Coffee is one of the most popular drinks in the world, and its popularity is high due to its rich, complex flavours. These flavours are created during the coffee roasting process, which involves heating the beans to a certain temperature for a certain amount of time. 

In this blog post, we will explore the science behind coffee roasting and how it affects the flavour of the coffee.

The coffee roasting process

Coffee roasting is a complex process that involves a series of chemical reactions. The process begins with the green coffee beans, which are the seeds of the coffee plant. These beans are harvested, cleaned, and then roasted to create the coffee we know and love.

There are many different methods of roasting coffee, but the most common is to use a coffee roaster. A coffee roaster heats the beans to a certain temperature for a certain amount of time. The temperature and time vary depending on the desired roast level and the type of coffee being roasted.

During the roasting process, the beans go through several stages. The first stage is the drying stage, which occurs at around 200°C. During this stage, the moisture in the beans evaporates, and the beans turn from green to yellow.

The second stage is the browning stage, which occurs at around 180-220°C. During this stage, the beans start to turn brown as the heat causes the Maillard reaction to occur. This is a chemical reaction between the amino acids and the reducing sugars in the beans, which creates a range of new compounds and gives the coffee its characteristic flavour and aroma.

The third stage is the development stage, which occurs at around 200-250°C. During this stage, the sugars in the beans start to caramelize, and the acidity and bitterness of the coffee start to develop.

The final stage is the cooling stage, where the beans are rapidly cooled to prevent further roasting and to lock in the flavours and aromas created during the roasting process.

The Science of coffee roasting

Coffee roasting is a complex chemical process that involves many different reactions. These reactions are influenced by several factors, including temperature, time, and airflow during roasting.

One of the key reactions that occur during coffee roasting is the Maillard reaction. This is a reaction between the amino acids and reducing sugars in the beans, which creates a range of new compounds and gives the coffee its characteristic flavour and aroma.

The Maillard reaction occurs at temperatures between 140-165°C, and it is responsible for the browning of the beans. During the Maillard reaction, the amino acids in the beans react with the reducing sugars to form a range of new compounds, including melanoidin, which gives coffee its characteristic flavour and aroma.

The Maillard reaction is influenced by several factors, including the temperature and time of roasting, the moisture content of the beans, and the type of coffee being roasted. 

For example, lighter roasts are roasted at lower temperatures and for shorter periods, which results in a lower Maillard reaction and a lighter flavour profile. 

Conversely, darker roasts are roasted at higher temperatures and for longer periods, which results in more Maillard reactions and a darker, richer flavour profile.

Another key reaction that occurs during coffee roasting is the caramelization of the sugars in the beans. This occurs at temperatures between 200 and 250°C, and it is responsible for the development of the coffee’s acidity and bitterness. During the caramelization process, the sugars in the beans are broken down into simpler compounds, which contribute to the flavour and aroma of the coffee.

The caramelization reaction is also influenced by several factors, including the temperature and time of roasting, the moisture content of the beans, and the type of coffee being roasted. For example, lighter roasts have a higher moisture content, which makes it more difficult for the sugars to caramelize. This results in a lighter, more acidic coffee. Conversely, darker roasts have a lower moisture content, which makes it easier for the sugars to caramelize, resulting in a darker, more bitter coffee.

Another factor that influences the flavour of coffee is the degree of roast. There are several different roast levels, ranging from light to dark. Each roast level has its own unique flavour profile, which is influenced by the Maillard reaction and caramelization process.

Light roasts are roasted at lower temperatures and for shorter periods, which results in a light brown colour and a mild flavour profile. Light roasts have a higher acidity and a lighter body than darker roasts.

Medium roasts are roasted at slightly higher temperatures and for slightly longer periods, which results in a medium brown colour and a slightly stronger flavour profile. Medium roasts have a balanced acidity and body.

Dark roasts are roasted at higher temperatures and for longer periods, which results in a dark brown colour and a strong, robust flavour profile. Dark roasts have lower acidity and a heavier body than lighter roasts.

The type of coffee being roasted also influences the flavour profile of the coffee. Different varieties of coffee have different flavour profiles, which are influenced by factors such as the climate, soil, and altitude where the coffee is grown.

For example, coffee grown in high-altitude regions tends to have a brighter acidity and a more complex flavour profile than coffee grown in low-altitude regions. Similarly, coffee grown in volcanic soil tends to have a more intense flavour profile than coffee grown in non-volcanic soil.

In addition to the type of coffee, the processing method also influences the flavor of the coffee. There are two main processing methods: washed and natural.

Washed coffee is processed by removing the fruit from the coffee cherry before drying the beans. This results in a cleaner, more acidic flavour profile.

Natural coffee is processed by drying the whole coffee cherry before removing the fruit. This results in a sweeter, more fruity flavour profile.

Conclusion,

In conclusion, the flavour of coffee is influenced by a wide range of factors, including the type of coffee, the processing method, and the roasting process. During the roasting process, the Maillard reaction and caramelization process create the unique flavour and aroma of the coffee.

The degree of roast also influences the flavour profile of the coffee, with lighter roasts having higher acidity and a lighter body, while darker roasts have lower acidity and a heavier body. Ultimately, the flavour of coffee is a complex interplay of many different factors, and each cup of coffee is a unique experience that reflects the skill of the roaster and the character of the coffee itself.