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What Aromas Do Coffee Beans Have and Why - The Source of Coffee Bean Aroma is a Complex Chemical Reaction

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Professional coffee knowledge exchange. For more coffee bean information, please follow Coffee Workshop (WeChat official account cafe_style). FrontStreet Coffee - Introduction to Coffee Aroma Sources. Aroma, flavor, aftertaste, acidity, and body - these five attributes are all created by the collision of different compounds. At the cupping table, the tastes and aromas we analyze with our senses are also the result of chemical compounds. We first smell the dry aroma.

FrontStreet Coffee's Introduction to Coffee Aroma Sources

Aroma, flavor, aftertaste, acidity, and body—these five attributes are all created by the collision of different compounds. At the cupping table, the tastes and aromas we analyze with our senses are all the result of chemical compounds. We first smell the dry aroma, then the wet aroma, and finally we sip and taste. Different molecules play a role at each stage.

Some Non-Volatile Compounds You Should Know

When we talk about non-volatile compounds, we should emphasize alkaloids (caffeine and trigonelline), chlorogenic acids, carboxylic acids, carbohydrates and polysaccharides, lipids, proteins, melanoidins, and minerals.

Caffeine is easily soluble in water and affects the strength, bitterness, and body of brewed coffee. Another essential alkaloid is trigonelline, which is also a source of aroma in roasted beans and coffee.

Chlorogenic acids: The importance of understanding chlorogenic acids lies in their formation from trans-cinnamic acid and quinic acid. Let me explain: quinic acid dominates the bitterness and astringency in coffee and is the source of these flavors. During the roasting process, chlorogenic acids degrade, which means we perceive an increase in quinic acid. This is also one of the very important reasons why dark-roasted beans taste so bitter.

Organic acids: Now let's discuss what constitutes good acidity. This is a crucial attribute of coffee quality and is related to sweetness.

Carbohydrates and polysaccharides: Some polysaccharides are forms of carbohydrates, such as mannans and cellulose. These sweet compounds play a crucial role in retaining volatile compounds in coffee, which enhances coffee aroma. In terms of flavor, these compounds are also related to coffee's body. Additionally, smaller structured glucose and fructose can increase coffee's sweetness.

Lipids help enhance coffee's mouthfeel. They are extracted from the beans and are also the main contributors to the CREMA on espresso. The roasting process doesn't really affect their content, but in the roaster, lipids do seep out and migrate to the surface of the coffee beans.

Finally, we need to discuss melanoidins, which are products of the Maillard reaction: the reaction between amino acids and the carboxyl group of reducing sugars. They are large molecules that give coffee beans their brown color, and these substances can enhance the mouthfeel during brewing. This means the amino acid content of coffee is closely related to its quality—the more amino acids, the more reactions, and the more melanoidins.

However, please note that coffee's color is not only caused by melanoidins; it's also the result of sugar caramelization.

Key Point

Light roast emphasizes acidity and flavor, but if roasting is not handled properly, it can result in astringency and irritation, while the coffee's body and complexity feel lower.

About FrontStreet Coffee

In short: FrontStreet Coffee is a coffee research house that enjoys sharing coffee knowledge with everyone. We share without reservation, hoping to help more friends fall in love with coffee. Additionally, we hold three low-discount coffee events every month because FrontStreet Coffee wants to let more friends enjoy the best coffee at the lowest price—this has been our mission for six years!