The initial spark for this series of experiments and articles came from discussions regarding a class that I have been teaching for the Roasters Guild. The essence of the class is that it is the job of the coffee roaster to shape roast development to accentuate a coffee's positive attributes.
So, what are you looking for in a particular coffee? Do you want a sweeter coffee? A brighter one? Are you roasting for espresso and would like more body and lower acidity? All of these characteristics can be altered through roast development. In part 1 of this series we looked at stretching out the time after the end of 1st Crack and found that it had a tastable impact on the perceived acidity due to the breakdown of acids and compounds. In part 2 we stretched out the 1st Crack itself and noted how it affected the perception of body and mouthfeel due to the breakdown of particular carbohydrates. In both experiments we saw sweetness greatly affected by the amplification of the interactio of body and acidity, as well as prolonged caramelization.
For part 3 I wanted to stretch out the drying stage of the roast, when the bean is losing moisture in the form of steam but there is not yet any expansion of the cells. There is some yellowing, but there is no Malliard reaction just yet. The Malliard reaction is the chemical reaction between a combination of sugars and amino acids which produce odors when cooking. In coffee, it produces those toasty aromas that you get before entering 1st Crack. Once the Malliard reaction begins, we start to enter the browning stage of the roast.
For this experiment I stretched the initial drying time, before any yellowing had occurred. I chose once again to use a Bourbon coffee from Rwanda, a coffee with delicate floral and citrus features, but also a range of sweetness with a potential for a balanced body and clear acidity. I used the Probat PRE-1Z electric sample roaster again because of the control it gives the user with repeatability of results.
Here are the roasts:
You can see in the logging that the variance between roasts is approximately 30 seconds, with Roast 1 being the control, or middle roast, Roast 2 the long roast, and Roast 3 the short roast. You will also note that the length of the 1st Crack, as well as the drop time (30 secs after the end of 1st Crack) are approximately the same for each roast.
For tasting, I again focused mostly on body, acidity, and sweetness; rather that specific flavor notes. Here are my cupping notes on these roasts:
When tasting these coffees with the various panels, Roast 1 was the most common favorite, but most everyone did comment on the longer finish and sweetness in Roast 2. One common thread that I've seen in the panels for this whole series is that the people who prefered manual pour-over brewing methods prefered the shorter roasts in each experiment.The front loaded brightness and short dry finish has a certain appeal to them. In my opinion, I think these shorter roast profiles do fare well in pour-over brew methods, with the brightness prominent in the cup. But, in auto-drip machines and press pots, the dryness in the finish as well as aggressive acidity become a little too much.
The other interesting finding is that the results were almost identical to those in part 1 where we stretched out the time after 1st Crack. In both experiments, the longer roasts reduced acid, in a way similar to cocoa roasting. In the shortest roast, the brightness is all in the front of the palate; in the middle roast, the acidity is more centered, a more dynamic cup; and in the long roast brightness is in the finish but quite muted compared to the the other two roasts.
One interesting difference between this trial and the one in part 1 is that the long roast had a long sweet finish. In part 1 the long roast was pretty flat and the sweetness had begun to take on some cocoa bitterness due to prolonged caramelization. But here, in part 3, by stretching out the drying stage, acidity breaks down with no prolonged caramelization, so you are able to accentuate a pleasant sweetness. This is pretty key for roasting for espresso.
We've learned through this set of experiments that you can alter the perceived acidity by stretching out the time after the end of 1st Crack (Part 1), alter the perceived body and mouthfeel by stretching out the 1st Crack itself (Part 2), and alter the perceived acidity as well as sweetness by stretching out the drying stage of the roast (Part 3). The question that remains for me is whether or not there is a significant difference to be found in the cup between stretching out the initial drying stage and if you were to stretch the roast during the first part of the browning stage, once the Malliard reaction begins. Perhaps a part 4 is in order...