Know The Science Behind Perfect Coffee Roasting

From earthy and nutty to fruity and floral flavours, coffee is an endless journey of discovery. But have you ever wondered why some coffees have a more complex aroma and taste than others? You can find an answer to this in the roasting process. 

Coffee roasting is a detailed and complex process combining art and science to produce the perfect coffee. While coffee roasting may seem like a simple process, many factors affect the final product. In this blog, we will explore the science behind perfect coffee roasting.

  1. It is essential to understand the chemical changes that occur during coffee roasting. Raw coffee beans contain various acids, proteins, and sugars that contribute to the unique flavour profile of each coffee variety. During roasting, these compounds undergo a series of complex chemical reactions that produce hundreds of different aromas and flavour compounds. These reactions are known as the Maillard reaction and Caramelisation.

The Maillard reaction occurs when the amino acids in coffee beans react with sugars under high heat, creating a wide range of flavour and aroma compounds. This reaction is responsible for the nutty, chocolatey, and fruity notes in coffee. Caramelisation, on the other hand, occurs when the sugars in coffee beans are exposed to high temperatures, producing bitter and sweet flavours.

  1. The degree of roasting also plays a significant role in the final flavour and aroma profile of the coffee. Roasting for longer periods, or at higher temperatures, will produce a darker roast with a more intense flavour profile, while lighter roasts will produce a more delicate flavour. Roasting also affects the level of acidity in the coffee, with lighter roasts typically having a higher level of acidity.
  2. Another factor that affects coffee roasting is the roasting method itself. Different roasting methods, such as drum roasting, fluid bed roasting, or paddle roaster, can produce different results in terms of flavour and aroma. For example, drum roasting typically produces a more even roast and uniform flavour profile, while direct flame roasting can result in a smoky or charred flavour. Established coffee companies use one or more such roasting processes. For example, NESCAFÉ uses all three coffee roasting processes to provide great-tasting coffee.

Effect of Degree of Roast on Coffee’s Aroma and Taste

Light Roasts: Lightly roasted coffee beans have a light brown colour and a subtle aroma. They are known for their bright acidity and delicate flavours, with notes of fruit and floral tones. These coffees have a light body and a clean finish.

Medium Roasts: Medium-roasted coffee beans have a richer flavour than light roasts. They have a darker colour and a slightly stronger aroma. Medium roasts are known for their balanced acidity and sweet and savoury flavours. These coffees have a medium body and a smooth finish.

Dark Roasts: Dark roasted coffee beans have a dark brown colour and a bold aroma. They have a lower acidity than light and medium roasts and are known for their deep, smoky flavours. Dark roasts have a full body and a lingering finish.

Roasting coffee beans also creates a range of aroma compounds that give coffee its distinctive smell. These compounds are formed during roasting and released when the beans are ground and brewed. 


Coffee roasting is a complex and multifaceted step in the coffee-making process and plays a significant role in developing coffee’s aroma and taste. The degree of roast can impact the coffee’s acidity, body, and flavour, while the range of aroma and flavour compounds formed during roasting give coffee its unique and complex taste profile. Understanding the impact of roasting on coffee’s aroma and taste can help coffee lovers choose the perfect roast for their taste preferences.

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