The Challenge of Roasting for Brew Methods
NEWSLETTER 040
SUNDAY, 04 AUGUST 2024
AUTHOR: MAXWELL COLONNA-DASHWOOD
READ TIME: APPROX. 16 MINUTES
To taste a roast, you must brew the coffee. An obvious and simple statement to make. The problem is that the way you make the coffee impacts the way it tastes, it changes what you “see” of that coffee and that roast.
A cup of coffee is an expression of several choices. This results in a presentation of a given coffee, both in terms of green coffee and roast profile. Scott Rao recently shared a small experiment in his newsletter (take a look, always worth a read!) where a friend and industry colleague of his blind tasted different roasts of the same coffee. He sent this green buyer coffees roasted in a variety of ways, none were roasted to extreme differences, and all were reasonably light, but there were differences. The taster had about a 1.5 point swing in scoring for the same green coffee depending on the roast. The point was to highlight how sample roasting can affect the coffees you select as a roaster and that focusing on sample roasting well is important. I am not sure on the details of the experiment, but I expect they were cupped coffees, brewed with the same water and grinder settings etc. Essentially the variables would have been quite tightly controlled.
It would be interesting to do a similar test with brewed coffee made in many ways to see how much that could impact scoring. I think when you start changing several variables such as water and brew method the range in scores of the same coffee would be wider than 1.5 points even with the same roast. A linear way to approach this would be to simply say it’s important to get the details right otherwise the coffee won’t be displayed properly. However, what is “properly”?
Customer Feedback and Brewing Variability
Recently I have been revisiting this concept in relation to the brewing aspects of our set up, both at the roastery and at the cafes. A customer messaged us to say they thought one of the Peru geishas was disappointing and didn’t taste of much. Obviously not the feedback you want! Ha. It is also interesting because I had been saying that this was one of my favorite coffees we had on offer recently. We immediately found the QC sample and brewed it, A few of us tasted it blindly and thought it tasted brilliant. It would be easy to simply contact the customer and say we tasted it, and it tasted great, and to leave it at that. Coffee is subjective and the element of taste is a key factor in a discussion around an individual’s taste experience. This specific coffee is a delicate washed Geisha. Maybe the profile is not intense enough for the preference? However, a key question for any remote (people tasting a coffee in different locations) conversation about taste is to try and understand if you taste the same thing. It’s at this point you start to discuss and share brewing parameters and the equipment used. You try to recreate that brewing scenario but, in many cases, when people are all using different grinders and brewers around the world, as well as waters, you can’t fully mimic the brews, and you don’t really know the exact tasting experience. The only way for this to really happen is to stand in front of the same brew and to taste it together. In this instance we endeavored to find an opportunity to do this and share a taste experience to discuss at our London Café. We haven’t managed to get the timings lined up just yet, but hopefully we do, and we can see how the experiences and preferences line up. The coffee is dosed up in the freezer and ready to be tasted and discussed.
Roasting Adjustments for Different Methods
I have had our coffee at some cafes who have interesting espresso brewing set ups and enjoyed the coffee, but also noted it didn’t taste like how I think of “our coffee”.
As part of the investigative process with the Gesha , I brewed the coffee as a pour over using a few different devices and techniques. In our cafes and at the roastery our go-to filter method is a coarse ground longer brew time AeroPress. Sometimes with a cool bloom. We ended up here following several brewing decisions. We felt the brews were closer to the cupped coffees, and by grinding coarse we could get cleaner balanced coffees (because the grinder is less aggressively grinding and mushing the coffee up). By grinding coarser you can also avoid the sediment heavy cloudy brews that are common with finer ground AeroPress brews, as less particulates make it round the paper filter.
You definitely see some strong preferences around brewing devices in coffee, and I think many inherently see pour over coffee as superior.
When we took this Peruvian Gesha and brewed a pour over on v60 and Orea, we did notice that the coffee presented very differently. The delicate florals were less present, the coffee was less clean, and I wouldn’t have scored it as high by quite a way. Naturally, I started to extrapolate in my brain and think “what if 80% of the filter coffee we sell is brewed on a pour over?” and we aren’t optimising our roasts for this”. Interestingly as we started to taste through different coffees and the filter roasts on both the AeroPress set up and the pour over it was not consistently the case. Some performed very well on the pour over. However, on the AeroPress set up we liked every roast, as you would expect, as that’s what we had QC’d against when profiling the coffees.
There are multiple variables to adjust in roasting, but to simplify our preference, we typically preferred lighter colour roast with a lower end temp when brewing the pour overs. Whereas we preferred a slightly more developed roast with a higher end temp on the AeroPress. It’s always surprising I think to see how significantly different the brews can be. The roast tastes clean and aromatic with the coarse AeroPress, but then heavier, and a touch roasty with the pour over. Even when adjusting for the difference in grind the difference is significant.
There are multiple observable differences that one wonders how much they impact the difference, such as different paper filters and the brew temperature variations of slurries in pour overs versus the temperature profile of a 4-minute immersion brew etc. These parameters are interesting to study, isolate (where possible) and try to account for in brewing.
The Science behind Brewing Methods
The exact science behind the difference is curious to consider and I think quite hotly debated when you start to dig into it. At least in terms of the exact way the mechanisms play out in these brews. If you think in terms of rate of reaction, this starts to make sense. In this case, our reaction is coffee compounds being dissolved into the solvent (water). For the dissolving of compounds into a solvent, the rate of reaction is dependent on the concentration of those compounds both in the coffee itself and in the water. So at the very start it is fastest, because there are no coffee compounds dissolved in the water. Once you already have lots of coffee compounds dissolved into the water, the rate of dissolution drastically reduces, for a few reasons. A key reason in this context of immersion brewing seems to be that a greater percentage of the solution is ‘coffee’ (rather than water), and so for each interaction (2 particles coming into contact), fewer of the particles are water, and there is no “new” hot water joining the party dissolving from scratch. In a pour over the first water added dissolves some coffee and leaves. Then there is a slurry that is a mix of water with different amount of dissolved coffee in it across the time of the brew. You start to think of lots of different little experiments you could do to try and isolate the impact, and some bigger ones that would need scientific expertise and help. it’s also very likely it will be different coffee to coffee, as we found with our coffees.
Regardless of the scientific answer (of which I know some scientists who continue to define more precisely with experimental modelling), it creates a significant challenge for the roaster, as do variables like water. Each roaster typically makes choices about how to set all these different parameters and how to benchmark their own product. Simply put, you most typically have a brewing set up to QC your roasts and see if you are happy with them. The most common process for this is cupping. Bearing the above in mind, cupping would be an immersion brew. Then you brew your coffee in a “real world” scenario such as a filter coffee or an espresso. For us that’s typically different roast approaches for each. Obviously with espresso there’s lots of choices one makes there, grinder, brew ratio, turbo shots etc that will all play into how you feel about that coffee and its roast.
It is clear that you can’t test for all brewing scenarios, much like the water conundrum. A roaster can take two different approaches to address this. Work within a tight box, with highly specific parameters that they have chosen. They can then encourage their customers to directly mimic these parameters to get the same result as them. Alternatively, they can try and develop products that perform well in a variety of scenarios. I think this is ultimately limited and I think I end up somewhere in the middle, understanding your coffee in a variety of brewing “boxes” that are conducive to each other. By this I mean that you avoid the compromise issue of making something that tastes nice in lots of scenarios but never great. I do think you can roast coffee that tastes great in a number of scenarios. At the moment we are making our coffee more often on both percolation and immersion methods when profiling and checking quality. For a while I have brewed espresso at home on a cheaper grinder to see the difference to an EK43. Historically I was quite anti brew guides as things like water and grinder made it hard to truly replicate the brew by following some basic parameters. I am rethinking this though as its clear we can offer more information to think about when brewing our coffees.
With this in mind, expect us to provide some more guidelines on how to get the best our of our coffees, and we will continue to explore the conundrum of optimising roasts for brewing conditions!
Best,
Maxwell
