CGA Degradation

CGA Degradation is one of the most important chemical reactions that occurs inside the coffee bean during roasting. Chlorogenic acids (CGAs) are a group of phenolic compounds that are naturally present in high concentrations in green coffee. As the bean is heated, these acids begin to break down, transforming into other compounds that significantly impact the coffee's taste, aroma, and mouthfeel.

What is CGA Degradation? It is a complex process that happens primarily during the browning phase of the roast. As the temperature rises, the CGAs decompose into quinic acid and caffeic acid. These new compounds are responsible for much of the perceived acidity and bitterness in the final cup. If the roast is too light, the CGAs may not fully degrade, leading to a harsh, astringent, or overly acidic cup. If the roast is too dark, the degradation continues, potentially leading to a flat, bitter, or burnt flavor.

In practice, managing CGA degradation is a key part of a roaster's job. By controlling the rate of rise (RoR) and the total roast time, a roaster can influence how much of these acids are broken down. This allows them to highlight the bright, fruity acidity of a high-altitude coffee or to mellow out the sharpness of a more robust variety. It is a delicate balancing act that requires a deep understanding of roasting chemistry.

Why does this matter to the consumer? Because the way a coffee is roasted determines how those inherent chemical compounds are expressed in your cup. Understanding CGA degradation helps explain why different roast levels taste so different, even when using the same green coffee. It is the science behind the art of roasting, ensuring that the roaster can bring out the best possible flavor from every bean, whether you prefer a light, vibrant filter coffee or a rich, bold espresso.