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.
What is espresso?
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.
A delicate balance of man and machine
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.
Heat & Pressure
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.