Coffee Bean Roasting Degrees, Dark Roast Coffee Beans, What Are the Characteristics of Dark Roast Coffee Beans

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FrontStreet Coffee - Introduction to Dark Roast Coffee Beans Characteristics

Coffee beans undergo different changes during various roasting stages. After green coffee beans absorb heat, their color begins to change from green to yellow, and the moisture content of the beans starts to decrease. Thermal energy converts the moisture inside the coffee beans into steam → carbon dioxide is produced inside the coffee beans → the internal pressure of the coffee beans reaches 25 bar (pressure unit) → First Crack: coffee beans produce a highly representative cracking sound during the roasting process.

Flavor Development

The longer the roasting time, the acidity gradually decreases and bitterness increases.

After dehydration, the coffee beans begin to release thermal energy and turn brown, also shedding a layer of silver skin. Roasted coffee beans increase in volume by 1.5 to 2 times, while losing at least 11% of their weight.

Continuing to roast the coffee beans will continuously produce carbon dioxide → Second Crack.

The color of the coffee beans deepens, entering the medium-dark roast stage. At this point, the weight loss reaches 22% of the original. After the Second Crack, the coffee beans develop surface oil due to thermal decomposition reactions and begin to carbonize. Without careful attention, they can easily burn.

As the roasting time extends, acidity gradually decreases while bitterness increases, and many aromatic molecules begin to volatilize.

By the end of roasting, nearly eight hundred aromatic compounds are developed, and the flavor, acidity, sweetness, and body of the coffee beans reach maturity. However, roasting can sometimes bring out undesirable flavors in coffee. In the final stage, aromatic compounds are destroyed, replaced by bitterness, while acidity disappears entirely and body decreases accordingly.

Proper roasting can highlight the natural acidity of the original coffee beans. The thermal energy from roasting destroys more than forty types of chlorogenic acids in the coffee beans, breaking them down into quinic acid and caffeic acid. Both of these substances have astringent properties that may affect the mouthfeel.

In Summary

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Important Notice :

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