What is espresso?
Espresso is first and foremost a brewing method. Espresso is not a type of roast as often thought, like French Roast which is always roasted to a particular point in the roasting process. It is actually referring to the method of extraction or the ways the coffee is brewed, like French press vs. pour-over. The method of extraction is accomplished by 150lbs+ of water pressure applied to a finely ground coffee bed from 20-30 seconds. The grind of the coffee is fine to allow for more surface area of the coffee in order to achieve a very quick extraction. The hot, pressurized water extracts solubles and oils from the coffee grounds, then passes through the metal basket filter, giving it a unique, rich taste and creamy mouthfeel. Paper filters have the effect of filtering out many of the insolubles in coffee, but metal filters tend to allow them, which gives the coffee a thicker mouthfeel. This 150+ lbs of hot, pressurized water is supplied by commercial espresso machines that have the power to do it. Home espresso machines often lack the pressure power to properly extract the espresso.
The SCA’s (the Specialty Coffee Association) definition of espresso, an organization which strives to further coffee education and research, encompasses the broad range that espresso recipes can fit into. It doesn’t encompass every recipe or all the ways that espresso can be prepared, but is a basic working definition:
Espresso is a 25-35 ml beverage prepared from 7-9 grams (14-18 grams) of coffee through which clean water of 195-205 degrees has been forced at 9-10 atmospheres of pressure, and where the grind of coffee is such that the brew time is 20-30 sec.
While brewing, the flow of espresso will appear to have the viscosity of warm honey, and the resulting beverage will exhibit a thick dark, golden crema. Espresso should be prepared specifically for, and immediately served to its intended customer.
Kettle’s basic recipe for espresso:
Espresso is a 32 gram drink made with 195-205 F water that has been forced at 9-10 atmospheres of pressure through 18 grams of coffee and where the grind of the coffee is such that it takes approximately 24-28 Seconds.
(An atmosphere of pressure is the standard unit of measurement for pressure at sea level.)
This recipe can change, but the basic understanding that espresso is a brewing method using pressure and a find grind for quick extraction.
What does espresso taste like?
Espresso is an extremely high ratio of coffee to water, so the flavor profile of espresso is usually intense. The body is typically thicker than a brewed coffee and any acidity in the coffee is intensified. The larger the shot, or the lower the ratio of coffee to water, the less intense the acidity and body will be, which can be a great thing when done well.
Espresso should have crema on top when it is served. Crema is the bubbly surface of the espresso shot, which helps hold in aromas (a bonus feature). If the coffee used to make espresso is fresh (less than 2 weeks old), the crema will not dissipate too quickly.
There is much to be said about espresso, but this brief explanation should clarify exactly what this mysterious beverage is on the menu. It is a wonderful, super complicated and fickle beverage that can rock your world or make your face contort.. with little room in between. It is the crown jewel of every specialty coffee shop and every barista chases "the god shot" (the illusory perfect shot). It is also as diverse as it is complicated to create.