Kind of weird that they keep emphasizing "espresso" seeing how an Americano/Lungo/Allongé is basically just an espresso with added water (I might've offended some Italians just now). So why not just focus on the active ingredients instead? Maybe to distinguish from all the capsule coffees most people drink?
They gave pretty decent detail for recreating the sample they analyzed. That's probably better than assuming any sample of coffee would have similar compounds and ratios.
"True" espresso is extracted at around 100PSI of water pressure, so the coffee most people drink, at least in America, may not have the relevant compounds present of they are only extracted at the higher pressure of a true espresso.
adding milk and sugar might change something about the effect of espresso. controlling for that would make the entire study much more complicated.
i'm more surprised about them not calling it simply (black) coffee. possibly because espresso preparation is quite defined versus various methods of how to brew coffee.
Espresso is very different from black filter coffee, because the filters used in other brewing methods do not allow oil and particulate to pass through, so the composition of the drink will be different.
Espresso filter too - the basket has holes small enough to keep the grounds out the cup. The only coffee drink I know that has no filtering at all is Turkish coffee.
If anything wouldn't this argument suggest you should isolate and quantify the active ingredient? Certainly there is more variation between two espressos than, say, two 80 mg caffeine capsules.
