Where Do Coffee's Fruity Flavors Come From? Why Are the Citrus and Berry Flavors in Pour-Over Coffee So Distinct?

The Hidden Fruit in Coffee

Citrus, passion fruit, strawberry, grape... We've been familiar with these fruit flavors since childhood. Even with our eyes closed, we can identify their origins upon tasting, and by combining this with the texture from chewing, it's no surprise we can distinguish more specific varieties. For instance, we can differentiate whether citrus comes from sugar tangerines, wo oranges, or navel oranges.

Yet when it comes to coffee, we often marvel at the richness of these fruit flavors and wonder why they appear in this beverage. After all, isn't it just made by grinding dark beans and steeping them in water? What connection could it possibly have to these fruits?

Coffee, in essence, is a fruit. Different growing regions, varieties, and climatic factors all affect its quality and flavor. Many friends are aware of this. However, most fruit aromas aren't present from the beginning but are instead transformed during an extremely short ripening period. This is also why more and more farmers are now required to harvest only fully red fruits—aiming to achieve fuller sweetness and aroma in coffee.

The Science of Fruit Aromas

During the growth phase, fruits store carbohydrates in the form of starch granules within their cells, while enzyme systems responsible for providing conversion enzymes prepare to begin their work. During the ripening phase, the breakdown of carbohydrates increases sugars (such as glucose), makes the fruit texture softer, and simultaneously produces numerous ester-based and carbon-based aromatic compounds.

Coffee is no different. Each green bean contains 60% carbohydrates, 10% protein, 10-15% fat, along with components like chlorogenic acid, caffeine, and trigonelline. The reason coffee has "fruity flavors" ultimately stems from the many aromatic compounds it contains that resemble fruit aromas, mostly esters, ketones, and alcohols. For example, fatty acids, terpenes, amino acids—these components are all pre-stored sources of fruit aroma in green beans.

I wonder if any of you have smelled green coffee beans. They don't possess the captivating coffee aroma we're familiar with, let alone various tempting fruit flavors. FrontStreet Coffee believes they only have a faint grassy, grain-like scent.

In fact, the aromatic compounds in coffee that FrontStreet Coffee mentioned above are stored in green beans in a stable form, in a "hidden" state. Roasting is the key to truly converting them into volatile aromas, primarily thanks to the Maillard reaction and caramelization.

The Magic of Roasting

When green coffee beans are heated to a certain degree, they begin to undergo complex degradation and polymerization reactions. The amino acids that make up proteins in green beans, along with reducing sugars like glucose, fructose, and lactose, continuously generate aromatic compounds during the sustained heating process. In this process, over 600 volatile aromatic compounds are produced within the coffee beans.

As the reaction time accumulates, coffee first develops fresh floral and fruit notes, then transitions to mellow and deep fruity-floral profiles, followed by rich nutty and fermented notes, and finally caramelized compounds. However, the floral and fruit aromas produced earlier gradually disappear during this process. This also explains why it's difficult to detect floral-fruity flavors in dark-roasted coffee beans. If pursuing floral and fruit flavors, it's best to choose coffee with medium to light roast levels.

Of course, medium to light roast levels not only affect the conversion amount of light aromatic substances but also determine higher levels of various organic acids in coffee (citric acid, malic acid, lactic acid)—meaning the brewed coffee will fall within the "acidic" spectrum.

The Final Step: Brewing

Brewing is the final step in flavor expression. In the process from seed selection, cultivation, processing, roasting, to brewing, the earlier stages have greater impact on coffee flavor. By the time we reach brewing in the later stages, the impact on coffee flavor is relatively minimal. Under the combined effects of olfactory sensations from various fruit or floral compounds and acid quality perception, our brains connect this experience to moments of eating certain fruits from memory.

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FrontStreet Coffee

No. 10, Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

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