How to Make the Perfect Espresso, According to Science
You already know how to make a cup of coffee that will blow your mind.
And now, thanks to the American Chemical Society, you can bring your A game to perfecting that espresso. Yes, chemists have unlocked the secret to making the best possible espresso every time. Of course, this isn't just a big deal for espresso aficionados who love to sip from their little shots while smoking cigarettes with attractive strangers in cafes overlooking the Seine, or whatever it is that hardcore espresso devotees do. The perfect espresso will also mean better lattes, cappuccinos, and much more.
Chemist Christopher H. Hendon was tired of feeling like each cup of espresso he brewed was a crapshoot. As he put it, "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."
He looked at every step of the process: grinding the coffee, packing the grounds, the water pressure used in brewing, and the mineral chemistry of the espresso.
They found that "hard" water, which is to say water with more magnesium and calcium, gives the coffee a stronger flavor than "soft" water, because compounds that affect the flavor will stick to the minerals. The amount of bicarbonate in the hard water can also give the espresso a more bitter taste.
Freshly roasted beans contain compounds that evaporate quickly, so, if you use beans that were roasted a while ago, they're going to be less flavorful. (That said, for beans stored at a cooler temperature, the compounds will evaporate slower.)
As far as grinding the beans, smaller is generally better for increasing surface area. However, if the particles get too small, they'll stick together, which can make it harder to extract the flavor. So, basically, you want to make sure your grinder knows what they're doing.
As to brewing, the traditional drip pot isn't ideal, because it mainly passes water through the center. The perfect espresso maker would make sure the coffee passes through the grounds in a uniform manner.
Hendon, whose research has won him the title "Dr. Coffee," has partnered with baristas to come up with a brewing process that optimizes the grinding size and coffee-to-water ratio. You can watch his press conference on the subject here and read the full American Chemical Society press release at EurekAlert!