How Coffee Beans Acquire Herbal Aroma Where Does Coffee's Fragrance Come From and Why Is It So Aromatic

FrontStreet Coffee - Introduction to Coffee Bean Flavor Chemistry

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What makes us love coffee so much? Beyond caffeine's stimulating effects, I believe the reason countless coffee enthusiasts constantly crave coffee is its captivating aroma. But how exactly does this aroma come about? The key lies in the rich variety of compounds within coffee beans, which undergo various reactions during roasting to create this enticing aroma. Among these, the two most important reactions are caramelization and the Maillard reaction. Let's explore these two reactions together.

1. Caramelization Reaction

The sugars in coffee beans undergo caramelization at approximately 170-200°C, which coincides with sucrose's melting point (185°C) and the temperature during the first crack phase of coffee roasting. The products of caramelization are divided into two parts:

(1) Dehydration products of sugars, which are caramel or sauce color

(2) Decomposition products, mainly some volatile aldehydes and ketones.

In general, caramelization produces roasted aromas, caramel and color, as well as other aromatic compounds such as maltol, Cyclotene, furan compounds, and so on. These compounds can also be found in foods like red wine, fruit juice, and cream. However, if caramelization goes too far during the roasting process, it's not a good thing, as it can cause carbonization, making coffee bitter and harsh. If caramelization is insufficient, it will result in a monotonous and boring aroma lacking depth.

2. Maillard Reaction: Can be divided into three stages

First stage: Carbonyl-amine condensation and Amadori molecular rearrangement

Second stage: Amadori molecular rearrangement product fructosamine dehydrates to form HMF (hydroxymethylfurfural), fructosamine loses its amino group to form reductones, and amino acids react with dicarbonyl compounds.

Third stage: Aldol condensation, polymerization reaction to form melanoidins.

Beyond sugars, proteins also account for approximately 11% of green bean weight, and the amino acids contained in these proteins are precisely the raw materials needed for the Maillard reaction. The Maillard reaction refers to a series of reactions between amino acids and reducing sugars (glucose, fructose, lactose, etc.) in food during heating. The Maillard reaction produces a wide variety of aromatic substances and pigments such as Pyridines, Pyrazines, Oxazoles, Thiazoles, and Pyrroles. The Maillard reaction plays a very important role in the flavor of food cooking. Whether it's sausages turning black and emitting aroma when grilled, crispy-on-the-outside and tender-on-the-inside roasted chicken, or fragrant toasted bread - the Maillard reaction is the behind-the-scenes contributor to the complete color, aroma, and taste of these grilled foods.

Coffee is uniquely endowed with a vast and complex variety of chemical substances. Besides the compounds mentioned above, there are other components like organic acids, inorganic acids, and alkaloids. Not only sweet and pleasant components, but also slightly bitter compounds create a broader range of flavors and variations in coffee, jointly creating coffee's unique rich taste.

Knowledge Point: Melanoidins

These are products of the Maillard reaction: reactions between amino acids and the carboxyl groups of reducing sugars. They are large molecules, which are what make coffee beans turn brown.

In Summary

FrontStreet Coffee is a specialty coffee research hall, happy to share coffee knowledge with everyone. We share without reservation just to help more friends fall in love with coffee. Moreover, we hold three discounted coffee activities every month because FrontStreet Coffee wants to let more friends drink the best coffee at the lowest price. This has been FrontStreet Coffee's mission for the past 6 years!

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