Madeline asked: “Can you make drip coffee so strong that it is espresso?”
It’s an excellent question. You might be surprised how many people will tell you that the difference between coffee and espresso all depends on the bean you start with, or how that bean is roasted. It’s true that some coffee beans can be selected and roasted with espresso in mind, but that’s hardly the whole story.
Coffee can be made in hundreds of different ways—leave it to humans’ drug-fueled ingenuity to combine water and a caffeinated seed so tirelessly—from automatic and manual pourover drip, to French press, cold brew, and other “total immersion” methods, to prepackaged pod systems and instant soluble powders.
All of those produce a familiar beverage—coffee—which we can call “brewed coffee” to distinguish it from espresso coffee.
Espresso, on the other hand, is a unique concoction that differs from brewed coffee in several important and interrelated ways:
How Is Espresso Made?
Unlike other coffee-making methods, where the water is allowed to soak and steep with the ground coffee at a leisurely pace, espresso is made under pressure (literally). An espresso machine heats water to 200 degrees and uses a pump to force it through the ground coffee at 9 times normal atmospheric pressure, in half a minute, directly into the cup. (It’s ready in a hurry, but that’s not why it’s called espresso.)
Each serving is made to order “expressly” (that’s not why it’s called espresso either) — as compared to brewed coffee, which is often made in advance in batches.
How Strong Is Espresso?
That method means that espresso comes out quite a bit more concentrated than brewed coffee. Whereas a standard mug of joe contains about 1.5 percent dissolved material (and 98.5 percent water, accordingly), a cup of espresso is made up of more like 10 percent coffee matter and 90 percent water. That’s why it tastes so strong! And that’s why espresso is so ideal for mixing with foamed milk to make lattes and cappuccinos: It’s concentrated enough to hold its own even when heavily diluted with dairy.
The Big Difference Between Espresso and Other Coffee
Another effect of the process, which pushes the water under pressure through compacted ground coffee and then through a metal filter with tiny holes (measured in fractions of a millimeter), is that oils from the ground coffee, which can’t pass through a paper filter, are forcibly expressed into the cup. (That’s why it’s called espresso!)
Broken into minuscule droplets, the oils form an emulsion in the beverage, which gives espresso its thick, rich body and intense, complex flavor. And this is what sets espresso apart from just very strong coffee. Even if you dripped a tiny amount of water through a megadose of finely ground beans in your drip machine to get the same concentration, the absence of pressure would mean there’s no emulsion, and hence no espresso, just strong, strong coffee.
Some of the emulsified oil lingers as a distinctive and beloved orange froth on top of the espresso, called crema.
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The ground coffee acts as a porous stopper during the espresso brewing process, preventing the pressurized water from just gushing through the filter. So the size of the grind is powerfully important: Avid home espresso baristas may spend a thousand dollars on a precision grinder. Too coarsely ground and the water flows too quickly through the coffee grounds, so the pressure drops and the brew is thin and weak; too finely ground and the water can’t get through at all, or dribbles so slowly that it makes a bitter syrup. The aim is to dial in the proper fine grind so that the espresso cup is full just about 30 seconds after the brewing starts.
To make that possible, the beans are usually roasted till they’re on the darker side. Coffee beans puff up a bit (very much like popcorn) when they are roasted, and the darker-roasted ones expand more, making them more fragile and porous, and hence easier to grind evenly into a fine consistency. The roast also forces some of the oils to the surface of the bean, where they can be more readily extracted; and develops the robust flavor we associate with espresso.
Which Has More Caffeine?
Does espresso have more caffeine than brewed coffee? Much more, right, because it’s more concentrated? Well, yes, if you drank a 12-ounce coffee mug full of espresso you’d be rocketing around like a superball. (Don’t do this.) But a standard double shot of espresso is just about 2 ounces. So a serving of espresso gives you around half the dosage of caffeine that you get from a regular cup of coffee.