Stretchin' Out the Roast: Part 1

This article details one method to determine an ideal roast for a coffee;  in four roast experiments, the time between the end of 1st crack and the beginning of 2nd crack is lengthened, and the roast stopped at the same point each time.  Then by tasting and comparing the results, I arrive at some conclusions about what roast brings out the characteristics of the coffee I enjoy more.  Other articles will cover the effect of stretching other segments of the roast.

I did four roasts of the same coffee, each time stopping at the first sound of 2nd crack.   Each batch had roughly 30 seconds more time between the cracks than the previous batch. In tasting the results, I'm looking more at the effect on certain characteristics of the coffee and not the quality of the green coffee itself.

Because everybody will have a different roasting situation even with the same equipment, this article is less about how to stretch the roast and more about the effect in the cup.  For this article I used a Probat PRE 1Z single barrel electric sample roaster. This machine can produce the same roast over and over again; with just some minor adjustments to airflow you can really shape the roast profile. The roaster does not have a bean probe, so my parameters were the physical changes to the beans themselves in relation to time. Here are the roast particulars.

Roast A:

  • Start temp: 320 degrees F
  • Yellow Stage: 5:15
  • 1st Crack starts: 7:30
  • 1st Crack ends: 8:39
  • End: 9:37

Roast B:

  • Start: 318 degrees F
  • Yellow: 5:20
  • 1st C: 7:36
  • 1st C end: 8:42
  • End: 10:07

Roast C:

  • Start: 320 degrees F
  • Yellow: 5:25
  • 1st C: 7:38
  • 1st C end: 8:46
  • End: 10:40

Roast D:

  • Start: 320 degrees F
  • Yellow: 5:18
  • 1st C: 7:33
  • 1st C end: 8:43
  • End: 11:00

The coffee I used was from the Coko Cooperative in Rwanda. This is an ideal coffee for this type of experiment because of it's a fantastic bourbon varietal with characteristics of cocoa and cola sweetness, orange blossom floral attributes and clean mandarin orange acidity. Delicate features with sustained sweetness, balanced body, and clean finish.

I cupped these roasts myself along with one untrained cupper and then again with a panel of 8 people, some trained and some untrained cuppers.   I asked the panel to look specifically at which coffee had the most Brightness, the most Sweetness,  the most Body. The  panel did not know what they were tasting.

First I'll post my impressions from the intitial cupping:

- Roast A: wet aroma, bright and lively, short finish, front loaded, very sweet and bright on front of the palate. most malty sweetness   Sweetness: yes, malt, sensed in the front of my palate;  Body: condensed;  Acidity: agressive, front-middle

- Roast B: long sweetness with a peak in the middle, more shape to body. more defined body  Sweet: lasting through finish, candy;  Body: syrupy;  Acidity: middle

- Roast C: flabbier body wise, lots of sweetness in finish with brightness near the rear of the palate. front of palate is open which maybe lends to the flabbiness.  Sweet: yes, a little cocoa sweet/bitter in finish, fruit sweet;  Body: broad, thinner syrup;  Acidity: middle, yet slightly muted compared to B

- Roast D: wet aroma muted brightness, the body and acidity seem to be more integrated, but with less dynamic in the cup. Not devoid of sweetness or acidity though acidity is muted in comparison. most bitter. more caramelized with slight roasty note in front   Sweet: center, more caramelized, bitter cocoa;  Body: flatter;  Acidity: stretched throughout palate

In the panel cupping, the findings were:

- Roast A was the sweetest for half the panel
- Roast B was the brightest and was the favorite for most
- Roast C was the sweetest for half the panel, and also had noticeably more body
- Roast D least sweet, least bright, but more body although it was flat.  The untrained cuppers noted that this was the most balanced cup.

With the panel, we discussed how the perceived acidity moved back through the palate with each successive roast. In the shortest roast, the acidity was front and center. In the middle two roasts, there was generally more brightness in the middle of the palate with the third roast having a brighter finish. In the fourth roast the acidity was very muted and the perception of the coffee was rather flat. There is an interesting geography to this idea if you look at it that way. Where we perceive acidity on the palate had a rather large influence on our perception of body. Where the brightness was more in the middle of the palate, the roasts seemed to have a rounder and open body, with more flavors throughout the palate, while the shortest roast with the aggressive up-front acidity had very thin body through the finish.

In terms of sweetness, the general rule is the more caramelization the less sweetness. But in these tests what was noticeable was not just the level, but the type of sweetness. In the shortest roast the sweetness was more malty while the second roast had more candy sweetness. The third roast had fruited sweetness and the fourth, more of bitter cocoa sweetness and began to show some carbon/roasty notes. Keep in mind that each roast was roasted to approximately the same level, they just took progressively longer times to get there.

What this line of testing shows is that altering the length of time between the first and second cracks can help shape the flavor profile of a coffee by featuring sweetness and acidity in different ways. There is some room to play here to get the coffee to express itself a little differently.

The panel discussed which roast would feature best in different brewing devices. The shorter two roasts would probably feature very well in manual pour over methods since the acidity would be expressed clearly. The first roast would probably be too sharp for a french press or even auto-drip machine. The last two roasts would most likely be the ones to try as espresso.

The lesson here is this: if you really want to know the potential of any coffee, then it is smart to look at more than one roast of it. You can look at roast level sure, but  also look at altering the time between cracks. For the the next article in the series we're going to look at the effects on the cup when we stretch out the first crack itself.

Part 2

 Any idea when part 2 will happen? This was a very interesting article and and I am excited to see the second installment. 

Sam

Stretching out the roast

Hey there.  This is a topic that has interested me lately.  Two questions.  For your roaster, what did you do to extend the roast.  Was it temperature and airlow.  Sercond, for the Behmor (other than opening up the door a little bit) what can I do to slow down the roast heading into first crack in order to extend the roast.  I tend to roast on a P4 setting.  Thanks.

John 

Hey John

I used an airflow adjustment to extend the roast. In an open-faced style sample roaster, increasing the airflow draws the hotter air out while pulling cooler air into the the drum. That roaster use quartz elements as the energy source, which are not the responsive to the minor adjustments necessary to carry out this type of test. I'm not experienced personally with the Behmor myself to answer the second question, but that would be an excellent question for the Sweet Maria's forum, I know there are folks on there that could answer that for you. 

Roast profile

How did you vary the roasting time?  The only variable I know is temperature.  Can you give us the temperature at the end of each roast, even if it is the roaster temperature and not the bean temp? 

coffeefreak

the environmental temp reading was about 340 degrees for each roast. If there were a bean probe, it would pro'lly be around 410-415 (depending on probe/machine) 

 How and why do you go from

 How and why do you go from yellow to 1st. cr in 2:13-16mins. ? How many degrees of BT spread would you approximate between these reference points?

Ed

It is a sample roaster, roasting only 100 grams at a time. THe total time for a batch this size in a sample roaster is around 8:30-10 mins depending on the roast. It's a scale thing. I woud say that the temp spread would be from 300-375 in about tha span, but it got from 240-300 in about the same time.

 

Really important to remember that this wasn't about the how, but about the result of stretching out this specific part of the roast in the cup. Didn't make it about the how, because that's going to be so different for everybody, but I think that the forum is an awesome and more appropriate place for that discussion.