Burner on our Diedrich CR-25

Burner on our Diedrich CR-25 Roaster

When it comes to learning about coffee, nothing seems to be more difficult to understand than coffee roasting. I want to break down some barriers and give you the roaster-perspective on some pretty common questions I hear on a regular basis.

-Roaster Nick

Question 1. What Causes the Difference Between Light, Medium, and Dark Roast?

This is a great question, and yet a super hard one to answer because everyone uses the same terms with different meanings. Basically, one person’s dark roast is another person’s medium roast. Some people’s idea of a light roast is another person’s medium roast. So that being said things are complicated. But, I’m going to tell you how I define these terms with a cool analogy.

Imagine you go to your local craft bakery and purchase an outstanding loaf of sourdough. You want to toast it in order to bring out some of the natural flavors taking place inside the bread.

The first level is what we’ll call “lightly toasted.” At this level, the bread has begun to caramelize ever so slightly, bringing out some sweet flavors and giving it a beautiful color. All of the natural flavors the baker worked to bring out in the sourdough are still readily available, just enhanced.

The second level we’ll coast “medium toasted.” At this level, the bread has caramelized even more than the previous stage, causing an ever so slight but pleasant bitter-note to be introduced to the bread’s flavor. You can still taste many of the attributes of the original plain sourdough, but now there’s a distinct flavor of “toasting” that’s been added to the bread.

Level three is “dark toasted.” At this level, the predominant flavor you’ll be tasting is “toasty-ness.” The original flavors of the sourdough have been more or less covered up by the flavor of the toaster doing what it does best. I’d expect at this place there’s more of a bitter and slightly ashy flavor reminiscent of a burnt marshmallow. Additionally, I’d like to think at this stage it becomes quite hard to tell what kind of bread you’re actually eating. Maybe it’s a sourdough, or maybe it’s been swapped out for a rye bread. At this stage, it’s hard to tell the difference. 

Now, applying this to coffee is quite simple. In the above paragraphs, each time I said “bread” replace this word with “coffee beans” (or coffee seeds if you prefer). Each time I say “toasty or toasted” replace them with “roasty or roasted.” Lastly, replace “toaster” with “roaster,” and there you have how I would break down roasts. Light roasts will mostly have unique and original flavors that display the inherent qualities of the coffee seeds themselves. Medium roasts tend to have a slightly roasty flavor, but still the main focus will be on the inherent flavors of the beans, whereas dark roasting covers up the inherent flavors with qualities of the roasting process, which we call roastyness.

Sewana Green

Green Ethiopian Beans – Sundried / Natural Processed Heirloom Varieties

Green Mexico Coffee

Green Mexican Coffee – Fully Washed Processed Pluma Variety

Question 2. What causes major flavor differences in coffee beans?

Another great question! There is a multitude of factors going into what gives coffee its flavor. I’ll do my best to break them down into some really simple pieces:

Environmental Factors: The first factors that influence the flavors of coffee are environmental factors, such as weather and climate, geographical location, soil quality, and I’ll even add plant variety into this fold. All these factors will have some level of influence on the final cup quality. Most people think the plant-variety has the most impact, but this has been debated. Each one of these factors will play an important role in creating final quality in the cup.

Fermentation Factors: Once coffee cherries (yes, beans are the seed of a fruit!) have been picked they must undergo a fermentation stage to remove the outer layers of the fruit from the beans within. There are several different fermentation methods which I’ve written about elsewhere, and whatever method the farmer chooses will have a huge impact on the final flavors found in the cup.

Processing/Roasting Factors: The final two stages are where quality can really be made or broken. Once the beans have been fermented they must be processed at a local mill. This includes removing defective beans, making sure the beans have the correct amount of moisture, etc. Some mills do a good job of processing beans, while other mills struggle to find processes that help keep the coffee tasting its best. (It should be noted sometimes coffee is purposefully processed to a lower quality to be “price conscientious”) When the beans finally arrive at the roastery, assuming all the other stages went well, it’s still possible to ruin perfectly-good beans with really bad roasting techniques. Unfortunately, raw-coffee beans can’t be made to taste any better in the roaster. The inherent qualities will either be exposed or covered-up depending on how the head-roaster goes about roasting the beans.

These three factors play largely different roles in how the flavor will be changed, but they all ultimately will lead to a different experience in the final cup!

Question 3. Does the roasting machine make a big difference in flavor?

This is a question I get a lot from people who work in coffee. I’m going to say yes and no. Yes, because not all roasters function exactly the same. Some roasting machines use drums with flames underneath to roast the beans, while other roaster may use hot air alone to roast. There is disagreement here on whether or not there is a true taste different here, but I believe I can taste a difference in these two machines.

This being said, going back to the original question, the flavor differences between the two machines are quite small. As someone who has been trained to taste flavors coffees in a multitude of ways, I can taste some of these small and unique differences each roasting machine brings. The average coffee drinker, however, probably can’t taste these differences, so in some ways the differences are insignificant. Furthermore, as long as you’re using good techniques in your roaster, most coffee should taste great regardless of the machine.

I tend to believe that it’s ultimately the person behind the machine, and the choices that person makes, that will decide the ultimate quality. There is no doubt that great tools allow a master craftsperson’s skills to truly shine.

*At Utopian we roast on two drum-roasters: a Diedrich CR-25 Kilo and a Probat P12 Kilo. Even between these two roasters there are some flavor differences.

Question 4. How long does it take to roast a coffee?

Most of the time, my roasts are anywhere from 10-12 minutes long from start to finish. For a select few roasts, I will purposefully go to 13 minutes or slightly longer, or even roast faster than 11 minutes.

Overall roast time will vary from machine to machine and from coffee to coffee, but most of the time I’m roasting faster it is due to using a smaller batch size in a given machine. For example, I can roast a smaller batch (10#’s) much faster than a larger batch (50#s) and achieve similar results in the final cup.

When you include my warm-up and cool-down times between each roast, it takes me anywhere from 18-20 minutes to start a roast, finish, cool down and then warm up the machine for the next batch.

Question 5. How do you choose to roast a coffee? 

This is still something I am figuring out each time I get a new coffee in the building, but there are several key factors that give me indications on how I should go about roasting a given coffee:

  1. Process: I’ve come to understand that beans processed using a dry-process/natural method need a much different approach than a fully-washed coffee, which both need a different approach than a honey-processed coffee. This is usually the first place I start when deciding how to approach roasting a coffee.
  2. Origin: I’ve become very familiar with how coffees from certain origins will react to heat within the roaster, and the approach I’ll need to take to get to the roast level I’d like to see. For example, our Colombia from Cauca needs more energy upfront than our Guatemala from Huehuetenango to reach a similar development level.
  3. Freshness: Coffees that have aged in the warehouse for 6 months may require different energy inputs than an Ethiopia fresh off the harvest. Knowing this will greatly influence how I go about roasting a coffee.
  4. Batch Size: I know that I can use less energy in a smaller batch than in a larger batch with the same beans.
  5. Roast Level: I will slightly adjust the way I introduce heat into the roast. For example, if I want to roast a coffee to a medium or dark profile I may keep higher heat on the beans to ensure enough energy is stored in the roaster through the latter parts of the roast.

All of these factors play into how I will approach a roast. There are odd exceptions, in particular if a coffee has an odd moisture-content, but other than this I feel very confident when approaching roasting a new coffee.

I hope fans of Utopian Coffee find these questions and answers helpful. I don’t believe roasting should be a secretive science. The more you know about roasting, the more you can appreciate the flavors I work hard to deliver into the final cup.

Sample Roasting

Sample Roasting Time