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The Ultimate Guide To Roasting Coffee

The Ultimate Guide To Roasting Coffee

Roasting coffee is what makes it delicious, but it’s something you might think needs to remain in the hands of a professional roaster.

This isn’t true – anyone can roast coffee and today it’s easier than ever!

What does it mean to roast coffee?

When coffee is roasted, coffee cherry seeds are heated to extract their flavor and increase their solubility, or how well they can dissolve in water.

Solubility helps you to further extract the beans in the best way, FYI. So, with that in mind, let’s look at how coffee is roasted and how you can roast coffee so that you get a tastier cup of coffee (hint: you don’t need any fancy equipment).

A Brief History Of Coffee Roasting

It’s amazing to think that roasting coffee is a practice that goes centuries back, all the way to 1258 A.D., when Egyptian Muslim leader Sheik Omar had been driven into the desert and had nothing to eat so he ate berries that tasted bitter to ward off starvation.

To make them taste better, he roasted them and added water to them. He felt refreshed after eating these berries and coffee was born as a beverage!

Around a century later, Arabs would regularly roast coffee beans over a fire before making coffee grounds out of them.

They would mix the grounds with animal fat. This beverage was called “qahwa,” which means “that which prevents sleep,” as 428 Roasters reports. That’s pretty accurate considering coffee is perfect for when you need to pull an all-nighter!

As time went on, coffee roasting became more and more popular. Some of the earliest roasting tools were perforated, thin pans. They were put over an open flame to roast coffee beans.

The person who was in charge of the process would make use of spoons to move the beans around the pan so that they would not burn and would give the beans an even roast.

By the 17the century, people started using cylindrical roasters. These kept the coffee beans enclosed and drew heat into the chamber to roast the beans.

These roasters were controlled with hand cranks so that it was easier to move the coffee beans around and ensure an even, tasty result.

Then, in the 19th century, commercial roasters were appearing in Europe and the United States, but it was still common for people who loved coffee to roast coffee at home. Industrial roasters were large cylinders that were used to roast coffee beans over a source of heat.

Coal or wood was traditionally used, but then when natural gas came about this was preferred because it prevented the coffee beans from tasting smoky.

In the 1875, Germany passed the first coffee law to ensure its purity by stating that the coffee roasting trade would occur in factories, not in people’s private homes!

During this century, there was a large amount of experimentation when it came to roasting coffee, such as by using different heating and ventilation techniques. Around 1889, Carl Salomon used hot gas ventilation to make roasting techniques even faster – just 20 minutes long!

His coffee roasting technique was used by many people for many years to come. Even today, some coffee roasting machines still use his design as their foundation, such as by making use of hot air that’s blown into a drum to heat coffee beans.

When the 20th century came around, electricity was accessible to more people and this played an important role in how coffee was made and roasted.

Many companies used electricity and electric motors to decrease the amount of labour involved in coffee roasting as well as to have greater accuracy when it came to the end result.

By making use of electricity, coffee roasters had more control of the process, such as how much heat to use on the beans, and were able to replicate the roasting conditions with success.

Why Do We Need To Roast Coffee?

If coffee beans weren’t roasted, they wouldn’t have any flavor – and coffee certainly wouldn’t be as popular as it is today, with more than one billion people in the world enjoying coffee every single day.

The process of roasting coffee beans puts the beans under stress and causes them to change a lot, not just when it comes to their color but also when it comes to their chemical characteristics.

The thing to remember about roasting coffee, however, is that it is quite unique and complex depending on the roaster’s preferences. By tweaking various elements of the coffee roasting process, roasters can evoke many different flavors and strengths of coffee.

The Science Behind Coffee Roasting

The process of roasting coffee makes use of volatile and non-volatile components, both of which are important. The volatile components create the coffee’s aroma. The non-volatile ones are responsible for the flavors we love, such as slight bitterness or sweetness.

When roasted, coffee beans also experience reactions, both endothermic and exothermic. Endothermic reactions are when energy is absorbed in the form of heat.

Coffee beans experiencing these reactions change color, start releasing aromas, and lose their moisture.

Then, the exothermic reactions involve the energy being released and moisture being eliminated. The coffee beans will rupture and release their stronger aromas and flavors.

How Coffee Goes From Green To Brown

It might be strange to hear this, but coffee beans start out green in color.

They have a grassy aroma and if you didn’t know they were coffee beans you wouldn’t imagine that they were because they don’t smell like coffee. Coffee beans are really seedlings of purple or red fruit that are similar to cherries.

The two main coffee bean types are Robusta and Arabica. It’s said that Arabica beans have less caffeine and are more full of flavor than Robusta beans. 

When they are roasted, coffee beans start to take on a delicious coffee taste and smell. In fact, roasting coffee beans can extract up to 100 aromas that contribute to its deliciousness.

The Three Stages Of Roasting Coffee

The Three Stages Of Roasting Coffee

Earlier, we touched on the chemical changes that occur in coffee beans when they are roasted, but there are three roasting stages that coffee beans go through. These are:

Drying Stage

Coffee beans have humidity of up to 12 percent so they need to be properly dried before they can be roasted.

This takes a few minutes and a drum roaster is usually used for this process. The drum reaches high temperatures – usually up to 160 degrees Celsius – so it’s important that the coffee beans are watched closely to prevent them getting burned.

This stage helps to gather energy for the coffee beans because this will be required at a later stage of the roasting process.

Browning Stage

After the drying stage, the beans will start to smell a bit like toast! Now they have to undergo the browning stage, which involves chemical changes: aroma precursors begin to change into compounds.

What’s known as the Maillard reaction also begins during this stage. This is when sugars and amino acids react. This creates many different smells and color compounds, which is why coffee takes on different colors during the roasting process.

The process of roasting coffee needs to slow down during the browning stage so that flavors and aromas can develop properly. When the stage nears its end, the coffee beans start to crack and pop like popcorn! 

Development Stage

Now that the coffee beans have cracked, they are in the development stage. During earlier stages of roasting, the coffee had gathered energy and this is what causes the beans to crack.

During the development stage of roasting, the aroma compounds of the coffee beans continue to develop. Again, the process needs to be treated carefully and it has to slow down so as to prevent a smoky or sharp coffee flavor.

How To Choose The Right Roast

How To Choose The Right Roast

As you know, there are different levels of roasting, but which one should you choose?

Roasters will be able to tell what level the coffee is on with the use of a color meter. Or, they can taste the coffee beans. Here’s a rundown of light, medium, and dark roasts so you can see how they differ.

Light Roasts

Light coffee roasts are acidic and fruity, as a result of high quantities of a compound known as 5-hydroxymethylfurfural.

Light coffee roasts are usually made at temperatures that are between 356 degrees Fahrenheit to 401 degrees Fahrenheit. They usually go by the names half city, light city, and cinnamon roast.

You should choose a light roast if you want brighter or acidic coffee with a lighter body. If you like roasting your own coffee, a light roast is a good one to try because the process isn’t time intensive.

Medium Roasts

To make medium-roast coffee, you’ll want to use temperatures between 410 degrees Fahrenheit and 428 degrees Fahrenheit.

The beans will be dry and their roast level will start to develop after they have cracked for the first time. Medium coffee beans have a stronger flavor than light roasts. This type of roast is usually called “American” because it’s such a popular coffee roast in the U.S.

Dark Roasts

By comparison, dark roasts are a bit more bitter. The flavors can even be more burnt. By eliminating some of the 5-hydroxymethylfurfural, the coffee can become less fruity but the quantity of sulfuric compounds increases.

Dark roasts include Italian Roast, Espresso Roast, and French Roast. They are made at temperatures around 464 degrees Fahrenheit, but you need the correct equipment for them because such high temperatures can be very dangerous, plus there’s always the risk of burning the coffee.

Coffee beans that are dark roasted will have an oily appearance and low levels of acidity.

Other Types Of Roasts

Other Types Of Roasts

You might’ve heard about blonde or cinnamon roasts, but what do these terms mean?

Here’s a rundown of some typical coffee roasts. Although there are many more types of roasts with unique names, these are some that usually cause some confusion.

Blonde Roast

This type of coffee refers to a roast that’s undergone an even shorter roasting process than a light roast. Starbucks made the term “blonde roast” popular a few years ago and it stuck!

Blonde roasts tend to have a more natural coffee flavor than other types of roasts, and this is as a result of how they’re roasted for a shorter time. Blonde roasts are commonly consumed in an espresso.

Double Roast

This coffee roasting technique is sometimes called “doppio tostado,” which means double roasting. It’s quite unique and when coffee is roasted twice it draws out more of the sweetness that you don’t find in darker coffee roasts.

Cinnamon Roast

Not to be confused with a blonde roast, a cinnamon roast is a light roast that got its name because the beans are only roasted until they have a color like cinnamon. The word “cinnamon” doesn’t refer to their flavor, though.

Full City

This is when the coffee beans are a medium-brown color and have some oils on their surface. Full city coffee offers interesting flavors. It’s usually bittersweet coffee with chocolate or caramel notes.


This is considered to be the darkest coffee roast you can get, even darker than French and Italian roasts. The coffee beans are almost completely black in color and very shiny. The coffee is ruled by a burnt flavor but there are some subtle sweet notes present. 

Short Vs. Long Coffee Roasting

Short Vs. Long Coffee Roasting

It’s important to consider how long the roasting process lasts, as this is what plays such a crucial role in how the final product will taste.

If you roast coffee beans at a faster rate, this will boost the content of aroma compounds, however there is always the risk of burning the coffee beans. Quicker roasting times also strengthen the berry, chocolate, and nut flavors of the coffee, however. 

That said, there are benefits to longer periods of roasting.

These will reduce the amount of acidity in the coffee beans, which is great for coffee types such as espressos. Roasting coffee at a slower pace allows the breakdown of organic acids and this is what reduces the coffee’s overall acidity.

Manual Vs. Automatic Roasting

Manual Vs. Automatic Roasting

There are two main types of roasting techniques: manual and automatic. Here’s what to know about them.

Manual Coffee Roasting

Manual coffee roasting can vary quite a bit, such as when it comes to when to stop heating the coffee beans. It basically depends on how well roasted you want the beans to be.

There’s no technology behind manual roasting. This means that the coffee roaster needs to pay a lot of attention to detail to the coffee as all the elements of the roast (such as aroma, temperature, and flavor) will depend on him or her.

Automated Coffee Roasting

Automated roasting makes use of profiling software that’s connected to a roasting machine. After the preferences for the beans have been put into the software, this is then transferred to the machine that will do all the work.

The reason why automated coffee roasting is appreciated is because it makes the roasting process a lot more convenient. Just press a button and the machine will do all the roasting for you! It’s also easier to maintain the same results with every roast. 

What Machines Do Professional Roasters Use?

What Machines Do Professional Roasters Use?

Professional roasters will make use of loaders in which the coffee beans are poured. The coffee beans then enter a backing line which transfers them into a drum. There are burners underneath the drums to heat the coffee beans at the optimal temperature.

The beans are then sent into a roaster, where they are roasted for about 15 minutes.  A roast such as espresso will be in for longer while other types of coffee, such as filter coffee, will be in for less time.

Once the coffee beans have been roasted, they can then enter a “de-stoner.” This machine sifts out any foreign particles that could be present with the coffee beans, such as small stones, twigs from the coffee plant, and others.

After the coffee beans have been successfully roasted and de-stoned, they will be ground and then packaged. Alternatively, they are sold as freshly-roasted coffee beans. 

Roasted coffee beans can be expensive to purchase because after the coffee beans have been roasted they have to be shipped quickly in order to maintain their freshness.

If you want to save money, you can make your own roasted coffee beans. 

How To Roast Your Own Coffee Beans At Home

How To Roast Your Own Coffee Beans At Home

If you want to roast coffee beans at home, you might wonder if you can use appliances you currently have as an alternative to a roasting machine. Here’s the lowdown:

Roasting Coffee Beans With An Oven

You can use your oven, whether gas or electric, to roast coffee beans.
Here’s what to do:

  • Heat the oven to 500 degrees Fahrenheit.
  • Put your coffee beans in a perforated pan or steamer, and place this on a cookie sheet. Use the middle rack of your oven.
  • You’ll have to watch the process closely as you’ll need to open the door of the oven every minute or so to move the beans around in the pan.
  • It will take approximately five minutes for you to hear the coffee beans start to crack. Once you do, you should check them every minute so that you can get the color and aroma that you like.

Roasting Coffee Beans With Your Stove

An even more effective way of roasting coffee beans at home is to make use of your stove, as Food Republic reports. This is said to produce coffee beans with more flavor than when they’re roasted in the oven. However, you’ll need a skillet with a lid. 

  • Start by putting your skillet on medium heat. Add the beans to it, then cover the pan.
  • When you hear the coffee beans have started to pop, you should shake the pan around. Again, it will take about five minutes for this to happen.
  • Just like with the oven-roasting instructions, you need to keep an eye on the beans once they start popping so that you can control the darkness of the roast.
  • However, a good tip via Food Republic is to remove the coffee beans from the heat before they have reached the color you want. This is because they will continue darkening for a while.

Roasting Coffee Beans With A Popcorn Machine

Yes, it’s possible to make your own coffee with a popcorn machine! As you have probably gathered by now, roasting coffee at home is quite similar to making popcorn because of how the coffee beans have to pop.

Using a hot air popcorn popper is great if you’ve never roasted coffee beans at home because it will allow you to experiment with different roasts and get the hang of the process. Here’s how to do it.

  • Switch the popcorn popper on and allow it to heat up for about half a minute.
  • Then, add your coffee beans. A good amount is about half a cup.
  • Keep an eye on the process – again, it will only take a few minutes. 
  • You’ll see the beans change color so you’ll get to stop the process when you think you’ve got the right roast.
  • When you’re satisfied with the way your coffee beans are looking, switch off the popcorn popper and remove the beans. 
  • Place them on a baking sheet to ensure that they cool down quickly.

How To Purify Your Coffee Bean Batch

How To Purify Your Coffee Bean Batch

Once you have cooled your coffee beans, you need to look through them to remove any beans that didn’t get roasted properly. There are three types of these beans that you should remove so that they don’t degrade the quality of the entire batch.


These are beans that have low amounts of sugar in them so they didn’t manage to fully mature and therefore didn’t become dark brown in color.

The lack of sugar prevented them from getting caramelized. These will look like they haven’t been roasted enough but they will taste burnt, so you don’t want them in your coffee.

Pea Berries

These berries are considered to be a natural defect and will be found in every coffee batch. What are pea berries?

Every coffee cherry has two seeds that are facing each other. But, around those seeds you’ll see fruit pulp and skin. With pea berries, they have a single seed.

Elephant Ears

These got their name because of their shape – they look like elephant ears. When the coffee seed formed, some of it slipped out and this made it less dense.

How To Store Coffee Beans At Home

You have your own roasted coffee beans! It’s exciting and we bet you can’t wait to try them out. However, spare a thought for how you’ll store them because this will ensure that they retain their freshness.

  • Make sure you put your roasted coffee beans in an airtight container that’s opaque instead of clear to ensure that light won’t be able to penetrate it.
  • Keep the roasted coffee beans at room temperature in a dark and cool place.
  • You’ll probably want to keep them in a kitchen cupboard, but avoid storing the beans in a cabinet or cupboard that’s close to a heat source, such as an oven, as this could cause the beans to get hot and lose their freshness quicker. 

Can You Freeze Your Roasted Coffee Beans?

This is a tricky question because coffee can easily absorb moisture as well as any odors from the fridge or freezer.

If your coffee beans aren’t stored in an airtight container, they can easily be exposed to oxygen, which can result in them losing their freshness at a quicker pace than you’d like.

If you’re dead set on storing coffee beans you’ve roasted at home in the freezer, make sure that you use an airtight container. You should also consume the beans within about six weeks.

Where To Buy Green Coffee Beans

Where To Buy Green Coffee Beans

It’s not always easy to find coffee beans that haven’t been roasted, but you’ll have luck by trawling the internet. Websites such as Sweet Maria’s have green coffee beans on offer.

This site also has an excellent reputation so you can be guaranteed of the bean quality. Another one worth mentioning is Heirloom Coffees.

When purchasing green beans online, make sure that you start with a small amount so that you can try them out and see how you fare when roasting them, as well as if you like the coffee taste that they produce. Then, if you’re happy you can go ahead and purchase more.

How to choose high-quality beans

  • Make sure that the beans are of a similar shape, color, and size. This is important so that they will roast evenly and provide a balanced flavor.
  • Avoid purchasing coffee beans that have white around the edges or have faded color on the edges. These signify that they were improperly dried or they were stored in humid conditions, which will negatively impact the type of coffee you can make with them.
  • Find out how the coffee beans were processed. Dry processing is when the coffee cherry is picked from the tree and left to dry out in the sun, and it produces a sweeter flavor. Wet processing involves removing the bean from the coffee cherry before it has dried, which makes it cleaner but a bit more acidic.
  • Know your regions! Coffee beans that are grown in different regions will provide different flavors. Generally, opt for coffee beans that hail from Central and South America if you’re looking for medium or light roasts, but choose beans from East Africa or the Middle East if you want bolder flavors. If you want a darker roast, your best bet is to choose beans that come from Colombia. 

Related Questions

What’s the shelf life of roasted coffee beans?

It takes a long time – sometimes even years – for coffee to become stale but coffee beans that have been roasted do start to lose their freshness after approximately one month after they have been roasted.

What should you do with coffee bean chaff?

Chaff is the layer around the coffee bean that gets shredded like a husk. It’s good to collect the coffee chaffs and put them in your compost heap. They contain nitrogen that’s good for the soil.

What is slim roast coffee?

This type of roast doesn’t actually refer to the process of roasting coffee. Slim Roast Coffee is actually a diet product. It contains Italian dark roast coffee and green coffee bean extract, as well as other ingredients like green tea extract and ginseng extract. 


If you want to roast your own coffee, you have many options available at your disposal. You can roast green coffee beans in the oven, with a popcorn popper, or on the stove. In this article, we’ve provided you with information on how to make your own roasted coffee.

This is a fantastic way to ensure that you start drinking coffee just the way you like it, whether that’s a light, medium, or dark roast.

We’ve also looked at other important information related to roasting coffee, such as what exotic coffee roast names actually mean and how you should store your roasted coffee once you’ve made it so that it maintains its freshness and deliciousness.

Last Updated on May 15, 2021

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