What Products are Generated by the Caramelization Reaction During Roasting? What Happens When Caramelization is Excessive or Insufficient?

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FrontStreet Coffee: Brief Overview of Caramelization in Coffee Roasting

Caramelization Reaction

The sugars in coffee beans undergo caramelization reactions at approximately 170-200°C, which coincides with the melting point of sucrose (185°C) and the temperature during the first crack phase of coffee bean roasting.

The products of caramelization reactions are divided into two parts:

Dehydration products of sugars, which are caramel or sauce color

Decomposition products, mainly some volatile aldehydes and ketones.

In summary, caramelization reactions produce roasted aromas, caramel and color, as well as other aromatic substances such as maltol, cyclotene, furan compounds, etc. These compounds can also be found in foods like red wine, fruit juice, and cream.

However, excessive caramelization during roasting is not a good thing, as it can lead to carbonization, making coffee harsh and throat-grabbing. Insufficient caramelization will result in monotonous and bland aromas lacking complexity.

Volatile and Non-Volatile Compounds

We may have heard that volatile and non-volatile compounds exist in roasted coffee beans. Typically, volatile compounds are the source of coffee aroma, while some non-volatile compounds are the source of coffee flavor. But what exactly are they?

Volatile compounds are organic chemicals with high vapor pressure at room temperature. Many of these are formed during the Maillard reaction in the development phase of roasting. When aromatic volatile compounds are released, we perceive this distinctive coffee smell. They include:

• Aldehydes: Add fruity, green plant aromas.

• Furan compounds: Contribute caramel flavors

• Pyrazines: Have earthy odors.

• Sulfur-containing compounds, including 2-furylthiol. Some of these have aromas typically described as "roasted coffee beans," but other aromas cannot be detected in isolation. For example, methanethiol smells like rotten cabbage.

• Guaiacol: Has smoky, spicy notes.

Carbon dioxide is a volatile compound that does not affect aroma but does influence the body of coffee.

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