The Science of Delicious Coffee: How Acids, Sugars, and Alkaloids Shape Every Sip
In brewed coffee, over 800 flavor and aromatic compounds have been identified. For coffee enthusiasts, the most exciting part is figuring out how these compounds form and how they influence the flavor and mouthfeel of coffee. There are plenty of books that dive deep into the chemistry of coffee, but for those who aren’t chemists, reading them can be a snooze—even with all the caffeine you consume! So today, we’ll focus only on a few of the main compounds.
Acids and Sugars: The Key to Coffee Flavor
As both roasters and coffee lovers, we’re particularly interested in two types of compounds: carbohydrates (sugars) and organic acids. The interplay between these compounds largely defines the coffee experience. To understand this, just think of the difference between cheap white wine and a decent wine. Cheap wines have low sugar content and only one or two prominent acids, which makes them taste sharp, thin, and harsh. Good wines, on the other hand, have rich acid profiles—some with sweetness and fruitiness—which form the foundation for all the flavors and aromas.
Acids Affect Coffee Quality and Complexity
Green coffee beans naturally contain acids we’re familiar with, such as citric acid (also found in oranges, lemons, and limes) and malic acid (found in apples), as well as some acetic acids formed by the breakdown or reaction of sugars and other compounds.
The quality and complexity of coffee depend on the balance of these acids in the beans. This balance is influenced by a variety of factors, including the coffee variety, mineral content of the soil, temperature, humidity, and roasting level.
In unroasted beans, the main acid is chlorogenic acid, making up 5–10% of the dry weight. It has grassy, bright, or overly sharp flavors and also contributes bitterness. Most chlorogenic acids break down during roasting, forming other acids like caffeic acid and quinic acid. These acids have milder sourness and bitterness and, at lower concentrations, provide a complex, pleasant balance to coffee’s taste.
Sugars: The Main Source of Sweetness
One of the most important sugars in coffee beans is sucrose, which contributes noticeable sweetness to the final brew. During roasting, as the beans darken, sugars break down, which is one reason dark roast coffees taste more bitter and less sweet than light roasts.
Sugar molecules also undergo caramelization and participate in the Maillard reaction with proteins, turning the beans brown and producing a variety of aromatic compounds. Throughout roasting, caramelization and Maillard reactions occur simultaneously. Caramelization produces sweet, caramel-like, buttery, and vanilla aromas, while Maillard reactions create roasted, floral, spicy, and chocolatey notes.
Sucrose content peaks when the coffee cherry is fully ripe, which is why we prioritize beans from hand-picked, fully red cherries. Robusta beans have significantly less sucrose (and chlorogenic acid) than Arabica, which is why roasted Robusta tends to be more bitter and less complex than Arabica.
Alkaloids Complete the Coffee Flavor Profile
Another key group of compounds in coffee is alkaloids. The most famous is caffeine, but there’s also the lesser-known trigonelline. Coffee first caught human attention because of caffeine’s stimulating effects—a major reason why many people drink coffee, and why they crave it.
Caffeine is bitter, and bitterness is an essential part of coffee’s overall flavor profile. Trigonelline is also bitter but partially breaks down during roasting, helping form many aromatic compounds. Its breakdown products include niacin (vitamin B3), with each cup containing 1–3 mg depending on coffee concentration and brewing method. Just a couple of cups can provide your daily recommended intake of 14–18 mg.
评论
发表评论