The importance of degassing coffee after roasting

The main reason coffee needs to “rest” after roasting is due to the degassing process. After roasting, coffee contains gases, mostly CO2, which acts as a barrier preventing water from interacting with coffee, adversely affecting the extraction process. Degassing allows the coffee to off-gas, releasing carbon dioxide (CO2) that can hinder extraction during brewing.

It’s important to note that the presence of CO2 in coffee doesn’t imply lower quality; on the contrary, it serves as an indicator of freshness and plays a crucial role in the stability of coffee in its packaging. CO2 is an important marker of recent roast and contributes to crema formation and overall cup profile.

Degassing coffee should be done in moderation to ensure the coffee doesn’t become stale. Excessive degassing can lead to a flat and less appealing flavor profile.

The ideal degassing time for coffee is when the CO2 has escaped adequately, without affecting the flavor of the coffee beans. The necessary degassing period for coffee typically ranges from 3 days to 2 weeks. However, it is challenging to specify an exact duration because it is influenced by various factors such as brewing methods, coffee processing techniques, and roasting levels. Among these factors, the key factor is the roasting level.

Lighter roasts require a shorter resting period, typically 3-4 days. During this ideal resting period, coffee continues to degas, allowing its flavor profile to gradually evolve and reach its full potential. In the case of dark roasts, the degassing period will be longer, typically ranging from 5-7 days after roasting

During the roasting process, coffee beans come into contact with high temperatures, leading to water loss, structural transformations, and the creation of various chemical reactions. This results in enticing flavor compounds, elevating the coffee’s overall profile.

Here are some chemical reactions that occur inside coffee beans during roasting:

The Maillard Reaction

The Maillard Reaction is a chemical reaction between amino acids and reducing sugars under high heat. Amino acids and sugars form new compounds with distinctive colors and flavors, enriching the complexity of taste and color. This reaction can occur in various ways, contributing to a diverse flavor profile.

Caramelization

Caramelization is a form of pyrolysis that occurs around 120-180°C. High temperatures cause long, complex carbohydrate chains to break down into hundreds of new compounds, adding significant bitterness, acidity, and aroma to the coffee. This reaction occurs continuously until the roasting process concludes, contributing to sweet aromas like caramel, baked bread, and nuts.

Acid Decomposition

The acidity or acidic properties bring vibrancy, subtlety, complexity, and a refreshing quality to coffee. Coffee without acidity becomes flat, dull, and lacks a lasting impression. Acidity plays a crucial role in making coffee lively and distinctive.

Formation of Flavor Compounds

The roasting process enhances the development of aromatic notes within the coffee beans, bringing them closer to the consumer. This is achieved by forming flavor compounds that can dissolve in water.

* Volatile Compounds

The rapid increase in volatile aromatic compounds occurs when the moisture content of coffee drops below 5%. Caramelization, Maillard reactions, as well as the degradation and transformation of amino acids, sugars, phenolic acids, and lipids collectively contribute to the development of aromatic compounds, including:

• Aldehydes, provide the aroma of green fruits.
• Furans contribute to the scent of caramel.
• Pyrazines, with an earthy aroma.
• Guaiacol imparts a smoky, spicy scent.
• Sulfur-containing compounds like 2-furfurylthiol, create the characteristic “coffee roasting” aroma.

* Non-Volatile Compounds

These are stable compounds at room temperature that significantly contribute to coffee flavor. Examples include caffeine, which is responsible for bitterness, sucrose for sweetness, and lipids for a rich body. Acids or melanoidin compounds formed during the Maillard reaction also belong to the group of non-volatile compounds.

In summary, XLIII Coffee has explained why it’s necessary to let coffee degas after roasting instead of using it immediately. The roasting process introduces complex chemical reactions to coffee, and therefore, patiently waiting for the coffee to degas appropriately allows us to appreciate its remarkable changes.

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