Espresso is a mysterious drink. Not many people really know what it really is, how it’s made, or even what it should taste like. We've all been lured into a haze of misunderstanding and misinformation by the likes of Starbucks, Nespresso, Krups, and countless other brands looking to make espresso easy and cheap. Don't take the bait. Espresso, done right, is wonderful. Here's how the best in the business do it.
Espresso is not type of coffee bean, or a type of roast. Espresso is simply a method, a way to brew coffee. In fact, any coffee can be brewed as espresso—though some types taste better than others.
Making espresso involves pushing hot water through a compact ‘puck’ of grounds at high pressure, usually at around 9 bar (9 times the atmospheric pressure at sea level). The reason you see bags of coffee labeled as espresso is either because its contents are pre-ground to a fine size that suits espresso brewing, or it is a blend that has been crafted to create a balance of flavors when brewed as espresso.
To brew great espresso, a confluence of events must occur that marries human judgment with mechanical precision. It starts with decisions made by the roaster. Will they be making a blend of different coffee types to create a balance of flavors, or will they use a single-origin bean to highlight an experience unique to that particular variety?
Once a bag of beans has found its way to a human person preparing a drink, it is up to that person to make sure the beans are fresh, meaning no more than 2 weeks from the roast date, and ground immediately before brewing. There are certain aromatics in ground coffee that will evaporate within 20 minutes of grinding, so quickness is paramount. The grind size will vary based on characteristics of the coffee such as age, bean variety, and roast-profile. Even at the highest level there is no secret formula, with adjustments being made according to taste. The coffee is then precisely dosed, compacted into a basket, or portafilter, and finally meets the mysterious espresso machine.
All espresso machines utilize boilers containing a heating element that brings the water to the proper temperature. The pressure to pull a shot is generated by either a piston (found in older manual machines), steam power (in modern low-end machines), or a motor-driven pump. Commercial machines use a rotary pump that keeps constant pressure, whereas smaller machines use a vibration pump that generates pressure only as the shot is being pulled.
The name of the game in a good espresso machine is stability. Any fluctuation in heat, even to the tune of a couple of degrees Farenheit, can alter the taste of the coffee and make it impossible to pull consistently good shots. High-end espresso machines rely on a few important mechanisms for maintaining heat and pressure throughout the brewing process.
The first must-have is a double boiler system, where one boiler heats water for the brew, and another heats water for the steam wand. The two processes have different temperature needs—212 F for steam, 200 F for espresso. Having separate boilers will ensure that neither process throws the other off.
The other important mechanism is a PID (proportional-integral-derivative) controller. PID is a generic term for a controller that maintains a set value using control feedback loops. Many common devices use PIDs—a cruise control in a car might use one to maintain a certain speed based on calculating incremental changes over time. In espresso machines, the PID maintains constant water temperature, controllable to the degree. Without it, the heat level is prone to wide swings and makes consistency extremely difficult.
There are of course other aspects to a good espresso machine, mostly having to do with build quality, longevity, and ability to withstand the rigors of a commercial setting. The type of metal that the boilers are composed of, the pre-heating system featured, whether it is plumbed or reservoir-based—it all contributes to what is possible when you let the coffee flow.
Whatever you've had in Starbucks, or from a pod, or in a deli, does not reflect even a fraction of what a well-made espresso tastes like. Therein lies the problem—the majority of casual coffee drinkers have never actually had a good shot, so they don’t know what to expect.
Espresso made from freshly roasted, freshly ground coffee, made on a commercial machine by someone who has paid close attention to the process, should taste rich and sweet. Each coffee has its own flavor profile—fruity, chocolatey, floral—but it should never taste burnt, ashy, bitter, or sour. While most blends are meant to be mellow and appeal to a broad audience, you might want to try a single-origin coffee something totally different. And remember, it can be an acquired taste. Don't give up if you don't like what you taste at first! Also, don't get hung up on the tasting notes you see in specialty cafes. Not only are they often out-of-date, they push you toward pre-conceived notions when you really should be seeing, and tasting, for yourself.