How to Roast Coffee: A Step-by-Step Guide

Coffee is one of the most popular beverages in the world, and there are many different ways to enjoy it. But what makes a great cup of coffee? The answer is not just in the brewing method, but also in the roasting of the coffee beans themselves. I'm writing this post today based on a video I uploaded over at our YouTube channel so check it out if you want to see more on this topic!

I'm prepping for some big wholesale orders, and thought it would be the perfect time to share my process. We'll explore the key stages, the equipment I use, and some of the tricks I've learned along the way. Ready to unlock the secrets to amazing coffee? Let's get started!

The Roasting Process

There are four main stages to the roasting process, keeping it simplere for now here is an overview:

1. Drying: In this stage, the green coffee beans are heated to remove moisture and they'll change colour from green to yellow.
2. Development: During the development stage, the beans are properly 'roasting' now and this causes the beans to change color from yellow to brown and to develop their flavor.
3. First Crack: At first crack, the beans start to make a popping sound as the internal pressure builds up. This is a critical stage in the roasting process, as it is when the beans develop their aroma.
4. Second Crack: The second crack occurs when the beans are heated to a higher temperature (this is how you make a dark roast). This can result in a bitter taste, so it is important to monitor the roast carefully and stop it before the beans reach this stage.

What do you Need?

To roast coffee, you will need the following equipment:

• Roaster: There are many different types of roasters available, from small home roasters to large commercial roasters. We got started on a Cormorant electric roaster which cost us about £2k and our current production roaster (at time of writing) is a 5kg Roastmax gas roaster and cost us about £15k.
• Green Coffee: An essential part of the process! You can buy these from many online retailers e.g. Redber or Pennine Tea & Coffee, if buying from these just choose something you like the sound of lest you fall victim to analysis paralysis.
• Air Tight Container: You will need something to store your coffee in and ideally this would keep the oxygen out, we really like the Airscape cannisters which many places stock now.
• Computer: You can roast by sight and smell alone but honestly a laptop to hook up to your roaster will make life much easier as you learn about the roasting process.
• Scales: Every roaster is going to have a maximum amount that can be roasted efficiently inside of it. For example our 5kg Roastmax drops in efficiency above 3.5kg. You'll need to weigh your green beans before roasting and your roasted beans afterwards as part of your quality control process (checking for consistency).

The Roasting Process: A Visual Guide

I use a handy piece of software called Artisan to track my roasts. It's open source (free!), and I highly recommend it to anyone looking to get serious about home roasting. Just make sure your roaster has a USB port so you can connect your laptop and gather data.

Before we fire up the roaster, let's break down what we're looking at on the screen. At the bottom, we have the roast time in minutes. On the left, you'll see the bean temperature, measured by a probe inside the drum. Keep in mind, those beans are constantly moving, so the readings won't always be perfectly smooth. That's totally normal!

Now, the real star of the show is on the right: the "rate of rise" (ROR). This tells us how quickly the bean temperature is increasing. During the crucial "development" phase, I aim for an ROR between 5 and 9 degrees Celsius per minute. Too slow, and the roast might stall. Too fast, and we risk scorching the beans.

Alright, time to get roasting! First, I set my variables on the roaster itself and log them in Artisan. For this batch, I'm going with:

• Drum Speed: 80% (how fast the drum rotates)
• Burner: 80% (the heat applied to the drum)
• Air Speed: 65% (how fast the fan blows cool air into the drum)
• Damper: 3 (controls how much air moves through the drum exhaust)

Once the beans are in the drum, the bean temperature (the green line) takes a nosedive. They're room temperature, so they cool the drum down initially. We call this the "turning point" or "TP" when the bean temperature starts to climb back up and continues untl the end of the roast. As long as that green line looks like a big Nike tick by the end of the roast, we're good.

Now, I'm keeping a close eye on that blue line – the rate of rise (ROR). Remember that the ROR is the speed at which the bean temperature is increasing over time. At first, it shoots up way past my maximum target of 9 degrees Celsius per minute. But that's okay! In this initial "drying phase," we want to get those green beans warmed up and dried out as quickly as possible. They're too moist to burn at this stage, so we can build up some momentum.

Next up is the "development phase," where the magic really happens. The beans transition from yellow to brown, and those delicious caramel and sweet flavors start to develop. I aim to spend about 40% of the total roast time in this phase, gently reducing the heat as we approach "first crack."

First Crack: The Sound of Coffee Magic

First crack is a key moment in the roast. It's when the beans have absorbed enough heat that CO2 bursts out, making a popping sound. You can actually hear it! As first crack approachs I'll open a little flap in the roaster and listen closely. This generates a lot of heat, so we need to be careful not to overcook the beans (or burn ourselves).

Ideally, that blue line (ROR) should steadily decline throughout the roast. In this batch, it dropped a bit too quickly after first crack, which tells me I could have backed off the heat a little sooner. Live and learn!

The Final Touches

I stopped this roast at 220 degrees Celsius (according to my slightly miscalibrated machine!). These Brazilian beans spent about 23% of the time in first crack and 45% in development. Not perfect, but pretty darn good!

Once the beans are cool, I weigh them to see how much weight they lost during roasting. For these Brazilian beans, I'm aiming for around 15.5% weight loss.

Beyond the Roast

The final step? The dreaded defect sorting! Picking out any discolored or imperfect beans is a tedious task, but it's all part of ensuring top-notch quality for our customers. (A bean sorter is definitely on my wish list!)

Of course, the ultimate test is the taste! I'll give the beans a chew right after roasting and then 24 hours later I'll brew a cup to see how those flavors have developed.

That's a Wrap!

Roasting coffee is a blend of science and art. I hope this post has given you a glimpse into my process and inspired you to learn more about this fascinating world.

Roasting coffee is a fun and rewarding experience. By following these tips, you can make delicious coffee at home.

Here are a few other things to keep in mind:

• Experiment with different roast profiles. There are many different roast profiles that you can use to create different flavors of coffee.
• Don't be afraid to make mistakes. It takes some practice to get the hang of roasting coffee. Don't be discouraged if you don't get it right the first time.
• Share your coffee with friends and family. Once you've mastered the art of roasting coffee, share your delicious creations with others.

I hope this blog post has helped you learn more about the process of roasting coffee. If you have any questions, please feel free to leave a comment below or get in touch!

I would also like to add that it is important to be safe when roasting coffee. Roasting coffee beans can produce harmful fumes, so it is important to roast them in a well-ventilated area. You should also wear gloves and eye protection when handling hot beans.

I hope you enjoy roasting your own coffee!

Chris