it's always nice to have a starting point.

frank

#6: Post by **johnny4lsu** » February 25th, 2014, 9:11 pm

That is a legit idea!! Great way to share!!

#7: Post by **another_jim** » February 25th, 2014, 9:21 pm

dogjamboree wrote:Are there any similar guidelines for maximum ET as measured in the drum on dry process coffees (or washed for that matter)?

The idea is to measure the highest temperature to which the beans are exposed, ideally the surface of the drum. The problem is that this is hard to do, and mearures from one roaster do not necessarily carry over to another.

My Quest figures of 475 to 525 are based on the air just outside the drum, close to where the drun in being heated, but shielded from the heate source itself. Most of the ET sensors for ventilated drum roasters are placed in similar spots, and the figure I have is a useful starting point. However, don't hestate to experiment, since there can easily be a 25F shift from one location to another, even when both are perfectly good spots. The idea is to find the "red-line temprature" in your roasting device that produces the fastest roast with no charring or tipping.

February 25th, 2014, 10:15 pm

Thanks Jim -- I'll play around and try to hone in on that hottest spot.

#9: Post by **TomC** » February 25th, 2014, 10:52 pm

pShoe wrote:... I used a reasonably low batch size (112g) to keep MET on the low side. I have read many times that roasting DP has to be gentle, and the best way I know how to accomplish that is roasting smaller batches and keeping the heat low.

You can walk the line on a larger batch size as well, and keep the beans away from the drum as much, and get away with a higher MET, which will give you a roast that doesn't bake out your fine aromatics and flatten anything.( Very small batches put the beans against the wall of the drum more often and are more susceptible to the MET of the roaster than larger batches). Your only evidence of "too high an MET" are two things, one, tipping, which you have to try pretty hard to do something silly on the Quest in order to make happen, and 2, find overly developed roast notes lingering in an otherwise underdeveloped coffee. When dark roasted distillate notes cling to the outer surface of your DP coffee, and there's any hint of a lack of development of flavor in the bean in general, you have evidence of too high an MET. Otherwise, I tow the line of pushing my coffee as fast as I can without encountering the fingerprint of the roaster too much, or developing distillates in favor of finer aromatics and raw sugar sweetness.

Jim says it in a very simple take away message that's easy to remember.

another_jim wrote: The idea is to find the "red-line temprature" in your roasting device that produces the fastest roast with no charring or tipping.

another_jim wrote:If you run too hot, there's a risk of getting a charred note from the deposited sugars.

February 26th, 2014, 12:14 am

TomC wrote:Otherwise, I tow the line of pushing my coffee as fast as I can without encountering the fingerprint of the roaster too much, or developing distillates in favor of finer aromatics and raw sugar sweetness.

In your experience, what is the typical total roast time you aim for when roasting a DP coffee? If that is a little broad, I am more interested in DP Ethiopians the most as that is what I have found to like.

I am also interested if you guys generally take a different approach when roasting a DP coffee for brewing and espresso. If so, how do the profiles differ?