If you were to ask me if espresso is bitter, I’d say, “well no, not when made properly.” In truth, my stance is about as much coffee homerism bluster as it is objective fact; most everyday folks—not those of us swimming in the depths of coffee’s deep end—would likely say that yes, it is in fact bitter. But what do they know anyway? Let’s assume though, for the sake of science, that they are right and that espresso is bitter. Well, a new study suggests that it is these bitter characteristics in coffee that can enhance a person’s ability to perceive sweetness as well as inhibit bitterness.
Per New Atlas, scientists at Aarhus University in Denmark led by associate professor Alexander Wieck Fjældstad, MD found that, regardless of caffeine content, consuming coffee made the drinker more sensitive to sweetness in things consumed shortly thereafter. To reach these findings, 156 subjects were given tests to establish their baseline taste and smell levels, after which they were instructed to drink a lukewarm espresso. (Side note: is there any temperature descriptor more unappetizing than lukewarm? Is there a single food or drink that sounds more appetizing when prepended with “lukewarm”?)
Following a palate-cleansing cup of tap water, the subjects ran through the basal tests a second time to measure any changes. The researchers found that while subjects showed no change in their sense of smell, “sweet tastes were amplified following the coffee consumption.” Subjects were also found to be less sensitive to bitter tastes. Researchers saw similar results when conducting the same experiment with decaffeinated coffee, suggesting that caffeine plays little to no role in the phenomenon.
“This may explain that if you enjoy a piece of dark chocolate with your coffee, it's taste is much milder, because the bitterness is downplayed and the sweetness is enhanced,” Fjældstad states. “We already know that our senses have an effect on each other, but it's a surprise that our registration of sweetness and bitterness is so easily influenced.”
These findings run counter to prior research on the subject. It was previously believed that exposure to bitter compounds—specifically caffeine and quinine, both of which are present in coffee—inhibited a person’s ability to perceive sweetness, but this study suggests a more complicated calculus is afoot in sensory perception. One potential explanation, according to the researchers, is that a combination of other compounds in the espresso is affecting flavor perception.
What I want to know then is this: if espresso contains both sweet and bitter flavors, does that mean that a second espresso consumed immediately after the first will be perceived as sweeter and less bitter because of the sensory effects of the first one? And once we are, say 15 spros deep, do we think we are just drinking lukewarm (again, gross) sugar water? Seems like a question for science or a coffee drinker braver than myself.