By Kimberly J. Decker, Contributing Editor
Coffee and tea make rich topics for study, from the chemical constituents of their flavors to their cultivation and processing to debates over brewing techniques, levels of roast and the merits of loose leaves versus bags.
One pleasant side effect of our infatuation with coffee and tea is the understanding we’ve gained of how to extend their pleasures beyond the cup. Coffee and tea flavor profiles complement so many foods that it’s almost unfair not to share them with everything from crème brûlée to barbecue sauce.
Coffee complexity
Coffee is a model of complexity, with the number of identified flavor constituents growing with each improvement in analytical techniques. “Currently, around 1,000 different substances have been identified in coffee," says Ben Kranen, principal flavorist, global flavour creation & technology group, Givaudan, Naarden, the Netherlands. “Using coffee-derived ingredients will give us many of those substances in one pour."
While complexity doesn’t necessarily correlate with deliciousness, coffee’s chemical intricacy does set it apart from simpler flavors. “You’ve got amyl acetate in banana. You’ve got benzaldehyde in cherry. Even in something as complex as strawberry, there’s a known number of components that give you each characteristic strawberry flavor," says Paulette Lanzoff, technical director, Synergy, Wauconda, IL. Not so with coffee. “There’s so much more going on," she says. “There is no one particular flavor fingerprint." While this may make things more intriguing to the palate, it definitely makes designing coffee flavors “more challenging for the flavor chemist," she says.
Bean there, done that
To understand what underlies coffee’s complexity, you have to start with the bean. According to Leigh Ungerbuehler, global category manager, beverages, Givaudan, Cincinnati, two main species give us most of the coffee we drink: Coffea arabica and C. robusta. Robusta, grown at lower elevations, produces a bean with more acidity and less complexity or body than arabica; this suits it to blending, dry-mix applications and products that require a lower price. Arabica, on the other hand, is the “premier species responsible for all of the high-quality espressos and coffees in the world," she says. “Most high-end coffee shops and cafés use only arabica coffee in their drinks."
But even within the arabica species, flavor differences are “seemingly infinite," Ungerbuehler says. One factor is where the beans grow. “Arabica coffee grown at higher altitudes provides a bolder, acidic profile, and arabica grown at lower altitudes has a milder, less-acidic profile," she says. Coffees of African and Arabian origin tend to display medium acidity; spicy, wine-like and cocoa notes; and citrus, berry and “wild flavors," too. Latin American coffees are usually medium to high in acidity, well-balanced, sweet, intense and tangy. And Asian and Indo-Pacific coffees, she says, offer lower acidity, hearty-earthy notes, “power" balanced by smoothness, a flowery character and some bitterness.
Then there’s the effect of processing on the green fresh-picked beans, which have little flavor of their own—at first. It’s only after drying and fermentation that coffee develops the character that fans recognize. As Ungerbuehler says, in areas like Africa with limited water, coffee beans are often left to dry as a whole cherry in what’s known as the “natural" process. “The outside turns almost black, and the dry bean is loose inside the dry hull," she explains. “This gives a fruity, red-berry profile, as the sugar in the cherry ferments during the process." By contrast, the “honey" process involves removing the cherry, or exocarp, while leaving the inner mucilage on the bean to produce the light-brown color and sweet, honey-like flavor that lends the process its name. Finally, the “washed" process, favored in areas of South America, uses friction and water to clean the bean completely of cherry and mucilage prior to drying.
Roasting kicks off a cascade of hydrolytic, caramelization and Maillard reactions that transform coffee chemistry to yield heterocyclic byproducts like mercaptans and pyrazines, as well as glycols similar to those in bacon. According to Kranen, the degree of roast is the pivot in establishing how much bean you actually taste. “It is possible to start with two green beans from entirely different places and roast them to a point where they taste very similar," he says. “The higher the roast, the less it matters what type of bean you’ve started with."
Coffee’s chemical fingerprint
The task of the flavor chemist is to comb through coffee’s thousand-odd flavor constituents to find those that add most to coffee’s character. “We have a pretty good idea now which ones they are," says Kranen. Starting at the base of the profile, you get the “heavy" compounds responsible for body, taste and mouthfeel. In the middle, he says, nutty, roasted, buttery, fruity, chocolate and malty notes emerge. “This is the most-distinguishing part between the different coffee origins and varieties," he points out. “The most-challenging part, however, is the top. This is where you find the very volatile fresh notes that really determine the fresh character and fill the room when brewing coffee."
