The Ultimate Guide to Coffee Roasting

Experience the art and science of coffee roasting with Cupper’s Coffee & Tea. Learn from our master roasters and savor the results in every cup.

Get ready to experience the art and science of coffee roasting! With every bean having its own unique characteristics, the perfect roast is no easy feat. Our master coffee roasters Josh and Jo are true artists. They know how to give each roast the love and attention it deserves.

But the perfect roast isn’t just about timing and technique. It’s also about finding the ideal roast degree to bring out the full potential of each bean. Josh and Jo know how to strike the perfect balance to create an unforgettable cup of coffee. So sit back, relax, and savor the delicious results of our master roasters’ artistry!

Roasting coffee beans is a process that takes much training and practice to become a master. Each coffee bean is different from the next. This means that Josh needs to give every roast the same level of attention. The basics of coffee roasting involves applying heat to green coffee beans. This has to happen in a controlled setting and fashion. Roasting changes the chemical nature of the coffee bean. This is a process that continues even after the roasting is complete. This brings out the aromas and flavours trapped within the bean. Roasting coffee is 100% a science and an art.

Note: This article focuses on roasting coffee in a drum roaster, which is the roaster we use at Cupper’s Coffee & Tea.

The Basics of Coffee Roasting

There are many factors and steps that go into a good coffee roast. These steps are standard across all drum roasters. Each is important, and has an impact on the final product. And as stated above, each is both a science… and an art!

Meet Cupper's Drum Coffee Roaster

Drum roasters rotate the green coffee in a steel drum above a burner. That’s a very basic description, but is standard across all drum roasters. Many, like ours, have an overhead hopper to drop the green beans into the drum. They also often have a tamper that is pulled out during roasting to check the degree of roast. There is a weighted door on the front of the drum that we open when the roast is complete. The near-finished coffee then rotates on a cooling tray.

During the roasting, air is pulled through the drum and out the vent on the top of the roaster. This helps control the temperature, moisture, and chaff from the green coffee. The heat for our roaster is generated by four natural gas burners under the drum.

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The Charge Temperature

The first step in coffee roasting is preheating the roaster’s drum. We call this the charge temperature, or charge temp. The charge temp varies on many factors. For example, the charge temp needs to be higher for a larger batch of beans. This is because the temperature will drop much faster when you add more beans vs. a smaller batch. Another variable is how the farmers processed the green beans. Some of our natural processed coffees need a lower temperature than washed coffees.

For more information on coffee processing, read our Beginner’s Guide to Coffee Beans.

The charge temp has a huge effect on the complete roast time. One of the ways Josh controls the roast is by making sure the drum is set for the correct charge temp. He accounts for the correct temperature for the beans used and the size of roast he is planning.

Weighing the Green Beans

White the coffee roaster is heating, Josh or Jo weighs out the raw green coffee beans. The weight of the coffee will be lower once roasted. Coffee will lose a significant percentage of its moisture during the roasting process. But even though the weight of the beans is lower, the size of the bean actually almost doubles. The roasting process heats the moisture in the beans. This creates pressure inside the bean and causes the bean to expand. In the end, this results in a larger roasted bean that also weighs less than its starting green bean stage.

The Browning Stage

Josh and Jo then add the weighed green beans into the drum through the hopper. At first the beans tumble around the drum and absorb the heat of the roaster. During this stage the Maillard reaction begins.

You may be familiar with the Maillard reaction if you have ever taken a cooking or baking course. The Maillard reaction is the browning of food during cooking. It’s due to a chemical reaction between amino acids and sugars in food. This is the reaction that turns cooked food the delicious golden brown colour. Without the Maillard reaction, you end up with cooked food, but it has very little flavour and no colour. It’s the Maillard reaction that creates bread crusts, seared steaks, or crisp French fries.

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During the browning stage the green coffee beans go from their pale green colour to a pale yellow. Then they start to brown as they head towards the next stage of the roast.

First Crack

Once the roast reaches around 175° C, the beans are hot enough that they start to give off heat. At this point, they start cooking each other. In other words, they become exothermic. At this stage Josh adjusts the roaster to prevent the temperature from spiking up. Instead, we want to keep a constant steady increase in the temperature in the drum. If the roast temperature is not lowered the coffee may taste smoky or sharp in a way that undesirable.

When the coffee gets to a point where it is exothermic, it begins to crack as the steam starts to escape from the beans. You can often hear this sound outside the roaster as well. This stage is the “first crack”. The cracks start to happen at the ends of the crease that runs the length of the coffee bean.

Second Crack

Second crack is where the magic happens in coffee roasting. It’s the moment when the beans start poppin’ and the roastin’ gets real. This also is the point of roasting where the coffee goes from medium to dark roast.

With second crack, the beans start releasing their deeper inner gasses. The roasters hear a sound like small popcorn on the stove. The actual crack often extends the cracking at the end of the bean that started with first crack. But different from first crack, it can also be small craters blown out of the smooth surface of the beans. These indentations are a sure sign of second crack.

The extra heat causes the sugars in the beans to caramelize. And that’s not all – the oils in the beans start to surface, giving the coffee a mouthfeel that’s oh-so-smooth. It’s not for the faint of heart. It takes a skilled hand and a watchful eye to navigate this part of the roasting process. Timing at this point is critical. A few seconds can make all the difference between a perfect roast and a burnt batch.

For those who prefer their coffee on the bolder side, second crack is where it’s at. The resulting roast has complex flavours that’ll make your taste buds dance. But for those who prefer a lighter roast, second crack can take it a bit too far and create a brew that’s a bit too bitter.

How Dark To Roast Coffee?

Roast degree is a crucial aspect of the roasting process. It impacts the flavour, aroma, and body of the coffee. The roast degree refers to the level of roasting the coffee beans undergo. There are 3 roast categories: light roast, medium roast, and dark roast. It’s important to pay close attention to the roast degree when roasting coffee. The degree of roast has a huge impact on the quality and flavour of the coffee. It’s essential to consider what degree of roast you want to end at before starting the roast.

Flavour Notes in Coffee

Heating coffee beans causes the sugars, proteins, and acids to transform. This releases ideal flavours and aromas. Coffee flavours and aromas are diverse almost beyond believability.

These notes are all found within different coffees:

- Nutty
- Sweet
- Savoury
- Spicy
- Floral
- Fruity
- Woody
- and more!

In fact, there are over 850 flavour and aroma compounds documented in roasted coffee. A masterful small-batch roaster knows how to identify and bring out these compounds.

There are a huge variety of factors that play into the subtle tastes and aromas in your coffee. These tastes and final aromas also depend on:

where the coffee is grown
the altitude of the area
the season’s length
the soil type
the amount of rain and other weather factors and
that season’s growing conditions.

Coffee also takes on the flavours of other products grown in the region. This can include nuts, fruit, flowers, and chocolate. When shopping for coffee beans seek out roasters with descriptions of each coffee.

Light Roast

We roast a light roast coffee until the beans reach a light brown colour. This type of coffee has a delicate flavour with bright acidity and subtle fruit and floral notes. It’s an excellent choice for those who prefer a lighter, more complex coffee. This coffee remains in the roaster until first crack. The first crack is audible as the coffee drops in the cooling tray.

Medium Roast

We roast a medium roast coffee until the beans reach a medium brown colour. This type of coffee has a more robust flavour with a balance of acidity, sweetness, and bitterness. It’s a popular choice among coffee drinkers who want a well-rounded and balanced cup. We develop this coffee a little past the first crack, so there is no popping. It’s stopped several degrees C before starting second crack.

Dark Roast

We roast a dark roast coffee until the beans reach a dark brown colour. This type of coffee has a fuller body with notes of caramel, chocolate, and smokiness. During the roasting process the oils contained in the bean come out. Darker roasted beans may have a slight oiliness to them. This is a good choice for those who prefer a stronger, more robust coffee.

The darker the roast the more the original flavour of the bean is overcome by the flavour of the roast. It can be hard to distinguish the flavour of the bean with a very dark roast. The greener a coffee is, the more chlorogenic acids are present. Some of the acids are pleasing to taste, but some of them have an unpleasant taste. The goal is to cook off the unpleasing acids while keeping the flavour of the bean intact.

There are also some general qualities associated with different types of roasts. To read more about different coffee roasts, see out our Beginner’s Guide to Coffee Beans.

Other Factors In Roasting Coffee

So you thought you had all the information needed to go start roasting your own coffee. You’re well on your way… but there’s additional factors that play into this. Some can be controlled, others can not. Those you can’t control you can only manage or adapt to.

Airflow

When it comes to roasting coffee, airflow is a star player on the team. Airflow helps regulate the temperature and humidity levels in the roasting chamber. As the coffee beans roast, they give off steam and moisture. That moisture needs to escape, or else the beans could end up overcooked. steamed, and ruined. Airflow whisks away the moisture and keeps the temperature optimal for roasting.

We manage airflow by our venting on the top of our roaster drum. By adjusting the airflow, we can control how fast the moisture evaporates from the beans. This fine-tuning allows for the creation of unique coffee flavours that we all know and love. Airflow might seem like a small detail, but it plays a big role in the coffee roasting game.

Cooling

Once Josh knows that the coffee is seconds before its peak flavour he dumps it into the cooling tray. Because the beans are emitting heat they will continue to cook until they cool. It seems contrary, but the coffee must drop mere seconds before it’s reached its peak. This is like cooking a roast in the oven. You want to pull the roast out before it’s done because it will continue to cook after removing it. If you want a medium done roast, you need to pull it out of the oven while still medium rare.

The fan under the perforated cooling tray draws cold air through the hot beans. The coffee beans remain in motion as the agitation arm stirs them. If a batch of coffee isn’t cooled with this agitation it can result in an uneven roast. The coffee beans may even become brittle and taste stale. It doesn’t take long to cool the coffee beans. They’re done cooling and are put in a bin before the next roast is ready for the cooling tray.

Resting

After roasting, coffee beans need to rest to off-gas and develop their flavours and aromas in full. During the roasting process, roasting the high heat causes the cell walls in the beans to break down. This releases many compounds, including carbon dioxide (CO2) gas. These compounds contribute to the flavour of the coffee. If the CO2 gas is still trapped inside the bean it can interfere with this flavour. This is because the gas can react with the compounds in the coffee, producing a bitter and sour taste.

By letting the coffee rest in bins after roasting, the CO2 gas can escape. This creates a more stable and predictable environment for the flavours to develop. We wait at least 24 hours after roasting is complete. Thus we ensure a smoother, better well-rounded cup of coffee. This is one of the reasons we never cup coffee the same day it’s roasted. We also try to avoid grinding the coffee within 24 hours of roasting to really give it the time it deserves.

How Fresh is Fresh?

We go to a lot of effort to source the best green coffee beans we can buy. It’s also important that all our coffees are fresh roasted. The flavour of a coffee bean keeps developing for a few days after roasting. In fact, according to many experts the “sweet spot” for coffee begins on the 4th day after roasting.

People are always struck by the amazing smell of coffee when they first walk into the store. There’s nothing like that fresh roasted coffee aroma. Did you know that over 90% of what you taste actually comes from what you smell? So if you love the smell of our coffee, you’re going to go nuts for the taste.

Cupper’s has built our world-wide following by timing our roasts according to how much of it we use in a day. Every coffee on our coffee bar is in that sweet spot: the best of fresh. For keeping your coffee at it’s flavourful best, we recommend Airscape Canisters.

Our Coffee Roaster

Our custom built Coffee Roaster takes the fine art of coffee roasting to a whole new level. At Cupper’s, we “cup” (taste-test) coffee from roasters all over Canada and the U.S. to make sure we stay at the top of our game. (To learn more about cupping coffee, check out our article Cupping Coffee: The Ultimate Tasting Guide.) With pride, we can say our coffee is richer, more flavourful, and better balanced than most others.

Our roasting equipment is top-notch, and so are our master roasters, Josh and Jo. A lot of roasting equipment doesn’t give heat and airflow control to a precise enough level. (Think of the difference between a blow torch and a gas stove.) So, our answer was to build a custom coffee roaster that is “tricked out” to meet our super-high standards. To help us, we enlisted a friend with a PhD in thermal dynamics, and a local fabricator. Thus the concept for our roaster was born.

It was all very complicated, and got a little wild there for a while, but our guys knew what they were doing. There was a lot of tinkering, figuring, reconfiguring, and resetting! We even had them slow down the RPM (rotations per minute) of the drum to increase the sweat-time of the coffee. These small improvements in our roaster translate into BIG improvements in our coffee. We can refine our roasts in ways that other roasters can’t match.

The Art & Science of Roasting

Coffee roasting is a true art and real science. Roasting coffee beans is a process that takes a lot of training and practice to become a master. Each coffee bean is different from the next. This means that our master roasters need to give every batch the same level of attention. Josh and Jo take great care in ensuring that each bean receives the love it deserves. These skilled roasters understand the unique characteristics of each bean. They work hard to bring out the best in every batch. The result is an unforgettable cup of coffee that you can savor and enjoy.

We roast fresh coffee every day. If you’re in the store and you’re interested, come and watch Josh and Jo create magic. Our success is a testament to the artistry of our master roasters, coffee roaster, and the beans we source.