Learn about the key stages of coffee roasting and discover why you're coffee can taste so different from roaster to roaster. The speed at which the coffee beans pass through each stage is called the roast profile. Roasters try to keep the coffee consistent by ensuring the roast profile for each bean is kept exactly the same each time. There are really only two variables important to coffee roasting - temperature and time. By careful variation of these two important factors it is possible to bring out different qualities of the coffee bean that each roaster wishes to accentuate.
The duration of the coffee bean roasting process can be influenced by several key factors. These include the volume of beans being roasted at one time, the inherent moisture level within each bean, and the specific variety of coffee bean.
Additionally, the age of the beans before roasting and the environmental conditions of the area where roasting takes place, such as temperature and humidity, also play significant roles.
Each of these elements can affect how quickly or slowly the beans roast.
So what are the basic stages that the coffee bean goes through during the coffee roasting process?
Here they are...
Stage 1 - Drying
The raw coffee bean starts off containing around 10 - 12 percent moisture. The coffee roaster is usually preheated when the raw bean is first loaded in and during the initial few minutes it looks like nothing is happening.
During this stage the bean is warming up and the water contained inside is beginning to evaporate. A large amount of energy is required for this first part.
Stage 2 - Browning
So the beans have dried out and they now begin to brown. In some cases the coffee beans go quite a bright yellow before turning brown. The aroma at this stage resembles cooked rice.
The browning reactions going on inside the coffee bean cause it to expand and it begins to shed it's thin papery skin (the chaff). This chaff is a fire hazard so hot air is constantly passed over the beans inside the roaster to blow it away into a special chaff collector, which is attached to the exhaust of the roasting machine.
At this stage the smoke starts (although most of it may still be steam).
Stage 3 - First Crack
Once the so-called first crack stage has been reached, gases and water vapour have been building up inside the coffee bean and it begins to emit an audible cracking sound when the pressure is finally released. The sound is very similar to that of pop-corn, although a little quieter.
At this stage the coffee bean has been roasted enough to be used to make coffee. Although it's up to the roaster to decide at what point the roasting stops. They may continue a little longer.
Light roasted coffee is usually stopped on or just after the first crack stage and you'll usually get the real flavour of the bean at this point. Although it is generally true that the acidity will be quite high and you may get a lot of sourness - especially when making an espresso.
Stage 4 - Roast Development
Here is where the delicate art of coffee roasting comes into it's own and much of it boils down to the opinion of the roaster. The flavour of the end result is mainly governed by how long the coffee bean is subjected to heat after the first crack stage.
As the roast develops, the acidity drops and the sweetness increases as the sugars and acids are caramelised. The level of sweetness reaches a peak before beginning to dissipate as further caramelisation occurs.
Think about the sweetness of sugar syrup compared to caramel and even molasses (treacle). As the heat is applied to sugar, the less sweetness is present. The same is true inside the coffee bean.
The coffee bean becomes browner and the surface smoother. There are various terms to describe the roast level during this phase: from "cinnamon" to "city" to "full city" - it's essentially the medium roasted phase and the coffee undergoes a transformation into something wonderful!
Stage 5 - Second Crack
At the end of the development stage the beans begin to crack again.
This time it's a quieter more crackly sound and signifies that the structure of the bean is beginning to break down. They become darker, oils will appear on the surface and they start to look a lot more shiny.
Beyond second crack is the French or Italian roast stage and, essentially, the original and unique flavour of the coffee begins to disappear. The bitterness is high because the sugars present in the coffee bean have begun to burn.
If you want to explore the different flavours of each origin then these extremely dark roasts are not for you. The uniqueness of the bean and its terroir has gone and a coffee from Brazil will taste very similar to one from Ethiopia.
The Importance of Quickly Cooling Coffee Beans After Roasting
When it comes to perfecting the roast of coffee beans, timing and temperature control are crucial. Immediately after they reach the desired roast, it's imperative to cool the coffee beans rapidly. This quick cooling process is essential because it halts the roasting process.
If the beans remain hot for too long post-roast, they continue to cook due to residual heat. This can lead to over-roasting, where the beans might turn burnt or charred, negatively impacting their flavor and aroma. The controlled quick cooling ensures that the beans develop a rich, even flavour profile, preserving the quality and characteristics desired from the roasting process.
Stage 6 - Enjoying Your Coffee
Sorry, did I say 5 stages? Of course, this is the bonus stage!
If you'd like to try out some of our lovely freshly roasted coffee beans, visit our coffee bean shop.
Additional Information
How Long Can Roasted Coffee be Stored?
Whole roasted coffee beans can be stored for up to one year if kept in a cool, dry place.
For roasted ground coffee, the storage time is shorter because it is more susceptible to moisture and heat. To maintain the freshness and aroma of ground coffee, it is crucial to store it in an airtight container immediately after grinding.
What are the different colour groups of roasted coffee beans?
Roasted coffee beans are categorized into various colour groups, each with distinctive characteristics:
1. Light Roast or Cinnamon Roast: This category features beans that are light brown in colour. They exhibit a notably high acidity level and retain a dry surface without any oiliness.
2. Medium Roast: Beans in this group have a medium brown hue and are known for their robust flavour profile. Similar to the light roast, these beans also lack any oily surface.
3. Medium Dark Roast or Full City: These beans appear darker and start to show a slight oil sheen on their surface. They offer a balance of sweetness and sourness with reduced acidity, making them complex in taste.
4. Dark Roast or Espresso: In this darkest roast category, the beans take on a very dark colour and an oily surface. They have a pronounced bitterness, and the intense roasting process tends to overshadow the original flavours of the beans.
These differences in roasting levels are primarily achieved by varying the roasting time and finish temperature, affecting the beans' colour, taste, and oiliness. The process may continue until the beans go through what is known as the second crack, especially evident in the darkest roasts.
What factors can influence the roasting time of coffee beans?
The duration of the coffee bean roasting process can be influenced by several key factors. These include the volume of beans being roasted at one time, the inherent moisture level within each bean, and the specific variety of coffee bean.
Additionally, the age of the beans before roasting and the environmental conditions of the area where roasting takes place, such as temperature and humidity, also play significant roles. Each of these elements can affect how quickly or slowly the beans roast.
Why do roasters pay close attention to appearance and fragrance during roasting?
Roasters pay close attention to the appearance and fragrance of coffee beans during roasting because these sensory cues are critical indicators of the quality and characteristics of the roast. Proper assessment of these factors ensures that the beans are roasted to the desired specifications, impacting the final taste and aroma of the coffee.
Where does coffee roasting typically take place relative to where coffee is grown?
Typically, coffee roasting is carried out in the country where the coffee is consumed, rather than in the country where it is grown. This practice allows for fresher roasting closer to the point of consumption and can be tailored to local taste preferences. Read our blog post on the origins of coffee for more information.
Who is responsible for the roasting process, and what does it entail?
The roasting process is overseen by a master roaster, who is responsible for carefully managing the roasting time and temperature. This role requires a high level of skill, particularly in monitoring the beans’ appearance and fragrance to ensure quality.
What exactly is affected in the coffee beans by the roasting process?
The roasting process affects various attributes of the coffee beans, including their brightness, acidity, flavours, and aromas, which are all crucial for enhancing the sensory experience of the brewed coffee.
What chemical changes do coffee beans undergo during roasting?
During the roasting process, coffee beans undergo pyrolysis, a chemical reaction that alters their composition by reducing moisture content and transforming the compounds within the beans, which develops their distinct flavours and aromas.