Coffee Roasting Process: The Stages To Which Coffees Are Developed


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As they always say, a coffee bean is actually a seed, which can be found inside a coffee cheery. This coffee bean is all that we need to make a great cup of coffee at home. But before you can have a taste of it, it goes through a roasting process to which the flavors develop.

From the coffee production where the coffee beans are planted, grown, taken care of until the cherries are harvested. These cherries are then further processed. They are processed in either the dry or wet methods. Then after raw green coffee beans have been produced, this is where the roasting process takes place.

There are different ways to implement it, different preferences in the type of roasts. In this article we’ll talk about the process of coffee roasting and the different stages to which the coffees are developed.

Coffee Roasting Process

Coffee roasting is a process of developing the flavors and other aroma compounds of coffee. It involves heat treatment that produces (physical and chemical) changes in the structure and composition of raw green coffee.

Simply means transforming the raw green beans into what we’ve recognized as brown or dark-brown colored beans.

It’s one of the most important processes of making the perfect coffee that you love. You need to roast those raw beans to bring out the aromas and flavors that are locked inside.

However, while it produces different complex aroma compounds, these compounds can either make or break the final coffee flavor. So, some roastmaters have to complete numerous hours of coursework and hands-on training to guarantee a successful roasting development.

Further Reading: Why Do We Need to Roast the Coffee Beans? (All You Need to Know)

What is Roaster?

A roaster is simply a machine or roasting equipment where we enter the coffee beans, then further heated with either direct or indirect flame. It comes with different designs and probably different techniques to how it operates.

Every roasting machine may perform differently, and each may have unique functions and characteristics that influence the heat. Sometimes, it is possibly defined by its size or capacity.

A typical roasting machine has a certain property that is used to adjust and modulate the flame and the pressure inside the roasting chamber, which makes it faster to control.

Most roaster operators use roasting machines that we’ve typically known as “drum roasters”, which are usually made of steel, containing cylindrical chamber where the coffee beans rotate. It is indeed the best machine to use as many roasters and even brewers prefer it because of its special design that affects the thermodynamics or momentum of roasting.

You can have the consistency that you want in roasting as this kind of roaster is very stable and offers full control. You can have the necessary adjustments if needed.

Furthermore, this setup is very common in the coffee roasting industry as it’s today’s standard.

Important: The use of a roaster is essential to the entire process of roasting. But there are many different ways to which you can apply heat to the beans that use different roasting equipment. Those roasting machines provide consistent and excellent results, however, they are expensive and are on commercial levels.

Luckily there are some home coffee roasters out there that you can use to get started. I recommend the Sandbox Smart R1+C1,Coffee Bean Roaster for home roasting. This item has a smart heating system that preserves the best aroma and flavor, while providing a more convenient way of roasting.

The Fresh Roast SR540 is an alternative. Although it has a lot of features, which is sometimes overwhelming, this unit is still easy to use and gives you great control to achieve the roasting preferences.

In the end, we do prefer a roaster that makes the work faster without ruining the coffee beans to get the desired flavor. Also, to maximizes our time to do the things that needed to be done.

How are Coffees Developed?

In some context, to develop means to treat something by such a method in order to produce a visible image. 

But when it comes to coffee, appearance is not the only thing that is produced, a lot of complex compounds are also developed such as tastes, smells, etc. Development simply refers not just to the physical changes but also to the chemical reactions that happen during the entire roasting process. 

Therefore, give the effort to at least monitor if there’s a transformation happening as well as to taste your beans as sometimes, what we think on a coffee is all down to personal preference.

SIDENOTE: If you’re wondering if the roasting is the same as developing, I guess it’s not? When you apply heat to the coffee beans, that’s what we call “roasting”. If you tend to see a significant change, then probably, that’s what we call “development”.

So, how coffee flavors are developed during the roasting process? 

Technically, the coffee beans are already developing (but not the start of real development, which typically at the “first crack”) once you enter them into a drum roaster. However, the process takes time as the beans will go through several stages.

Each stage contributes to the bean’s progress in achieving a successful development (the flavor that we want to achieve) at the end of the entire process. 

In this guide, we’ll walk you further to how these coffee flavors are produced and developed. Understanding each roasting stage gives you the insight that each of them offers a specific yet special duty to which contributes to what we’ve known as “coffee”.

The Stages of Roasting

Basically, there are three main stages in the roasting process known as drying, browning, and development or roasting stage.

However, some coffee experts break the roasting stages down into different ways to which stages like pre-heating, yellowing of beans, the first and second crack, and even cooling also take place.

Let’s walk further through these stages and discuss how they can influence your coffee flavor.

1. Pre-Heating

Like the thing with cooking, you need to pre-heat your pan before you start frying or even toasting, as well as baking, you need first to pre-heat the oven before using it.

The same thing with coffee roasting since it requires a lot of concentration, including your ability to sense everything. You need to pre-heat everything, from the roaster to the coffee bean itself, to make things much easier to monitor. 

Prior to roasting, it’s essential to start with a hot drum or roaster before feeding the raw green coffee beans into it, otherwise, you can’t obtain the perfection and the consistency that you want in a coffee.

Before the drying phase, you need to have a starting temperature – depending on the size of your roaster and amount of coffee to be charged – to maintain a consistent result. You can also save time as the roaster is already pre-heated to the necessary temperature for drying the beans.

2. Drying Stage

This is the primary process where you get the water out of the coffee beans by means of drying – you load them into your roaster and let them dry for several minutes – so that the necessary flavors may also be developed in the next phases or stages.

The raw coffee bean has a humidity of 9–12% and it needs to be totally dried before the actual roasting takes place (before browning or developing starts).

The drying stage typically lasts 6–8 minutes (it depends to roast operators, some want it slow while others want it fast) in a drum roaster, having a consistent (or may adjusted) temperature that is about 160 ⁰C until the end of this stage. 

In line with the temperature, you need to be careful in applying heat to the coffee beans so that you don’t burn or even undercook them, especially with drum roasters which create too much heat in the start, creating an illusion to which the beans are perfectly roasted on the outside but undercooked in the inside. 

What Will Happen to the Coffee Beans at this Stage?

Once the coffees are charged (or entered as the first batch) into the drum roaster, the initial roasting (known as drying) also starts.

After a minute, assuming that the temperature hasn’t changed, the beans would normally absorb the roasting machine’s heat, the moistures inside them also start to reduce.

Then at the near end of this phase, expect the coffee bean to change in color – from green to yellow. This is when the first roasting reactions happen, a time when the beans start to swell and the aromas tend to smell. 

Expect the beans to have transformational changes as different chemical reactions occur during this phase. Here are some of the changes in this stage:

  • As mentioned, the change in color is one of its main transformations – from green to yellow, which also signs as the end of the drying stage.
  • The internal pressure of a coffee bean tends to increase, you will also notice a slight increase in its volume.
  • The loss of mass and density. Typically, due to the evaporation of moistures.

However, these major transformations within this stage have nothing to do with the taste yet and do not even directly affect the coffee’s final flavor.

But this does not mean that the drying stage can be neglected. It’s indeed necessary to maintain the nice flow of the roasting process, making the coffee beans ready and preconditioned, and to have a successful development in the succeeding phases.

3. Browning Stage

For the second stage, of course, the beans are still left inside the drum roaster until the acids react to create different aromas, as well as to create brown color – typically, from yellow to brown.

The browning stage takes place when the sugars inside the beans are caramelized and the aromas start to smell. Caramelization occurs simply because the beans are exposed to high temperatures inside the roasters. From a 160 ⁰C temperature. The coffee also starts to smell like a freshly toasted bread.

Speaking of brown color, the thing that is responsible for browning and why it occurs during this stage is the “Maillard Reaction”. By the means of slowing down the speed to which the temperature rises, you allow the triggering of this reaction in this process.

“Maillard reaction is a nonenzymic reaction between sugars and proteins that occurs upon heating and that produces browning of some foods (such as meat and bread).”

When it comes to coffee, it’s the reactions between sugars and amino acids that occur during roasting. The Maillard reaction occurs due to reducing sugars and amino acids that take place in high temperatures, and once it reacts, it creates hundreds of different flavors and allows the formation of different complex aromatic compounds. 

The best way to ensure a successful flavor development in this stage is, of course, managing the time and the temperature properly. You may let the roast to naturally slows down – as most roasters prefer it, or speed the process a little bit. Just be careful and always maintain the consistency that you want in coffee.

Now, at the end of this stage, you will start hearing a cracking noise, which is called the “first crack”. That means that the development stage or the actual roasting is about to begin. 

4. Fist Crack

A cracking noise, it’s exactly what it sounds like, sometimes it sounds like popcorn popping inside your kernel. It occurs due to the accumulated steam pressure inside the bean that’s getting too high – the gases and water vapor have built up inside – which causes the bean to crack. Typically, the pressure is due to the rising temperature.

5. Development Stage

This is the final roasting stage where the coffee tends to develop. 

The final result or the final flavor will totally depend on how long the coffee beans are further subjected to heat after the browning stage. After the first crack, you may still process it to achieve dark-brown colored beans, also known as “dark roast coffees”.

The time to expect the development is when the preferred aroma compounds and desired flavors are coming out. The beans become browner or darker, and the bean’s surface becomes smoother.

This is the moment when a coffee bean tends to explode as so much energy or pressure have been collected during the drying and browning stages. Time and temperature have also contributed to it. 

Typically, the development stage covers the 10–20% of the entire roasting process, depending again on the desired flavor profile and roast degree. You may let it in the roasting machine a little longer to let the sugars caramelize, or pull it out from the roaster because you want a medium roasted coffee. Whatever it is, it’s your choice!

6. Second Crack

If you’ve decided to further roast the beans, expect the coffee to create more cracks, which allows the Carbon Dioxide and the other organic gases inside the bean to escape. These occurring cracks and the breaking of most of the remaining fibers in the beans are probably signs of “second crack”.

So, if the roasting process continues, it will then reach the second crack. The second crack is quieter compared to the first one, which means the structure of the bean comes to an end to break down.

This is usually the time the oil inside the beans are already coming out, creating a shiny appearance on the surface.

How Long Should It Last?

Generally, it will always depend on the person who roasts the beans and to how the roasting equipment works. While there are necessary procedures to follow, there will always be a time that you will rely on your senses. 

But for the sake of experimentation, there’s always an approximation; Considering the 3 main stages of roasting.

When it comes to the drying stage, ideally, it should last within the 40% – 50% of the entire roasting process. For the browning stage, it should cover 40%. And lastly, the 10%-20% is for the coffee’s development, but sometimes, it will depend on our own preference.

How Fast is Too Fast? Slow is Too Slow?

  • Not so Fast but Not Too Slow!

When it comes to the drying stage, you may want to avoid roasting your beans too fast. Sometimes, the needed heat will not be delivered inside the beans or may lead to unequal distribution of heat.

The drying stage is where the beans are heated for the moistures inside to come out and evaporate. But on the other hand, you wouldn’t also obtain a consistent result if the process is too slow with just the right amount of time.

  • Or You May Want to take it Slow!

When it comes to browning stage, if you will speed up the process, the quality that we want in coffee will not be developed as well. The sufficient time to flourish the flavors and aromas will not be maximized.

This is why, during this phase, it’s recommended to take it slow. Slowing the process means you’re letting the natural browning of beans to take place.

  • But You May Need to Roast it Fast!

For the last stage, fast roasting might be a good idea, or might be not? In some cases, you roast the beans fast enough to get more desired aroma compounds because you can’t attain it if it’s too slow.

Fast roasting at the beginning of the development stage creates a high amount of aroma compounds. 

But when it comes to the last stage, all the flavors and aroma compounds are already coming out. Therefore, you’ll need to roast the beans that fast to avoid over-roasting or over-cooking.

  • Just Roast the Beans!

However, some roaster says that if we do not slow down the roast at the development stage, we easily get coffee that is smoky-tasting and the flavor is too sharp.

So, which is right and which is wrong?

All mentioned above are just merely a guide. We’ve always said that roasting will always depend on our own perception.

The fast roast comes in to enhance the coffee flavors, as well as a slow roast to get that desired flavor. Indeed, experimenting with roasting is the key to find that perfect profile.

The Types of Roasts

How do you know if the stage is already done? If the coffee is ready for grinding?

Well, the answer is you should first know the type of roast you want. The roast degree is one of the most important factors in identifying a certain roast profile and is sometimes associated with these stages. 

The best way to ensure that you obtained a nice and well-developed coffee is by tasting it. However, most of the time, you can easily measure it simply by the bean’s color.

While you can monitor the color of the coffee bean in every stage to help you understand and stop the development process, it will not always come to the appearance to which you can easily determine.

Development isn’t a scale like color, maybe it’s yes or maybe it’s a no. Color is sometimes deceiving.

Therefore, you need to know the difference between light roast and dark roast coffee and even medium roast to choose the one that suits your preference. If you are able to identify their differences, then you have a guide to the taste you can expect.

Assuming you already know the difference between these roasts, the final decision is in you!

If you’re looking for a light roast coffee, the bean is already in light brown after the browning stage, the moment you heard the first crack. Then this is the time to pull the coffee beans out of the roaster for cooling. 

On the other hand, if dark roast coffee is what you want, wait until it reaches and finishes the development stage – the beans are in dark brown at this point. This time, you can achieve fully developed flavors and aroma compounds in your cup.

SIDENOTE: What is the difference between roast levels and roast stages? Roast levels refer to the roast types, the levels to which you roast your coffee beans, from light – to medium – to medium-dark – to dark – to burnt. Roast stages, on the other hand, refer to the process to which the coffees are roasted, from drying – to browning – to the end of roasting. 

Cooling

Of course, you need to cool the beans down. Pull the coffee beans out of the roaster and let it settle into room temperature. It’s sometimes necessary so that the roasting process will eventually stop.

If you don’t take the batch out, the remaining heat inside the chamber will continue to roast the coffees.  

Final thoughts

In the end, we have learned that roasting is essential to the development of coffee. We’ve further tracked each of the roasting stages that helped us understood the importance of it in achieving the flavor that we want in our cup.

In conclusion, roasting is indeed an art, even if we’re lacking in experience, it is something that we can learn. Learning to roast may not as easy as you think, but it may give you great experience and fun to find the best roast profile that will suit your preference when it comes to coffee

Therefore, with all the information you gathered about roasting, don’t hesitate to try and explore it even at home.

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