NEW ORLEANS — It may be a bit unorthodox to mix coffee with chemistry, but by doing just that, a group of scientists claim they’ve figured out how to consistently pour the best shots of espresso possible.
“One day you might have a good cup of coffee and the next day you might not. From a scientific perspective, it has always puzzled me why we couldn’t do the same thing twice,” says lead researcher Dr. Christopher H. Hendon, in a release by the American Chemical Society. “My research looks at every variable that goes into making espresso coffee, from grinding and packing the ground coffee, to water pressure and mineral chemistry.”
Hendon, nicknamed “Dr. Coffee” by his colleagues, discovered in a previous study that brewing coffee with “hard” water — tap water with higher levels of magnesium and calcium — tends to have a stronger, more bitter taste. For his study on the perfect espresso, he focused on grinding the beans and the process of brewing, hoping to figure out how those crucial parts of the process affected the taste of the finished product.
He found that the grinding process provides more overall surface area for the beans, but at a certain point, the particles can become too small and lose flavor.” There is a point in grinding coffee beans when you make too many small particles, which stick together and result in reduced extractions,” explains Hendon.
How fresh the beans are make a notable difference, too. That’s because over time, compounds in the beans escape and the flavor of the coffee worsens. Storing coffee in the fridge helps slow this aging process of sorts.
When it comes to the water, he says that water should come into contact with the grounds uniformly — which does not happen when using a traditional coffee pot.
So Hendon turned to a team of baristas to help him figure out how reach the top level of taste, using his research on brew ratio and grinding size to perfect their method. “By predetermining the coffee-to-water ratio, as well as the water pressure, the maximum extraction can be systematically determined,” he says. “The barista can then iteratively improve their espresso reproducibility, while reducing waste coffee mass.”
Of course, replicating this process in every Starbucks across the country may be a bit more of a challenge, albeit a worthy one.
“If every single café in America was to implement the procedure, it would save the U.S. $300 million a year by reducing the amount of coffee beans used to make espresso, while improving reproducibility,” says Hendon.
Americans drink more than three cups of coffee every day each on average, contributing a big boost to the coffee industry, which is worth more than $40 billion in the U.S. alone, according to the National Coffee Association.
This research was presented at the 255th National Meeting & Exposition of the American Chemical Society in 2018.