The Origin of Coffee Bean Aroma: Understanding the Compounds Behind Coffee's Fragrance

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FrontStreet Coffee - Introduction to Coffee Bean Flavor Compounds

Non-volatile substances in coffee include: alkaloids (caffeine and trigonelline), chlorogenic acids, carboxylic acids, carbohydrates and polysaccharides, lipids, proteins, melanoidins, and minerals.

Caffeine

Caffeine is water-soluble and will affect the strength, bitterness, and body of a brewed cup of coffee. Another essential alkaloid is trigonelline, which helps enhance the aroma of roasted coffee beans and brewed coffee.

Chlorogenic Acids

Regarding chlorogenic acids, it's important to understand that they are formed from trans-cinnamic acids (including caffeic acid, ferulic acid, and p-coumaric acid) and quinic acid. Among these: quinic acid is the cause of coffee's bitterness and astringency. During the coffee bean roasting process, chlorogenic acids degrade - which means an increase in quinic acid. This is one of the reasons why dark-roasted coffee beans have stronger bitterness.

Organic Acids

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

Let's look at the types of acidity: Some relatively "sensitive" acids in coffee are citric acid, malic acid, and chlorogenic acid. Some acidic substances degrade during the roasting process (for example, chlorogenic acid), while other acidic substances increase in concentration during roasting. For instance, formic acid, acetic acid, lactic acid, and so on.

Carbohydrates and Polysaccharides

Regarding polysaccharides, you should know about arabinogalactans, mannans, and cellulose. These wonderful compounds play important roles in retaining volatile compounds in coffee and also contribute to aroma formation. Additionally, smaller sugars and fructose contribute to the formation of coffee's sweetness.

Lipids

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

Volatile Compounds and Special Flavors

Roasted coffee beans contain over 1000 volatile compounds. However, only a small portion of these are aromas that we can perceive. Some researchers believe that approximately 20-30 volatile substances in our coffee play substantial roles.

So what are the volatile compounds? These include hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters, pyrazines, pyrroles, pyridines, furanones, phenols, and more. Although these names sound very scientific, following them can trace back to the characteristics of coffee.

Furans and furanones usually give us caramel and roasted coffee flavors. Pyrazines may be related to nutty flavors. Of course, the quantity and mutual interaction of some other compounds produce negative flavors - guaiacol molecules (phenolic compounds) bring medicinal and rubbery tastes.

These aromatic substances are released when coffee is heated, and besides their inherently attractive flavors, the main appealing factor of these aromatic components is that they can increase blood flow to the hypothalamus in the brain, which is the area that controls the right brain's pleasure sensations. Therefore, coffee aroma helps enhance feelings of pleasure and can also increase the amplitude of brain waves, thereby improving concentration and work efficiency. The brain always has its preferences for pleasant tastes, making you unable to resist pleasant-smelling aromas or mood-enhancing foods, which is also an important reason why many people cannot resist sweets.

Knowledge Point: Melanoidins

Melanoidins are products of the Maillard reaction: the reaction between amino acids and the carboxyl groups of reducing sugars. They are large molecules, which are the substances that turn coffee beans brown.

In Summary

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