The subject of burnt coffee draws passionate theories from every corner. Everyone has suffered through a charred-tasting cup of joe, where the best part of waking up becomes a disappointing start to the day. Science has something to say about this, as does the army of baristas who wield the power to determine the quality of your coffee experience.
Bitter vs. Burnt
First, a distinction must be made between bitter and burnt coffee: all coffee has varying degrees of bitterness, owing to the chemical compounds in the beans. While no coffee bean starts out tasting “burnt,” bitterness in coffee is partly a reflection the kind of beans used. Arabica beans, overwhelmingly preferred in American coffee shops, have fewer bitter compounds than their rival; Robusta, which costs less to produce, and have a bitterness some coffee drinkers find nearly unpalatable. Robusta contains almost twice as much bitter caffeine and chlorogenic acid as Arabica. Bitterness strength is not a precise predictor of likeability, however, as it is coffee’s bitterness that gives it its famous “bite”; in fact, a moderate amount of bitterness may be the primary contributor to coffee’s universal popularity, much like that of beer.
Burnt-tasting coffee, on the other hand, is never desirable. The taste has become popular and accepted, however, with the proliferation of coffee chains that may deliberately introduce burnt flavors in an effort to drive sales of value-added products and ingredients like sweet foods, milk and flavored syrups. Coffee is relatively inexpensive to produce, and it is the ability to sell “add-ons” alongside the main product that can make a crucial difference in boosting profits for coffee companies.
Efforts to brand coffee as more “European” or “exotic” are also at play here; it is true that European (particularly Italian) styles of coffee tend toward a darker roast, though if the beans are roasted properly, the only result will be an increased strength and “darker” flavor.
How To Burn Coffee
While over-roasting coffee beans may be the main culprit in burnt coffee, a host of other factors may be at work. Regarding espresso (to which the complaint of “burnt-tasting” is most common), the act of pulling a shot involves proper measuring of grounds; proper tamping (pushing grounds into the group head); correct water temperature (93° C); and correct grind. All of these affect extraction, the percentage of the grounds that are dissolved in water, of which the ideal is considered to be 18-22%. When coffee is over-extracted, a burnt-tasting compound called tannic acid is included in the more desirable flavors. The key to delicious coffee is extracting as many good flavors, and as few bad ones, as possible.